LAT Electronics, Data
Acquisition & Instrument Flight SoftwareACD-Test-Stand #3
Noteworthy for this test-stand
can handle 4 FREE card connections on the primary GASU and 4 on the redundant GASU for a total of 2 complete BEA assemblies
supply voltage and frequency to FREE can be varied with this version of GASU to explore FREE margins
only tested at room-temperature
CAUTION
the CALSTROBE delay and/or the TACK delay in the trigger sequencing register must not be set to 02 (hex). If set to 02(hex) the AEM will continually assert the NSCMND lines to all 12 FREE boards.
can not be subjected to thermal-vacuum tests, temperature cycling, vibration tests
THERE IS a typo in the JL153 connector pin assignment in the LAT-TD-03827-02 document (only applies when the FREE 3.3V is to be margin tested). Look for release 3 for correction, expected to be released 5-28-04. Error is that the voltage adjust pins called out adjust the GASU DAQ voltage, not the FREE voltage. No damage can be done but the FREE voltage won't change. The pin assignment is correct in LAT-TD-03664, so use that one.
Since the ACD-power switching circuit is incorporated on a separate PCB in the GASU as opposed to on the GASU board itself, the thermal impedance from the power-switching circuit to the enclosure is much larger than the flight board. Thus one needs to make sure that the power dissipated by the power-switching circuit is limited. Since the current is self-limiting, the voltage dropped across the switching circuit must be limited for duration larger than 10 second. With the power-switch turn-on, the 28V output must be > 10V, the 3.3V output > 2V. In other words the outputs can't be shorted with the respective low impedance to ground for more than 10 sec.
The power-switch circuit and new monitoring circuit is supplied below.
The resistors in the power and monitoring section are still being optimized to yield the proper range/resolution. Results are given in a document below.
The GASU-Power Supply supplying the input power to the 12 FREE switching circuits is set at 3.7V. The final value will be chosen after more tests have been completed . The output voltage range can be shifted via the V-adjust function to yield the range desired.
Here are copies of the documents for reference. Retrieve directly from LAT-DOCs for released versions.
LAT-TD-03664 GASU-Based Teststands: Describes GASU-based test-stands; has pictures of GASU panel connectors, JL153 pin assignments, etc.
LAT-TD-03827-02 Test for EGSE ACD G3 Test Stand with GASU Instrumented to Simultaneous Test up to 4 FREE Cards (including Safe-to-Mate) Revision 02: Test procedure to test this G3 test-stand, includes set-up diagram/instructions for test-stand, use in conjunction with LAT-TD-03664
NCR's (none to date)
Supporting Documents:
As-built Power-Switch and Current Monitoring Section on GASU DAQ Board of Test-Stand #3: Note that on one of the boards we loaded the ten 0.1 Ohm 5% resistors in parallel, while the other has one SM 0.01 Ohm 1% resistor with a wire added. So the performance is slightly different, see results below:
Results from measurements on the current monitoring circuit (note that the primary and redundant results are different because of the variations in the current sense resistor values.)
LAT-TD-00639 ACD Electronics Module
LAT-TD-01545 Global Trigger Electronics Module
LAT-TD-01547 Command/Response Unit
LAT-TD-01546 Event-Builder Module