Minimizing Power Dissipation Effects
When measuring resistors designed for temperature measurements (or other resistive devices with large temperature
coefficients), be aware that the multimeter will dissipate some power in the DUT.
If power dissipation is a problem, you should select the multimeter's next higher measurement range to reduce the
errors to acceptable levels. The following table shows several examples.
Range Test Current DUT
100 Ω 1 mA 100 µW
1 kΩ 1 mA 1 mW
10 kΩ 100 µA 100 µW
100 kΩ 10 µA 10 µW
1 MΩ 5 µA 25 µW
10 MΩ 500 nA 2.5 µW
Errors in High Resistance Measurements
When you are measuring large resistances, significant errors can occur due to insulation resistance and surface
cleanliness. You should take the necessary precautions to maintain a "clean" high–resistance system. Test leads and
fixtures are susceptible to leakage due to moisture absorption in insulating materials and "dirty" surface films. Nylon
and PVC are relatively poor insulators (10
9
Ω) when compared to PTFE insulators (10
13
Ω). Leakage from nylon or PVC
insulators can easily contribute a 0.1% error when measuring a 1 MΩ resistance in humid conditions.
Agilent Truevolt Series DMM Operating and Service Guide 89
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