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Monroe Electronics Electrostatic Voltmeter - Isoprobe® - model 244A User Manual

Page 8

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8

C.

PROBE-TO-SURFACE SPACING:

CAUTION:

When operating at probe-to-surface spacing of less than 0.125 inches (3mm) --
BEWARE OF PROBE-TO-SURFACE ARC-OVER.

Air is subject to dielectric breakdown when the probe-to- surface spacing is low
and the surface voltage is high. A destructive arc-over can occur damaging the
surface under test and/or the sensitive circuitry of the probe.

REFER TO FIGURE 2-1 TO DETERMINE THE SAFE PROBE-TO-SURFACE
SPACING FOR A GIVEN UNKNOWN VOLTAGE.

Probe to surface spacing should be maintained as close as physically reasonable
for best performance. Typical spacing range is from .005" (0.1mm) for unknown
voltages below 500 volts to over .125" (3mm) for unknown voltages up to 3000
volts.

As probe to surface spacing increases instrument performance will suffer:

1. Decreased Accuracy

2. Decreased Speed-of-Response

3. Decreased Surface Resolution

4. Increased Noise

5. Increased Drift

ARC BR EAK DOWN VS. PRO BE-T O-SURF ACE SPAC ING


FIGUR E 2-1

TYP. BREAKDOWN TEST DATA • = SIDE VIEWING

PROBE-TO-SURFACE SPACING