9
C’. Alternating-voltage measurements
The alternating-voltage ranges are mainly used for measuring the L.F.
output voltage of some apparatus, or for examining the voltages of the
mains transformer, etc.
D'. A.C. Measurements
It is sometimes desired to measure the current consumption of some
apparatus. To do this, incorporate the meter in one of the leads of the mains-
voltage circuit. The power consumption in watts is then found by
multiplying the measured current by the voltage, provided that the apparatus
presents an ohmic resistance.
Where transformers are concerned, there is always a self-inductance, so that
the number of VA has to be multiplied by the power factor (cosφ), which as
a rule amounts to 0.80 - 0.85 for radio receivers.
METER CIRCUITS FOR THE VARIOUS
MEASURING RANGES
In the diagrams on pages 10 and 11 the circuit diagram of the meter is
always completely shown; the fat-printed lines represent the circuit
operative for the measuring range in question.
