A multimeter, also called a voltahmmeter or VOM, is a device for measuring the resistance, voltage and current of electronic circuits; some of them also have continuity and diode test capabilities. Multimeters are compact, lightweight and battery operated; they can be used to measure a wide variety of electronic components in different situations, and, therefore, are an essential tool for anyone wishing to test or repair an electronic circuit.
Steps
Method 1 of 5: Measure Resistance
Step 1. Connect the multimeter to the circuit
Insert the black probe into the common terminal and the red probe into the terminal designated for the measurement of volts and ohms; this terminal may also be identified with the diode test symbol.
Step 2. Turn the dial to the resistance measurement mode
This could be indicated with the Greek letter Omega, which is the symbol that identifies the Ohms (unit of measurement of resistance).
Step 3. Turn off the circuit
Step 4. Remove the resistor you intend to measure
If you leave the resistor in the circuit you may not get an accurate reading.
Step 5. Connect the probe tips to the resistor terminals
Step 6. Read the measurement on the display, taking care to note the relative unit of measurement
If, for example, you just write down 10, it could mean 10 ohms, 10 kilo-ohms, or 10 mega-ohms.
Method 2 of 5: Measure the Voltage
Step 1. Connect the multimeter to the circuit
Insert the black probe into the common terminal and the red probe into the terminal designated for volts and ohms measurement.
Step 2. Set the multimeter to the mode for the type of voltage to be measured
You can measure volts DC (direct current), millivolts DC, or volts AC (alternating current). If your multimeter has auto-range functionality, then you don't need to select the type of voltage to be measured.
Step 3. Measure the AC voltage by placing the probes at the ends of the component
Polarity does not need to be taken into account.
Step 4. Observe polarity for DC or millivolt voltage measurements
Place the black probe on the negative terminal of the component and the red probe on the positive one.
Step 5. Read the measurement on the display, taking care to note the relative unit of measurement
If you prefer, you can use the “touch-hold” function which allows you to keep the measurement on the display even after removing the probes; the multimeter will beep with each new voltage reading
Method 3 of 5: Measure the Current
Step 1. Choose between the designated terminal for measurements up to 10 amps and the terminal designated for measurements up to 300 milliamps (mA)
If you are not sure of the current value, start with the terminal at 10 amps, until you are sure that the intensity of the current is less than 300mA.
Step 2. Set the multimeter to current measurement mode
This could be indicated by the letter A.
Step 3. Turn off the circuit
Step 4. Break the circuit
To measure current, you need to connect the multimeter in series with the circuit. Place the black probe at the ends of the circuit break, respecting the polarity (the black probe on the negative terminal and the red probe on the positive one).
Step 5. Turn on the circuit
The current will begin to flow through the circuit and through the multimeter, from the red probe to the black probe, and then continue in the circuit.
Step 6. Read the display, keeping in mind whether you are measuring amps or milliamps
You can choose to use the “touch-hold” function.
Method 4 of 5: Test the Diodes
Step 1. Insert the black probe into the common terminal and the red probe into the terminal designated for Ohm, Volt or diode testing
Step 2. Set the diode test function by turning the selector
It could be represented with the diode symbol (an arrow with a vertical line at the tip).
Step 3. Turn off the circuit
Step 4. Test Direct Polarization
Place the red probe on the positive terminal of the diode and the black one on the negative terminal. If the reading is less than 1 but greater than 0, then the forward bias is good.
Step 5. Invert the probes to test the Reverse Polarization
If the display shows “OL” (which stands for “overload”, ie overload)”, it means that the reverse bias is good.
Step 6. If you detect, testing forward bias, “OL” or 0, and testing forward bias, 0, then the diode is bad
Some multimeters emit a “beep” if the reading is less than 1. The “beep” is not necessarily an indication that the diode is good, as it would also be emitted for a shorted diode
Method 5 of 5: Measure Continuity
Step 1. Insert the black probe into the common terminal and the red probe into the terminal designated for Volt and Ohm measurement
Step 2. Set the multimeter to the same mode used for the diode test
Step 3. Turn off the circuit
Step 4. Place the probes on the terminals of the circuit section you want to test
It is not necessary to respect the polarity. A reading below 210 ohms indicates good continuity.
