PMMCDC METERS

MOVING IRONDYNAMOMETER

Shunt-Type Ohmmeter

When Rx = 0, no current in meter.When Rx = ∞, entire current flows through the meter.Proper selection of R1 gives full-scale deflection on open circuit.

DYNAMOMETER TYPE INSTRUMENTSFor both ac & dc measurements

• These instruments are similar to the permanentmagnet type instruments, except that the permanentmagnet is replaced by a fixed coil.

• The coil is divided into two halves, connected inseries with the moving coil.

• The two halves of the coil are placed close togetherand parallel to each other to provide uniform fieldwithin the range of the movement of moving coil.

DYNAMOMETER TYPE INSTRUMENTS

04‐03‐09 Nkp/eee skcet

Electrodynamometer Type

DYNAMOMETER TYPE‐Ammeter & Voltmeter

MOVING‐IRON INSTRUMENTSFor both ac & dc measurements

• Attraction (or Single‐iron) Type Moving‐Iron Instrument

Repulsion (or Double‐Iron) Type Moving‐Iron Instrument