- Do It Yourself Auto Repair
How To Use Ohm Meter or Multi Tester To Check Resistance
A Common Multi Tester With An Ohms Tester "Click To Enlarge"
Checking resistance in a circuit is very simple, but it may be confusing to some who have no electrical knowledge.
- When you check resitance, you are looking for the resistance the path holds to the flow of electricity. Think of it as a pipe. When you downsize the pipe, or increase the length of the pipe, less water can flow. The same rule applies to electricity. When you increase the resistance with different materials, smaller wire, or longer length, less power will flow.
- Remember that a "0" Ohms reading means the same thing as a direct short, or path with no resistance. You will see that light bulbs, electric motors and other components will show some resistance, while a solid length of wire checked end to end will show no resistance unless it is very long in length.
- Start with a good meter with good batteries. If the batteries are below a certain level, it may cause readings to be inaccurate. More expensive models will usually notify you when the batteries are low.
- Set your meter to the range that you think the resistance will fall into. I usually start with the highest scale, but most meters today are very friendly and have only 3 or 4 ranges. Try the highest scale first.
- Place the leads on the two points you are testing, being careful that the leads do not touch each other, and check the reading. Remember, you are measuring the "Resistance to electrical flow"
- Note the reading on the scale. If there is "0" ohms, that means there is a contact and path for electricity to flow. If you are testing components, the manufacturer may provide specs for Ohms.
Place the leads on the circuit you want to test, being sure the leads do not touch each other.
Checking An Incondecesent Light Bulb
Above photo shows a light bulb being tested. The filament in an incondecesent bulb is a continuous metal wire that enters (Terminal 1) the vacume of the bulb and exits the vacume of the bulb (Terminal 2) The wire is curled inside the vacume to create more resistance (Longer Length) and to increase surface lighting area of the filament. If the bulb filament shows high resistance, this means the filament is most likely broken or there is a bad connection to the element. If the Ohms test shows low resistance or no resistance, the filament is good
I hope this Tutorial has helped you. Happy Testing