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Tip 4: Power dissipation effects
When measuring resistors designed for temperature measurements or other resistive devices that vary with temperature, be aware that the meter will dissipate some power in the device-under-test. The effects of this power dissipation can affect the measurement accuracy.
If power dissipation is a problem, you can select a higher measurement range, one which uses a lower current source thus reducing the self-heating. Some multimeters, such as the 34420A offer a low power setting. Using the low power setting or a higher resistance range requires a multimeter with good resolution. Below is a table showing the power dissipated by a resister by range and how a low-power setting can reduce the power.
| Normal | Normal | Low Power | Low Power | |
|---|---|---|---|---|
| Range | Test Current | DUT Power at Full Scale | Test Current | DUT Power at Full Scale |
| 1Ω | 10 mA | 100 µW | 10 mA | 100 µW |
| 10Ω | 10 mA | 1 mW | 10 mA | 1 mW |
| 100Ω | 10 mA | 10 mW | 1 mA | 100 µW |
| 1kΩ | 1 mA | 1 mW | 100 µA | 10 µW |
| 10kΩ | 100 µA | 100 µW | 10 µA | 1 µW |
| 100kΩ | 10 µA | 10 µW | 5 µA | 2.5 µW |
| 1MΩ | 5 µA | 25 µW | 5 µA | 25 µW |