A Method for Improving Conversion Rate and Accuracy of a Capacitance-to-Digital Converter


Share / Export Citation / Email / Print / Text size:

International Journal on Smart Sensing and Intelligent Systems

Professor Subhas Chandra Mukhopadhyay

Exeley Inc. (New York)

Subject: Computational Science & Engineering, Engineering, Electrical & Electronic


eISSN: 1178-5608



VOLUME 7 , ISSUE 5 (December 2014) > List of articles

Special issue ICST 2014

A Method for Improving Conversion Rate and Accuracy of a Capacitance-to-Digital Converter

Prashanth Vooka / Boby George

Keywords : capacitance-to-digital converter; sinusoidal excitation; conversion rate; accuracy; capacitive sensor

Citation Information : International Journal on Smart Sensing and Intelligent Systems. Volume 7, Issue 5, Pages 1-6, DOI: https://doi.org/10.21307/ijssis-2019-088

License : (CC BY-NC-ND 4.0)

Published Online: 15-February-2020



Capacitance-to-Digital Converter (CDC) ICs available in the market use square wave excitation signals but a sinusoidal excitation is preferred in various applications, such as ice detection, liquid level measurement, humidity measurement, proximity sensing, etc. A dual slope technique based CDC that employs a sinusoidal excitation has been reported recently, but it requires a large number of excitation cycles, to complete an accurate conversion. This paper presents an improved CDC that employs a specially designed method to achieve high accuracy even when a much smaller number of excitation cycles, than the reported scheme, are employed to complete the conversion. A prototype CDC has been developed and tested. In comparison with an existing CDC, the new CDC achieved a substantial reduction (by a factor of 4000) in the number of excitation cycles during integration period, resulting in an improved update rate. Worst case error observed from the prototype CDC was less than 0.24%.

Content not available PDF Share



[1] L. K. Baxter, Capacitive Sensors Design and Applications. New York: IEEE Press, 1997.

[2] R. Pallas-Areny, J. G. Webster, Sensors and Signal Conditioning. New York: Wiley, 2001.

[3] A. Troiano, E. Pasero, and L. Mesin, ―New system for detecting road ice formation,‖ IEEE Trans. Instrum. Meas., vol. 60, no. 3, pp. 1091-1101, Mar. 2011.

[4] Y. Kim, S. Cho, D. Shin, J. Lee and K. Baek, ―Single chip dual plate capacitive proximity sensor with high noise immunity‖, IEEE Sensors Journal, vol. 14, no. 2, pp. 309-310, Feb. 2014.

[5] B. George, H. Zangl, T. Bretterklieber and G. Brasseur, ―A combined inductive–capacitive proximity sensor for seat occupancy detection‖, IEEE Trans. Instrum. Meas., vol. 59, no. 5, pp. 1463-1470, May 2010.

[6] D. Goeger, M. Blankertz, H. Woern, ―A tactile proximity sensor‖, proc. of IEEE Sensors 2010, pp. 589-594, 1-4 Nov. 2010. 

[7] J. Das, S. Dey, S. M. Hossain, Z .M. C. Rittersma, and H. Saha, ―A hygrometer comprising a porous silicon humidity sensor with phasedetection electronics,” IEEE Sensors Journal, vol. 3, no. 4, pp. 414-420, Aug. 2003.

[8] S. C. Bera and H. Mandal, ―A flow measurement technique using a noncontact capacitance-type orifice transducer for a conducting liquid‖, IEEE Trans. Instrum. Meas., vol. 61, no. 9, pp. 2553-2559, Sept. 2012.

[9] W. Q. Yang, ―A self-balancing circuit to measure capacitance and loss conductance for industrial transducer applications,‖ IEEE Trans. Instrum. Meas., vol. 45, no. 6, pp. 955-958, Dec. 1996.

[10] V. J. Kumar, P. Sankaran, and K. S. Rao, ―Measurement of C and tanδ of a capacitor employing PSDs and dual-slope DVMs,‖ IEEE Trans. Instrum. Meas., vol. 52, no. 5, pp. 1588-1592, Oct. 2003.

[11] B. George and V. J. Kumar, ―Analysis of the switched-capacitor dualslope capacitance-to-digital converter‖, IEEE Trans. Instrum. Meas., vol. 59, no. 5, pp. 997-1006, May. 2010.

[12] 24-Bit Capacitance-to-Digital Converter with Temperature Sensor [Online]. Available: http://www.analog.com/static/importedfiles/data_sheets/AD7747.pdf

[13] K. Cyril Baby and B. George, ―A capacitive ice layer detection system suitable for autonomous inspection of runways using an ROV,‖ in Robotic and Sensors Environments (ROSE), 2012 IEEE International Symposium on, pp. 127-132, Nov. 2012.

[14] S. C. Bera, H. Mandal, S. Saha and A. Dutta, ―Study of a modified capacitance-type level transducer for any type of liquid,‖ IEEE Trans. Instrum. Meas., vol. 63, no. 3, pp. 641-649, Mar. 2014.

[15] P. Vooka, A. Ranjan and B. George, ―A novel capacitance-to-digital converter for capacitive sensors with AC excitation,‖ in Proc. 19th IMEKO TC 4 Symposium and 17th IWADC workshop, pp. 246-249, Jul. 2013.

[16] Application note, 1999, AN017, ―The integrating A/D converter (ICL 7135)‖. [Online]. Available: http://www.intersil.com/content/dam/Intersil/documents/an01/an017.pdf

[17] Datasheet, MSP430G2553, Mixed Signal Microcontroller, Dallas, TX: Texas Instruments, 2011. [Online]. Available: http://www.ti.com/lit/ds/symlink/msp430g2553.pdf