What is Digital Multimeter (DMM), Working and How to Use?

A Digital Multimeter (DMM), is a test instrument that is used to measure electrical values, for example, voltage, current, resistance, continuity, and many other measurements. Digital multimeters are widely used in the industries by electricians, electronic engineers, some hobbyists, etc.

The price of the digital multimeter varies. Some can be purchased very cheaply and others are very expensive depending on the specification and the accurate measurement a multimeter can take.

In the past years, analog multimeters were used but these are rarely used nowadays because digital technology has come into the picture making the digital multimeter and having the capability of measuring frequency, capacitance, continuity, and temperature beyond the current, voltage, and resistance.

Digital Multimeter Parts

A Digital multimeter physically has three parts a display, switch or selection knob, and the connections for the test probes.

• Display

The display of the digital multimeter is very easy to read. Most of the multimeters have four digits, the first of which can either be 0 or 1 and there will be a positive (+) or negative (-) indication as well. A few m m have illuminated display as well so that it can be read in the low light also.

• Selection Knob

The selection knob of the multimeter allows reading different things such as milliamperes, voltage, current, continuity, temperature, etc.

• Testing Probes

There are two leads or probes in the multimeter one is having a black color and one is having a red color. The black color is used for common or ground and inserted in the com port of the multimeter. The red lead goes into the mAVΩ port and is positive. This port allows the measurement of current (I), voltage (V), and resistance (Ω).

*There are different kinds of feeds for crops that can be used such as alligator type, tweezer type, etc.

How To Use Multimeter?

Multimeters can be used to check the voltage, current, resistance, continuity, and many other measurements. We will explain how to check the voltage, current, resistance and continuity in the following paragraphs.

How to check Voltage with Multimeter

We will learn how to check the voltage with a multimeter by following the steps given below. We will understand it by an example.

1. Let us assume we want to check the voltage of the wall clock battery.
2. Set the selection knob of the multimeter to “2V” in the DC (direct current) range. We have selected 2V because we know the battery of the clock is “1.5V”. If we have to measure voltage more than that of any circuit, then we will select the knob accordingly otherwise the reading will not be proper or accurate and a value of ‘1’ will be displayed if we have selected under voltage knob.
3. Then, put the red probe into mAVΩ and the black probe into COM.
4. After that, connect the red probe to power or ‘+’ and the black probe to the battery’s ground or ‘-‘.
5. If the battery is new, you will see around 1.5V on the display and if the battery is old or discharged, then you will see a voltage of less than 1.5V.

Now if you are measuring DC voltage then you have to select the knob where the ‘V’ is written and have a straight line. A straight line means DC voltage. If you are measuring AC voltage, then we have to select the Knob to the V with a wavy line next to it. But extra care is to be taken while testing the AC voltage or it should be checked with the tester.

Now, what will happen if we interchange that black probe with red and the red probe with black. If we interchange the probe, then nothing will happen, just the “-” sign will come there while taking a reading.

How to check Resistance with Multimeter

The multimeter tool is very handy to measure the resistance of a resister. Let us understand, how we can calculate the resistance with a multimeter.

First of all, pick any random resistor and set the selection knob of the multimeter to 20kΩ. Then hold the probes and with the resistor legs. The multimeter will display either 0.00, 1, or the actual resistor value.

• In this case, if the meter reads 0.91, meaning this resistor has a value of 910Ω.
• If the multimeter displays OL or reads 1, it’s overloaded. You will need to try a higher mode such as 200kΩ mode.
• If the multimeter reads the value 0.00 or nearly zero, then the knob needs to lower the mode to 2kΩ or 200Ω.

How to check Continuity with Multimeter

Continuity is basically testing the resistance between two points. If the resistance is less, then two points are considered electrically connected and the tone will be emitted. But if the resistance is high then the two points are considered to be electrically disconnected and no tone will be emitted. This test ensures whether the connection between two points is electrically ok or not. Let us understand how we can check the continuity with the help of a multimeter.

• First of all, turn the selection note to the continuity mode on the multimeter.
• After that, join the two problems to check the multimeter is functioning ok and a beep sound will come. It means the circuit is ok and now we will check the circuit.
• To check whether the wire is broken or not, connect one end of the wire with one probe and the other end of the wire with other probe. If there is a beep sound then the wire is ok and if there is no beep sound, then the wire is not ok.

This is how we can use the multimeters to check the various things in an electrical circuit and can help to troubleshoot the system.

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