Takano
To do cross check with this result, I tried to estimate the calibration factor by another method.
Takano method
- Scan PZT around the cavity resonance with dithering and record the error signal and input signal
- Estimate the gradient of the error signal in [cnt/cnt] around the resonance
- Divide the gradient by the actuator efficiency 1.3e-10 [m/cnt] obtained by the previous measurement, and we get the calibration factor [cn/mt].
Figure1 shows the timeseries of this measurement. I estimated the calibration factor with this data, and I got the value of 1.9e13 [cnt/m], which is ~ 3000 times larger than the value estimated by OMC TRANS!
I found that the dither amplitude is different when OMC is locked and unlocked by 30 times (unlocked: 10,000, locked: 300), and the normalized factor of the error signal (OMC-LSC_NORM_OUT) didn't work properly (normalized factor around the resonance is 5~6, whereas the actual transmission value is 28) because of the lowpass filter with cutoff frequency at ~ 0.1 Hz. Taking into considering these factors, still the estimated value is higher than ~ 20 times. I will check other foactors which can affect the calibration.
