HP 6038A - 3-18 INITIAL SETUP AND INTERCONNECTIONS; 3-19 CONNECTING THE LOAD

the sensing Jumpers are tightened securely. Check that the rear-
panel label indicates that the unit is set for the line voltage to
be used. There should be no cables connected to the rear panel
HP-IB connector. Check that the recessed OVP ADJUST con¬
trol on the front panel is fully clockwise. The HP-IB address
switches may be set to any address from 0 to 30 for this
procedure.
a. Press top of LINE rocker switch to turn unit on. Fan
should operate. Check that display shows HP-IB address
set by rear-panel switches. After address display, CUR¬
RENT indicator should remain on and either CV or CC
indicator should remain on. (SRQ indicator will remain
on if rear-panel PON SRQ switch has been set to 1.)
b. Press momentary-contact DISPLAY SETTINGS pushbut¬
ton switch and check that VOLTS display indicates 0.00
and AMPS display indicates 0.00.
c. Press momentary-contact DISPLAY OVP pushbutton
switch and check that VOLTS display indicates 65 ± 2 V.
d. Turn OUTPUT ADJUST knob clockwise, press DISPLAY
SETTINGS switch, and check that AMPS setting has in¬
creased. CV indicator should be on and CC indicator
should be off.
e. Press momentary-contact OUTPUT ADJUST pushbut¬
ton switch once; VOLTAGE indicator should turn on and
CURRENT indicator should turn off.
f. Turn OUTPUT ADJUST knob clockwise and check that
output voltage increases from zero to full output voltage
as indicated on VOLTS display. Continued clockwise rota¬
tion may cause VOLTS display to iridicate -+- OL, and ER¬
ROR indicator will light (turns off one second after
clockwise rotation stops).
g. Check overvoltage protection circuit by turning OVP AD¬
JUST control counterclockwise until OVP circuit trips.
Output should drop to 0 V, CV indicator turns off, and
DISABLED and OV indicators turn on (SRQ and
VOLTAGE indicators remain on).
h. Reset OVP circuit by turning OVP ADJUST control fully
clockwise and turning unit off and back on. Output
voltage should come on at 0 volts.
I. To check constant current circuit, turn power supply off
and connect a wire (AWGi?16, 1 mm^ or larger) across
-i- and -terminals on rear panel.
J. Turn power supply on and press OUTPUT ADJUST
switch once to turn on VOLTAGE indicator. Turn OUT¬
PUT ADJUST knob clockwise, press DISPLAY SET¬
TINGS switch, and check that VOLTS setting has in¬
creased. CC indicator should be on and CV indicator
should be off.
k. Press OUTPUT ADJUST switch once; CURRENT in¬
dicator should turn on and VOLTAGE indicator should
turn off.
l. Turn OUTPUT ADJUST knob clockwise and check that
output current increases from zero to full output current
as indicated on AMPS display. Continued clockwise rota¬
tion may cause AMPS display to indicate -f OL, and ER¬
ROR indicator light (turns off one second after clockwise
rotation stops).
m. Turn off power supply, remove short from output, and
read following instructions before connecting load to
supply.
3-18 INITIAL SETUP AND
Turn off input ac power before changing any rear-
pane! connection and make certain all wires and
straps are property connected and terminal block
screws are securely tightened before reapplying
power. Be certain to replace both terminal block
cover before reapplying power.
3-19 Connecting the Load
3-20 Load connections to the power supply are made at
the -f-and -terminals on the rear panel. Two factors must be
considered when selecting wire size for load connections, con¬
ductor temperature and voltage drop.
3-21 To satisfy safety requirements, the wires to the load
should be at least heavy enough not to overheat while carry¬
ing the power supply output current that would flow if the load
were shorted. Stranded AWG#16 copper wire 1 mm^ cross-
section area) is rated for 13.5 amps at 105°C conductor
temperature. (The maximum allowable conductor temperature
is based on +60°C ambient temperature plus 45°C temperature
rise because of continuous dc current). This rating is based on
use of a twisted pair to connect the load to the supply. If the
wire insulation is rated for less than 105°C or if the wires are
located such that heat build up is a factor, larger wire sizes must
be used. The minimum load wire size is AWG #16 (Imm^).
3-22 The wires must be property terminated with connec¬
tors securely attached. Do not connect unterminated wires to
the power supply.
3-23 The minimum wire size required to prevent overheating
will not usually be large enough to provide a good voltage
regulation at the load. For proper regulation the load wires
should be large enough to limit the voltage drop to no more
than 0,5 volts per lead. Table 3-2 lists resistivity for various wire
sizes and the maximum lengths that may be used to limit voltage
drop to 0.5 volts for various currents. Lengths are given in
metres and (feet).
3-24 To determine maximum lengths (in metres or feet) for
currents not listed, use the formula:
maximum length = _^22_
current x resistivity
where current is expressed in amps and resistivity is expressed
in ohms/kilometer or ohms/ICKK) feet. If load regulation is
critical, use remote voltage sensing (paragraph 3-40).
3-5