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Diagnostic Testing and Troubleshooting
Troubleshooting the Instrument
5
5-23
Table 5-10. Relating Selftest Errors to Instrument Problems (cont)
Error
Code
Error Code
Description
Suspect
Assembly
Error Code
Discussion
10
Inguard reference
balance test failed.
A3 A/D
Converter
PCA
Background The A/D converter uses two very precise
voltages for operation: +3.45V dc and -3.45V dc. These
voltages are applied to resistor network A3Z1-1 and
A3Z1-3, with a balanced output at A3Z1-2. When the two
reference voltages are exact, the A3Z1-2 output is nearly
zero.
Failure This error occurs when the output of the balance
reference check at A3Z1-2 is not nearly zero.
Correction Troubleshoot the reference voltage circuitry
at A3U12 and A3U20 and related components. During
proper operation, A1U12-6 is within a few microvolts of
ground potential. Check the inputs and outputs of A3U12
and A3U20 and look for an incorrect output, indicating a
device failure.
11
Inguard overload
detection failed.
A3 A/D
Converter
PCA
Background This self-test is created by configuring for
an ohms measurement, with treeing relays pulled in, but
no channel relays are set. This creates an overload
measurement as the A/D converter tried to measure the
resistance of an open circuit.
Failure The error occurs when the A/D converter did not
detect an overload condition for measuring an open
circuit.
Correction There is a problem in the ohms conditioning
circuitry or possibly a problem in the A3U30 Stallion
device. The dc buffer might also be affected. Normally,
this error occurs in conjunction with other errors. If there
are not other errors, then the signal conditioning circuitry
is more likely at fault. Also check the ohms current source
at A3U31 and related components. When the precision 1
mA current sink is operating correctly, the voltage across
A3R128 is exactly 3.45V dc and the voltage across A3Z7-
9 and A3Z7-11 is 1.00V dc. If all the voltages are correct,
the A3U30 Stallion device becomes more suspect.
Содержание NetDAQ 2640A
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Страница 242: ...2640A 2645A Service Manual 7 10 Figure 7 2 A2 Display PCA Assembly 2620A 1602...
Страница 243: ...Schematic Diagrams 7 7 11 Figure 7 2 A2 Display PCA Assembly cont 2620A 1002...
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Страница 258: ...2640A 2645A Service Manual 7 26 Figure 7 5 A4 Analog Input PCA Assembly 2620A 1604...
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