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Model 6517B Electrometer Reference Manual
Surface resistivity
Surface resistivity is defined as the electrical resistance of the surface of an insulator material. It is
measured from electrode to electrode along the surface of the insulator sample. Since the surface
length is fixed, the measurement is independent of the physical dimensions (for example, thickness
and diameter) of the insulator sample.
Surface resistivity is measured by applying a voltage potential across the surface of the insulator
sample and measuring the resultant current as shown in the following figure.
The Model 6517B automatically performs the following calculation and displays the surface resistivity
reading:
ρ
= Surface resistivity (per square).
S
R = Measured resistance in ohms (V/I).
K
= P/g
S
Where:
P = The effective perimeter of the guarded electrode (mm).
g = Distance between the guarded electrode and the ring electrode (mm).
Refer to the figure "Circular electrode dimensions" below to determine dimension g.
6517B-901-01 Rev. C / August 2015
Figure 45: Surface resistivity measurement technique
ρ
= K
R
V
S
Section 4: Basic measurements
4-23
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