Leakage Current Errors
The DMM's input capacitance will "charge up" due to input bias currents when the terminals are open–cir-
cuited (if the input resistance is >10 GΩ). The DMM's measuring circuitry exhibits approximately 30pA of
input bias current for ambient temperatures from 0 to 30 °C. Bias current doubles for every 8 °C change in
ambient temperature above 30 °C. This current generates small voltage offsets dependent upon the
source resistance of the DUT. This effect becomes evident for a source resistance of greater than 100 kΩ, or
when the DMM's operating temperature is significantly greater than 30 °C.
Unnecessary Signal Errors
Both 3A and 10A terminals are available for AC and DC current measurements. If signals are applied to ter-
minals not being used for the current measurement, measurement errors may occur. The unused ter-
minals are protected but the additional signals may interfere with current measurements. For example,
applying inputs to the 3A terminals while making measurements on the 10A terminals will typically cause
errors.
Unnecessary signals applied to the Hi and Lo Sense terminals can also cause errors. AC or DC voltages
above 15 volts peak on the sense terminals are likely to cause measurement errors.
Measurement Tutorial
192
Keysight True
volt
Series Operating and Service Guide
