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3-67
An HP-IB system may be connected together in any
configuration (star, linear, or combination) as long as the
following rules are followed:
1. The total number of devices is no more than 15.
2. The total length of all the cables used is no more than
two metres times the number of devices connected
together, up to an absolute maximum of 20 metres.
(The length between adjacent devices is not. critical as
long as the total accumulated cable length is no more
than the maximum allowed.)
NOTE
IEEE Std 488-1978 states that caution should be
taken if individual cable length exceeds 4 m.
3-68
It is recommended that no more than three connector
blocks be stacked together, as the resultant leverage can exert
excessive force on the mounting panels. Be certain that all
connectors are fully seated and that the lock screws are firmly
finger tightened. Do not use a screwdriver. The screwdriver
slots in the lock screws are provided for removal purposes
only.
3-69
Paragraph 3-82 provides information for operating
the 6Q34A in an HP-IB system. The Tutorial Description of the
Hewlett-Packard Interface Bus and other documents listed in
Section I provide additional information that may be helpful
when designing an HP-IB system.
Output
3-71
An amplified and buffered output signal from the
current-monitoring resistor is available between terminals A1
and A2 on the rear panel. This signal can be connected to a
remote voltmeter to indicate the amount of output current.
The signal varies from 0 to 5 volts to indicate a zero to full scale
(10A) current output. The - terminal of the voltmeter should
be connected to terminal A2. Output impedance at terminal
A1 is 10k; a load of 1 megohm will maintain 1% reading
accuracy.
3-72
Protective Circuits
3-75
The 8Q34A is configured for local operation (RMT in¬
dicator off) and constant voltage mode (CV (NORMAL) in¬
dicator on) when the unit is turned on. Output voltage is set to
zero, output current is set to 1 ampere, and the OUTPUT AD¬
JUST knob is configured to adjust output voltage (VOLTAGE
indicator is on). Pressing the OUTPUT ADJUST pushbutton
switch alternately configures the OUTPUT ADJUST knob to
adjust output voltage and output current, as indicated by the
VOLTAGE and CURRENT indicators. Note that the OUTPUT
ADJUST knob will vary whichever output parameter, voltage
or current, is indicated by the VOLTAGE and CURRENT in¬
dicators, even when the other parameter is limiting the output.
For example, assume the voltage limit is set to 50 V but the
unit is in constant current mode with a 25 V output. Rotating
the OUTPUT ADJUST knob when the VOLTAGE indicator is
on will vary the 50 V limit, even though the voltmeter will not
change until (and if) the voltage limit is adjusted below 25 V
When the 6034A is under remote control (RMT indicator on),
neither the VOLTAGE or CURRENT indicator is on and the
OUTPUT ADJUST knob has no effect.
Constant Voltage Operation
3-77
To adjust the supply for constant voltage operation:
a. With supply turned off, connect load to output terminals,
and connect a short across load,
b. Turn on supply. Press OUTPUT ADJUST pushbutton
once so that OUTPUT ADJUST knob controls current, and
adjust for the desired maximum output current. (It may be
necessary to turn up voltage setting slightly.)
c. Press OUTPUT ADJUST pushbutton once so that OUT¬
PUT ADJUST knob controls voltage, and adjust voltage to
zero.
d. Remove short from load, and rotate OUTPUT ADJUST
knob for desired output voltage.
e. If a load change causes the current limit to be exceeded,
the supply automatically crosses over to constant current
operation and the output voltage drops proportionately. In
setting the current limit, make an adequate allowance for high
current peaks that could cause unwanted mode crossover.
3-73
Protective circuits within the 6034A may limit or turn
off the output in case of abnormal conditions. The cause for
the protective action can be determined by observing the
front-panel indicators (lights and meters). An overrange con¬
dition is indicated by the UNREGULATED indicator on, the
VOLTS and AMPS meters reading relatively high, and the
MODE indicators off. An overvoltage condition is indicated by
the OVP indicator on, both meters reading near zero, and the
MODE indicators off. An over-temperature condition is in¬
dicated by the OTP indicator on, the MODE indicators off, and
both meters dropping to near zero from the readings that
existed when the overtemperature condition occurred. If the
6Q34A receives an invalid request via HP-IB (eg: syntax error
or out of range), the INVALID REQUEST indicator turns on;
the unit ignores the invalid request and remains at the
previously set value. If the primary power voltage drops below
approximately 70% of nominal, the level detector will turn off
the output. In this case, the UNREGULATED indicator is on,
the MODE indicators are off, and both meters read zero (the
supply will probably reset).
3-79
To adjust the voltage limit in constant current mode,
a load resistor is used in place of the actual load. The
resistance value of the load resistor must be chosen to permit
no more than 1A to flow at the desired voltage. Use Ohm's
Law, R - E/I, to determine the minimum resistance value that
can be used (E = desired voltage limit, I = 1A or less.) Any
larger value is acceptable, but see WARNING following step
b. Be certain that the power rating of the load resistor is ade¬
quate. For example, assume that a limit of 60 V is to be set. A
60-ohm resistor will draw 1A at 60 V, and will have to dissipate
60 W. A 120-ohm resistor will draw 0.5A, and will have to
dissipate only 30 W. To adjust the supply for constant current
operation:
a. With supply turned off, connect load resistor, turn power
on, and rotate OUTPUT ADJUST knob for the desired max¬
imum output voltage.
3-12
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