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Figure 81. External Voltmeter Measurement Error on CC Power Supply
CC Source Effect (Line Regulation)
Definition: The change ∆I
OUT
in the steady state value of dc output current due to a change in ac input voltage
over the specified range from low line (e. g., 104 volts) to high line (e. q., 127 volts), or from high line to low
line.
Measurement is accomplished by turning the variable autotransformer of Figure 79 through the specified input
voltage range and noting the change in the reading on a digital voltmeter or differential voltmeter connected
across the current monitoring resistor; this change, when divided by the value of the current monitoring resistor,
yields the change in output current. The power supply will perform within its source effect specification at any
rated output current combined with any rated output voltage.
CC Load Effect (Load Regulation)
Definition: The change ∆I
OUT
in the steady state value of dc output current due to a change in load resistance
from short circuit to a value which yields maximum rated output voltage.
Load effect is measured by closing or opening the switch in Figure 79 and noting the resulting static change on
the digital voltmeter or differential voltmeter connected across the current monitoring resistor. The power
supply will perform within its load effect specifications at any rated output current combined with any rated
line voltage.
CC PARD (Ripple and Noise)
Definition: The residual ac current which is superimposed on the dc output current of a regulated supply.
PARD may be specified and measured in terms of its rms or (preferably) peak-to-peak value.
The peak-to-peak voltage measured on the oscilloscope across RM is divided by RM to obtain the peak-to-peak
ripple current. For the rms value, a true rms voltmeter reading is taken across RM after first utilizing the
oscilloscope to insure that the input waveform to the rms voltmeter has a 2f
L
(f
L
= ac input line frequency)
fundamental component and is free of extraneous signals not coming from the power supply output.