Circuits, Formulas and Tables Electrical Engineering  Basic vocational knowledge (Institut für Berufliche Entwicklung, 201 p.) 
7. Measurement Circuits 

Voltage measurement (A)
Voltage measurement (B)
By connecting in series of a resistor (Rv), an extension of the measuring range of the voltmeter is obtained
Current measurement (A)
Current measurement (B)
By connecting in parallel a shunt resistor (Rp), an extension of the measuring range of the ammeter is obtained.
Voltage and current measurement for
the determination of the resistance
The currentexact connection is used when the resistance (Rx) to be determined, is very high.
Current and voltage measurement for
the determination of the resistance
The voltageexact connection is used when the resistance (Rx) to be determined is very small if the resistance Rx is calculated according to the following equation:
_{}
Voltage measurement (low voltage)
Voltage measurement (highvoltage 
voltmeter with voltage transformer)
Current measurement
Current measurement (amperemeter
with current transformer)
Power measurement (low voltage)
Power measurement (high voltage)
electric meter connections
electric meter
connections
Voltage measurement
2 voltage transformers in
Vconnection
Current measurement
Current measurement
Power measurement
Single wattmeter method
use:
equal phase loading, accessible PENconductor
result:
total power = 3 × measuring result
Power measurement
Twowattmeter method
use:
unequal phase loading, nonaccessible PENconductor;
measuring instruments of the same type have to be used
result:
total power = P_{1} + P_{2},
when P_{1} > P_{2}, the total power = P_{1}  P_{2}
Power measurement
Twowattmeter method
2 movements combined into one instrument
Power measurement
Threewattmeter method
use: unequal phase loading, accessible PENconductor
result: total power = P_{1} + P_{2} + P_{3}
Power measurement
Three  wattmeter method
3 movements combined into one instrument
Meter circuit (threewire meter)
Meter circuit (fourwire meter)
Measurement of the power factor (cos
j)
Measurement of the frequency (single
frequency meter)
Measurement of the frequency (double
frequency meter)
Measurements in a Highvoltage Power
Plant