LIGO Document E1500355-v1
- In initial LIGO we had and absolute and independent time marker in the frame files. It was an IRIG-B signal digitized in one of the end stations. We lost this feature as part of the timing upgrades in Advanced LIGO. We propose to add the IRIG-B channel back to the science frame, derived from an independent GPS clock.
- The existing aLIGO Timing GPS modules (D1002546) brings out the serial port of the Trimble GPS receiver through a Lantronix Serial->Ethernet adapter to an Ethernet port on the front-panel. It is now desired to read out the GPS module directly from the serial port to a port on the Beckhoff system Serial Concentrator. To do this cleanly, modify the GPS module to bring the embedded serial port on a DB9 cable to a DB9 feed through, mostly likely on the back panel D1002555. This change needs to be reflected in drawings and likely requires updating the
test procedure (T1000659) to use a direct serial port. In addition, this change requires updates to the Beckhoff EtherCAT software (already completed at LHO). All of this work is (implicitly) part of this ECR.
for associated changes to get the serial output of the GPS receiver, see also https://services.ligo-wa.caltech.edu/integrationissues/show_bug.cgi?id=1111
approved by Dennis Coyne
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