What is a voltage meter?

voltage meter

A voltage meter (or voltmeter, its more common name) is a device that measures the electrical potential difference, or voltage, between two points in an electrical circuit. A common use of a voltmeter is to determine whether a battery has any electricity left.

Both analogue and digital voltmeters exist, so the full range at RS, with digital varieties becoming increasingly popular in recent years.

If you’re looking to learn more about these devices, their history, and how they work, just keep reading!

A brief history of voltage meters

Danish chemist and physicist Hans Christian Oersted discovered the relationship between magnetism and electricity, or electromagnetism—the principle by which voltmeters and similar measurement instruments function—in 1820.

Businessman and innovator Andrew F. Kay invented the first digital voltmeter in 1954, which displayed numeric values via a series of lights. He based his invention on the idea that analogue voltmeters were not accurate enough.

Voltage meter applications

Voltage meters have two main applications:

  • Testing and troubleshooting electrical circuits,
  • Measuring voltage within electrical and electronic devices.

Using a voltage meter, you can measure voltage at various points along a circuit. This process can help identify problems such as short circuits, open circuits, or other issues that may cause a circuit to malfunction.

Panel-mounted voltmeters, which sit at a fixed position on a surface, are usually used to monitor appliances such as generators. The devices can immediately alert electrical professionals to any faults so they can be solved quickly.

You might also use a voltmeter to determine the input and output voltage of:

  • Batteries
  • Motors
  • Medical equipment
  • Machinery
  • Panelboards

How does a voltage meter work?

Voltage meters work by measuring the difference between positive and negative voltage input. Essentially, they’re a sort of ammeter, calculating voltage by assessing electrical current and following Ohm’s law.

A typical voltmeter has three main components: a positive input terminal (which is normally red), a negative input terminal (which is normally black), and a display (which can be analogue or digital).

To use a voltmeter, you’ll need to:

  • Attach the positive lead to the circuit’s positive end,
  • Attach the negative lead to the circuit’s negative end,
  • Check the reading on the display.

Modern voltmeters can measure both alternating current (AC) and direct current (DC).

Safety considerations when using voltage meters

Safety is a critical consideration when working with or around any electrical equipment. Whether you’re using a digital or analogue meter, always take the following precautions:

  • Take care not to drop the meter,
  • Avoid overloading the meter,
  • Do not attempt to repair the instrument without appropriate training and equipment,
  • Check circuit connections carefully before applying power to a meter,
  • Do not touch any electronic components inside the equipment,
  • Avoid touching the probe tips to each other while they are connected to anything else,
  • Never change settings (i.e., voltage to current) while the probes are connected to a circuit.

A quick summary

To summarise, voltage meters are handy electrical testing devices designed for determining voltage levels between two points in a circuit. Make sure to follow the precautions outlined above to ensure safety when working with this equipment.


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