Multi-meters are commonly used by electricians to test the voltage of circuits that require work and for troubleshooting circuits to locate the source of a problem. Testing the a circuit with a multi-meter prevents one from becoming subject to an electric shock, or allows one to pinpoint the exact source of trouble in an electric circuit. However, electricians are not the only ones that are able to use a multi-meter, there are multi-meters designed for residential use. The commercial multi-meters are available in digital and analog formats and may easily be used by anyone; the following sections explain how to use a multi-meter to test various characteristics of an electrical circuit.
How to Use a Multimeter
A multimeter works using two probes, one red and one black, which connect on the front of the meter. The black lead plugs into the COM slot, while the red lead connects to the MAV slot. Above the slots for the leads is a dial for adjusting the setting of the meter, the different settings are for the different characteristics to be tested. For digital meters, there is a digital display that provides a detailed reading of whatever aspect of an electrical circuit is being tested; while the analog provides a meter display that moves to show the information on what is being tested. The red and black leads have probes built into the end; the probes are used to connect to the different individual parts of the circuit for testing.
Testing Voltage of Simple Circuits
To test for voltage in a simple circuit, one must first locate the ground wire and the power wire of the component being tested. The black probe connects to the ground or the negative wire, and the red connects to the positive or the power wire. The multimeter must also be adjusted to read voltage and the voltage setting should be higher than that of the voltage being produced. There are different settings for the level of voltage to be tested; if the circuit is producing more voltage than the meter is set to read than the readout will display a one. For example; If one is testing the power of a standard nine volt battery and the meter displays a reading of one, then the voltage setting is set too low and should be adjusted to be able to read over nine volts. Testing a battery may be completed with a multimeter by connecting the black probe to the negative terminal and the red probe to the positive terminal.
The resistance of resistors may also be tested, although it requires knowledge of resistor color codes. There are several settings for measuring resistance on a multimeter , and as with measuring voltage the setting must be slightly above the resistance that is being produced. A resistor may be tested by applying the black and red probes to separate legs on the resistor, the reading will be displayed in Ohms. It is important to consider tolerance and environmental factors that may affect the resistance rating of a resistor, which may make the reading higher or lower than specified by the color codes.
Testing Current in Simple Circuits
In order to test the current of the circuit the meter, the probes must complete the circuit in series. To connect the meter in series one may remove the positive wire and connect the black probe to the positive wire, while the red probe is connected where the positive wire should be. This allows for the current to flow from the power source through the device, then continue through the circuit to provide an accurate measure of the current being produced by the circuit.