SRM pitch: 666urad per count on channel C1-SUS-SRM-OLPIT-INMON

SRM yaw: 557urad per count on channel C1-SUS-SRM-OLYAW-INMON

 

ITMY pitch: 470urad per count on channel C1-SUS-ITMY-OLPIT-INMON

ITMY yaw: 491urad per count on channel C1-SUS-ITMY-OLYAW-INMON

 

Since I'm going to calibrate all the other oplevs with the rougher technique of estimating the angle from the OSEM signals directly, I thought I would check the result of such an estimation for the oplevs I have calibrated already. My method was as follows:

 

dA = change in angle

dx = change in OSEM flag position

dV = change in OSEM PD voltage

dC = change in OSEM counts

D = optic diameter

L = distance between OSEMs = D/sqrt(2)-0.002m = 0.052m

dV/dx = OSEMs volts per meter flag position change = 1700 V/m

dC/dV = OSEM counts per volt = 2^16/40 = 65536/40 counts/V

 

counts per radian = dC/dA = dV/dx  x   dC/dV   x  1/L = 1700*65536/40/0.052 = 5.3564x10^7 counts/rad

 

radians per count = dA/dC = 1.867x10^-8, or 0.019 urad/count

 

This is around a factor of 1000 smaller than what I measured earlier, reported in entry 5468. I guess this might be an issue with the whitening filter on the OSEMs, but my initial feeling was that this was only a factor of a few. If anyone can see a big obvious mistake in my above calculations please let me know!