Unipolar Mode - HP 59501B Operating And Service Manual

3-87 CC Programming
3-68 The following paragraphs provide calibration pro¬
cedures which are applicable to all power supplies listed
for CC programming in Table 3-1. Calibrating the supply
for CC programming with the 59501B consists essentially
of two adjustments:
1. Setting the supply's output current to zero
when the 59501B is programmed to zero.
2. Setting the supply's output current to a
desired maximum value when the 59501B is
programmed to maximum.
3-69 Calibration. To calibrate a 59501 BVpower supply
combination for CC programming, proceed as follows:
If necessary use D/A FULL SCALE ADJUST
to obtain the required resolution.
e. Turn off supply and open output terminals.
Turn on supply.
f. Adjust power supply's VOLTAGE control for
the desired maximum output voltage. If a load
change causes this voltage limit to be exceeded,
the supply automatically crosses over to con¬
stant voltage operation at this voltage limit
point and the output current drops propor¬
tionally. If desired, the front panel VOLTAGE
control can be disabled and replaced with a
fixed resistor of proper value (see applicable
power supply Operating and Service manual).
3-70 Test Setup.
a. Connect 59501B to an HP-IB controller.
b. Connect 59501B to power supply (CC program¬
ming), see Table 3-1.
c. Connect a resistive load in series with an external
current monitoring resistor across supply's out¬
put terminals. Refer to Section V of applicable
Operating and Service manual for resistor values,
power ratings, and CC test setup diagram, etc.
Connect a DVM across the current monitoring
resistor.
d. On 59501B , set mode switch to UNIPOLAR
and turn POWER SUPPLY FULL SCALE
ADJUST {COARSE and FINE) fully CCW.
. e. On power supply, set front panel VOLTAGE-
control fully CW.
3-71 Calibration Procedure.
a. Apply power to the controller, the 59501B
and the power supply. Allow 30-minute warm¬
up.
b. Program 59501B to "2999''and set POWER
SUPPLY FULL SCALE ADJUST (COARSE
and FINE) for desired maximum output current.
(Voltage reading on DVM must be converted
to the equivalent output current).
c. Program 59501B to "2000" and set ZERO
ADJUST on 59501B for zero output current.
Note that for power supply models 6427-6483,
zero current may not be attainable. When cali¬
brating the CC output of one of these supplies,
choose a convenient point, e. g. 10% or 20% of
maximum output and set ZERO ADJUST to
obtain this value. Data words "2100" and
"2200" correspond to the 10% and 20% output
points, respectively,
d. Program 59501B to "2999" and set POWER
SUPPLY FULL SCALE FINE ADJUST on
59501B. for desired maximum output current.
3-72 Sample Program. The sample program provided in
example 4 can easily be modified for CC programming by
substituting I (current) for V (voltage) and by monitoring
the output current using the test setup of paragraph 3-70.
3-73 USING 59501B AS A LOW LEVEL
DC SIGNAL SOURCE
3-74 When used as a low level dc signal source, 59501B
output terminals A1 and A2 are connected directly to the
user's device. In this application, power supply programming
network terminals A3 through A6 are normally not used.
As described previously, two programmable output ranges
are available in the selected operating mode (UNIPOLAR or
BIPOLAR). The output ranges available.at terminals A1
and A2 are as follows:
Range
Unipolar
Bipolar
High
0 to 9.99V -10 to 9.98V
Low 0 to 0.999V
-1 to +0.998V
3-75 Unipolar Mode
3-76 Calibration. The ZERO ADJUST allows the output
to be adjusted to zero (±250 millivolts) when the 59501B
is programmed to zero (2000). The D/A FULL SCALE
ADJUST allows the output to be adjusted to 9.99V (±5%)
when the 59501B is programmed to maximum (2999). The
59501B is normally calibrated to provide a unipolar output
range from 0V to 9.99V. The reason for this is that the
59501B is programmable in 999 steps and using this range
results in a round number for resolution (voltage change per
step). For example, in the high range resolution is 9.99V/
999 or lOmV per step, if the output'is set to 10V, resolution
is 10/999 or 10.01001 mV per step. Calibration procedures
for operating in the unipolar mode are provided in paragraph
5-29.
3-17