What is a Multimeter and How to Check the Voltage of a Live Wire?

What is a Multimeter

What is a Multimeter?

It is a device that is used to measure various electrical properties of a circuit or electronic component. It is a versatile tool that electricians, engineers, and technicians commonly use for troubleshooting and testing electrical circuits and general electrical measurements.

What Does a Multimeter Do?

The primary functions of a multimeter include:

Voltage measurement: It can measure direct current (DC) and alternating current (AC) voltage levels in volts.

Current measurement: It can measure DC and AC current flow in amperes (amps).

Resistance measurement: It can measure the resistance of a circuit in ohms.

Continuity testing: It can check for the presence of a complete electrical connection or continuity between two points.

What are the Types of Multimeters?

There are two main types of multimeters:

Analogue Multimeter

It uses a mechanical needle to display readings on a scale. Although less common nowadays, analogue multimeters are still used in some applications due to their simplicity and ability to read changes in values quickly.

Digital Multimeter

It uses a digital display to show readings numerically. Digital multimeters are the most common type used today due to their accuracy, ease of use, and ability to provide precise measurements.

WHAT ARE THE TYPES OF MULTIMETERS

What are the 4 Components of a Multimeter?

Following are the four components of a multimeter

Display

It is an LCD display, or a rotating needle in the case of an analogue multimeter, that displays readings and results of the test.

Rotatory Knob

This component allows you to toggle between different modes of the multimeter. You can select the modes between voltage, current, and resistance according to your need.

Probes:

Every multimeter comes with two probes, one red and one black, that are connected to the device under testing to establish an electrical connection. The red probe is connected to the VΩmA port, and the black one to the COM port.

Input Ports:

Input ports are where the jacks of both probes go. There are three ports that can be found on a multimeter, i.e.:

COM: Short for common, it is used for the negative or the ground part of an electric circuit.

VΩmA: It is used to measure voltage, resistance, and current up to 200mA.

10A: It is a special input port that is used to measure electric current exceeding 200mA.

How to Use a Multimeter?

You can follow the following guidelines to use your multimeter:

Safety Precautions

  • Before starting, make sure the multimeter is in good condition.
  • Use proper safety gear to measure high voltages and currents.
  • Keep your fingers away from the metal probe tips and avoid touching exposed conductors.
  • Always disconnect power sources and discharge capacitors before attempting resistance measurements.

Voltage Measurement:

  • Begin by attaching the black probe (COM) to the common or ground terminal of the multimeter.
  • Next, link the red probe to the positive terminal of the component or the circuit that requires measurement.
  • If the reading surpasses your chosen range, switch to a different range before taking another reading.

Current Measurement:

  • Adjust the multimeter’s rotary dial to the current (A) mode.
  • Introduce a break in the circuit and establish a series connection between the circuit and the multimeter.
  • Connect the black probe to the negative side while the red probe is to be linked to the positive side.
  • Observe the multimeter’s screen for the displayed measurement results.

Resistance Measurement:

  • Deactivate the power source to the circuit or component for which resistance measurement is intended.
  • Configure the multimeter to the resistance (Ω) mode.
  • Attach the black probe to the COM port and the red probe to the component’s leads designated for measurement.
  • When measuring resistance within a circuit, ensure no power source remains connected to prevent inaccurate readings.
  • The resistance value will be shown on the screen of the multimeter.
Measuring the Voltage of Live Wires with Multimeter

Measuring the Voltage of Live Wires with Multimeter

If you want to measure the voltage of a live wire, here are a few steps that you can follow:

Step 1: Set up the Multimeter:

We know that the multimeter is designed to work with different parameters. That is why you will need to set up your multimeter for the voltage measurement. Here is how it can be done:

To measure the AC voltage, you will use the section marked with V and a wavy line that indicates the AC waveform.

To measure DC voltage, you will use the section marked with V and a straight line indicating DC waveform.

Once you have selected your parameter, you will insert the probes into their respective ports, as we have discussed in the earlier sections.

Step 2: Test the Wires

Once the multimeter is set, you can test the live wire using the following methods:

Method 1: Connect the red probe with the live wire and the black probe with the neutral wire and take the reading.

Method 2: Connect the red probe with the live wire and the black probe with the earth wire and take the reading.

If you are getting a negative reading, it may be because you have reversed the positions of red and black probes. Verify that they are in the correct positions, and then take the reading again.

Step 3: Get the Results

After connecting the probes to the wires, the multimeter will show the results on its LCD. There are two possible outcomes that you can expect, which are:

  • If the reading is 220 or 230 volts, it means the wire is live, and the current is flowing through it.
  • If the reading is zero, it means the wire is not live, and there is no current flowing through the wire.

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