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Entry  Tue Sep 20 18:03:45 2011, Paul, Update, SUS, ITMY and SRM oplev calibrations - measured and estimated 
    Reply  Tue Sep 20 19:00:49 2011, Paul, Update, SUS, ITMY and SRM oplev calibrations - measured and estimated 
    Reply  Wed Sep 21 00:37:01 2011, rana, Update, SUS, ITMY and SRM oplev calibrations - measured and estimated 
       Reply  Wed Sep 21 09:10:15 2011, Paul, Update, SUS, ITMY and SRM oplev calibrations - measured and estimated 
Message ID: 5487     Entry time: Tue Sep 20 18:03:45 2011     Reply to this: 5488   5494
Author: Paul 
Type: Update 
Category: SUS 
Subject: ITMY and SRM oplev calibrations - measured and estimated 

The measured calibration factors for the oplevs are as follows:

 
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!
 
 
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