Significant Differences Between Voltmeters and Ammeters

In a laboratory, there are two electronic instruments which are most frequently used. They are the voltmeter and the ammeter. Both the instruments are basically galvanometers used to measure current. Though at many times both the instruments are considered to be one and the same, there are differences in their functionality, their structure and connection. Let us check these significant differences between voltmeters and ammeters below:

Difference Between Voltmeter and Ammeter

Functionality Difference between Voltmeter and Ammeter: The basic difference between a voltmeter and ammeter is that the voltmeter is used to make an accurate measurement of potential difference, while the ammeter is used to measure current flowing between two points. Their difference lies in their functionality. Both the instruments measure two aspects of an electrical measurement: the voltage and the amperage. In modern laboratories, instead of a voltmeter and an ammeter, multimeter instruments are used.

External Circuit Difference between Voltmeter and Ammeter:The connection circuit of a voltmeter is different from an ammeter. The voltmeter is always connected in parallel while measuring the voltage across a conductor element or resistor. On the other hand, an ammeter is connected in series to measure the current flowing through a circuit element. In other words, voltmeter is connected in parallel to circuit points across which voltage needs to be measured and an ammeter is connected in series of the circuit through which the current flow needs to be measured.
Internal Circuit Difference Between Voltmeter and Ammeter: There is internal difference between the two as well. A voltmeter is produced by adding a high resistance element in series with the galvanometer coil. The high resistance addition makes the reading of the proportional to the voltage being measured. A perfect voltmeter should have infinite internal resistance so that there is no disturbance in measurement and no current is drawn. On the other hand, a perfect ammeter should have zero internal resistance so that there is no voltage drop while measuring current.

Basic Differences

A voltmeter is used to connect a high impedance on the test points, so that we get an "open circuit" between the test points. This is done so that there is no voltage drop on the tested circuit. An ammeter is used to connect a low impedance on the test points, so the we get a "short circuit" between the test points. This is done so that there is no current drop on the tested circuit.