Monroe-electronics Electrostatic Fieldmeter - Static Monitor - model Manuel d'utilisateur télécharger pdf (Page 52)

Convergent field lines such, as these tend to “enhance” the measurement and cause the apparent field strength

to increase, thus producing a high reading. Although this may be relatively inconsequential where a direct

measurement of surface voltage is desired — for example, where a probe whose specified sensitivity is 10kV/cm

is being used at 1cm to produce an indicated full scale value of up to 10,000 volts — given a large enough

surface and a properly sized shroud, that same probe could be used to produce a measurement of surface

voltage up to 100,000 volts at 10cm with fairly good accuracy.

Tests performed in our laboratory produced the following:

Some conclusions may be drawn from the data shown in Figure 17 :

1. An "F” probe produces a reading about 12% high with no shroud at 1" (25mm) and about double at 4"

(100mm).

2. When provided with a 6" diameter shroud, the error drops to fewer than 10% at spacings of up to

almost 4".

3. A shroud is unnecessary on an "E" probe at 1" or less and would produce the same improvement as

with the "F" probe at greater spacing.

4. As a general rule of thumb, a shroud (or the size of the face of the probe) should be about 1½ times

the spacing to keep errors to about 10% or less.

0.8

1.2

1.4

1.6

1.8

0 2 4 6

Inches from Target

Enhancement Factor

"F" probe without shroud

"E" probe

without shroud

"F" probe with

6" dia. shroud

1036 DATA

Figure 17

1 2 ... 47 48 49 50 51 52 53 54 55 56 57 ... 95 96

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Monroe-electronics Electrostatic Fieldmeter - Static Monitor - model Manuel d'utilisateur Page 52