Rectifier Ammeter

The meter is generally used for measuring the particular quantity. The unit of current is ampere, and the meter which measures the current is known as the ammeter. The rectifier ammeter uses the moving coil along with the rectifier for measuring the current. The main use of the rectifier is to convert the alternating current into the direct current.

The rectifier ammeter consists the four rectifier elements which arrange in the form of the bridge along with the moving coil ammeter. The circuit diagram of the bridge rectifier elements is shown in the figure below.

rectifier-ammeter-working

In DC moving coil instrument the shunt is used for protecting the moving instrument from the heavy current. But in case of rectifier ammeter, the use of the shunt is not possible because the current passing through the moving coil instrument varies continuously because of the rectifier resistance.

Advantages of the Rectifier Ammeter

The advantages of the rectifier ammeter are explained below in details.

  1. The frequency range of the instrument can easily be extended from 20Hz to high audio frequency.
  2. The instrument requires very low operating current.
  3. It has the uniform scale.
  4. The accuracy of the instrument lies between ±5% under normal operating condition.

Factors Affecting the Performance of the Rectifier Ammeter

The following are the factors which affect the performance of the rectifier ammeter.

  1. The waveform of the current and voltage affects the working of the rectifier instrument.
  2. The element of the rectifier has some resistance which affects the performance of the instrument.
  3. The variable temperature also affects the working of the instrument.
  4. The rectifier has some capacitance and this capacitance effects the operation of the instrument.
  5. The instrument has low sensitivity for ac as compared to dc.

The small size transformer is used in the instrument because of the low burden.

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