Other Sources of Measurement Error
Settling Time Effects
The multimeter can insert automatic measurement settling delays. These delays are adequate for res-
istance measurements with less than 200 pF of combined cable and device capacitance. This is particularly
important when measuring resistances above 100 kΩ. Settling due to RC time constant effects can be
quite long. Some precision resistors and multi–function calibrators use large parallel capacitors (1000 pF
to 0.1 µF) with high resistor values to filter out noise currents injected by their internal circuitry. Non–ideal
capacitances in cables and other devices may have much longer settling times than expected just by RC
time constants due to dielectric absorption (soak) effects. Errors are measured when settling after the ini-
tial connection and after a range change.
Loading Errors (AC volts)
In the AC voltage function, the input of the multimeter appears as a 1 MΩ resistance in parallel with 100 pF
of capacitance. The cabling that you use to connect signals to the multimeter also adds capacitance and
loading. The table below shows the multimeter's approximate input resistance at various frequencies.
Input Frequency Input Resistance (kΩ)
100 Hz 941
1 kHz 614
10 kHz 137
100 kHz 15.7
For low frequencies, the loading error is:
At high frequencies, the additional loading error is:
Keysight Truevolt Series Operating and Service Guide
189
Measurement Tutorial
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