Keithley 8009 Instruction Manual - page 26
Volume Resistivity:
V
throu
centimeters. Likewise, the electrical re
insu
Volu
opposit
the sam
calculations:
or
Wher
Surface Resis
the surface of an
along the surface of
measurement
and diameter) of
Surface resistivity (
surface of the insulator s
perform
Wher
3.3
Resistivity nomographs
With test voltage and measured current (and sample thickness for volume
resistivity) known, resistivity can be approximated by using the appropriate
nomograph. Figure 3-2 shows the nomograph for surface resistivity and Figure
3-3 shows the nomograph for volume resistivity.
Surface Resistivity:
The surface resistivity nomograph (Figure 3-2) is made up
of three scales; voltage, resistivity and current. Perform the following steps to
determine resistivity:
1. Plot the test voltage value on the voltage scale.
2. Plot the measure current value on the current scale.
3. Draw a straight line connecting the plotted voltage and current values.
4. Read the surface resistivity value (in ohms) from where the drawn line inter-
sects the resistivity scale.
An example is shown in the graph. The dashed line connects a test voltage of
200V to a measured current of 3
×
10
-10
amps (0.3nA). The dashed line intersects
the resistivity scale at just under 4
×
10
13
¾ (3.56
×
10
13
¾ by calculation).
Figure 3-2
Surface resistivity (
σ
) nomograph
14
15