Electrical resistance is the amount of opposition, or resistance, a material or wire creates in a circuit or between two points on a wire and can be easily measured using an analog multimeter. Resistance is measured in Ohms, which is one of the basic settings on virtually every multimeter that has even been made. This simple step by step guide will show you how to measure resistance using an analog multimeter.
Step 1 - Power Off Circuit or Equipment
Before use your multimeter to measure the resistance in a circuit or wire, you should always turn off any equipment that is attached to the circuit. If you do not power off the equipment, you risk damaging both the equipment and multimeter.
Step 2 - Power on the Analog Multimeter
Set the power selector switch for your analog multimeter to the 'On' position.
Step 3 - Set the Multimeter to Measure in Ohms
Depending on the interface on the front of your analog multimeter, you will need to set the selector switch to the ohms position, or you may need to set it to the symbol which represents ohms: the Omega sign. On a very few multimeters, the setting may actually have the label resistance. Whichever naming scheme your multimeter uses, choose the selection setting that measures resistance in ohms.
Step 4 - Insert Lead Probes or Clips
Insert the black and red probe leads or clips into the appropriate slot. Some multimeters only come with two slots, which are marked positive and negative. If this is the case, insert the red one into the positive slot, and insert the black lead into the negative slot. However, some multimeters will have slots or holes that are marked specifically for measuring resistance. If you're unsure about which slot to insert the probe lead in, refer to the instruction manual for your multimeter.
Step 5 - Test the Analog Multimeter
Before you actually test for resistance, you should test the multimeter to make sure that it will display an accurate reading. Therefore, touch the tips of the probe leads or clips together. If the multimeter is functioning properly, you should see a result of infinite ohms. This is actually an indication that there is no resistance, or 0 ohms, in the connection between the two probes. However, analog multimeters do not display in terms of zero; therefore, the needle will shoot over to the opposite end of the scale where the infinity symbol is located.
Step 6 - Test the Resistance in the Circuit or Wire
Place both probe leads or clips on either side of the wire or resistor that you want to test. While making contact with the two points, carefully read the reading that is shown on the analog graph and needle scale. You can use this number to compare with the specified resistance rating for the resistor or circuit that you have tested.