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Sensors 2016, 16(11), 1899;

A Digital Lock-In Amplifier for Use at Temperatures of up to 200 °C

School of Automation, Huazhong University of Science and Technology, Wuhan 430074, China
School of Chemical Engineering and Environment, Beijing Institute of Technology, Beijing 100000, China
Well-Tech R&D Institutes, China Oilfield Service Limited, Beijing 101149, China
Author to whom correspondence should be addressed.
Academic Editor: Vittorio M. N. Passaro
Received: 2 October 2016 / Revised: 2 November 2016 / Accepted: 3 November 2016 / Published: 11 November 2016
(This article belongs to the Section Physical Sensors)
Full-Text   |   PDF [4325 KB, uploaded 11 November 2016]   |  


Weak voltage signals cannot be reliably measured using currently available logging tools when these tools are subject to high-temperature (up to 200 °C) environments for prolonged periods. In this paper, we present a digital lock-in amplifier (DLIA) capable of operating at temperatures of up to 200 °C. The DLIA contains a low-noise instrument amplifier and signal acquisition and the corresponding signal processing electronics. The high-temperature stability of the DLIA is achieved by designing system-in-package (SiP) and multi-chip module (MCM) components with low thermal resistances. An effective look-up-table (LUT) method was developed for the lock-in amplifier algorithm, to decrease the complexity of the calculations and generate less heat than the traditional way. The performance of the design was tested by determining the linearity, gain, Q value, and frequency characteristic of the DLIA between 25 and 200 °C. The maximal nonlinear error in the linearity of the DLIA working at 200 °C was about 1.736% when the equivalent input was a sine wave signal with an amplitude of between 94.8 and 1896.0 nV and a frequency of 800 kHz. The tests showed that the DLIA proposed could work effectively in high-temperature environments up to 200 °C. View Full-Text
Keywords: digital lock-in amplifier; high temperature; SiP; MCM; thermal resistance; LUT method digital lock-in amplifier; high temperature; SiP; MCM; thermal resistance; LUT method

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Cheng, J.; Xu, Y.; Wu, L.; Wang, G. A Digital Lock-In Amplifier for Use at Temperatures of up to 200 °C. Sensors 2016, 16, 1899.

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