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AC (alternating current) is an electrical current whose magnitude and direction vary sinusoidal with time.
Current, I
Reverses at regular time intervals
Has alternately positive and negative values (e.g. V+, V-)
Sinusoidal waveform (sine wave)
Fundamental of AC current and AC voltage waveform
RMS value
Effective value of varying voltage or current
RMS value = constant DC value
Average Voltage/Average Current
Vavg = 0 because positive and negative cancels out each other
AC Voltmeters/AC Ammeters
Show RMS value of voltage/current
DC Meters
Show RMS value when connected to vary DC source
AC METER
AC METER PRINCIPLES OF METER MOVEMENT
E L E C T R O D Y N A M O M E T E R
A P P L I C A T I O N
Standard meter
Transfer instrument
Wattmeter
Frequency meter
Video on Electrodynamometer
I R O N - V A N E
A P P L I C A T I O N
Indicator application such as in automobiles
Video on Iron-Vane
E L E C T R O S T A T I C
A P P L I C A T I O N
Measurement of high voltage when very little current can be supplied by the circuit being measured
Video on Electrostatic
T H E R M O C O U P L E
A P P L I C A T I O N
Measurement of radio-frequency as signals
Video on Thermocouple
D' A R S O N V A L
(PERMANENT MAGNET MOVING COIL)
A P P L I C A T I O N
Meter movement for measuring direct current or voltage and resistance
Rectification of alternating current
Using of one or more diodes to convert alternating current to direct current
This method is used as PMMC instruments have sensitivity than electrodynamometer or moving non-instruments
Video on D'Arsonval (PMMC)
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