Non-contact measurement of dc voltages using nonlinear elements

In this work, it is shown that dc voltages may be measured via a capacitive interface, provided that the capacitance between the measurement system and the dc voltage source being measured is nonlinearized. This nonlinearization is achieved by the addition of a nonlinear capacitor in series with the coupling capacitance. Two types of nonlinear capacitor are used—multilayer ceramics and varicap diodes. Currently available multilayer ceramics have a larger value than desired but prove the concept, while the small capacitance of the varicap diode allows measurement on real wires. Results show that over a low voltage range (−8 V to +8 V), the voltage on a conductor can be measured if the coupling capacitance between source and electrode is larger than 20 pF, which equates to an electrode length of 5 cm when wire compliant with MIL-W-81044-22 is used. Detection is performed by momentarily applying a voltage at a node within the measurement system, then measuring the time it takes for this voltage to decay to a threshold level—the capacitive nonlinearity causes this time delay to be dependent upon the dc input voltage whose value is being measured.

[1]  Design of MEMS electrometer for highly sensitive charge measurement , 2009, 2009 9th International Conference on Electronic Measurement & Instruments.

[2]  Lord Kelvin,et al.  V. Contact electricity of metals , 1898 .

[3]  Cynthia Furse,et al.  Down to the wire [aircraft wiring] , 2001 .

[4]  A.A. Seshia,et al.  A micromechanical electrometer approaching single-electron charge resolution at room temperature , 2008, 2008 IEEE 21st International Conference on Micro Electro Mechanical Systems.

[5]  Cynthia Furse,et al.  Down to the wire , 2001 .

[6]  Marcelo Haberman,et al.  A capacitive electrode with fast recovery feature , 2012, Physiological measurement.

[7]  K.H. Lundberg,et al.  A Self-Resonant MEMS-Based Electrometer , 2007, 2007 IEEE Instrumentation & Measurement Technology Conference IMTC 2007.

[8]  J. R. Macdonald,et al.  The Charging and Discharging of Nonlinear Capacitors , 1955, Proceedings of the IRE.

[9]  Abdel-Rahman M. Jaradat,et al.  Artificial Voltage-Controlled Capacitance and Inductance using Voltage-Controlled Transconductance , 2008 .

[10]  Paul Record,et al.  Non-contact voltage measurement using electronically varying capacitance , 2010 .