The VISIR Remote Laboratory: Analysis of Limitations and Proposals for Improvement

Abstract

Engineering education depends on hands-on experimentation, but laboratory access is often limited by time, availability, and resources. Remote laboratories mitigate these barriers by enabling online access to real experiments, with the Virtual Instrument Systems in Reality (VISIR) standing out as a long-established system for teaching electronics and electrical circuits. Based on an extensive literature review and on substantial experience, this study qualitatively analyzes VISIR and identifies limitations related to scalability, interoperability, and integration with emerging technologies. From these insights, the paper proposes a set of improvements and technologies to enhance or replace key components while preserving its core infrastructure. The conclusions contribute to practical recommendations for those developing remote laboratories for electrical circuits and analog electronics education, thus offering achievable design suggestions and outlining directions for future research and development.

1. Introduction

In engineering education, laboratory activities are essential for experimentation, allowing students to connect theoretical concepts to practical applications through active problem-solving techniques [1]. These activities are designed to enhance experimental skills and knowledge, providing students opportunities to practice and apply engineering concepts [2]. However, some resources required to conduct practical experiments, such as hands-on activities, are often difficult to access in traditional laboratories [3] due to constraints such as limited bench space, inadequate time slots for using the equipment. strict safety regulations, and the high cost of equipment. Factors contributing to these challenges also include increasing student numbers, the demand for advanced technological and experimental tools, and limited financial resources [4]. However, it is also essential to consider access to practical experiments for students with special needs or disabilities, as many virtual laboratories currently lack adequate accessibility features, limiting their full participation [5].

These hands-on activities are associated with both traditional and online laboratories. Because no universally accepted laboratory classification fully covers all existing, emerging and alternative scenarios, a strong consensus has emerged regarding two fundamental aspects: the user’s relative location in relation to the experiment (local or remote) and the nature of the experiment (real or virtual) [6]. The term “online” is used broadly to describe virtual and remote systems, as both allow users to access them via the Internet without requiring physical presence. However, these systems differ significantly in terms of functionality. From a technical perspective, online laboratory experiments must be designed to align with theoretical knowledge and be robust enough to withstand potential failures during use, especially when compared to traditional laboratories.

As didactic tools for conducting practical activities at a distance, online laboratories offer a potential solution, enabling students to engage in practical experiments and gain a deeper understanding of the subjects being studied. These platforms can increase student interest in engineering by helping them overcome obstacles through hands-on experimentation, as they provide flexible and accessible environments that bridge theoretical knowledge with practical application [7]. Online laboratories facilitate remote or virtual experiments over the Internet, with users and equipment often located in different physical spaces. The final goal is to provide access to laboratories anytime and anywhere [8], mitigating problems related to student numbers, limited laboratory space, and the availability of human resources. Online laboratories also present an economical alternative to traditional laboratories, as they can mitigate financial and infrastructural challenges, creating a new paradigm for learning with the potential for sharing software and hardware resources between educational institutions, leading to lower investment and operational costs [3]. In the case study presented in [3], replacing a traditional laboratory with the VISIR remote laboratory eliminated approximately 20% component waste and became more cost-effective for groups larger than 22 students, due to equipment sharing and the absence of elimination costs. The motivation for implementing these systems includes providing access to experiments and equipment, maximizing the use of expensive resources, enabling equipment sharing across institutions, and offering students greater opportunities to engage with experiments. Furthermore, online laboratories allow students to perform experiments before working with physical equipment, reducing the possibility of costly or hazardous errors and enhancing safety [9].

The idea of performing remote experiments was initially proposed in 1991 [10], marking the beginning of developments that have led to the current state of remote laboratory implementations in engineering education and other scientific fields, making it a well-established field of research. The main goal of remote laboratories is to provide an experience similar to that of a traditional laboratory. According to [11], remote laboratories present several educational advantages over conventional ones, while still maintaining many of their core features. The COVID-19 pandemic accelerated the widespread use of remote laboratories in education, prompting rapid innovations [12] that have resulted in more stable, efficient, and reliable solutions, making remote laboratories a viable and attractive option for teaching engineering subjects, especially in the post-pandemic era. Furthermore, the growth of remote laboratory systems since the beginning of the century can be attributed to two key factors: the need for high-quality technological tools for laboratory experiments and the reduction in funds allocated to physical infrastructure and equipment [13]. The authors of [14] offer an in-depth review of the evolution of remote laboratories from 2000 to 2022, detailing new perspectives, concepts, and innovations in the field. While remote laboratories have significant benefits, they also present challenges that need to be carefully addressed and overcome.

An example of a widely deployed and disseminated remote laboratory is the VISIR. Described as “perhaps the most powerful, spectacular, and frequently used remote laboratory in the world”, this system allows users to remotely design, implement, and measure analog electronic and electrical circuits, offering an experience similar to that of conventional laboratories. Despite the physical distance between the user and the laboratory equipment, the system transmits real-time data from actual components and circuits, something that simulation software cannot provide. Unlike virtual laboratories, remote laboratories involve various sources of error that can and should be analyzed and understood. VISIR remote laboratory acts as an online version of a traditional laboratory workbench, enabling the implementation and measurement of physical circuits on a virtual breadboard interface (Figure 1) [15], which is part of the User Interface (UI). However, whereas the data in this system are real and obtained in quasi-real time, it does not directly originate from the virtual breadboard’s depicted instruments, and the physical setup of the circuit does not exactly match its virtual representation. In other words, e.g., there are software and hardware components that measure electrical current, but the Fluke 23 multimeter shown to users is not actually present in the laboratory.

Several systems have been developed for this specific type of remote laboratory, such as those presented in [16,17,18], each aiming to achieve similar objectives but differing in their educational focus, design approaches, and functional capabilities. The VISIR remote laboratory offers the ability to control parameters and values using the same tools and components as a traditional laboratory. However, its key advantages, when compared with other concurrent systems, are the ability to support simultaneous interactions by multiple users with minimal delay and also giving users the freedom to perform their own non-predefined experiments [19]. This allows users to design identical or different circuits and monitor the same or varying signals in real time and concurrently, much like in a physical laboratory with multiple workbenches. The maximum number of simultaneous users can be adjusted through a configuration setting. Simulations reported in [20] suggest that, under worst-case conditions with a 300 ms response time per experiment, approximately 100 concurrent users is the upper limit to maintain an average response time below two seconds, with network latency deliberately excluded from the simulation. In typical classroom Wi-Fi conditions, additional latency can be expected from a few tens of milliseconds to a few hundred milliseconds, depending on load and congestion. However, this time measurement only covers part of the server’s operation and does not account for network delays between servers or the server processing time itself.

The VISIR remote laboratory has seen widespread adoption, before and after the COVID-19 pandemic, with its popularity mainly attributed to its distinctive technical and scientific features that ensure system performance, scalability, and flexibility. These qualities not only distinguish VISIR from other solutions but also represent a tangible improvement over the current state of the art in similar systems. However, this does not necessarily mean that the underlying technology is sophisticated, scientifically pioneering, or truly innovative. Therefore, the primary aim of this paper is to carry out a qualitative systematic analysis of the VISIR remote laboratory, drawing on the literature and on significant practical experience. Following this analysis, exploratory proposals for improvements are provided to address these limitations. The proposals presented are intentionally hypothetical, aiming to stimulate academic and technical discussion and to guide future research, rather than proposing closed and validated solutions. The goal is to provide a general overview and identify potential paths for technological development, from which prototypes or in-depth case studies could emerge. While the proposed solutions are not essential for maintaining system functionality, they serve to demonstrate potential technological enhancements that could resolve existing problems. It is important to note that this paper deliberately excludes pedagogical discussions, focusing instead on conceptual, economic, and functional aspects to improve the VISIR remote laboratory. The goal is to identify gaps and explore potential technologies to update a system that has not received significant improvements for some time, i.e., since Ingvar Gustavsson, the VISIR remote laboratories founder, passed away in 2017.

The structure of the paper is as follows: Section 2 provides an overview of the VISIR remote laboratory, to demonstrate some of the technical ideas behind its operation, and recent improvements made by system owners. Section 3 discusses the system’s limitations but also shows some strengths, while Section 4 outlines proposed solutions to address these constraints. The last section, Section 5, presents the conclusions.

2. VISIR Remote Laboratory Technologies

This section provides an overview of the VISIR remote laboratory, a well-established system whose foundational characteristics and technical details are most thoroughly documented in earlier publications, such as [21,22,23], which remain the most comprehensive sources. It is important to note that the VISIR remote laboratory was originally developed at a higher education institution for educational purposes [24], specifically designed to support engineering education, particularly in part-time study programs where students’ time and flexibility were limited [25].

2.1. An Overview

The VISIR remote laboratory is widely recognized as a valuable tool in engineering education, with users around the world and installations in multiple countries and institutions [26]. Its primary aim is to foster the development of experimental skills and competencies, as emphasized by many authors [3,27,28]. The first publication about this remote laboratory dates to 2001 [29], where the system was described in conceptual terms. Since then, the literature focusing only on the VISIR remote laboratory, including conference proceedings, journal articles, theses, and book chapters, has expanded significantly [30,31]. Notably, the system earned the Online Lab Award in 2015 in the Remote-Controlled Laboratory category, awarded by the Global Online Laboratory Consortium (GOLC). Additionally, VISIR was the first remote laboratory to support a Massive Open Online Course (MOOC) in electronics [19]. Its widespread acceptance and recognition are further underscored by its compliance with the Accreditation Board for Engineering and Technology (ABET) criteria, which ensure that it meets the recognized standards for engineering education [32]. The significance of this system is further highlighted by the fact that, as shown in the study presented in [27], the leading author in the field of virtual laboratories includes a publication about it among their most cited works. All this recognition is evidence of the system’s potential and its effectiveness, which combines computer technology, various software tools, and both commercial and proprietary hardware components (Figure 2).

The VISIR remote laboratory consists of a physical setup that includes, among other components, a server that communicates with clients via a web interface, and Component Boards where all the electronic components and shortcut wires are installed. The system is divided into three main blocks: the experimental setup, including the Switching Matrix (SM) and other elements, the servers (Web Server, Equipment Server, Measurement Server), and the client interface (a web browser that provides users with access to and interaction with the available experiments). The VISIR remote laboratory combines a physical measurement system with an efficient and effective educational tool for teaching and learning analog electronics and electrical circuits, and for that purpose, it integrates hardware and software components. So, this system is not intended to replace traditional experimental classes, but rather to complement them, i.e., students can perform experiments remotely before or after doing them in a conventional laboratory, gaining experience with tasks like building circuits and performing measurements.

The original VISIR remote laboratory architecture is shown in Figure 3. It can be observed that the system is structured into multiple hardware and software interlinked components (i.e., the software includes the Measurement Server, while the hardware contains the SM). It is important to note that this remote laboratory uses a distributed client-server architecture to enable the exchange of information and data between its distinct components.

2.1.1. Hardware

The VISIR remote laboratory hardware can be divided into two main components: the instrumentation platform and the proprietary SM. The instrumentation platform is based on a PCI eXtensions for Instrumentation (PXI) chassis and its modules, provided by National Instruments, Austin, TX, USA (NI) [23]. These modules include a DC power supply, a digital multimeter, a function generator, and an oscilloscope, performing the same functions as their conventional homologues. Although most modern instruments in traditional laboratories feature remote-control capabilities via Internet connections, breadboards do not inherently offer such functionality. To address this, the VISIR system includes the SM, a remote-controlled circuit wiring manipulator.

The SM is a stack of PCI/104-sized Printed Circuit Boards (PCBs) designed specifically for the VISIR laboratory. It facilitates the connection between various electronic components, shortcut wires, and instruments. New circuits are created by adding or removing components and wires on the Component Boards. The SM contains seventeen nodes (tie-points that act as connection points, enabling each conductor formed by the stacked connectors to behave as a node in a circuit), primarily used for connecting components and shortcuts. However, only ten of these nodes, including GND, can be used to interconnect components and shortcuts. Additionally, the SM connects the PXI modules to the circuits defined by the users, allowing them to introduce signals or voltage (using the function generator or DC power supply) and perform measurements [23]. Designed by Blekinge Tekniska Högskola (BTH), the SM includes a microcontroller that identifies each board and controls its components, as well as several reed relays. These relays replace traditional connections between components, shortcut wires, and equipment that would otherwise be made using physical cables [34,35].

2.1.2. Software

The software package for the VISIR remote laboratory is released under a GNU General Public License (GNU GPL) [26], except for the firmware of the SM board controller, which is sold as part of the system. Another proprietary piece of software used in the VISIR remote laboratory is the Laboratory Virtual Instrument Engineering Workbench (LabVIEW), which operates the Equipment Server [35]. LabVIEW is a graphical, object-oriented programming language developed to simplify communication between hardware (such as the PXI chassis, digital multimeter, oscilloscope, and function generator) and software. In the VISIR remote laboratory, LabVIEW is primarily used to create the Equipment Server, an internal tool for hardware interaction [23]. In addition to these core software elements, the VISIR remote laboratory incorporates two additional tools: the OpenLabs, which functions as a type of Remote Laboratory Management System (RLMS), and a Virtual Instructor, although it is not as effective as a conventional virtual instructor available in other areas. The OpenLabs, implemented through the Web Server, controls access to various resources, including scheduling, profile management, and other administrative functions [36]. The Virtual Instructor, if the rules outlined have been properly defined by the technical staff, protects the system by preventing users from creating circuits that could damage the equipment [37]. It compares the components and circuits constructed by the user with a predefined file (i.e., MaxList), which specifies permitted components and allowable electrical currents and voltages [38]. This system ensures that users cannot inadvertently create harmful circuits, safeguarding the equipment and components; otherwise, an error message is displayed.

The UI is browser-based, enabling users to build circuits, perform measurements, view signals, and configure instruments. Each instrument interface replicates its real-world counterpart, providing typical functions found in a conventional laboratory. Since 2012, the system has been compatible with mobile platforms, with a simulated workbench displaying and managing the breadboard and instrument front panels. This implementation is built with HyperText Markup Language (HTML), version 5, i.e., HTML5, using Cascading Style Sheets (CSS) templates and powered by JavaScript for interactions. Other technologies, such as JavaScript Object Notation (JSON) and Extensible Markup Language (XML), are also used. With a web browser and Internet access, users can interact with the system from almost any device. A “Perform Measurement” button, located at the bottom right of the UI, allows users to retrieve measurement results corresponding to their circuit.

The VISIR remote laboratory software adheres to international standards, enabling users to operate distributed online laboratory tools and interact with various electronic software interfaces or application programming interfaces [39,40].

2.2. Latest Developments

Since its last major documented update in the summer of 2008, technology has advanced considerably. The most significant update was made by BTH in 2015, when the Flash-based web interface was replaced with one built using HTML5. This technological shift was essential to ensure compatibility with all modern web browsers, thereby improving Internet accessibility. It is important to note that the current release (version 4.1) of the VISIR remote laboratory includes open-source software, allowing users and developers to freely expand its features and functionalities. As an example, the x-y mode function of the oscilloscope, previously available in a Flash-based web interface, is one of the improvements that could be reinstated, as no community-developed HTML5 plugins currently restore this functionality, and this gap was not formally documented and recorded in the open-source repository, https://github.com/JohanZackrisson/visir_html5 (accessed on 17 June 2024).

While members of the user community occasionally contribute with minor improvements, these updates are not mandatory for the system’s core functionality. Many of these enhancements are driven by the need to customize the system for specific institutional users. Consequently, there has been limited documented development by the higher education institution that originally designed the system, apart from updates such as those proposed in [41], along with standard hardware and software upgrades. Among the most recent upgrades is a solution described in [42], which addresses a problem where instrument configurations were not recorded when users saved their circuits. In [43], a conceptual study on intelligent algorithms and an additional hardware board is introduced, enabling dynamic control and monitoring of circuit building, thus overcoming the physical limitation of the SM that previously prevented direct connections between specific components. Another significant development, outlined in [44], involves replacing the traditional 2D interface with a 3D representation of the laboratory environment, components, and breadboard.

Originally designed to operate independently, the VISIR remote laboratory does not natively integrate with any RLMS, which makes it difficult to monitor and manage users’ activities, even though OpenLabs enables data collection from all conducted experiments. However, many educational institutions have integrated the system with WebLab-Deusto, an open-source RLMS launched in 2000. WebLab-Deusto, developed in Python (2.7 version) with an HTML interface, was created to facilitate the usage and development of remote laboratories. It also allows for detailed logging of user actions, such as circuits designed and measurements taken [45]. Additionally, WebLab-Deusto integrates easily with Moodle, a widely used Learning Management System (LMS), enabling seamless access to experiments hosted by other institutions. By collecting data through the VISIR dashboard (VISIR-DB), educators can gain insights into how students engage with the remote laboratory and monitor their learning progress [38]. The combination of these two tools enhances the functionality of the VISIR remote laboratory and deepens the understanding of users’ interactions.

In [46], the application of Learning Analytics (LA) in a remote laboratory context is explored, resulting in the development of the Laboratory Experimentation Data Analysis (LEDA) educational data mining framework. LEDA aims to link users’ interaction behaviors with their learning outcomes, providing valuable feedback for instructors.

Although the VISIR remote laboratory includes all typical instruments found in a conventional laboratory, it initially lacked support for multiple instances of similar devices. Adding modules to the PXI chassis, as done at Universidade Federal de Santa Catarina (UFSC), from Brazil, with two digital multimeters, increases costs and requires software modifications but allows simultaneous electrical voltage and current measurements.

Other adaptations to the VISIR remote laboratory include the integration of a Field Programmable Analog Array (FPAA) tool [47], an extension for remotely programming microcontrollers [48], and support for the Internet of Things (IoT) technologies [49], which allows users to perform experiments involving Raspberry Pi, sensors, and actuators. A fully remote working environment for Raspberry Pi is also available as part of the VISIR remote laboratory toolset.

Using the VISIR UI and an adapted Measurement Server, LabsLand developed HIVE [50]. This innovative technological approach builds on the VISIR remote laboratory but uses entirely different hardware (e.g., a dedicated SM and a basic instrumentation platform) along with some open-source software components. Effectively, it constitutes a new remote laboratory designed for LabsLand’s specific needs, leveraging insights gained from using, studying, adapting, and developing VISIR systems. This highlights the system’s versatility and its potential for application in other projects. Additionally, LabsLand has overseen numerous VISIR implementations at institutions such as the University of Georgia (UGA) and Universidad Nacional de Educación a Distancia (UNED) of Costa Rica [51]. These implementations include optimizations such as optional caching of measurement results.

3. Limitations and Strengths Identified

The VISIR remote laboratory has been extensively used in academic research and daily teaching [28], creating an expectation among users for its consistent functionality. However, the absence of a long-term design strategy has left several problems either unresolved, inadequately or insufficiently identified, or only partially addressed. The authors of [52] developed a roadmap outlining the planned steps to address and overcome these issues and highlighted some limitations across various dimensions, but essentially emphasized the urgent need for improvements to address potential threats to its sustainability. According to [53], netCIRCUITlabs, developed by Emona Instruments, is considered more flexible than the VISIR remote laboratory, partly due to its switchable boards that enable the creation of more complex circuits and integrated assessment features, e.g., presenting the work for assessment directly from the experiment. However, the two systems differ in capabilities, i.e., netCIRCUITlabs does not support multimeter measurements, a feature available in the VISIR system.

Given that VISIR serves as both a physical measurement tool and an educational platform, its limitations were categorized into (1) technical, (2) financial, (3) UI, and (4) educational and/or pedagogical constraints. Additionally, operational problems outside these categories were identified and discussed. This analysis draws not only on feedback from system users and owners’ experiences, but also on published scientific literature. The literature-based reported results were obtained by creating a database of all documents, including papers, technical reports, and theses, that deal exclusively with the VISIR remote laboratory since its foundation. In total, 391 publications were collected from common scientific databases, such as Scopus, Google Scholar, IEEE Xplore, ACM Digital Library, SciELO, and Web of Science. The search used terms such as “VISIR” and/or “Virtual Instrument Systems in Reality”, restricted to publications between 2000 and 2025, excluding duplicates and those that did not deal directly with the remote laboratory but only mentioned it. Moreover, all the institutions that use and/or own the system were invited to provide theses, technical reports, and any relevant documents. As this research aimed to capture a broad view of the existing limitations of the remote laboratory, all documents were included, with no specific weight assigned. Starting from the documents in the database, a systematic and exhaustive manual documental analysis of their content was carried out. All authors participated in this process, independently identifying and categorizing the text excerpts in which limitations were presented, ensuring a comprehensive and rigorous identification through interpretation. It is important to highlight that, among all the publications analyzed, only 37 clearly and explicitly address the limitations of the VISIR remote laboratory. These 37 publications therefore represent the full set of documents in which such limitations were unequivocally reported. This reinforces the significance of the present study, which not only consolidates dispersed information into a single coherent document but also provides a critical analysis of the technologies involved, identifying existing weaknesses and proposing recommendations for future improvements. This approach transforms the study into a valuable resource and a valuable scientific contribution for those seeking to implement improvements. Nevertheless, the robustness of this analysis could be further strengthened by detailing the inclusion/exclusion criteria, describing the coding procedures used to identify limitations, and reporting the reliability between evaluators, aspects that are recognized as areas for enhancement in future work.

The following subsections provide a detailed discussion of the VISIR remote laboratory limitations along with potential solutions, while the final subsection summarizes its main strengths.

3.1. Technical Weaknesses

The VISIR remote laboratory faces limitations related to the storage capacity of its SM, which restricts the number of experiments that can be made available to users, as a maximum of only fifteen independent Component Boards can be stacked together [54]. The Component Boards contain sockets, each permanently connected to a reed relay, where the components and shortcuts that form the circuits must be physically placed [23]. The VISIR remote laboratory design requires minimizing the number of reed relays, as additional elements introduce capacitance and resistance, which can significantly affect circuit properties, a consideration relevant for any system utilizing switching relays. To accommodate different experiments, components must frequently be swapped out, reducing the range of experiments that can be conducted simultaneously [55]. However, this limitation can be addressed through the Platform Integration of Laboratories based on the Architecture of VISIR (PILAR), a federation that brings together entities owning VISIR remote laboratories, in which each partner acts both as a provider and a user of experiments [56]. Additionally, the function generator output is permanently connected to Node A of the SM through a reed relay on the Source Board, limiting Node A’s flexibility. Each component is permanently connected to a specific node, making experimental assembly more complex compared to using a standard breadboard in a traditional laboratory, and limiting the number of components that can be used in a single experiment. Another SM limitation is that it only supports circuit creation with up to eight nodes.

To implement a connection, it must be physically feasible within the constraints of the SM. While the design allows a modular approach, by adding or removing components and shortcut wires on the Component Boards, it also introduces certain challenges. For example, components installed on the SM cannot always be directly connected to each other without the use of additional shortcut links. All components and shortcut wires must be connected to predefined nodes, requiring users to have a deep understanding of both the hardware and the software involved [21]. The MaxList files, which define the allowed components, shortcut wires, their connections, and the instruments available for each experiment, impose logical limitations on the direct combination of components. Furthermore, improper configuration of these files can result in system damage, as the Equipment Server does not automatically check circuits, increasing the risk of user error or equipment misuse.

Repeated use of the SM has revealed additional drawbacks. The cables linking nodes to components on the Component Boards (Figure 4) can develop continuity breaks, faulty contacts, or short-circuits due to the bus connector layout. The sockets on the Component Boards, where components and shortcut wires are physically placed, are small and may not reliably accommodate certain elements, such as diodes, leading to poor connections. Maintenance, updates, and adjustments to installed components are also challenging because the stacked Component Boards often need to be individually removed to access specific elements. The SM design further presents issues related to operational consistency. For example, the improper operation of reed relays, potentially due to capacitors lacking proper discharge cycles or the disconnection of energized coils, can lead to incorrect measurements or reliability concerns, particularly when high-risk components, such as capacitors and inductors, are used. These limitations highlight the challenges associated with maintaining, updating, and ensuring the system’s long-term usability.

Although the reed relays in the VISIR remote laboratory are rated by the manufacturer for 3 × 10⁸ operations (equivalent to two operations per second continuously for five years) [23], under conditions of 1 V_DC and 10 mA, malfunctions are more frequent than expected. These problems, often random and intermittent, only become apparent during experiments. Diagnosing faulty relays requires removing all relays from the boards, halting the laboratory operations and significantly increasing maintenance time. This situation is further aggravated by the lack of maintenance status notifications, leaving users confused about the cause of system unavailability. Implementing an automatic fault diagnosis mechanism (i.e., periodic self-tests by software) could make these tasks easier and reduce downtime.

Each board in the SM is controlled by a Microchip PIC16F767 microcontroller, while the Source Board additionally employs a PIC18F4550 microcontroller to manage communications [25,54]. Unfortunately, the source code for these microcontrollers is proprietary and unavailable to VISIR remote laboratory owners, making the system dependent on third-party proposals, i.e., this specific hardware does not easily allow integration with alternative solutions (hardware or custom modifications), limiting the system’s flexibility. Moreover, it makes it impractical to combine Component Boards from several VISIR systems, thus not facilitating opportunities for reuse or recycling.

A further hardware and software limitation in the current VISIR remote laboratory setup is the inability to remotely control devices from non-NI manufacturers or to interface with a different SM other than the existing one.

Software challenges further complicate system management. The Equipment Server, developed in LabVIEW, is extensive, not adequately documented, and reliant on intricate block connections, making updates and maintenance difficult [57]. Similarly, the Measurement Server, written in C++, is also inaccessible, offering only a non-editable command prompt, limiting transparency and customizability. Additionally, interoperability between servers is limited, as communication between multiple servers is problematic, and delays (e.g., a ±25 ms switching transient delay) further reduce overall system efficiency [55].

LabVIEW’s graphical programming nature makes comparing code revisions complicated, and its licensing requirements impose restrictions on access and availability. The lack of integration between the Measurement Server and the Equipment Server further affects system performance, exacerbated by the fact that LabVIEW does not compile into binary code, leading to inefficiencies. Another problem is the reliance on a proprietary setup. Although VISIR incorporates open-source software, its dependence on specific hardware vendors restricts flexibility and hinders improvements. Operational problems arise from the system architecture, which relies on TCP/IP standards for server communication. This introduces delays, particularly under heavy traffic or when additional time gaps occur between transitions. Users may experience slow responses due to queue length or measurement errors, such as when the multimeter is misconfigured (e.g., reading AC signals in DC mode) [58]. Experiments that require synchronized measurements, such as capacitor discharge cycles, are constrained by oscilloscope time base limitations, typically capped at 50 ms [59]. Thus, this may result in measurement time, which can be larger than ideal when measuring with an oscilloscope, or too short to achieve the correct values. These problems are compounded by the reliance on proprietary PXI chassis and modules, which require specific drivers provided by NI.

User scheduling presents another challenge. The VISIR remote laboratory has limited capacity for managing a satisfactory number of simultaneous users and requires the implementation of a booking system. WebLab-Deusto offers only a “first-come, first-served” mechanism, resulting in unpredictable waiting times without the option to pre-schedule sessions. However, it offers an extensible authentication mechanism, storing all users in the database. As a result, the users only need to log into their LMS to access the VISIR remote laboratory without additional credentials. Recognizing this problem, the UNED developed an external booking system, designed not only for accessing the VISIR remote laboratory but also for other tools requiring prior reservation. Nevertheless, access to the VISIR remote laboratory, whether through an active reservation or available time slots, is provided directly by WebLab-Deusto [60].

The discontinuation of support for older modules, such as the PXI-1033 chassis, creates compatibility problems with modern operating systems, further limiting VISIR remote laboratory reliability and scalability. Additionally, when measuring DC voltage, the multimeter may display a non-zero value due to low-frequency noise (the multimeter module on the PXI chassis has a 3½-digit resolution by default, allowing fast DC measurements). The absence of a protective enclosure for the SM exposes it to safety and reliability risks, while the lack of a stable mounting base contributes to further instability (Figure 5).

Overall, the proprietary nature of VISIR’s hardware and software, along with operational and maintenance challenges, poses significant barriers to system optimization and long-term usability.

3.2. Financial Problems

One of the barriers to the widespread adoption of the VISIR remote laboratory is its high cost, which exceeds €40,000. This includes the SM, a PXI chassis with its modules, a LabVIEW license (a proprietary, non-open-source software), and a computer to integrate the hardware and software components. Compared to similar bench instruments offering remote control or observation capabilities, the PXI chassis and modules are notably expensive. While the cost of developing and maintaining a real-time remote laboratory like VISIR is understandable, it significantly limits dissemination, particularly in countries lacking financial resources for conventional laboratory equipment. According to [61], the reliance on specific hardware for which VISIR was designed further inflates costs, resulting in an excessive price per laboratory session. This is due to the use of advanced PXI instruments and expensive commercial software. It should be noted that there are alternative solutions, within the same application domain, that do not depend on commercial software, as they are designed to operate independently of NI hardware.

The proprietary nature of the SM creates additional challenges. Its limited potential for reuse outside the VISIR system makes the equipment dependent on third-party support, with little opportunity for financial return on the initial investment beyond its operational use.

Regarding the existing computer, it does not have the ability for an automatic restart in the event of a failure in the operating system or in one of the several servers. Additionally, modern computers no longer include Peripheral Component Interconnect Express (PCIe) slots, preventing the attachment of the NI PCIe-8361 card, a critical component that connects the PXI chassis and its modules to the software via a PCI cable. This limitation increases the cost of deploying a new VISIR laboratory or replacing a damaged one, as additional hardware purchases may be necessary. Beyond that, the computer capacity and the institutional policies for accessing it can be an obstacle for users connecting to the VISIR remote laboratory.

The PXI modules support self-calibration via an option in the NI-MAX software; however, this does not ensure the accuracy of the settings and may introduce additional measurement errors. Therefore, purchase costs must also account for manufacturer-performed calibration.

Operational constraints also arise from the need for specialized technical staff. Creating, designing, debugging circuits, and maintaining both software and hardware components require expertise in electrical engineering, electronics, and computer science. Due to security problems and issues related to the web interface, the VISIR remote laboratory requires constant IT support, usually provided by the host institution’s IT services. All these specialized technical staff involve significant costs, which means that almost all systems installed are developed, maintained, operated, and managed by graduate students, teachers, and researchers, as the organizations usually do not have the financial resources to allocate permanent staff.

Physical infrastructure further adds to the costs. The VISIR hardware setup requires an Uninterruptible Power Supply (UPS) to ensure that the computer shuts down safely before the PXI chassis, as well as air conditioning to maintain optimal operating temperatures for the hardware. Another potential risk is the absence of a worldwide trademark registration for VISIR. This exposes it to potential legal disputes, including the possibility of losing the right to use the name if it infringes on an existing trademark. Establishing a strong, globally recognized and protected brand requires considerable time and financial investment, and this vulnerability could result in substantial financial and reputational losses.

3.3. User Interface Drawbacks

According to [14], one of the major challenges with remote laboratories is the lack of immersion, which can significantly affect user performance during experimentation. However, as first noted by the authors of [62], the VISIR remote laboratory has achieved significant global dissemination, with its primary strength being its ability to foster a deep sense of involvement. This strength is largely attributed to its realistic graphical interface, which closely resembles the workbench setup of conventional laboratories, enabling users to implement circuits and manipulate instruments in a familiar environment. Similarly, ref. [52] highlights this realistic interface as one of the system’s key strengths. Yet, ref. [63] reveals that teachers, in their feedback on the system’s pros and cons, cited the outdated UI as a drawback, particularly for the current generation of digital natives. For example, the system’s web pages (virtual breadboard interface, etc.) are not fully optimized for smartphone or tablet browsers, limiting accessibility and user-friendliness for all users. As a result, opinions are divided on whether VISIR remote laboratory’s sense of immersion is a strength or an emerging weakness. To address these concerns, Extended Reality (XR) technologies, such as Augmented Reality (AR) or Virtual Reality (VR), could enhance immersion further. This technology allows the entire remote laboratory to be converted into a full virtual laboratory environment that realistically simulates the behavior of the real physical laboratory. Nevertheless, according to [64], XR solutions are immersive, but so far, they lack data integration, and it would be necessary to develop a new Extended Remote Laboratory (XRL) for this purpose.

Various problems with VISIR’s UI negatively impact the user experience. For example, it lacks animations for components such as potentiometers and LEDs, and it does not feature a virtual breadboard interface with graphical representations of instruments, which could make circuit connections more intuitive and user-friendly.

Another significant limitation is the oscilloscope’s functionality within the UI, which features an outdated display and lacks a cursor function. The cursor is a valuable tool for measuring specific voltage or time values on a waveform, and its absence restricts the user’s ability to observe and analyze measurements. Interestingly, this feature was included in the original VISIR’s UI but was removed during the transition to the HTML5 version. Furthermore, the absence of a GND terminal in the oscilloscope channel layout limits the user’s understanding of the correlation with a conventional laboratory setup.

Another limitation is the lack of an area within the UI to display the experimental guide, requiring alternative methods (i.e., external platforms or documents to deliver) to provide this resource to users.

3.4. Educational and/or Pedagogical Threats

In addition to technical and financial challenges, the VISIR remote laboratory also faces problems related to its users, teachers, students, and technical staff, as discussed in [52,65,66]. For example, these publications identify the need for specialized support as a weakness and teacher resistance as a major obstacle. When VISIR is operated by users lacking prior knowledge of electricity or electronics, it requires considerable time for an expert (e.g., a teacher) to explain its functionalities, making teacher guidance crucial for effective student engagement and performance. Therefore, novice users must possess significant theoretical knowledge and familiarity with the system before they can effectively use it [67]. A possible improvement is to provide proper training for teachers and technical staff because it is essential for the system’s effective utilization.

As noted in [43], the design of the SM introduces redundancy in shortcut wires and components, leading to overuse of expensive hardware such as Component Boards. For example, while the system can measure a resistor’s resistance, the same resistor may not be usable for other experiments. Similarly, in circuits with two identical resistors, the system always measures the same one. This occurs because the most convenient way to wire the designed circuit is selected. When multiple identical components exist in the SM, the only solution is to tag each with a unique ID, ensuring the use of the chosen one, though this solution reduces flexibility. To address these limitations, laboratory activities must be carefully planned, and the system configured with appropriate components and shortcut wires, which decreases the diversity of pedagogical content that can be covered simultaneously. Consequently, this restriction reduces the diversity of pedagogical content that can be simultaneously covered, limiting the complexity of circuits that can be created due to the sparse node layout on boards [10]. Another problem with the SM, caused by the lack of nodes, is the limited placement options for a multimeter to measure electrical current. The multimeter must be connected in series with other circuit elements, requiring the placement of a shortcut between two SM nodes. This configuration restricts pedagogical flexibility by forcing users to place the instrument in predefined locations, limiting their understanding of alternative configurations. Furthermore, incorporating shortcut wires for electrical current measurement reduces space for other components, further constraining circuit design. Unfortunately, this issue can only be solved if the SM has more nodes available (e.g., increasing the number of available nodes in the SM), so it becomes a technical problem rather than an educational and/or pedagogical one.

The SM’s reed relays impose an electrical current limit of 500 mA [59]. Exceeding this threshold (which ideally should be set much lower, since operating at high electrical current levels shortens the reed relay lifespan) renders circuits unusable within VISIR, requiring technical staff to ensure that potentially hazardous circuits cannot be implemented. This limitation prevents certain real-world experiments from being conducted, further narrowing the range of experiments available. When users attempt to create invalid or unsafe circuits, the system always returns generic error messages [4], such as when a short circuit is detected or when a circuit cannot be mounted. However, these messages do not specify the exact problem, leaving users to troubleshoot independently. While erroneous measurements could serve as learning opportunities by demonstrating the consequences of incorrect configurations [58], the lack of detailed feedback often prevents users from understanding their mistakes. As a result, it cannot function as a conventional virtual instructor or an intelligent tutoring system available in other fields, so it can hardly be considered a virtual instructor at all. Additionally, it is not possible to list all the existing error messages or to change the language being used. This limitation exists because the situation has never been documented, and there is no written information available explaining how it works. Given current technological advances, a potential solution to this issue would be to adapt the content presented to students to better identify and diagnose errors, while also providing personalized feedback. These features could be implemented using Artificial Intelligence (AI) technologies such as machine learning for predictive analysis, Natural Language Processing (NLP) for improved interaction with users, and intelligent decision-making systems to enhance remote laboratory operations. Integrating these AI technologies into the VISIR system environment would enable more adaptive, efficient, and user-friendly functionalities, supporting both students and instructors.

The VISIR remote laboratory does not include a web camera (in contrast with other systems, such as netCIRCUITlabs) or a thermal camera, i.e., it lacks a visual feedback mechanism, and while electrical signals are inherently invisible, the absence of visual feedback, such as LED status indicators, the components heating, or the physical component views, gives the impression of simulation rather than a real experiment. This lack of feedback reduces user confidence in the system’s functionality and creates a less engaging experience, which can only be overcome through the installation of appropriate hardware devices.

Moreover, to understand the differences in educational and/or pedagogical outcomes when students use VISIR, in comparison with other remote laboratories, more recently developed and with other technologies, but designed for the same purpose, it would be necessary to carry out an in-depth study in collaboration with other educational institutions.

Despite its potential to provide high-quality engineering education, VISIR lacks a standardized model for designing and assessing teaching activities. This limitation complicates its efficiency, effectiveness, and global dissemination. While the VISIR remote laboratory enables real-time interaction with analog electronic and electrical circuits, this interactivity is often inferior to that of conventional laboratories. Users are unable to physically manipulate components or observe subtle physical phenomena, which reduces the hands-on experience essential for learning in traditional laboratory environments. Therefore, due to these limitations, it is not possible to provide an unlimited range of experiments, nor is it easy to design complex laboratory practices. Moreover, as the experiments available in the VISIR remote laboratory may be pre-defined and limited compared to those existing in a conventional laboratory, where users can adapt and design circuits freely, this system may not offer the same level of customization.

3.5. Major Strengths

While the VISIR remote laboratory has its challenges, it also offers several notable advantages. The most significant is its pedagogical value, as the system allows users to perform real measurements rather than simulated results, providing students with authentic laboratory experience, favoring the construction of fundamental practical skills in the field of engineering. Additionally, the UI features a visually accurate representation of the components placed on the virtual breadboard, enhancing the realism of the experience. As highlighted in [3,52,68], the VISIR remote laboratory promotes social integration by enabling accessible experiments without restrictions on space or time. Available 24-7, it allows users to repeat experiments to confirm previous results or explore new parameter combinations, thereby fostering independence and flexibility. Furthermore, the system extends the lifespan of components through built-in protections that prevent usage under conditions exceeding safe voltage or electrical current limits. For example, ref. [69] reports a resistor being used in over a million experiments, an outcome of durability unattainable in conventional laboratories. This durability also has environmental benefits, as it reduces the waste generation of electronic components. A possible future introduction of a device for real-time energy consumption monitoring, with feedback to users, allows for more efficient energy management, promoting conscious usage and contributing to sustainability and reducing environmental impact. VISIR’s versatility is another strength, enabling users to vary component values within a circuit and observe corresponding changes in real-time [51].

Another positive aspect is the possibility of integrating the VISIR remote laboratory with established LMS, such as Moodle, which simplifies automatic registration in the system, the delivery of tasks and the integration with assessment tools, even if these are carried out in the LMS environment.

In terms of usability, the system has been highly rated. According to [70], students at UNED (a public university specializing in distance education) in Spain scored it 4.06 out of five, demonstrating its effectiveness as a learning tool. Moreover, as noted in [50], even under concurrent usage, users typically perceive they have full control over the experiments. Unlike many remote laboratories, VISIR supports collaborative work in independent sessions, allowing multiple users to assemble and assess their own circuits simultaneously. This eliminates the common limitation where only one user controls the equipment while others merely observe. An additional strength is the existence of a global, active community spanning multiple countries and continents, which collaborates to address challenges and improve the system [8]. This VISIR community is articulated around the Special Interest Group (SIG) and the PILAR federation.

Finally, VISIR remote laboratory accessibility is noteworthy. It can be used on any device, computer, tablet, or smartphone, regardless of the operating system or browser. This inclusivity ensures that users can access the laboratory securely and without technical restrictions or barriers, making it a highly versatile tool for remote experimentation. Additionally, the VISIR remote laboratory, which is a platform that revolutionized experiential education, combining accessibility, security, realism and collaboration on a global scale, is one of the few worldwide with a dedicated book explaining how to use it in educational contexts [8].

4. Suggestions for Improvements

Selecting the right technology is crucial for remote laboratory systems, yet the VISIR remote laboratory is designed to function exclusively with its specified components. This design choice limits flexibility, particularly when integrating new instrumentation approaches or adopting technological advancements. Clearly, every feature or characteristic of the VISIR remote laboratory has its pros and cons. For example, while PXI modules are designed for accuracy and speed, they also come with a higher acquisition cost. Despite this constraint, the widespread adoption of VISIR, its large user community, and the abundance of related publications highlight a strong interest in further experimentation and system enhancement. Given this context, future developments for the VISIR remote laboratory should prioritize the integration of innovative technologies while reducing acquisition, maintenance, and operational costs. The primary objective is to improve the system’s overall infrastructure by optimizing each major component individually, rather than designing an entirely new experimental setup. To address the identified challenges, potential solutions will be grouped based on their functionality. These proposals are derived from three primary sources: (1) Practical experiences and initiatives from the VISIR remote laboratory community focused on finding alternative solutions; (2) A comprehensive analysis of currently available technologies and their associated costs, which must remain below those of the existing setup; (3) A review of implementation strategies used in the development of other remote laboratories with similar purposes. Alternatives will be explored with an emphasis on low-cost options that preserve the core characteristics of the current system. Each general proposal option will be analyzed in terms of its advantages, disadvantages, and feasibility. Although it is technically possible to implement multiple replacements simultaneously, this approach was not considered within the scope of this study to maintain focus and manage complexity. While the proposals are based on solid references, it is important to recognize that additional improvement paths may also exist. Other alternatives, potentially resulting from future technological advancements or from different educational and experimental needs, could complement or even replace the suggestions presented here. Therefore, the proposed solutions should be viewed as part of a broader and evolving panorama of possible innovations for the VISIR remote laboratory.

Integrating these proposed solutions into the VISIR remote laboratory is inherently challenging due to its relatively constrained architecture. Any modifications would require rigorous experimental validation to ensure compatibility and reliability. Testing and validating these changes would involve connecting the instruments and/or the SM to the proposed enhancements, with the strict requirement that no hardware or software modification introduces significant measurement errors or negatively impacts the system’s normal operation. This systematic approach ensures that improvements are both practical and aligned with the system’s established strengths, supporting a more sustainable and adaptable future for the VISIR remote laboratory.

4.1. Instruments and Computer Upgrade

The hardware components and equipment for the VISIR remote laboratory are selected with a focus on ease of integration into the existing system in mind. Recent technological advancements suggest that it is feasible to replace the current hardware with modular or commercially available standalone solutions. This approach simplifies the construction and validation of circuits under test using reliable measuring devices. While developing proprietary solutions is also a possibility, this approach would perpetuate problems related to ownership and exclusivity. Before proposing solutions to the aforementioned challenges, it is essential to assess whether the current system is over-engineered, particularly in relation to the PXI chassis and its modules, considering characteristics such as speed, precision, and reliability. Based on VISIR community feedback, the system could potentially operate effectively with instruments of lower specifications. While this might affect performance, the measurement results are expected to remain comparable, although with longer processing times. Importantly, these lower-specification devices would reduce acquisition costs, directly addressing one of the system’s primary challenges.

Most standard interfaces, such as GPIB, PXI, or USB, require a physical port, a specific controller, and specialized software to communicate with instruments. A potentially superior alternative is the adoption of LAN-based instruments, such as those compliant with the LAN eXtensions for Instrumentation (LXI) standard, which support open-source Application Programming Interface (API), e.g., Standard Commands for Programmable Instruments (SCPI), combined with the Representational State Transfer (REST) architecture over the Hypertext Transfer Protocol (HTTP). These instruments offer greater flexibility, interoperability, integrated software, simplified management, technological longevity, and enhanced robustness by connecting over a standard Ethernet link. LXI-compatible instruments are also modular and avoid the excessive cost and technical constraints of PXI-based architecture. However, while this is a technically feasible solution according to [71], migrating from PXI to LXI-based instruments would necessitate substantial reconfiguration of the existing system, probably without any significant performance losses (this is not critical because the PXI-based architecture is oversized for this type of use). Specifically, the current connection between the instruments and the computer would no longer be compatible, and significant modifications to the Measurement Server and Equipment Server code would likely be required. The integration of instruments that support Interchangeable Virtual Instrumentation (IVI) drivers, compatible with multiple development environments (e.g., LabVIEW, Python, or MATLAB), could help with these changes. However, as there is a lack of recent empirical references regarding latency or reliability in the specific context of the VISIR remote laboratory using LXI-based instruments, this highlights the importance of experimental validation before any large-scale adoption of any proposed improvement.

Another limitation in the current VISIR setup is the inability to remotely control instruments from different manufacturers, i.e., non-NI devices. A more straightforward alternative might be the NI VB-8012 (Figure 6), NI VB-8034, or NI VB-8054, which consolidate all the instruments from the PXI chassis modules into a single device. Obviously, other manufacturers than NI, such as Digilent, offer similar systems, like the ADP5470 (with a cost around €3600). Unlike the PXI modules, the NI VB-8012, which has the lowest specifications among the three mentioned above, does not require LabVIEW, though it still needs configuration via NI-MAX. This solution simplifies the system’s architecture while preserving essential functionalities. By carefully considering these hardware alternatives and their integration challenges, the VISIR remote laboratory can evolve into a more flexible, cost-effective (about €3000 while the PXI chassis and modules cost approximately €14,500), and robust platform for remote experimentation.

Although a Python library is available and the NI VB-8012 offers functionality comparable to the existing system, low-cost alternatives, such as the RedPitaya STEMlab (e.g., it is used for similar purposes in [61]), NI myDAQ, Analog Devices ADALM2000 (e.g., in [72] it was adopted, along with other devices, to achieve analogous objectives), and Digilent Analog Discovery 3, can replace the instruments, though each comes with limitations. For example, the Digilent Analog Discovery 3 implements some multimeter features via software, while the RedPitaya STEMlab can only generate voltages within a 0 to 1.8 V range, i.e., significantly below what is needed to implement some experiments. Physical communication between these devices and the SM could be facilitated through adapters and probes, and they can also be controlled using LabVIEW. However, these devices, costing between €250 and €1000 depending on the type of processor, memory, etc., cannot fully replace the PXI chassis and its modules without requiring additional changes to other elements of the VISIR remote laboratory. These modifications may affect software and hardware, but mainly the way in which the experiments are implemented.

An alternative to an all-in-one device is purchasing individual LXI-interfaced instruments, such as oscilloscopes and multimeters, and connecting them via a network. LXI instruments benefit from standardized drivers, enabling remote management over Ethernet. However, this approach could be less expensive than the PXI chassis and modules if the instruments have lower performance, but it introduces technical challenges, such as ensuring proper data paths between devices and the SM. Communication compatibility depends on correct firewall configurations and uniform address settings within the same range. Moreover, replacing PXI modules with LXI instruments is unlikely to improve system performance, as evidenced in [71]. Regarding modular solutions, commercial products from manufacturers like ADLINK Technology, Taoyuan, Taiwan (with the PXES2301 chassis), VTI Instruments, Irvine, CA, USA (with the CMX09 chassis and the EMX-2401 controller), or Keysight Technologies, Santa Rosa, CA, USA could technically replace the PXI chassis and modules. Although these options provide similar functionality, they are not inexpensive, e.g., the Keysight Technologies M9005A PXIe chassis and associated modules cost about €22,000, i.e., more than the current VISIR setup. Furthermore, one of the existing system’s limitations, the software’s reliance on commercial and proprietary hardware, would remain. However, devices from these manufacturers are typically designed to support multiple application development environments, which could most likely simplify integration with the Equipment Server and Measurement Server.

LXI interfaced instruments emerge as one of the most promising alternatives for communicating and controlling the instruments involved in a complex test and measurement system such as the VISIR remote laboratory, and also in order to enabling independence from a single manufacturer.

The computer hosting the VISIR remote laboratory servers could also be replaced with a more affordable solution, such as a single-board computer (SBC) with light virtualization capabilities. SBCs, including the BeagleBone Black, Espressif Systems ESP32, Arduino Portenta H7, Radxa ROCK 5B, or Raspberry Pi 5, have been successfully deployed in other remote laboratory applications, as demonstrated in [73,74,75]. These standardized, low-cost (they cost from €10 to €130) development boards are commonly used in data acquisition and processing systems. Deploying an SBC for VISIR would require addressing security and accessibility challenges while ensuring proper interconnection with the existing PXI chassis and SM, which may involve using USB ports or custom interfaces. SBCs offer two significant advantages over traditional computers, i.e., lower costs and reduced physical space requirements inside the laboratory. Moreover, with appropriate toolkits, SBC platforms can support LabVIEW, enabling data visualization and interaction with the SM. However, like any web-based application, they must be secured against potential vulnerabilities, e.g., with modern authentication systems such as OAuth2, TLS certificates and multi-factor authentication, while maintaining accessibility. Whatever the approach chosen, it will be necessary to implement a hardware or software watchdog to ensure that the computer restarts automatically in case of operating system or server’s failures.

With more powerful, faster, and resourceful embedded processors, remote laboratories can use these SBC platforms instead of traditional computers. For example, a Raspberry Pi 5 can be utilized as a system controller and a web server, reducing the cost and, probably, the complexity of the remote laboratory design, and improving flexibility without compromising essential core functionality. However, an external must be provided to connect these SBC to the NI PXI (chassis and modules).

4.2. Switching Matrix Improvements

The SM could be replaced either by a commercial device, a custom-built board, or a hybrid solution to expand its capabilities, such as implementing additional circuits, connecting multiple components in various configurations, and more. Other remote laboratories for electrical and analog electronic circuits, such as the Remote Wiring and Measurement Laboratory (RwmLAB) [76] and RemotElectLab [11], have adopted partial commercial solutions as soon as they were implemented. However, certain essential factors must be considered when selecting a replacement. These include the device’s component storage capacity, the number of available nodes, and the placement of power supply terminals across different nodes. Additionally, the device should allow direct connections between multiple components, avoid stacked board designs, and enable the safe discharge of components like capacitors (a feature not possible with VISIR). These requirements impose significant constraints on obtaining a device capable of upgrading the existing VISIR remote laboratory, making this the most challenging system part to replace. It is worth noting that an SM based on stacked boards, i.e., with a reduced distance between hardware elements, minimizes parasitic capacitances and increases the speed (or maximum operating frequency) at which the circuits can operate, without introducing significant noise.

Among commercial options, NI offers chassis-based systems (the NI PXI-2800, available for about €3000) with relay matrix modules (an example is the NI PXIe-2739, priced around €6300 each), arranged in rows and columns, to provide flexible switching capabilities that enable connections between any two channels. Such devices can support large-capacity arrays with numerous nodes, integrate with LabVIEW, and allow features like preventive maintenance of reed relays. However, they have drawbacks, i.e., it is necessary to obtain an additional chassis to place this one. Moreover, these solutions are costly (an SM for the VISIR remote laboratory, in its basic configuration, costs only around €7000, plus approximately €1000 for each additional Component Boards, up to a maximum of 15), may require rewriting server code to ensure correct relay state communication, and could have slower performance due to the relay types used. Additionally, replacing faulty relays in these systems can be difficult.

For solutions emphasizing LXI instruments, manufacturers such as Keysight Technologies (with the 34980A, a multifunction switch mainframe and modules, e.g., the 34934A) and Analog Devices offer products capable of creating electronic circuits by opening and closing relay connections or similar mechanisms, emulating a breadboard-like experience. While this approach resembles the existing VISIR remote laboratory’s existing system, it is unlikely to be significantly more cost-effective (it costs approximately €11,000 with a terminal block and connection cables). Moreover, it would require substantial changes to the current setup, including rewriting sections of the Measurement Server and the Equipment Server code, since maintaining the present USB connection between the matrix and the computer would no longer be viable. The system would also need to ensure compatibility with external instruments and support future expansion of the available nodes.

Another commercial alternative is using relay boards from manufacturers like Numato Lab (e.g., the URMC32, a 32-channel USB mechanical relay module that costs around €120). Other low-cost relay control devices include the Phidgets PhidgetInterfaceKit 0/0/8 (with a cost around €90), Figure 7, the Whadda WSI8090, and the USB-RELAIS-8 from DEDITEC. These devices typically support applications developed in LabVIEW and use USB interfaces with specific drivers. While they offer certain advantages, they also have limitations in scalability, capacity, configurability, and flexibility, so they are not able to directly replace the current SM due to their technical limitations and inability to meet all the functional requirements of the existing system. Overall, any replacement solution must carefully balance cost, technical feasibility, and compatibility while ensuring the VISIR remote laboratory retains its core functionality and allows for future scalability.

When utilizing an SM based on commercial equipment, it is essential to maintain control mechanisms consistent with those used for other laboratory instruments. Currently, no commercial device is able to directly replace the VISIR remote laboratory’s SM. A more viable solution may involve the development of a custom-built board, a proprietary alternative. This approach could overcome certain problems of the current system, such as physical limitations in interconnecting components. However, it would perpetuate some challenges of the existing system, such as dependence on exclusive hardware and limited flexibility in system upgrades.

Custom hardware could leverage modular commercial blocks for control, enabling compatibility with external devices and programmability through high-level languages. For example, interfaces like the Arduino MEGA or Raspberry Pi Pico could serve as intermediaries between the proprietary solution or a low-cost commercial device and a computer, effectively replacing the microcontroller on existing SM boards. This approach benefits from the availability of tools like the NI LabVIEW interface for Arduino and Python capabilities for managing the server’s XML files. A significant advantage is the potential reuse of the existing source code responsible for managing relay communications, streamlining development and reducing complexity.

Another option involves smart breadboards like the STEMTera (manufactured by SparkFun Electronics, with a cost around €70), which integrate a microcontroller to eliminate the need for wires and identify connected components. These devices connect to computers via USB but lack existing LabVIEW drivers, necessitating modifications to Measurement Server and Equipment Server code. Furthermore, smart breadboards have limited capacity to accommodate components, making them unsuitable for larger or complex experimental applications and much more suitable for prototyping or small-scale applications.

For all potential replacement options, and even for future updates, the VISIR community has suggested several global improvements to enhance usability and simplify maintenance. These include: (1) Test points: Adding test points to SM boards to allow voltage measurements at specific nodes; (2) Relay testing: Implementing regular automated routines for testing the reed relays; (3) Cable improvements: Replacing cables with jumpers on the Component Boards for ease of use and to improve usability and reduce connection errors.

Among the solutions presented, a device with an LXI instrument, regardless of the manufacturer, emerges as the most technically advantageous option, though not necessarily the most cost-effective. Additionally, if all instruments available in the system support the LXI standard, they can be connected to the computer, running both the Equipment Server and the Measurement Server, via a shared Ethernet connection, lowering costs and standardizing the technology employed. Considering the remote laboratory as a whole system, the adoption of a hybrid modular architecture emerges as a viable and scalable option. This approach could integrate a custom-designed SM (i.e., based on proprietary or semi-proprietary hardware), microcontroller-based control (e.g., with Arduino UNO or similar), Ethernet connectivity with LXI instruments, and open-source code to encourage community collaboration and collaborative development.

4.3. Server Software Enhancements

The VISIR remote laboratory’s server software plays a critical role in managing communication with the instruments and the SM, while also presenting experiment results in a user-friendly and accessible format. Although it is technically possible to replicate the VISIR software architecture on an SBC, it is inconsistent to use a low-cost and open hardware board with an expensive proprietary software license. In this context, it is more reasonable to use an application that consumes fewer computational resources than LabVIEW. The proposed enhancements aim to improve the flexibility, affordability, and usability of the VISIR remote laboratory, while maintaining its robust functionality and ensuring consistent system performance and behavior across different experiments. These improvements are organized into the following key categories:

• Transitioning from proprietary software

Currently, the Equipment Server relies on LabVIEW, as outlined in Section 2.1.2, which requires costly licenses and a dependency on proprietary software. To reduce operational expenses and improve long-term sustainability, open-source alternatives should be actively explored. Although no open-source platform matches LabVIEW’s comprehensive capabilities, viable options can be developed, such as custom solutions, using other programming languages that can replicate the required functionality while avoiding licensing fees. The following options present potential paths forward:

• LabWindows/CVI: This C-based tool from NI includes libraries for instrumentation control and signal processing. However, translating LabVIEW code into C is a labor-intensive process and requires considerable manual effort and expertise.
• Measurement Studio: A .NET-based toolkit by NI offers libraries for graphical controls, data analysis, and hardware interaction. Although powerful, it is not open-source and still requires a paid license.
• Python-Based development: Python presents a viable alternative for Equipment Server development, supported by a rich ecosystem of scientific and instrumentation libraries, such as: (1) PyVISA (v1.13.0): For controlling measurement devices through USB, PXI, and other interfaces; (2) nidaqmx (v0.7.0): To interact with NI hardware drivers; (3) Matplotlib (v3.8.4): To create data visualizations, transforming numerical and statistical data into static, animated, and interactive graphics; (4) SciPy (v1.11.3) and NumPy (v1.26.0): For data analysis, numerical computing, signal processing, and scientific calculations.

While Python has the advantage of being open-source and versatile, it is slower than compiled languages like C due to its high-level nature. This drawback must be weighed against its accessibility and cost-effectiveness.

2.

Enhancing existing systems

The Measurement Server, currently written in C++, is robust and does not require immediate significant updates. However, migrating it to Python could simplify the overall system architecture by consolidating instrument and component control within a single server. Such consolidation could simplify maintenance and development. Any migration effort must carefully address potential compatibility problems with other programs in the system, particularly those reliant on existing C++ code or interfaces.

3.

Intelligent tutor system

Introducing an intelligent tutor system to the VISIR remote laboratory could significantly enhance user experience by providing automatic support during experiment execution. This system would offer real-time feedback, assisting users with troubleshooting problems such as improperly connected or unconnected components, missing or incorrectly applied power supply links, or incorrect component values or measurement configurations. Such a feature would improve usability, diminish user errors, expand the overall pedagogical effectiveness, especially for novice users, and reduce frustration during experiment setup and execution. The intelligent tutor system could leverage rule-based systems, basic AI models, or even machine learning techniques trained on historical usage data.

It is possible to make the remote laboratory’s instruments and experiments independent of LabVIEW, particularly by using open-source technologies. But LabVIEW remains a good technical choice, since it is easier to master than Python, C or C++, and it has comprehensive technical support provided by NI. Thus, while transitioning away from LabVIEW could reduce long-term costs and increase flexibility, any such decision must be weighed against training overhead, user experience, and available technical expertise.

4.4. User Interface Actualizations

In the VISIR remote laboratory, the UI must include access to the full functionality of all instruments to enable a wide range of experiments and enhance user interactivity. A well-designed UI significantly improves accessibility, usability, and the overall learning experience by providing clear feedback, intuitive controls, and real-time interaction with user actions. The VISIR remote laboratory currently uses HTML5, ensuring compatibility with modern browsers and offering improved accessibility and usability. This format is widely adopted in web-based remote laboratories, as seen in [77,78]. To further enhance the UI, technologies that support seamless interaction across major browsers and mobile devices should be utilized. Implementing the interface with Asynchronous JavaScript and XML (AJAX) is recommended to create a more dynamic and responsive environment. AJAX enables faster server responses by minimizing data exchanges, enhancing interactivity. Combining HTML5 with AJAX can overcome limitations related to graphical environments, allowing for a more advanced, efficient, and visually appealing UI. Although cost-effective and efficient, these technologies may need to be supplemented with additional tools to ensure seamless operation of the entire remote laboratory system. Whatever, it must be ensured that the software always provides user interaction with the remote laboratory, either from a standalone application or from a web page. Moreover, integrating Progressive Web App (PWA) capabilities would enable offline usage and seamless operation across various platforms, mimicking native application behavior. Additionally, implementing WebSockets could facilitate real-time, bidirectional communication between the client and server, resulting in UI faster updates and enhanced interactivity, particularly during experiment execution.

A significant upgrade to the VISIR remote laboratory would be the integration of mixed reality (MR) technologies, offering users immersive experimental environments beyond the traditional 2D breadboard interface. For example, Figure 8 illustrates how a virtual wire can be drawn on a VR breadboard, showcasing the feasibility of incorporating VR into the VISIR system. Such technologies can make experiments more engaging and intuitive for users.

To address the needs of users with visual disabilities or age-related challenges, i.e., to ensure universal access and promote inclusion, the VISIR system can be adapted to support assistive technologies. Examples include screen magnifiers or screen reading applications, voice control, and the perception of images using electronic equipment capable of transmitting tactile vibrations, ensuring inclusiveness, and allowing a broader audience to benefit from the laboratory. Additionally, from a user experience perspective, features such as dark mode (for reduced eye strain), multilingual support (for international users), customizable themes, and responsive layouts should be included to provide visual comfort and adaptability across different devices and screen sizes. These features contribute to a more equitable learning environment, aligning with universal design principles and making the VISIR remote laboratory accessible to all users, promoting inclusion. In terms of accessibility, keyboard navigation improvements, high contrast viewing modes, and adjustable text settings align the system with accessibility standards.

4.5. Educational and/or Pedagogical Advancements

Improving the educational and/or pedagogical impact of the VISIR remote laboratory can be done through the implementation of different learning methodologies. These approaches can enhance student involvement, improve comprehension, and promote long-term permanence. Some effective methodologies that could be implemented are the traditional Inquiry-Based Learning (IBL), where students could formulate hypotheses and design their own experiments instead of following predefined procedures, or the Project-Based Learning (PBL), in which students could design, simulate and test circuits remotely, presenting their results in a single report. Moreover, gamification can also be implemented, introducing rewards for successful experiments, time-based challenges, or competitive circuit design tasks. Integrating quick feedback mechanisms and follow-up questions after each experiment session can also be placed in the system to guarantee the understanding of the knowledge under study. In addition, inexperienced users could also benefit from an interactive onboarding tutorial (short videos, etc.), which offers step-by-step guidance during initial use of the system.

However, these methodologies have limitations. For example, IBL requires more flexible experiment design capabilities within VISIR, whereas PBL demands extended access to the remote laboratory and the careful scheduling of experiments. For gamification, there is a risk of prioritizing competition instead of learning, and a substantial development effort is necessary to implement the mechanics along with the current system. Regarding the formative assessment and feedback, VISIR may need to integrate external assessment tools.

Some students may have difficulties without a structured guideline, so it is essential to create a roadmap for implementing these or other methodologies in a curriculum that includes a VISIR remote laboratory that has an educational and/or pedagogical tool.

To further improve the educational and/or pedagogical impact of the VISIR remote laboratory, the implementation of real-time feedback displays (e.g., potentially enhanced with artificial intelligence to provide immediate guidance and error correction during experiments) and progress dashboards could significantly enhance educational outcomes and would allow teachers and students to track progress over time. Additionally, establishing a repository of customizable experiments would enable teachers to create, share, and reuse activities tailored to their specific curriculum needs. These features would facilitate personalized learning, promote active engagement, and strengthen the overall pedagogical impact of the VISIR remote laboratory.

5. Conclusions

This study examined the VISIR remote laboratory through a qualitative analysis supported by a literature review and long-term implementation experience. The findings revealed several technical, educational and/or pedagogical, and operational limitations that constrain the system’s broader adoption and long-term sustainability. These include hardware rigidity, limited interoperability, high maintenance costs, and dependence on proprietary components, which collectively hinder scalability and innovation.

To facilitate possible future practical implementation, a phased roadmap is proposed (together, these measures aim to enhance performance, reduce costs, and improve accessibility while preserving pedagogical robustness):

• Phase 1—Server software migration and optimization: Transition the server software to a more flexible, modular architecture, enabling easier integration of new control and monitoring functionalities without disrupting current services.
• Phase 2—SM redesign: Introduce a more scalable and reconfigurable SM to support a broader range of experiments and reduce latency in switching operations.
• Phase 3—Enhanced interface: Upgrade communication protocols between instruments and the control software to improve data acquisition speed and measurement accuracy.
• Phase 4—Remote experiment expansion: Integrate additional experiment types and remote monitoring capabilities, leveraging the flexibility gained in earlier phases.

After over 20 years of global use and dissemination, the VISIR remote laboratory community regards it as a technically and pedagogically robust system. Despite this, several limitations have been identified, many of which pose threats to the system’s sustainability and the potential for broader adoption by other institutions.

The most significant contribution of this analysis is the identification and discussion of critical problems stemming from the system’s design, which relies exclusively on its current hardware and software. This inherent rigidity reduces the flexibility needed for innovative approaches. Key challenges include low hardware reuse, limited interoperability, prohibitive hardware costs, the lack of a long-term design strategy, and persistent problems with updates and stability.

Laboratory activities are essential in engineering education, and the VISIR remote laboratory offers an innovative technological solution to facilitate these practices. However, addressing its current limitations is crucial. Improvements should focus on reducing the cost of instrument deployment, enhancing the user’s experience, and simplifying the process of adding components to the SM. Additionally, the enhancements must ensure that institutions can operate the system without relying on expensive, complex proprietary solutions. Achieving software independence for instrument control would enable each institution to integrate its preferred equipment, meeting only basic compatibility requirements.

In summary, this study offers suggestive evidence and arguments for making some changes to the VISIR remote laboratory. It requires significant upgrades to increase its reusability, adaptability, remote accessibility, cost efficiency, ease of maintenance, flexibility, and performance, all while reducing dependence on third-party solutions. Without these improvements, the system will remain confined to a limited number of users within institutions that already have it, missing the opportunity to expand to a broader audience, particularly those facing challenges with traditional laboratory setups. However, the findings should be viewed as exploratory and qualitative, serving as a starting point for further empirical investigations.