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being tested. It is recommended that the tests be performed
in the sequence given, and that all data be recorded on the
test record provided at the end of the test procedures (see
paragraph 3-26).
3-6 Measurement Techniques
3-7 Setup for All Tests. Measure the dc output voltage
directly at the + S and - S terminals of the output under test.
Connect the output for local sensing and use adequate wire
gauge for load leads as described in Section IV of the
Operating Manual.
Many of the test procedures require the use of a variable
load resistor capable of dissipating the required power.
Using a variable load resistor requires that switches be used
to connect, disconnect, and short the load resistor. An
electronic load, if available, can be used in place of a variable
load
resistor
and
switches.
considerably easier to use than load resistors. It eliminates
the need for connecting resistors or rheostats in parallel to
handle power, it is much more stable than a carbon-pile
load, and it makes easy work of switching between load
conditions as is required for the load regulation and load
transient response tests. Substitution of the electronic load
requires minor changes to the test procedures in this section.
3-8 Current-Monitoring Resistor
current measurement error caused by voltage drops in the
leads and connections, connect the current monitoring
resistor between the - V and the load as a four-terminal
device. Figure 3-2 shows the connections. Connect the
current-monitoring leads inside the load-lead connections
directly at the monitoring points on the resistor element.
3-9 GPlB Controller. Most performance tests can be
performed using only the front panel keypad; however, an
GPIB controller is required to perform the voltage and
current readback accuracy tests. The test procedures are
written assuming that you know how to program the supply
remotely from an GPIB controller or locally using the
control keys and indicators on the supply's front panel.
Complete instructions on remote and local programming are
given in the Operating Manual.
NOTE
In the test programs that follow, the brackets < >
indicate a number to be sent. The <ch> specifies
the output channel number from 1 through 4. The
voltage and current values which are sent to the
specified output channel are given in Table 3-2.
The
electronic load
is
To eliminate output
.
3-10 Constant Voltage (CV) Tests
3-11 CV Setup. If more than one meter or a meter and an
oscilloscope are used, connect each to the + S and - S
terminals by a separate pair of leads to avoid mutual
coupling effects. Connect only to + S and - S because the unit
regulates the output voltage that appears between + S and -
S, not between + V and - V. Use coaxial cable or shielded 2-
wire cable to avoid noise pickup on the test leads.
3-12 Voltage Programming and Readback Accuracy. This
test verifies that the voltage programming, GPIB readback,
and front panel display functions are within specifications.
An GPIB controller must be used for the readback accuracy
portions of this test.
a.
Turn off the supply and connect a digital voltmeter
between the + S and - S terminals of the output to
be tested.
b.
Turn on the supply and select the desired output
(OUTPUT SELECT key on the front panel).
SELECT the low voltage range using the range
command:
VRSET < ch >, < 7(25W) or 16(50W)
or press range and volt ↓ buttons.
c.
Program the selected output channel to zero volts
by sending the string:
d.
Record the output voltage readings on the digital
voltmeter (DVM) and the front panel display. The
readings should be within the limits specified
below for the particular output type tested. Also,
note that the display indicates the output current
and the CV, RMT, and ADDR annunciators are on.
Note
that
approximately zero because there is no load
connected.
e.
Read back the output voltage from the selected
channel over the GPIB by entering and running
the following program.
3-4
VSET <ch>, 0
the
output
current
reading
10 OUTPUT 705; "VOUT? < ch >"
20 ENTER 705;A
30 DISP A
40 END
is
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