david.barker@LIGO.ORG - posted 09:02, Wednesday 09 February 2022 - last comment - 09:28, Wednesday 09 February 2022(61673)
Timing Error, Timing Master oven controlled crystal oscillator control voltage out of range
Daniel, Fil, Marc, CDS
Attached MEDM shows that the timing system is currently in error due to the MSR timing master OCXO control voltage being slightly below -4.5V.
Attached is a one year trend of this voltage shows that prior to 31st Aug 2021 this voltage was static. On that day the master was swapped with a new unit, and soon after that time the voltage has been linearly decreasing.The timing system will fail when this reaches -5.0V, which it will do in the next 3 weeks.
Daniel says there is no fix other than to remove the master from the rack and either fix the current unit or install the spare unit. This will take down all the front ends, so we would schedule the sw-msr-h1fe1 network switch upgrade at the same time.
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I believe this is a new OCXO. It can age up to 1ppm in the first year. The slope is about 0.1ppm/V. This would still be in spec, even so there is hardly any break in the downward trend.