craig.cahillane@LIGO.ORG - posted 23:53, Friday 11 September 2015 - last comment - 23:06, Sunday 13 September 2015(21421)
Two Signal vs Response Function Strain Uncertainty
C. Cahillane I have tracked down the differences between my Two Signal ( h = 1/C * DARM_ERR + A * DARM_CTRL ) and Response function ( h = (1 + G)/C * DARM_ERR ) calibration uncertainties. The trick lay in my weighting factors being slightly different with and without data included. The Two Signal calibration method requires DARM_ERR and DARM_CTRL from the beginning, whereas the Response function does not. This means that you must divide out DARM_ERR from the Two Signal method, or multiply it into your Response Function to get comparable results. I did it both ways, and got identical plots (Shown in Plot 1). I found a bug in my Response function method since I was not including the hard-coded minus sign on the x_pcal line I use to calculate kappa_tst and kappa_pu. Plot 1 and 2 are the same plot, but Plot 2 is zoomed in to show the data noise in the Two Signal method of calibration vs the smooth Response Function. I have also included the updated components plots for Magnitude (Plot 3) and Phase (Plot 4). Note that the uncertainty is inflated now compared to aLog 21390. The next step is to fix the kappa_C and f_c calculations, they still yield ~0.75 and >1000 Hz respectively. Sudarshan ought to be able to help me here relatively quickly. Then I must inform my sigma_(param) values more intelligently.
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C. Cahillane, K. Izumi Kiwamu noted that my magnitude strain uncertainty plots looked strange. My magnitude uncertainty in A_pu was 4%, and should dominate at low frequency, but it was not contributing at all. Similarly I noticed |C_r| uncertainty was not contributing at high frequency when it ought to. I have replotted my strain uncertainty components plots. I am reporting uncertainty in percentage, but my sigmas were using fractional values, i.e. I was multiplying by 0.01 and should have been using 1. The plots are repaired and look a bit more sensible.
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