: Electricity and Electrical
: How to Use a Multimeter
How to Use a Multimeter
Written by; Thomas O'Connor / TCCN Staff Writer
Added on: Thu Sep 17 2009
A multimeter is a piece of equipment that can be a very welcome addition to a home tool kit. A multimeter measures AC or DC voltage, current, and resistance.
You could have separate meters for each of these: a voltmeter for measuring voltage, an ammeter for measuring current, and an ohmmeter for measuring resistance.
A multimeter, however, combines all of these things. You can use it to test batteries, switches, components, motors, and power sources to diagnose electrical malfunctions.
You can buy either an analog multimeter or a digital one. Multimeters are designed to be sensitive to a certain range of values, so make sure you get a model that works in the range of what you test most.
For instance, you would want a meter to measure high voltage if you regularly test car batteries.
Here are what the various modes of a multimeter can do.
A multimeter in voltmeter mode measures the amount of AC or DC voltage going through a circuit. Voltage is the difference in potential energy between an appliance and a source of electricity.
For example, if you plug a fan into the wall, it will draw 120 volts from the outlet. To test voltage, choose AC or DC, choose an upper limit on the voltage, and then plug the device into the multimeter. The readout tells you if the device is functioning normally.
In ammeter mode, the multimeter measures current going through a closed circuit. It does this by interrupting the circuit. Digital multimeters are rated based on their intended application.
There are four categories of ammeters:
Category I (low current levels); Category II (residential branch circuits); Category III (distribution panels, appliance outlets, and motors); and Category IV (used where current levels are high, like main panels and house meters). Ammeters must always be connected in series.
When used as an ohmmeter, the multimeter finds the resistance in a circuit in units called ohms. To find the resistance at any point in a circuit, unplug the device, input an approximate range you expect to contain the resistance you think you'll get.
The multimeter passes a small amount of electricity from its battery through the circuit to measure resistance by comparing sent voltage to received voltage.
The basic steps for using a multimeter are as follows:
1. Disconnect the cord from the power source, unless you're testing a live circuit.
2. Plug test leads into the multimeter.
3. Select the function you want to measure (ACV, DCV, Resistance), and the maximum reading expected (device owner’s manuals usually will tell you the maximum expected reading).
4. Connect the probes to the cord or appliance.
5. Interpret the reading using the multimeter manual or the user's manual of the device you're testing.
If you do find a circuit somewhere in your home that just isn't checking out. Be sure to call a professional, you can find many right here in our local business directory.
Copyright: 2009 TCCN.ca