Rectifier Ammeter

1. Roll No: 17ES08

2.  Definition
 Working Mechanism
 Types (Half and Full wave)
 Efficiency Calculation
 Advantages and Disadvantages
 Applications

3. Rectifier Ammeter: The Instrument which uses
the rectifying element for measuring the voltage or
current is known as the rectifying instruments.
 This type of Ammeter uses the rectifier circuit and
the PMMC(Permanent Magnetic Moving Coil) as an
indicating instrument.
 The Sensitivity of the rectifying instrument is high
as compared to the moving coil and
Electrodynometer instrument. Which make it
reliable for use in measuring the current and
voltage.
 This Type of Ammeter can measure AC as well as
DC current because of the use of Rectifying
Elements.

6. Working Principle: The Rectifier Type uses; Bridge
Circuit, Multiplier Resistor (Rs) and
PMMC(Permanent Magnetic Moving Coil), to
measure the amount of current fed in its output.
 The Rectifying type Ammeter uses the Bridge
Rectified circuit to convert AC to DC which uses
the diodes in bridge combination.
 Because diodes can conduct well in the forward
bias condition and don’t allow the conduction in
Reverse Bias condition. This property of diode can
be implemented to convert AC waveform to DC
output.
 The Multiplier Resistor (Rs) is used to control
amount of Current of Voltage.
 PMMC is used to deflect the needle to fixed
position for reading.

8. Types of Rectifier Ammeter: The Rectifier ammeter
has two types depending on the type of Rectification.
 These are:
 Half Wave Rectifier Ammeter,
 Full Wave Rectifier Ammeter.
Half Wave Rectifier Ammeter: This type of Rectifier uses
one diode in its construction to measure the current at input.
 As single diode provides half wave rectification and cuts the
other half.
 This half wave rectified output can be fed to PMMC to move
the needle in a particular position depending on the amount
of current.
 The efficiency of this type of Rectifier Ammeter is less as
compared to the full wave, which is 45%.

11. Full Wave Rectifier Ammeter:
This type of Rectifier Ammeter uses Full Wave
Bridge Rectifier to measure input Current.
 In this Circuit the Bridge Rectifier conducts for
whole AC signal cycle, and gives the full
rectification i.e +ve and –ve both cycles are
utilized.
 This Full wave rectified output then fed to the
PMMC to get the Reading of Desired range.
 This type of Rectifier Ammeter has the efficiency of
90%, i.e double the efficiency of Half Wave Rectifier
Ammeter.

14.  Effects of Waveform: As the Rectifier output depends
upon input Waveform, the signal should be calibrated in a
proper manner or otherwise a error occurs in the reading.
 Effect of Temperature Change: As the
Resistance of Rectifying elements depends on the
temperature. This can also cause the output reading error.
 Effect of Rectifying Instrument: As the Rectifier
instruments have the property of imperfect capacitance.
Which allows the high-frequency current to pass through it.
 Decrement in Sensitivity: The Sensitivity of the
rectifier type instrument for AC operation is lower than the
DC operation.

15.  The frequency range of the instrument increases
from 20HZ to high-frequency range.
 The current operating range for such type of
instrument is much lower for voltmeter as
compared to the other AC instrument.
 The instrument has uniform scales for the large
range.
 The Accuracy of instrument is +-5 percent when it
is in normal operating condition.

16.  The Instrument Uses for measuring the
voltage whose range lies between 50-250 V.
 It use as a milli-ammeter or micro-ammeter.
 The rectifying instrument use in the
communication circuit for measurement.

17. Thank You