Testing Resistance (Ohms) with a Digital Multimeter
This test, using a digital multimeter, determines whether:
- an electrical circuit is complete or broken
- the resistance of a component matches the manufacturer’s specification
Figure 4: Ohm Test of a Load
Follow these steps to complete the resistance test procedure:
- Make sure all power is off on the circuit you are testing.
- Make sure that the component that you are testing is isolated from the complete circuit. Either remove the component from the circuit or isolate it with an open switch.
- Set the selector dial to Ω.
- Connect the test lead and probes to the component terminals as shown (Figure 4).
- Observe the readout window to obtain the Ω reading.
- Compare the results to the manufacturer’s Ω specifications. If the readings match the component, then resistance is not a problem. If the component is a load, there should be resistance that matches the manufacturer’s specs.
- If the reading is infinite (I) or overloaded (OL), then the component is open.
- If the reading is zero, then the component is closed (if it is a load then this is an internal short).
- If this is the last test you are doing, turn the meter to “off” and store it in a safe place.