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Message ID: 14588     Entry time: Thu May 2 10:59:58 2019
Author: Jon 
Type: Update 
Category: SUS 
Subject: c1susux in situ wiring testing completed 


Yesterday Gautam and I ran final tests of the eight suspensions controlled by c1susaux, using PyIFOTest. All of the optics pass a set of basic signal-routing tests, which are described in more detail below. The only issue found was with ITMX having an apparent DC bias polarity reversal (all four front coils) relative to the other seven susaux optics. However, further investigation found that ETMX and ETMY have the same reversal, and there is documentation pointing to the magnets being oppositely-oriented on these two optics. It seems likely that this is the case for ITMX as well. 

I conclude that all the new c1susaux wiring/EPICS interfacing works correctly. There are of course other tests that can still be scripted, but at this point I'm satisfied that the new Acromag machine itself is correctly installed. PyIFOTest has been morphed into a powerful general framework for automating IFO tests. Anything involving fast/slow IO can now be easily scripted. I highly encourage others to think of more applications this may have at the 40m.

Usage and Design

The code is currently located in /users/jon/pyifotest although we should find a permanent location for it. From the root level it is executed as


where PARAMETER_FILE is the filepath to a YAML config file containing the test parameters. I've created a config file for each of the suspended optics. They are located in the root-level directory and follow the naming convention SUS-<OPTIC>.yaml.

The code climbs a hierarchical "ladder" of actuation/readback-paired tests, with the test at each level depending on signals validated in the preceding level. At the base is the fast data system, which provides an independent reference against which the slow channels are tested. There are currently three scripted tests for the slow SUS channels, listed in order of execution:

  1. VMon test:  Validates the low-frequency sensing of SUS actuation (VMon channels). A DC offset is applied in the final filter module of the fast coil outputs, one coil at a time. The test confirms that the VMon of the actuated coil, and only this VMon, senses the displacement, and that the response has the correct polarity. The screen output is a matrix showing the change in VMon responses with actuation of each coil. A passing test, roughly, is diagonal values >> 0 and off-diagonal values << diagonal.

  2. Coil Enable test:  Validates the slow watchdog control of the fast coil outputs (Coil-Enable channels). Analogously to (1), this test also applies a DC offset via the fast system to one coil at a time and analyzes the VMon responses. However, in this case, the offset is enabled to all five coils simulataneously and only one coil output is enabled at a time. The screen output is again a \Delta VMon matrix interpreted in the same way as above.


  3. PDMon/DC Bias test:  Validates slow alignment control and readback (BiasAdj and PDMon channels). A DC misalignment is introduced first in pitch, then in yaw, with the OSEM PDMon responses measured in both cases. Using the gains from the PIT/YAW---> COIL output coupling matrix, the script verifies that each coil moves in the correct direction and by a sufficiently large magnitude for the applied DC bias. The screen output shows the change in PDMon responses with a pure pitch actuation, and with a pure yaw actuation. The output filter matrix coefficients have already been divided out, so a passing test is a sufficiently large, positive change under both pitch and yaw actuations.


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