How a Voltmeter Works

A voltmeter is an instrument that is used to check and measure the amount of voltage that is passing between two points in an electric current. It measures the amount of positive electrical charge as it enters one point within an electric circuit and then measures the negative input as it passes through another point.

How a voltmeter works
A voltmeter in simple terms comprises of a red positive terminal, as well as a black negative terminal and a display. Most types of multimeter include a voltmeter function.

A good case example to demonstrate how it is used is when trying to determine the amount of voltage left in a battery. Two wires are used; one wire is connected from the positive terminal of the voltmeter, to the positive end of the battery. The other wire is connected from the negative terminal on the voltmeter to the negative point on the battery.

It is important to note that mixing up the positive and negative connections, for instance connecting the positive terminal to the negative end of the battery can severely damage the voltmeter, particularly so if it is a needle point voltmeter.

Types of Voltmeters
A needle point voltmeter as the name suggests simply points out the number representing the voltage amount, just the way a watch with a minute hand pointing out the number of minutes into the hour. The disadvantage associated with this type of voltmeter is that at times the voltage being measured may be too weak to be able to push the needle to the correct reading, and ends up giving too low a voltage value.

The digital voltmeter therefore will indicate the voltage amount in a manner similar to the digits displayed by a calculator. These voltmeters are usually calibrated to display higher accuracy readings than their counterparts.

Handling Voltmeters
Voltmeters, and multitesters generally, tend to be fragile instruments that can be damaged by thoughtless actions like using a voltmeter made to measure small amounts of current to measure a large voltage. However, another unwise move is to use a voltmeter intended for measuring large voltages to measure small amounts of voltage. In this scenario, although the voltmeter will not get damaged the readings one will get will not be accurate. Both extremes should be avoided.

Another precaution to take is to first determine whether the voltage being measure is either a direct current, that flows in one direction, or is an alternating current, that flows back and forth. Different voltmeters are made to handle these different electric charges. Even in cases where, a single is capable of measuring both kinds of voltages, it must first be prepared as to whichever current it is to measure without which the voltmeter will be damaged to display faulty voltage readings.

One final caution is that while using a voltmeter, one should take care not to touch any of the terminals with their bare fingers as this will most likely result in being electrocuted, at times even to death. As much as possible, measuring of a voltage should be a hands free maneuver with the aid of alligator clips.

Kyle Richards is a multimeter specialist and DIY enthusiast. Read onto the next page to find out more about multimeters.