hva forstyrrer avlesningen når multimeteret tester små motstander?
Når multimeteret tester liten motstand, er det interferensstrøm, som vil generere forspenning og gi målefeil.
When a multimeter is used for small resistance tests, the current source is usually relatively large (1 to 10 mA). Even so, the interference current still exists, and the bias voltage is more common in small resistance tests. A common error is caused by potential differences across different metal nodes. For example, a copper/tin-lead solder junction can generate a bias of 5 uV/ degree . Therefore, it is very important to reduce the number of nodes, and try to use metals of the same material. A copper/copper junction produces a bias lower than 0.3 uV/ degree , and choosing a smaller resistance range can improve test results. For example, Keysight's multimeter 34420A has 1 Ohm and 10 Ohm ranges and provides a larger current source of 10 mA to generate a larger voltage for easy measurement.
