ALANTE DX/LT_SG_REVA_030112
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APPENDIX B - HOW TO USE AN OHM METER
Ohm’s law breaks down into the basic equation: Voltage = Current x Resistance. Current is generally measured
in amps, and resistance in ohms. Testing the resistance on an electrical circuit in your home or car can help you
diagnose problems with that circuit. You can use a simple ohmmeter for this task, but most professionals now use
the ohmmeter function of a multimeter (also called multitester or VOM, for volt/ohmmeter). Read on for instructions
on how to use an ohmmeter and test for resistance.
Ohmmeter or Multimeter (Volt/ohmmeter)
Circuit to test (with all power OFF)
Service manual
Step 1
Disconnect completely and/or turn OFF all power to the
circuit you are testing. You must have a completely dead
wire or circuit in order to ensure accuracy in measurement,
as well as your own safety. Your ohmmeter will supply the
voltage and current for your circuit so NO other power is
necessary. Testing a powered circuit can “cause damage to
the meter, circuit, and *you*.”
Step 2
Connect testing wires to the ohmmeter. The black wire
goes to the ground (common) outlet, the red wire to the
volt/ohms outlet.
Step 3
Consult a service manual for the normal range of
resistance for the circuit you are testing.
Step 4
Set the dial to the “ohms” setting with a multimeter. On an
individual ohmmeter, you may have to set a range for the
readings, in ohms, kilohms or megohms. Use the range you
located in your service manual to set the dial.
Figure 13. Multimeter (Set to Ohms)
