Amit RanaHow to use digital multimeter : 3 most widely used operations
Updated: Jan 13, 2022
Digital Multimeter is one of the most essential tools an electronics hobbyist should own. While developing electronics circuits, we come across lots of different parameters which needs to be checked, for example, voltage, current, resistance, continuity etc… there are separate instruments available for each of these parameters, and multimeter is the one instrument having facility for doing all above measurement. There are analog and digital multimeters available. But digital are becoming more common these days and hence we use digital multimeters, which is also referred as DMM. Now and onwards, we use simply multimeter for referring to a DMM. It’s basically a measuring instrument which can measure
Voltage (AC/DC)
Resistance
Continuity (diode test)
Current (AC/DC)
So this single instrument serves all the major tasks required in electronics measurement. If we don’t have multi meter, there are very few chances to troubleshoot a circuit. Multi meter enables us to measure parameters and debug lots of problems in electronics circuit. Let’s see how to use one of the most helpful of all instruments, multi meter!!!
Look at below image for understanding three major parts of multi meter.
A multi meter consists of three Major Parts
Display
Selection Knob
Probes
The display usually has four digits and the ability to display a negative sign. A few multi meters have back light displays for better viewing in low light situations.
The selection knob allows the user to set the multi meter to read different things such as current, voltage (V) and resistance (Ω). Have a look in above image
As shown in above figure, multi meter is having a central rotary switch for selecting various knob positions, each position corresponds to a particular parameter, the wheel can be easily rotated to select one of our required measurement knobs.
If we want to measure voltage, or say measure resistance, then we have to connect multi meter with the testing point in our circuit. This job is done by special wires which connect multi meter to components or test points of our circuit. These wires are called as probes. Two probes are plugged into two of the ports on the front of the unit. Have a look at below figure.
how to use digital multimeter
how to use digital multimeter
As you can see above, COM stands for common and is almost always connected to Ground or ‘- Negative’ of a circuit. The COM probe is generally black colored but there is no difference between the red probe and black probe other than color.
Apart from COM, there are two more ports on multimeter, One is labeled as mAVΩ. mAVΩ is the port that the red probe is conventionally plugged in to. This port allows the measurement of small current (up to 200mA), all the voltage (V), and resistance (Ω). The probes have a specific type connector on the end that gets easily fixed into the multimeter. Any probe with this kind of connector will work with this meter. This allows for different types of probes to be used.
How to use digital Multimeter : Measuring Voltage
To start, let’s measure voltage on a 9V battery Plug the black probe into COM and the red probe into mAVΩ.
measuring voltage
Set the multimeter to “20V” in the DCV range. Almost all electronics use direct current, not alternating current. Connect the black probe to the battery’s ground or ‘-’ and the red probe to power or ‘+’. Press the probes with a little pressure against the positive and negative terminals of the 9v battery. If you’ve got a fresh battery, you should see around 9.0V on the display (this battery is brand new, so its voltage is slightly higher than 1.5V).
If accidentally, you connect the probes in reverse direction, means red probe to negative and black to positive, the multi meter shows the negative reading, no harms!!!
negative measurement
If you’re measuring DC voltage in any circuit, you must know a tentative range of voltage that you’re measuring to set the knob. If the measured voltage is more than the specified range, the meter shows “1” means out of range