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VOLUME 7 , ISSUE 5 (December 2014) > List of articles
Special issue ICST 2014
Citation Information : International Journal on Smart Sensing and Intelligent Systems. Volume 7, Issue 5, Pages 1-5, DOI: https://doi.org/10.21307/ijssis-2019-091
License : (CC BY-NC-ND 4.0)
Published Online: 15-February-2020
A new Capacitance-to-Digital Converter (CDC) applicable for series RC sensors that requires/prefers sinusoidal excitation is proposed in this paper. The CDC presented works based on a dual-slope technique and it gives a digital output as a function of unknown capacitance of a series RC sensor, i.e., a capacitive sensor with a capacitor and a resistor in series in its electrical equivalent circuit. Output of the CDC is not sensitive to the series resistor. The CDC is useful for grounded as well as floating capacitive sensors, which needs to be excited with a sine wave for best performance. Applications of such capacitive sensors include ice detection, sterility testing of packed food products, etc. A sinusoidal Howland current source can be used to excite a grounded capacitive sensor while a simple current source with a special stabilization scheme that suppresses the effect due to static errors of opamp has been developed for floating capacitive sensor and presented in this paper. A prototype of the proposed CDC for a floating capacitive sensor has been built and tested in the laboratory. Measurement results for the sensor capacitance showed a worst case error of 0.13% for a range of 100 pF, proving the efficacy of the proposed scheme.
 S. N. Nihtianov, G. P. Shterev, B. Iliev and G. C. M. Meijer, ―An interface circuit for R-C impedance sensors with a relaxation oscillator,‖ IEEE Trans. Instrum. Meas., vol. 50, no. 6, pp. 1563-1567, Dec. 2001.
 S. N. Nihtianov and G. C. M. Meijer, ―Nondestructive on-line sterility testing of long shelf-life aseptically packed food products by impedance measurements,‖ Proc. IEEE Autotestcon, San Antonio, Tx, Aug. 30Sept. 2, 1999, pp. 243 -249.
 S. N. Nihtianov and G. C. M. Meijer, ―Indirect conductivity measurement of liquids in flexible containers,‖ in Proc. IMTC, vol. 2, Ottawa, ON, Canada, May 19–21, 1997, pp. 919–922.
 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.
 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.
 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.
 M. A. Atmanand, V. J. Kumar, and V. G. K. Murti, ―A microcontroller based scheme for measurement of L and C,‖ Meas. Sci. Technol., vol. 6, pp. 576–581, 1995.
 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.
 D. Goeger, M. Blankertz and H. Woern, ―A tactile proximity sensor‖, proc. of IEEE Sensors 2010, pp. 589-594, 1-4 Nov. 2010.
 Application note, 2013, AN-1515, ―A comprehensive study of the Howland current pump‖. [Online]. Available: www.ti.com/lit/an/snoa474a/snoa474a.pdf
 R. Nerino, A. Sosso, and G. B. Picotto, ―A Novel AC Current Source for Capacitance-Based Displacement Measurements,‖ IEEE Trans. Instrum. Meas., vol. 46, no. 2, pp. 640-643, Apr. 1997.
 D. X. Chen, X. Deng and W. Q. Yang , ―Comparison of three current sources for single-electrode capacitance measurement,‖ Rev. Sci. Instrum. 81, 034704 (2010).
 M. A. Krupka, ―Low noise, electric field sensor,‖ U.S. Patent 7 088 175, Aug, 08, 2006.