David.M, Jenne.D

This is a follow up post to https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=27721. The issue that I reported on Tuesday turned out to be a minor problem that I resolved by double checking the electronics in the CER. Now we are obtaining data from all six L4Cs currently in the LVEA. This allowed us to compare the three seismometers grouped together on the linoleum surface to the three positioned on the concrete. It seems as though there is only a very small difference which shouldn't cause any problems for us, I've attached two plots showing this. When looking at the plots it should be noted that L4C channels 1,2 and 3 are positioned on the linoleum, whereas L4C channels 4,5, and 7 are positioned on the concrete.

The first plot (L4Cs_STS.png) shows all 6 uncalibrated L4C signals overlapped and also the calibrated STS-2 signal in black (this is only relevant for the shape, the difference in calibration means the magnitude of the STS-2 signal is very different to the L4Cs).

The second plot (coherence_TFs2.png) shows on top the coherence between L4C2 (positioned on linoleum) and the STS-2 (in red) as well as L4C7 (positioned on concrete) and the STS-2 (in blue). We see that both have very nice coherence in our frequency band of interest (up to ~30Hz). The bottom plot shows two transfer functions between L4Cs on the same surface (red plot is both on linoleum and black plot is both on concrete) as well as two transfer functions between L4Cs on opposite surfaces (yellow and blue plots). We can see that the pairings on the same surface are slightly better matched, but all four transfer functions are quite nicely matched and flat. 

We should be able to position the L4Cs on top of the linoleum coating without having to cut any holes in it. 

EDIT: I fixed the first plot, which I accidently gave a linear frequency axis