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3.3 D’Arsonval Meter Movement with Full-wave Rectifier :
It is desirable to used a full-wave rather than a half-wave rectifier in ac voltmeter because of the higher sensitivity rating.
A.C TO D.C DIVERSION
INPUT
FULL-WAVE RECTIFIER
OUTPUT
Related E.Q.N
Bridge-type rectifier is most frequently used for full-wave rectification.
D2 and D3 conduct in positive half cycle while D1 and D4 conduct in negative half cycle.
D1 and D3 cannot be conduct on the same time. Similarly D2 and D4 cannot conduct simultaneously.
When full wave rectification is used, the pointer will deflect to 90% of full scale.
i.e => 10Vrms voltage is equivalent to 9Vdc
This means an ac voltmeter using full-wave rectificationhas sensitivity equal to 90% of the dc sensitivity or it twice the sensitivity of half wave rectification.
The multiplier resistor would be 90% of the value of the multiplier resistor for a 10Vdc voltmeter.
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