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JCI 131 Electrostatic Fieldmeter

for precise, high resolution continuous measurements of electric fields in adverse environmental conditions

The JCI 131 Electrostatic Fieldmeter is a compact and robust instrument for the precise measurement of electric fields in adverse environmental conditions. It is particularly suitable for long term continuous monitoring of atmospheric electric field conditions - such as those associated with thunderstorm and volcano activity.

JCI 131 electrostatic fieldmeter with weathershield mounting

JCI 131 electrostatic fieldmeter with goldplated brass case

Electric field measurement sensitivities of 2, 20, 200 and 2000kV m-1 are provided with high precision (better than 1%), low noise amnd a stable zero (both around 1V m-1 ). Used as a potential probe, well away from nearby structures, the sensitivity is about 10kV m-1 per kV of local space potential. The JCI 131 head unit requires +7.5V regulated power supplies and provides output signals proportional to the electric field (1V for 1, 10, 100 or 1000kV m-1) with indication of the sensitivity range of operation. The zero reading can be adjusted and the sensitivity range selected remotely. The sensing head unit can optionally be fitted with an integral serial data interface for direct linkage to a microcomputer for remote display and direct numerical recording of observations and time using proprietary software JCILOG. This software includes provision for sensitivity range selection by the instrument, manually at the keyboard or automatically by software. It also includes provision for setting thresholds to select the frequency of data recording (from 4 s-1 downwards) according to electric field values measured. Alternatively, up to four instruments, without interfaces, can be powered and operated from a JCI 168 Multiplexor Unit with observations displayed and recorded at up to 100 sets of readings a second using software JCILOG4.

The JCI 131 is based on a proprietary JCI design of 'field mill' electrostatic fieldmeter which does not need earthing of the rotating chopper (IEEE Trans Ind Appl 26 (6) Nov/Dec 1990 p1178). This design, together with use of an electronically commutated drive motor, is appropriate for long term continuous monitoring.

JCI 131 electrostatic fieldmeter showing internal structure with large spacing between sensing surfaces and rotors to avoid water bridging

Immunity to adverse environmental conditions is achieved using large (6mm) gaps from critical sensing surfaces to all other nearby surfaces, long insulation surface tracking paths and a sealed region for the signal processing circuit board. An additional circuit can be included to provide continuous monitoring of operational health when JCI 131 fieldmeters are used for long term measurements in onerous operating conditions - such as long term atmospheric electric field measurements. Operational health monitoring is achieved by modulating the voltage of the fieldmeter sensing head relative to the local earth with software assessment of the variation of the electric field observed compared to the variation expected.

SPECIFICATION FEATURES:

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