Alat Ukur Kumparan Putar

Alat Ukur Kumparan Putar Sebagai Amperemeter :

R_m = internal resistance of coil

R_sh = resistance of the shunt

I_m = I_fs = full scale deflection of movement

I_sh = shunt current

I = current to be measured

Koreksi efek kenaikan temperatur :

Alat Ukur Kumparan Putar Sebagai Voltmeter :

R_m = internal resistance of coilR_s = multiplier resistance

I_m = I_fs = full scale deflection of movement

v = voltage across the meter movement for current I_m

V = full range voltage instrument

 MULTIRANGE VOLTMETER

MULTIRANGE AMMETER

SERIES TYPE OHMMETER

 SHUNT TYPE OHMMETER

 The main advantages of  PMMC instruments are :

-     The scale is uniformly divided

-     The power consumption is very low (25 mW to 200 mW)

-    The torque-weight ratio is high which give a high accuracy. The accuracy is of the order of generally 2 percent of full scale deflection.

-     A single instrument may be used for many different current and voltage ranges.

-     Since the operating forces are large on account of large flux densities which may be as high as 0,5 Wb/m² the errors due to stray magnetic fields are small.

The disadvantage is :-     The cost of these instruments is higher than that of moving iron instruments