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The instrument we use to determine the potential electric difference between two points in an electric circuit is called a voltmeter. The symbol we use to depict the voltmeter in the diagrams of electric circuits is a V enclosed in a circle and connected by two lines showing the two points of measurement.
Over the course of time, there have been introductions of various kinds of voltmeters, such as the analogue voltmeter, digital voltmeter and finally the amplified voltmeters. Till a period of time when a multimeter was introduced.
A multimeter is an instrument that is used for measuring various electrical properties such as voltage, resistance and the current in an electrical circuit. This is an integral reason why we also call multimeters volt-ohm-milliammeters. This is because the instrument of the multimeter, as the name suggests, is equipped with a voltmeter, ammeter and ohmmeter.
These days, manufacturers find it more convenient to simply place a wavy line over the V which highlights the AC voltage. However, to highlight the DC voltage, the general practice is to place a dotted line and then a solid line over it above the V. You can also switch the voltage readings to get a reading in millivolts by making a change through the dial and setting it to mV.
Analogue Voltmeter
A galvanometer with a moving coil can also be used as a voltmeter simply by using the resistor in series with the instrument. The coil wire suspended inside a galvanometer is suspended freely inside it. The communication of the magnetic field of the coil and of the still magnet creates torque. This torque tends to make the coil in itself rotate.
The metre of such capacity will be sensitive enough to record electricity in the unit of ohms per volt. If a metre with a resistance sensitivity of a thousand ohms per volt would draw 1 milliampere or mA at full-scale voltage.
Digital Voltmeter
A digital voltmeter measures an unknown amount of input voltage by converting it into a digital voltage quantity and thus representing it in the digital voltmeter scale in a numeric form. Analogue voltmeters generally move their pointers across the scale with respect to the voltage a given electric circuit possesses.
The first digital voltmeter was introduced in 1954 by Andrew Kay. The measurements they show depend on a variety of factors. These factors can range from the digital voltmeter’s temperature, power supply, input impedance and much more.
The models of digital voltmeters vary according to price. The key difference which these voltmeters demarcate is the range of voltage they are able to measure. The digital voltmeters can measure up to 10 megaohms of voltage. However, the less expensive ones can only measure up to 1 megaohms of voltage.
Amplified Voltmeter
Sometimes we need to increase the sensitivity of a voltmeter. This can be done if the current which is required to deflect the metre pointer of a voltmeter is supplied by an amplifier and power supply instead of the circuit directly under test.
An amplified voltmeter can have various benefits such as, it can be a rugged moving coil instrument. This is because a rugged coil is less sensitive but with an amplifier, we need not use a sensitive coil. The second benefit is that since the sensitivity need not be high, the input resistance can be converted into high.
Conclusion
This article covers what are the different types of voltmeters which are being used. The instrument we use to determine the potential electric difference between two points in an electric circuit is called a voltmeter. It comes in three different types which are: Analogue, Digital and Amplified.
This article also explains how we used these instruments in an electric circuit. Including the function of each instrument played and the symbols, each instrument shows its usage.
