Digital Multimeters (DMM) are common tools for measuring resistance. In general, to measure resistance with a DMM requires the following steps:
- Turn power to the circuit OFF
- Turn the DMM dial to resistance/ohmmeter mode with a suitable resistance range.
But sometimes, even when we use a good DMM with a correct setting, the measured resistance still exceeds the specification for your components.
Here are some tips that may help to measure low expected resistance values.
Please note that the DMM test leads themselves have a very small resistance value , which can show up as extra resistance above tolerance on your measurements. For example, when measuring a resistor, TNPW120620R0BEEA (20 ohm ±0.1%) from Vishay, your DMM may read a value of 20.1 ohms, since there is a test lead resistance of 0.1 ohms.
Some DMMs have a function called relative mode. It may also be referred to as zero or Delta mode. This mode can automatically subtract the test lead resistance for a more accurate measurement.
There is a test method called the four-wire (Kelvin sensing) connection method which is a method to help measure a low resistance value. Please check out our post on Measuring Low Resistance Values to learn more.