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Difference between Ammeter and Galvanometer
Ammeter and galvanometer are both measuring instruments used to measure the current flowing through a circuit. The most significant difference between a galvanometer and an ammeter is that the ammeter measures only the magnitude of the current flowing in the circuit, while the galvanometer shows both magnitude and direction of the current in the circuit.
Go through this article to know more about ammeter and galvanometer and the key differences between these two measuring instruments.
What is a Galvanometer?
A galvanometer is an electromechanical measuring device used to measure the strength of current and direction in an electric circuit. A typical galvanometer consists of a moving coil, permanent magnet, iron core, non-magnetic frame, suspension wire and a spring.
The coil is placed between the two poles of the permanent magnet. When the electric current flows through the coil it produces a magnetic field around the coil which interacts with the magnetic field of the permanent magnet. Due to the interaction of two magnetic fields, a force is exerted on the coil and hence the coil starts moving.
A pointer is attached with the moving coil whose deflection shows the magnitude and direction of the current. In case of a galvanometer, the deflection of the pointer is directly proportional to strength of current flowing through the circuit.
A galvanometer can only be used to measure direct current (DC). The galvanometer is extensively used in bridges and potentiometer to detect the zero current.
What is an Ammeter?
An Ammeter, also called ampere meter, is a measuring instrument used to measure the strength (or magnitude) of the electric current flowing in a circuit. An ammeter can be used to measure both direct current (DC) and alternating current (AC).
An ammeter only measures the magnitude of current and not the direction. The accuracy of an ammeter is relatively higher than a galvanometer. The ammeter could be of an electromechanical or electronic (digital ammeter) device. For an ideal ammeter, the internal resistance must be zero.
Based on the construction and principle of operation, the ammeters are classified into following types −
- Permanent magnet moving coil (PMMC) ammeter
- Moving coil ammeter
- Electrodynamometer ammeter
- Rectifier ammeter
Note − A galvanometer can be converted into an ammeter by connecting a shunt resistance (small resistance value) in parallel with it.
Difference between Galvanometer and Ammeter
The following table highlights the major differences between ammeter and galvanometer −
| Parameter | Ammeter | Galvanometer |
|---|---|---|
| Definition | An ammeter (or ampere-meter) is a measuring device used to measure strength of electric current flowing in a circuit. | A galvanometer is an electromechanical measuring instrument used to detect strength and direction of the electric current in a circuit. |
| Symbol |  |  |
| Measuring quantities | An ammeter can measure only the magnitude of electric current. | A galvanometer can show the magnitude as well as direction of the current in the circuit. |
| Zero position | In ammeter, the zero position is marked on the left of the scale. | The zero position is marked on the center of the scale. |
| Device type | An ammeter could be of an electromechanical device (analog ammeter) or electronic device (digital ammeter). | A galvanometer is an electromechanical device. |
| Type of current measured | Ammeter can measure both direct current (DC) and alternating current (AC). | A galvanometer can measure only the direct current (DC). |
| Presence of magnetic field | An ammeter can work with or without the presence of magnetic field. | The presence of magnetic field is required for working of the galvanometer. |
| Accuracy | The accuracy of an ammeter is more than that of a galvanometer. | Galvanometer is less accurate. |
| Sensitivity | An ammeter is relatively less sensitive device. | The sensitivity of a galvanometer is comparatively more than that of an ammeter. |
| Substitution | An ammeter cannot be used as a galvanometer. | A galvanometer can be used as an ammeter by connected a small resistance (shunt resistance) in parallel with it. |
| Used as a voltmeter | An ammeter cannot be used as a voltmeter. | By connecting a resistance of high value in series with the galvanometer, it can be used as a voltmeter. |
| Applications | Ammeter is mainly used to measure magnitude of electric current in a circuit. | Galvanometer is mainly used in bridge circuits and potentiometer for the detection of zero current. |
Conclusion
From the above discussion, it can be concluded that both ammeter and galvanometer are measuring devices used for current measurement in the electric circuits. Both are connected in series with a circuit. The most important difference that you should note here is that an ammeter shows only the magnitude of current while a galvanometer shows the magnitude along with the direction of the current.
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