- Home Appliances
How to Do It Yourself Appliance Repairs Made Easy, Demystifying the Multimeter Volt Ohm Meter VOM
Let's be clear about what this thing is called. It is referred to as a multimeter, a Volt Ohm meter or a VOM. These names are all for the same thing. These complex little meters can be used to perform simple tests. Tests that anyone can perform.
Caution: never test anything that is connected to the power. Unplug the appliance.
Second, most of the testing for appliance parts is a continuity test. Now don't panic! You do not even need to know what continuity testing means in order to conduct this test.
For those of you who want to know what continuity is: Continuity is basically an "uninterrupted connection." Take any on/off switch in your life: Light Switch on = uninterrupted connection; Hair dryer on = uninterrupted connection; Toaster down = uninterrupted connection; Computer on = uninterrupted connection; Power On = uninterrupted connection. That means that all of these have continuity or an uninterrupted connection.
When the switches are off there is an interrupted connection = no continuity. Light switch off = interrupted connection = no continuity. And so on.
Now that you know the difference between an uninterrupted connection and an interrupted connection, consider this: The light switch is on but the light is off. Although there could be a variety of causes for this, for this example, let's say that the switch is bad. It is in the on position and should provide uninterrupted connection, but it is not. For some reason the switch has failed (something inside is broken).
At this point this is a theory. Now we can use our MultiMeter to test this idea. To do this, set the meter to an ohm ( Ω) setting the selector switch to somewhere in the middle of the scale.
DANGER: electricity is dangerous, do not test any device, wire, etc. before disconnecting the power.
Now touch the probes from the meter to each other and see what the meter reads. Touching the probes together produces a uninterrupted connection. Now to test a switch, touch the probes to both sides of the switch, with the switch on, the meter should read the same thing as the switch produces an uninterrupted connection.
If the meter shows an uninterrupted connection with the switch on and an interrupted connection with the switch off, then the switch is good.
If the meter shows an interrupted connection in both positions, the switch is bad.
Using this same kind of reasoning, appliance parts can be tested for continuity (uninterrupted connection) if it produces continuity, generally the part is good.
There are some exceptions to this rule, but that can be covered when necessary.
MultiMeter Volt Ohm Meter
Multi Meter Uses
Now the you know what continuity is, you can use your meter for other things. Voltage is another useful thing to know. Look at your meter. There are two leads coming from it one is black and the other is red.
The black lead is normally considered the hot leg and red the return. Looking at your meter, the dial has various settings. Locate the settings that say AC and DC. These may be listed as Voltage or VAC and VDC.
The electricity in your home is normally AC, electricity from batteries is DC. There is quite an explanation that is very technical but for these purposes, we just need the correct label.
If you want to test a battery, from a flashlight to the battery in your car, you would set the meter to a VDC setting that is closest to the expected voltage. For a 12 volt battery, like in your car, you would set the meter to 12 VDC, if the meter does not have 12 VDC, then go for the next highest setting like 24 VDC. This gives you a range that is safe. Use the RED probe on the positive terminal and the BLACK on the negative terminal.