How to measure resistance
Note: Due to the existence of a wide variety and types of testers, we will explain the most common method to measure resistance with a multimeter. This is the case for the analog multimeter, although it can also be used with the digital multimeter.
The range selector to measure resistance is different from of the voltage selector and the current selector. When the function selector is in ohms, the measured result is multiplied by the factor that is showed in the range (look at the picture)
Common ranges are: R x 1, R x 10, R x 100, R x 1K, R x 10K, R x 1M, where:
- K means Kilohms
- M means Megohms
Not all multimeters are alike, so it is very important to look carefully at the range selector.
For example, looking at the yellow color on the following image:
- If the multimeter scale shows 4.7 and the range is 1 K or 1000, the multimeter would be measuring a resistor value of 4.7 x 1000 = 4700 ohms or 4.7 K (Kilohms).
- If the multimeter scale shows 2.5 and the range is 10 M or 10 000 000, the multimeter would be measuring a resistor value of 2.5 x 10 000 000 = 25 000 000 ohms or 25 M (Megohms).
It is very important to choose the right function and the range before making a measurement. If you make a mistake, you may damage the multimeter. There is a different way if you want to measure a very low value resistor.
Additionally, the analog multimeters have two knobs that allow you to adjust the needle to zero (rest position) and the other to adjust the reading of zero ohms (0).
To accomplish this, you have to proceed as follows:
- put the function selector in Ohms
- put in the range selector in x 1
- join the test leads
At the end of the preceding process, the needle should be at 0 ohms, if not an adjustment have to be done with the knob, touching the multimeter leads together and checking that it reads 0 ohms.
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