Bug #276

ERROR 404.1 – Absolute value (x1 gain); -full-scale DAC output

Added by tin about 7 years ago. Updated over 4 years ago.

Status:ClosedStart date:19/07/2012
Priority:NormalDue date:
Assignee:tin% Done:

0%

Category:-
Target version:Keithley 2001 #2

Description

Cannot measure 4.21V ±0.4V at A/D IN.

DAC U531 is programmed to generate -4.21 VDC at PRECOMP+. That signal is then applied to ACF through R560 and U532 (DAC line pulled low). ACF is routed to AMP IN via U526, Q516, and the AC input buffer.

AMP IN is tied to the inverting and non-inverting paths of the variable gain amplifier (VGA). NETOUT (output of U519) is routed to the Zero-Crossing Amplifier which, based on the polarity, generates the appropriate COMP- signal that is applied to com- parator U507. The comparator selects the path that the AMP IN signal will follow through the VGA by closing the appropriate analog switches of U509.

The negative (inverting) AMP IN path is through R530, U515, U509, Q501, and U516 to pin 12 of the multiplexer (U511). The output (OUT) of the multiplexer is routed through buffer U342 to ACV/A. The signal on ACV/A is switched through U320 (/AC pulled low) to the A/D buffer (U322) which is configured for x1 gain. Measure +4.21V at A/D IN.

Suspected components

U531
U532
R560
U526
Q516
U519
U507
R530
U515
U509
Q501
U516
U511
U320
U322

History

#1 Updated by tin over 4 years ago

  • Status changed from New to Resolved

#2 Updated by tin over 4 years ago

  • Status changed from Resolved to Closed

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