Agilent Technologies 4349B Manual page 154

Note on Measuring Insulation Resistance of Capacitors
This section provides information on how to measure the insulation resistance of capacitors
using the 4349B and an external DC voltage source. It covers the following subjects:
The external DC voltage source.
How to select the optimum measurement range.
Additional errors caused by the external DC voltage source.
How to reduce the measurement error.
The External DC Voltage Source
When measuring a capacitor's leakage current (insulation resistance), the DC voltage source's
noise passes through the capacitor and ows into the ammeter. If the noise level is too high,
the current measurement accuracy is degraded. To avoid this problem, use a low noise external
voltage source.
How to Select the Optimum Measurement Range
The useable measurement range is restricted by the DUT's capacitance value. It is important
to consider not only the DC current measurement value but also the DUT's capacitance value
when selecting the measurement range. Select the optimum measurement range as follows:
1. Calculate the DC current measurement value (I
(R ) and the test voltage (V
dut
2. Select the lowest range that can measure the current value calculated in step 1 using
Table 6-1.
3. If the DUT's capacitance value is within the Measurable Capacitance of the range selected in
step 2, you can use that range for measuring the DUT.
If the DUT's capacitance value is higher than the Measurable Capacitance of the
range selected in step 2, change the measurement range to a higher range (or select a
slower measurement speed) until the DUT's capacitance value is within the Measurable
Capacitance.
6-8 Application Measurement
) from the DUT's (capacitor) resistance
m
) as I =V /R .
s m s dut
4349B