Monroe Electronics Electrostatic Fieldmeter - Static Monitor - model 177A - Manual (Page 7)

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Figure 2: Monroe Model 1036 Fieldmeter Probe
Electrostatic fieldmeters measure electric field strength by non-contacting means. All the charged
objects, voltage sources, and grounded conductors (including the fieldmeter probe housing) in the
general area affect the electric field strength measurement. The fieldmeter measures the electric
field strength only at its aperture. It does not have a viewing angle and it does not see the web or
object directly in front of it as a separate entity. This can be demonstrated by measuring the electric
field of an insulating sheet with a hole in it.
Figure 3: Insulating Sheet Electric Field Demo, Top View
The field over the hole will not be zero, even though there is no charge directly in front of the probe
head. This is because the electric field at the probe aperture is a function of each charge on the
sheet, and is also a function of the concentration of field due to the grounded probe itself.
Figure 4: Insulating Sheet Electric Field Demo
Place a charge on an insulating
sheet with a hole cut out of it
(hole to be larger than probe) .
Measure the electric field over
the sheet (a). Move the probe
over the hole and measure the
field again (b).
The measured field strength in
(b) will be less than in (a), but it
won’t be zero.
Probe
Probe Hole
Hole
(a) (b)
Insulating Sheet
+ + + + + + + + + + + + + + + + + + + + + +
Ground - -
- - - - -
- - -
Perpendicular
Field Lines
Probe
Insulating Sheet
Hole