7Measurement Tutorial
286 Keysight 34420A User’s Guide
Output Clamping (Dry Circuit Testing)
Resistance measurements on certain types of contacts may require a limitation on
the voltage levels used to make the measurement. Both the open circuit and the
measurement voltage should be considered. The need for voltage limitation arises
from the possibility that oxidation on the contact surfaces may increase the
resistance reading. If the voltage is too high, the oxide layer may be punctured
resulting in a lower resistance reading.
The meter provides a programmable level of open circuit clamping, called voltage
limited measurements (see page 83). This feature is available on the 10 and 100
ohm ranges. The open circuit voltage can be clamped at one of three levels,
20 mV, 100 mV, or 500 mV.
The table below shows the current and voltage levels used.
Range Test Current
Measurement
Voltage
(at Full Scale)
Open Circuit
Voltage (MV)
10 W 1 mA 10 mV 20, 100, or 500 mV
100 W 0.1 mA 10 mV 20, 100, or 500 mV
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