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Vibrating Capacitance Probe

IP.com Disclosure Number: IPCOM000074940D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Larson, DD: AUTHOR

Abstract

Shown is a probe for measuring electrostatic fields. The probe is pneumatically driven rather than electromechanically driven so as to eliminate spurious electrical noise. Sensing surface 10 effectively acts as one plate of a capacitor. The other plate of capacitance is the charged surface 12 whose electrostatic field is being measured. Conductive surface 10 is carried by a piston 14 which is pneumatically driven by a pressure source P(t).

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Vibrating Capacitance Probe

Shown is a probe for measuring electrostatic fields. The probe is pneumatically driven rather than electromechanically driven so as to eliminate spurious electrical noise. Sensing surface 10 effectively acts as one plate of a capacitor. The other plate of capacitance is the charged surface 12 whose electrostatic field is being measured. Conductive surface 10 is carried by a piston 14 which is pneumatically driven by a pressure source P(t).

Piston 14 is pushed forward by the pressure from the pressure source until ports 16 are uncovered. The pressure is then vented to the outside, and the conductive spring 18 pulls the piston back to the original position. Spring 18 also acts as the conductor between the sensing plate 10 and the coaxial cable 20. The shielding of the coaxial cable is grounded to the probe via the set screw 22.

In operation, the probe is positioned next to a charged surface to be measured. The piston is pneumatically driven in a reciprocating motion causing the voltage potential on the conductive surface 10 to vary as an AC signal. The AC signal is then conducted by the coaxial cable to detecting circuits as a measure of the electrostatic field sensed by the probe. The AC signal is proportional to the electrostatic field produced, by the charged surface 12.

The basic piston ported cylinder configuration for moving sensing surface 10 might be replaced by many pneumatic drive configurations. One example would be a conducti...