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Browse Prior Art Database

Rotary Electrostatic Probe

IP.com Disclosure Number: IPCOM000074941D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Larson, DD: AUTHOR

Abstract

Shown is a probe for measuring the electrostatic field from charged surface 11. Sensing surface 10 of the probe is alternately exposed to the electrostatic field from charged surface 11 by rotor 12 carrying a plurality of blades. The rotor is pneumatically driven by an air turbine. Pneumatic drive is used rather than electromechanical drive, so as to avoid unnecessary electrical noise. The air jet to drive the air turbine is supplied by an external pressure source through tube 14. Rotor shaft 16 is mounted on bearings 18 and carries turbine blades at area 20 of the shaft. Sensing surface 10 is electrically connected to coaxial cable 22. The shielding of cable 22 is electrically grounded to the probe via conductive mount 24.

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Rotary Electrostatic Probe

Shown is a probe for measuring the electrostatic field from charged surface
11. Sensing surface 10 of the probe is alternately exposed to the electrostatic field from charged surface 11 by rotor 12 carrying a plurality of blades. The rotor is pneumatically driven by an air turbine. Pneumatic drive is used rather than electromechanical drive, so as to avoid unnecessary electrical noise. The air jet to drive the air turbine is supplied by an external pressure source through tube
14. Rotor shaft 16 is mounted on bearings 18 and carries turbine blades at area 20 of the shaft. Sensing surface 10 is electrically connected to coaxial cable 22. The shielding of cable 22 is electrically grounded to the probe via conductive mount 24.

In operation, sensing surface 10 forms one capacitance plate in a capacitor while charged surface 11 forms the other capacitance plate. The electrostatic field produced by the charged surface is converted to an AC variation on sensing surface 10 by use of rotor 12, which successively blanks and unblanks portions of sensing surface 10. The rotor blades and the sensing surface fixed blades are shown in Fig. 2. The alternate covering and uncovering of the sensing surface blades produces an AC voltage signal on the sensing surface 10, which is carried by the coaxial cable to a detecting circuit. The AC signal is proportional to the electrostatic field produced by charged surface 11.

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