Performance Test - HP 6177B Operating And Service Manual

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TabLe 5-1. Test Equipment Required (Continued)
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'\EQUlRED
TYPE
CHARACTETUSTICS
Resistor
Value: See Paragraph 5-57.
±O.l%,
.
Watt.
Decade
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Range: [-lOOK.
Resistance
Accuracy:
o.
1,;
plus 1 ohm
Box Make-before-break contacts.
NOTE
A satisfactor;l substitute for a differ-
ential voltmeter is to arrange a refer-
ence voltage source and null detector
as shown in Figure 5-1. The reference
voltage source is adjusted so that the
voltage difference between the supply
being measured and the reierence volt-
age will have the required resolution
fo:- the measurement being made. The
voltage difference will be a function of
the null detector that is used. Exam-
ples of satisfactory null detectors are:
~
4.l9A null detector. a dc coupled
oscilloscope utilizing differential in-
put, or a 50mV meter movement wlth a
100 division scale. For the latter, a
2mV change in voltage will result in a
meter deflection of four divisions.
------CAUTION------
Care must be exercised wheri using an
electronic null detector in which one
input terminal is grounded to avoid
ground loops and circulating currents.
5-5 PERFORMANCE TEST
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5-6 The following test can be used as an incom-
ing inspection check and appropriate portions of
the test can be re~eated either to check the OpE;.J:-
aUon of the instrument after repairs or for periodic
maintenance tests. The tests are performed using
a 11SVac 60Hz, singie phase input power source.
If the correct result is not obtained for a particular
checK, do not adjust any controls; proceed to
troubleshooting (Paragraph 5-38).
5-7 CONSTANT CURRENT TESTS
-8 . For output current measurements, the current
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RECOl\·1MENDED
USE
MODSL
Calibrate programming current
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Adjust programmin;;- accuracy'
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5-2
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POWER SUPPLY
REFERENCE
. UNDER TEST
VOLTAGE
SOURCE
9
0
9
9
0
JU
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LOAD
NUll
DETECTOR
- +
\l99
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Figure 5-1. Differential Voltmeter,
Substitute Test Setup
sampling reSistor must be treated as a four termi-
nal device. In the manner of a meter shunt. the
load current is fed to the extreme s of the wire
leading to the resistor while the sampling termi-
nals are located as close as possible to the resist-
ance portion itself (see Figure 5-2). In addition,
the resistors should be of the precision, low noise,
low temperature coefficient (1es s than lOppm/oC)
type and should be used at no more than 10% of
their rated power so that the tempera.ture rise will
be minimized.
The latter. reduces resistance
CURRENT SAMPLING
TERMINALS
TO UNGROUNDED TO GROUNDED
TERMINAL OF
_---'-I,YIv--;r.vvvk:r-___
TERMINAL OF
POWER SUPPLY POWER SUPPLY
Figure 5-2. Output Current Measurement TechniC;L.e
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