Technologies 2017, 5(3), 48; doi:10.3390/technologies5030048
Development of a High-Speed Current Injection and Voltage Measurement System for Electrical Impedance Tomography-Based Stretchable Sensors
1
Autonomous System and Robotics Research Centre, University of Salford, Manchester M5 4WT, UK
2
Research Centre E. Piaggio, University of Pisa, 56122 Pisa, Italy
3
Department of Information Engineering, University of Pisa, 56122 Pisa, Italy
*
Author to whom correspondence should be addressed.
Received: 12 July 2017 / Revised: 20 July 2017 / Accepted: 21 July 2017 / Published: 26 July 2017
(This article belongs to the Special Issue Wearable Technologies)
Abstract
Electrical impedance tomography (EIT) is an imaging method that can be applied over stretchable conductive-fabric materials to realize soft and wearable pressure sensors through current injections and voltage measurements at electrodes placed at the boundary of a conductive medium. In common EIT systems, the voltage data are serially measured by means of multiplexers, and are hence collected at slightly different times, which affects the real-time performance of the system. They also tend to have complicated hardware, which increases power consumption. In this paper, we present our design of a 16-electrode high-speed EIT system that simultaneously implements constant current injection and differential potential measurements. This leads to a faster, simpler-to-implement and less-noisy technique, when compared with traditional EIT approaches. Our system consists of a Howland current pump with two multiplexers for a constant DC current supply, and a data acquisition card. It guarantees a data collection rate of 78 frames/s. The results from our conductive stretchable fabric sensor show that the system successfully performs voltage data collection with a mean signal-to-noise ratio (SNR) of 55 dB, and a mean absolute deviation (MAD) of 0.5 mV. The power consumption can be brought down to 3 mW; therefore, it is suitable for battery-powered applications. Finally, pressure contacts over the sensor are properly reconstructed, thereby validating the efficiency of our EIT system for soft and stretchable sensor applications. View Full-TextKeywords:
EIT; stretchable; pressure sensor; conductive fabric; wearable
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Russo, S.; Nefti-Meziani, S.; Carbonaro, N.; Tognetti, A. Development of a High-Speed Current Injection and Voltage Measurement System for Electrical Impedance Tomography-Based Stretchable Sensors. Technologies 2017, 5, 48.
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