Resistance Testing
When set for resistance testing (Ohms) the DVOM must never be connected in a live circuit.
The component or portion of a circuit being measured, must be isolated from the power source.
Most modern day DVOM's are self ranging when set to measure resistance, so the meter can not be damaged by out of range measurements.
The test leads may be used without regard for polarity, unless the circuit contains a diode.
The DVOM functions by placing a very small amount of current on the circuit being tested, the red lead must be placed on the anode side of the diode.
Typical Application of Resistance Testing
- Locating a Short to Ground (As Shown).
- Determining Resistance of Components (e.g. Temp Sensors and Injectors).
An Ohmmeter uses its internal power to test a circuit or component.
- Select correct function and range (Most meters are self ranging in this function).
- Disconnect power to circuit.
- Disconnect any circuit wired in parallel with circuit being tested.
- Connect test leads.
NOTE:
There must be NO current available to the circuit during the resistance (Ohmic) test. DVOM will indicate resistance (Ohms) of component or circuit being tested.