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5- 14
To avoid mutual coupling effects, connect each
monitoring device to the sensing terminals by a separate pair
of leads. Use twisted pairs or shielded two-wire cables to
avoid pickup on the measuring leads. Connect the load
resistor across the output terminals as close to the supply as
possible. When measuring the constant-voltage performance
specifications the current control should be set at least 2%
above the output current the load will draw, since the onset
of constant-current operation could cause a drop in output
voltage, increased ripple and other performance changes not
properly ascribed to the constant-voltage operation of the
supply.
6- 15
Rated Voltage and Voltmeter Accuracy. To
check that the supply will furnish its rated output voltage, pro¬
ceed as follows:
a.
Connect test setup shown in Figure 5-2. Set Ri_ to
maximum resistance initially.
b.
Turn on supply and turn up output voltage. If unit
switches to CC LIMIT mode, use OUTPUT ADJUST
controls to increase CC limit so that unit remains in
CV mode.
c.
Adjust output voltage until digital voltmeter (DVM)
indicates exactly 60 V (maximum rated output
voltage).
d.
Front-panel voltmeter should indicate 60.0.
e.
Disconnect DVM from power supply sense terminals
and connect DVM across current monitoring resistor
<Rm>-
f.
Reduce resistance of R[_ until DVM reads 33 mV, in¬
dicating that current output is exactly 3.3 A (max¬
imum rated power output). Ensure that power supply
remains in CV mode.
g.
Disconnect DVM from Rjyj and reconnect DVM to
power supply sense terminals,
h.
DVM and front-panel voltmeter should both indicate
60 V.
5-16
Load Effect (Load Regulation).
Definition: The change in the static value of dc output
voltage (AEoUT^ resulting from a change in load resistance
from open circuit to a value which yields maximum rated out¬
put current, or from the latter value to open circuit.
5-17
To check the constant voltage load effect, proceed
as follows:
a.
Connect test setup shown in Figure 5-2,
b.
Turn on supply and turn up output voltage. If unit
switches to CC LIMIT mode, use OUTPUT ADJUST
controls to increase CC limit so that unit remains in
CV mode.
c.
Adjust output voltage until DVM indicates 20 V.
d.
Disconnect DVM from power supply sense terminals
and connect DVM across Rm-
e.
Adjust resistance of Rj_ until DVM reads 0.1 V, in¬
dicating that current output is exactly 10 A (max¬
imum rated output current). Ensure that power
supply remains in constant-voltage mode.
f.
Disconnect DVM from Rpyi and reconnect DVM to
power supply sense terminals.
g.
Open switch SI to disconnect load
h
Record voltage indicated on DVM.
i.
Close switch SI to reconnect load.
j.
Wait a few seconds only to allow DVM to settle.
Reading on DVM should not differ from reading of
step h by more than 5 mV.
5-18
Source Effect (Line Regulation).
Definition: The change in the static value of dc output
voltage ( AEoyy) resulting from a change in ac input voltage
over the specified range from low line to high line, or from
high line to low line.
5-19
To check the source effect, proceed as follows:
a.
Connect
test
setup
shown
in
Figure
5-2.
POWER SUPPLY
DIGITAL VOLTMETER
Figure 5-2. Constant-Voltage Test Setup
5-3
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