Why exceed the specifications when measuring low resistance?

Equipment, Tools & Supplies Test and Measurement
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Digital Multimeters (DMM) are common tools for measuring resistance. In general, to measure resistance with a DMM requires the following steps:

  1. Turn power to the circuit OFF
  2. 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.

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