This morning there was some confusion over whether or not the EX ESD was completely off. Since the latest technique for getting some more mpc's is to turn off the EX ESD after the ifo has achieved full lock, it is important for operators to know if it is all the way off or not. After talking with Evan, he cleared up some of my confusions and this is what I've found
There are three different states that the ESD can be in:
- Driver ON, DC Bias ON
- Driver ON, DC Bias OFF
- Driver OFF
The confusion this morning arose from the ESD medm screen's "Active" light. The light was red but the Analog Monitors still had a few hundred counts to them. This is because the ESD DC Bias was OFF and the driver was on. To avoid this in the future, I added a third light to ESD Active. If the Active light is:
- Green - Driver ON, DC Bias ON [ abs(H1:IOP-SUSAUX_EX_MADC4_EPICS_CH0) >= 325 and H1:ISC-EXTRA_X_BO_3 = 0]
- Orange - Driver ON, DC Bias OFF [ (abs(H1:IOP-SUSAUX_EX_MADC4_EPICS_CH0) < 325 and > 50) and H1:ISC-EXTRA_X_BO_3 = 0]
- Red - Driver Off [ abs(H1:IOP-SUSAUX_EX_MADC4_EPICS_CH0) <= 50 and H1:ISC-EXTRA_X_BO_3 = 0]
(Legend on the medm so you don't have to memorize that, screenshot attached)
Hopefully this will eliminate any future bewilderment.
Also, we updated the guardian to turn the EX ESD on and off as appropriate.
In LSC_FF, if the EX bias has been ramped to zero, the guardian will write 1 to H1:ISC-EXTRA_X_BO_3. This is then reset to 0 after a few seconds (by Beckhoff?). This will inactivate the driver.
In DOWN, if the analog readbacks for the driver are close to zero, the guardian will again write 1 to H1:ISC-EXTRA_X_BO_3. This is again reset to 0 after a few seconds. This activates the driver.
Occasonally it seems that the reset mechanism freezes, so that cycling BO_3 does not do anything. In this case, it usually works to do the following:
caput H1:ISC-EXTRA_X_BO_4 0
caput H1:ISC-EXTRA_X_BO_4 1
And then write 1 to H1:ISC-EXTRA_X_BO_3.