American Journal of Sensor Technology
ISSN (Print): 2373-3454 ISSN (Online): 2373-3462 Website: Editor-in-chief: Vyacheslav Tuzlukov
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American Journal of Sensor Technology. 2018, 5(1), 7-16
DOI: 10.12691/ajst-5-1-2
Open AccessArticle

Single-chip Implementation of LVDT Signal Conditioning

Lars E. Bengtsson1,

1Department of Physics, University of Gothenburg, Gothenburg, Sweden

Pub. Date: December 14, 2018

Cite this paper:
Lars E. Bengtsson. Single-chip Implementation of LVDT Signal Conditioning. American Journal of Sensor Technology. 2018; 5(1):7-16. doi: 10.12691/ajst-5-1-2


The aim of this work was to prove that the signal conditioning electronics for linear variable transformers (LVDTs) can be implemented in inexpensive, general-purpose 8-bit microcontrollers, making expensive dedicated signal conditioning chips redundant. A low-cost, high-resolution signal conditioning solution for LVDTs is presented. Apart from a few external passive components, the entire solution is implemented in a low-cost, analog-digital hybrid microcontroller. The excitation sinusoid is generated by filtering out the fundamental frequency of a (self-sustained) pwm-generated square wave and the secondary coils’ signals are demodulated with classic peak detector circuits implemented in the microcontroller using a combination of its embedded analog and digital building blocks. A resolution of 1 μm over a range of ±6.35 mm for a commercial LVDT is reported and an uncertainty of 6 μm in the absolute value is deduced. The entire solution is implemented as surface mounted components on a small printed circuit board and the LVDT core displacement is displayed on an LCD display. Due to the simplicity and low-cost components required, this signal conditioning proposal has the potential to have a significant impact on commercial LVDT signal conditioning chips in the future since it is significantly less expensive than the present state-of-the-art signal conditioning chips offered by the main commercial suppliers and other solutions previously suggested in scientific literature.

displacement sensor demodulation excitation LVDT microcontroller peak detector

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[1]  M. Inc., “PIC16(L)F1777/8/9 28/40/44-Pin, 8-Bit Flash Microcontroller,” 2016. [Online]. Available: [Använd 21 February 2018].
[2]  T. Connectivity, “MHR Series Minitature General Purpose AC LVDT,” 2016. [Online]. Available: [Använd 14 February 2018].
[3]  R. Norhtrop, Introduction to Instrumentation and Measurement, 2nd Ed., Boca Raton, Florida: CRC Press, Taylor and Francis Group, 2005.
[4]  P. Cashman, F. Stott och M. Craig, “Hybrid system for fast data reduction of long-term blood-pressure recordings,” Medical and Biological Engineering and Computing, vol. 17, nr 5, pp. 629-635, Sept. 1979.
[5]  R. Hood Jr och R. Medero, “Adaptive incremental blood pressure monitor”. USA Patent 4461266, July 1984.
[6]  R. Medro, W. Rush, P. Howard och M. Ramsey, “Methods of automatied blood pressure detection”. USA Patent 4543962, October 1985.
[7]  D. Acanfora, L. Caprio de, S. Cuomo, M. Papa, N. Ferrara, D. Leosco, P. Abete och F. Rengo, “Diagnostic value of the ratio of recovery systolic blood pressure to peak exercise systolic blood pressure for the detectio of coronary artery disease,” American Heart Association, vol. 77, nr 6, pp. 1306-1310, 1988.
[8]  G. Parati, J. Saul, M. Rienzo och G. Mancia, “Spectral analysis of blood pressure and heart rate variablility in evaluating cardiovascular regulation. A critical appraisal,” Hypertension, vol. 25, nr 6, pp. 1276-1286, 1995.
[9]  T.-J. Lee, C. Shiu, W.-C. Hsiao och C.-C. Wang, “20 MHz Accurate Peak Detector for FPW Allergy Biosensor with digital calibration,” i Proceedings of the 2011 International Symposium on Integrated Circuits, Singapore, 2011.
[10]  G. Geronimo de, A. Kandasamy och P. O'Connor, “Analog peak detector and derandomizer for high-rate spectroscopy,” IEEE Transaction on Nuclear Science, vol. 49, nr 4, pp. 1769-17-73, 2002.
[11]  K. Koli och K. Halonen, “Low voltage MOS-transistor-only precision current peak detector with signal independent discharge time constant,” i Proceedings of 1997 IEEE International Symposium on circuits and Systems, Hong Kong, 1997.
[12]  J. Szczyrbak och E. D. D. Schmidt, “Site de Nicloas Liebeaux,” April 1997. [Online]. Available: [Använd 7 January 2018].
[13]  L. Bengtsson, “Interpolation of Microcontroller ADC by self-induced dithering,” International Journal of Smart Sensing and Intelligent Systems, vol. 6, nr 4, pp. 1366-1382, 2013.
[14]  R. Poley, “Signal Conditioning an LVDT Using a TMS320F2812 DSP,” Texas Instruments, Dallas, 2003.
[15]  G. Hoadley, “Telemetric system”. USA Patent 2196809, 9 April 1940.
[16]  Schaevitz, “The Linear Variable Differential Transformer,” i Proceedings of SASE, vol. 4, no. 2, 1946.
[17]  M. Félix, A. Lizárraga, A. Islas och A. González, “Analysis of a Ferrofluid Core LVDT Displacement Sensor,” i Proceedings of the 36th Annual Conference on IEEE Industrial Electronics Society, Glendale, Arizona, USA, Nov. 7-10, 2010.
[18]  A. Flammini, D. Marioli, E. Sisinni och A. Taroni, “Least Mean Square Method for LVDT Signal Processing,” IEEE Transaction on Instrumentation and Measurement, vol. 50, nr 6, pp. 2294-2300, 2007.
[19]  R. Pallàs-Areny och J. G. Webster, Sensors and signal conditioning, 2nd ed, New York: John Wley & Sons, 2001, pp. 229-238.
[20]  A. Flemming, “A review of nanometer resolution position sensors: Operation and performance,” Sensors and Actuators a: Physical, vol. 190, pp. 106-126, 2013.
[21]  P. Ferrari, A. Flammini, D. Marioli och A. Torini, “IEEE 1588-Based Synchronization System for a Displacement Sensor Network,” IEEE Transactionss on Instrumentation and Measurement, vol. 57, nr 2, pp. 254-260, 2008.
[22]  S. C. Saxena och S. B. L. Seksena, “A Self-compensated Smart LVDT Transducer,” IEEE Transaction on instrumentation and measurement, vol. 38, nr 1, pp. 784-753, 1989.
[23]  D. Crescini, A. a. D. Flammini och A. Taroni, “Application of an FFT-based algorithm to signal processing of LVDT position sensor,” i IEEE Instrumentation and Measurement Technology Conference, St Paul, Minnesota, USA, 1998.
[24]  H. Tariq, A. Takamori, F. Vetrano, C. Wang, A. Bertolini, G. Calamai, R. DeSalvo, A. Gennai, L. Holloway, G. Losurdo, S. Marka, M. Mazzoni, F. Paoletti, D. Passuello, V. Sannibale och R. Stanga, “The linear variable differential transformer (LVDT) position sensor for graviational wave interferometer low frequency control,” Nuclear Instruments and Methods in Physics Research A, vol. 489, pp. 570-576, 2002.
[25]  S.-T. Wu och S.-C. W. B.-S. Mo, “An LVDT-based self-actuating displacement transducer,” Sensos and Actuators A, vol. 141, pp. 558-564, 2008.
[26]  J. L. Hutter och J. Bechhoefer, “Calibration of atomic-force microscope tips,” Review of Scientific Instruments, vol. 64, nr 7, pp. 1868-1873, 1993.
[27]  R. Prosch, J. Cleveland och D. Bocek, “Linear variable transformers for high precision position measurements”. USA Patent 7038433, 2 May 2006.
[28]  Analog Devices, “AD598 LVDT Signal conditioner,” 21 December 2017. [Online]. Available:
[29]  Texas Instruments, “PGA970 LVDT Sensor Signal conditioner (Rev. A),” December 2016. [Online]. Available:
[30]  Philips Semiconductors, “LVDT Signal conditioner,” 12 November 2003. [Online]. Available: [Använd 7 January 2018].
[31]  T.-S. Kang, S. K. Kauh och K.-P. Ha, “Development of the displacement measuring system for a dual mass flywheel in a vehicle,” Proceeedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering, vol. 223, nr 10, pp. 1273-1281, 1 October 2009.
[32]  M. Beccaria och e. al., “The creep problem in the Virgo suspension: a possible solution using Maragin steel,” Nuclear Instruments and Methods in Physics Research A, vol. 404, nr 2-3, pp. 455-469, 1998.
[33]  A. Drumea, A. Vasile och M. B. M. Comes, “System on Chip Signal Conditioner for LVDT Sensors,” i Electronics Systemintegration Technology Conference, Proceedings of 1st, Dresden, Germany, Sept. 5-7, 2006.
[34]  R. E. Ellis, O. M. Ismaeil och M. Lipsett, “Design and evaluation of a high-performance haptic interface,” Robotica, vol. 14, pp. 321-327, 1996.
[35]  D. Nyce, Linear Position Sensors: Theory and applications, Hoboken, New Jersey, USA: John Wiley and Sons, 2004.
[36]  R. F. Graf, Oscillator Circuits, Newton, Maine: Butterworth-Heineman, 2006.
[37]  S.-T. Wu och J.-L. Hong, “Five-Point Amplitude Estimation of sinusoidal Signals: With Application to LVDT Signal Conditioning,” IEEE Transactions on Instrumentation and Measurement, vol. 59, nr 3, pp. 623-630, 2010.
[38]  E. E. Herceg, Handbook of Measurement and Control, Revised Edition, Schaevitz Engineering, 1976.
[39]  R. Ford, R. Weissbach och D. R. Loker, “A Novel DSP-based LVDT Signal Conditioner,” IEEE Transactions on Instrumentation and Measurement, vol. 50, nr 3, pp. 768-773, 2001.
[40]  F. F. Yassa och S. L. Garverick, “A Multichannel Digital Demodulator for LVDT/RVDT Position Sensors,” Journal of Solid-State Circuits, vol. 25, nr 2, pp. 441-450, 1990.
[41]  R. Weissbach, D. R. Loker och R. Ford, “Test and Comparison of LVDT Signal Conditioner Performance,” i Proceedings of the 17th IEEE Instrument and Measurement Technology Conference, Baltimore, USA, May, 1-4, 2000.
[42]  “AD598AD, Clock Signal Conditioner LVDT Differential, Single Ended 20-Pin SBCDI,” RS Components, [Online]. Available: [Använd 26 February 2018].
[43]  “MP-2000 Duual Channel LVDT/RVDT Readout/Controller,” TE Connectivity, [Online]. Available: [Använd 26 February 2018].
[44]  Sensor Solutions, “ATA-2001 – Analog LVDT/RVDT Signal Conditioner with digital calibration,” 2001. [Online]. Available: [Använd 7 Januari 2018].
[45]  Bureau Internatinal des Poids et Mesures, “Guide to the expression of uncertainty in measurements,” September 2008. [Online]. Available: