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How Do I Use a Voltmeter?

Voltmeters are used to measure the voltage traveling between two points within a circuit.
Analog voltmeters are typically easy to read.
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  • Written By: Jeremy Laukkonen
  • Edited By: Allegra J. Lingo
  • Last Modified Date: 16 August 2014
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Using a voltmeter can be a relatively simple task if you know a few things about them. The two main types of voltmeters are analog and digital, and the latter is often referred to as a digital volt meter (DVM). Some voltmeters are dedicated units that only measure voltage, while others are just one part of devices that measure amperage, resistance, and other things. If a digital voltmeter can measure a number of things, it is often referred to as a digital multimeter (DMM). The most important thing to remember about using a voltmeter is to set it to the correct scale, and failing to do so may result in a blown fuse or damaged device.

Analog voltmeters may appear complex, though they are typically easy to read once you understand how they work. Many analog voltmeters have several arcs drawn on the meter face and a needle that can rotate from one side of the arc to the other. Numbers will usually be printed along the arcs, allowing you to read the voltage. The scale you select will determine which arc you use.

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The scales on an analog voltmeter will usually be numbered according to the largest voltage they can measure. This means that the safest course of action is to choose a scale number that is larger than the voltage you expect. If you select too large a scale, the needle may not move or might move so little that you can not read it. In that case, you can always select a slightly lower scale without fear of damaging the meter.

Digital voltmeters often use scales as well, and other units may have an autoranging function. If it is possible to set a scale, choosing the correct one involves the same type of guesswork regarding the largest possible voltage, the same process as with an analog meter. Once it has been set up, the digital meter will allow you to read out a decimal voltage number, which can be easier than finding the right arc and counting the hash marks on an analog meter.

Voltage can be measured in parallel, so you can typically use a voltmeter without breaking the circuit you are testing. Measuring a voltage is typically as simple as touching the negative probe to the negative side of a circuit and the positive probe to the positive side. This is different from using an ammeter, since amperage must be measured in series.

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kentuckycat
Post 4

When I was in a physics class in college we had to make a small electricity experiment. My partner and I ended up using a car battery to power a few light bulbs and other small gadgets.

I believe most car batteries are 12 volts (at least ours was). Part of the project was using a voltmeter to see whether the reading on the battery changed with the number of things that we were powering with the battery. Given that most of the things didn't use much electricity, we never really saw a difference, but it was a fun project nonetheless.

cardsfan27
Post 3

@stl156 - Like jcraig said, most people would not need a voltmeter. If you did want to buy one, though, you can almost always find them at an electronics store or department. I would assume home improvement stores would have them as well.

After reading the article, I'm wondering what it means to be able to measure the circuit in parallel. Just thinking of a light bulb as an example, if you touched one probe the positive side and one to the negative, wouldn't the circuit have to travel through the voltmeter, thereby shutting off the light? Could someone explain why this doesn't happen?

jcraig
Post 2

@stl156 - I would say that having a voltmeter would be a novelty for the average homeowner.

I do a lot of home improvement projects, so I have a voltmeter that allows me to check and make sure that the power is turned off to electrical outlets or other devices before I start tinkering with them. Although it's probably not worth the price of buying a voltmeter, you can also use the device to test the charge in batteries. Like I said, for most people, a voltmeter would be a novelty item.

One final person I could imagine needing one is someone who works on cars so that they could check the electronic components of the wiring systems. Maybe there are other people who use them that I'm not thinking of.

stl156
Post 1

Is there any reason that a normal homeowner would need to have a voltmeter handy? Obviously someone like an electrician would have to have one, but are there any common uses for them around the home?

Also, where would you buy one of these? Are they common enough that you would be able to find one at Wal-Mart or a home improvement store?

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