Jason, Jim, Dave:

I've been looking into why when we restart the PSL front end models the shutter controlled by the diode room Beckhoff OPC gets closed. Specifically it happens when the h1pslpmc model is started.

The h1pslpmc model controls the shutter through ezcawrite to the Beckhoff channel H1:PSL-EPICSALARM. A ZERO keeps the shutter open, a ONE closes the shutter. Settings within the pmc safe.snap file are zero, so the front end should not output a ONE value on startup and the shutter should not close.

The shutter can be instructed to close by the model if the FLOW monitor (a raw ADC input to the model) lies outside of upper or lower limits. The FLOW signal is passed through a standard IIR filter module. Trending the INMON and the OUT16 of this filtermodule when we started the model last Tuesday reveals for the first second the OUT16 is ZERO while the  input is the ADC value. We suspect this is normal for an IIR integrating filter module. The zero OUT16 triggers the shutter close because it lies outside of the upper and lower limits.

The filter module does not have any filters loaded, has no offsets and has unity gain. We propose (and Jason agrees) that the next time we restart this PSL model we replace FLOW's filter module with an EPICS-OUTPUT part and see if we can get the shutter to remain open during the model startup.