Any kind of electrical work no matter what the application is - one of the best measuring tools is a multimeter. It is an electronic tool, which is used to measure voltage, current, resistance, and other values of electronic components ( such as a capacitor, diode, transistor, transformer, etc).
It is also known as a volt-ohm meter (VOM). Basically, two types of multimeter have come analog multimeter and digital multimeter. In these two types of multimeter, the most widely used multimeter is a digital multimeter.
The multimeter has two probes (red and black/positive and negative). They are used to connect with the circuit. And a display shows its measuring values. If you are a beginner and just starting how to use digital multimeter then this article will helpful for you. In this tutorial, you will learn -
• Continuity testing.
• Measuring voltage.
• Measuring Current.
• Measuring the resistance of a resistor.
• Measuring the capacitance of a capacitor.
How to use a digital multimeter?
Continuity testing
Continuity testing is used to test the complete path for current flow. It can be used to test switches, fuses, electrical connections, conductors, and other components. To test the continuity
1. At first switch on the power button of the digital multimeter(DMM).
2. In the digital multimeter, a beep or diode symbol is used to show continuity mode. Turn the dial in it.
3. Insert the black probe into the COM jack and the red probe into the VΩ jack.
4. Connect the test leads to each other for testing whether the multimeter is working or not. If the multimeter beeps then it is ready to test the circuit.
5. Now connect the test leads across the circuit being tested.
6. If the multimeter beeps then the circuit is closed which means it has continuity. If the circuit is open, then the digital multimeter will not beep.
7. When the test is finished, turn off the multimeter to preserve battery life.
Measuring voltage
Measuring DC voltage
1. At first switch on the power button of the digital multimeter(DMM).
2. In the digital multimeter, a DC voltage source V with a straight line is used as a symbol to show the DC voltage measuring mode. Turn the dial in it.
3. Insert the black probe into the COM jack and the red probe into the VΩ jack.
4. Connect the black lead to the battery's '-' side and the red lead to the '+' side.
Note: If the black lead is connected to the battery's '+' side and the red lead to the '-' side, then a negative sign will appear on the screen.
5. Read the measurement on the screen of the multimeter.
Measuring AC voltage
1. In the digital multimeter, an AC voltage source V with a wavy line is used as a symbol to show the AC voltage measuring mode. Turn the dial in it. If the voltage is unknown, set the range to the highest voltage setting.
2. Insert the black probe into the COM jack and the red probe into the VΩ jack.
3. Connect the test leads to the circuit.
Note: In the AC voltage, there is no polarity.
4. Read the measurement on the screen of the multimeter.
Measuring current
Measuring DC current
1. At first switch on the power button of the digital multimeter(DMM).
2. In the digital multimeter, a DC current source A with a straight line is used as a symbol to show the DC current measuring mode. Turn the dial in it.
3. Insert the black probe into the COM jack and the red probe into the mA jack.
Note: If there is a large current insert the red probe into the A jack.
4. Connect the test leads in series with the circuit.
5. Read the measurement on the screen of the multimeter.
Measuring AC current
1. In the digital multimeter, an AC current source A with a wavy line is used as a symbol to show the AC current measuring mode. Turn the dial in it.
Note: Most of the digital multimeter will not have the option to measure AC current. so do not try to measure AC current with your DC multimeter otherwise it might damage the multimeter permanently.
2. Insert the black probe into the COM jack and the red probe into the mA jack.
Note: If there is a large current insert the red probe into the A jack.
3. Connect the test leads in series with the circuit.
4. Read the measurement on the screen of the multimeter.
Measuring the resistance of a resistor
Steps for measuring resistance with a digital multimeter -
1. Turn off the ability to run the circuit. If a circuit includes a capacitor then discharge the capacitor before taking any resistance reading.
2. Rotate shaft in the resistance mode, which often shares a dial spot with one or more test modes( like continuity, capacitance or diode modes).
Notes: If the display shows OL, it means in resistance mode even before test leads are connected to the component, a digital multimeter(DMM) automatically begins taking a resistance measurement.
If the symbol M may appear, then it means the resistance of open test leads is very high. Pressing the RANGE button to manually set the range.
3. Insert the black probe into the COM jack and the red probe into the VΩ jack.
4. Connect the test leads across the component being tested. Make sure that contact between the test leads and the circuit is good.
5. Read the measurement on the display.
6. Turn off the multimeter to prevent the battery drain when the measurement is finished.
Advanced digital multimeter(DMM) option:
7. Press the RANGE button to select the specific fixed measurement.
Note: Be sure to note the annunciator(such as K or M) after the measurement on the display.
8. Press the HOLD button to capture a stable measurement. When the multimeter beeps, it recorded a new reading at each time.
9. Press the MIN/MAX button to capture the lowest and the highest measurement. When the multimeter beeps, it recorded a new reading at each time.
Measuring capacitance of a capacitor
To measuring the capacitance of the capacitor at first to ensure that the capacitor is fully discharged. If the capacitor is chared then it may cause shock in your hand. You can use a resistor(2kΩ) or screwdriver to discharge the capacitor.
After discharging the capacitor you can measure it safely. Here we discuss how to measure polar and non-polar capacitors using the multimeter.
Measurement of the polar capacitor
1. At first set the meter on continuity mode or ohm range(Set it at lease1000ohm = 1kΩ).
2. Insert the black probe into the COM jack and the red probe into the VΩ jack.
3. Connect the meter leads to the capacitor terminal. The red lead of the multimeter is connected to the big electrode and the black lead connected to the small electrode.
4. After connecting the leads of the multimeter it will show some number for a second(note the number) and then immediately it will return to the OL(Open Line) which means the capacitor is good condition. If there is no change, then the capacitor is dead.
Measurement of the non-polar capacitor
In the non-polar capacitor, there is no polarity so you can connect the leads of the multimeter to any electrodes of the capacitor. But in this capacitor, if there is no reading in the multimeter so the capacitor is in good condition and if the multimeter is showing some values then the capacitor is dead.
Diode testing
1. At first switch on the power button of the digital multimeter(DMM).
2. In the digital multimeter, a beep or diode symbol is used to show diode measuring mode. Turn the dial in it.
3. Insert the black probe into the COM jack and the red probe into the VΩ jack.
4. Connect the test leads to the diode.
Forward biased: The red or positive lead of the multimeter is connected to the 'p' side or anode and the black or negative lead connected to the 'n' side or cathode of the diode.
Reavers biased: The red or positive lead of the multimeter is connected to the 'n' side or cathode and the black or negative lead connected to the 'p' side or anode of the diode.
5. If the diode is connected in forward biased then the display will show the diode value. And if the diode is connected in reverse biased then the display does not show any value.
6. In the forward biased connection, the display shows lower resistance of the diode and in the reverse-biased connection, the display shows higher resistance.
Transformer testing
1. Continuity testing of a transformer
Set the multimeter at continuity mode and connect the two leads of the meter across the primary winding terminals and see if the buzzer of the multimeter is responding then the primary connection is good.
Similarly, test the secondary windings and see if the buzzer is running then overall the transformer is in good condition.
2. Identifying the primary and secondary windings of the transformer
For step-up transformer
Set the transformer at the ohm range and connect the two leads of the meter at any winding. See the multimeter and note the reading. Again repeat the process for other winding.
See the multimeter and note the reading, if in the first case the value of the resistance is bigger than the second case then obviously the first winding is secondary and the other is primary.
This is why because the number of turns in the primary winding is much more than secondary so the resistance is high.
For step-down transformer
Similarly set the transformer, and see if the first case the value of the resistance is bigger than the second case then obviously the first winding is primary and other is secondary. This is why because the number of turns in the primary windings is lower than secondary so the resistance is low.