Difference Between Ammeter and Voltmeter

Electricity, just like any other physical characteristic, can be quantified; although it is a bit more difficult. The two main characteristics of electricity are voltage and current and to measure them both, we have the voltmeter and ammeter. The voltmeter measure the voltage between two points while the ammeter measure the current through it.

To use an ammeter, you need to connect it in series to the component whose current you want to measure so that the same current that flows through the component would also flow through the ammeter. With the voltmeter, you only need to connect it in parallel to the two points you want to measure with the black lead as the reference. Because of the way they are connected, the ammeter needs to have a very low resistance while the voltmeter needs to have a very high resistance. If the internal resistance of the ammeter is high, it can restrict the flow further and result in a lower reading. The reverse is true with the voltmeter; a lower resistance can allow some of the current to flow through the voltmeter, thereby reducing the voltage reading.

With voltmeter, you can apply power to a circuit then measure voltages at different locations without removing the power source. A problem with ammeters is that you need to disconnect the circuit for a while to be able to insert the ammeter and get a reading. Although this might not be such a major problem for hobbyists, in applications where disconnecting components is not possible, an alternative type of ammeter is available; the contactless ammeter.

Contactless ammeters, or more commonly known as clamp meters, do not need to have the current flow through it to have a measurement. They rely on the Hall Effect to read the electric field that is produced by the current flowing through the wire. This electric field is proportional to the amount of current that produced it and a relationship can be established without having to disconnect any connection. Because it does not require the ammeter to be inserted into the circuit, it is also protected against surges that can damage the circuitry of the ammeter. There are no contactless voltmeters.

Summary:

1. An ammeter measures current while a voltmeter measure voltage
2. An ammeter is to be connected in series while a voltmeter is connected in parallel
3. An ammeter needs to approximate a short-circuit while a voltmeter needs to approximate an open circuit
4. Contactless ammeters are available while