[Mark B Jeff B Arnaud P]
Yesterday we did some software debugging in the staging building in order to run transfer functions on the assembled quad 08.
When driving the top mass, we usually monitor the lower stages osems, in both osem and euler basis. For some reason the model running for the quad doesn't record those channels (particularly the ones in the euler basis "WIT_{L/P/Y}_DQ"). We decided not to spend too much time understanding what the model situation was, and instead simply not monitor the lower stages channels during the top mass TFs.
The undamped transfer function measurements for the main and the reaction chain are attached.
[Mark Jeff Arnaud]
QUAD08 should be compared to the model called "wireloop" (=wires from UIM to PUM looping around PUM) instead of the "wire" one (=cable segments between UIM and PUM). The first attachment from the alog above was modified since I was using the wrong model for comparison. With the wireloop model there is still a small discrepancy in the second pitch mode (modeled at 1.33Hz and measured at 1.45Hz). By playing with the d values (defined p7 of T080188) I came up with a good match, cf attachment.
Here are the modified d values for reference :
new_dm = old_dm + 0.7mm
new_dn = old_dn + 0.7 mm
new_d4 = old_d4 - 0.8 mm
Also, after an other round of matlab debugging (pb with channel sampling rates in the matlab scripts, path definitions etc...) we were able to get spectra of TOP and UIM osems, with the suspension undamped. Results are attached in the second pdf.
The only thing to notice is the noise content at high frequencies for the left osem of M0 (cyan curve, 1st page). This might be harmonics from the large 60Hz signal.
Jeff B Andres Arnaud
This afternoon we tested the noise seen in the left bosem of the main chain. We swapped left and right osem cables (at the osem output), and measured a spectra before and after. When plugging the right channel to the left osem, the noise was still present in the spectra (cf screenshot) meaning the noise comes from the left osem itself.
Second attachment is a comparison of the transfer functions between different "wireloop" quads. The 2nd pitch mode frequency is varying from quad to quad, but the largest discrepancy is on QUAD08.
[Andres Arnaud]
Today we replaced the left osem of the main chain of QUAD08 in the staging building with an other BOSEM (stolen from one of the 3rd IFO TMS). New OLV were stored, offsets and gains were set in medm.
Results of individual osems spectra are attached. The M0 LF channel dosen't show the elevated noise seen yesterday anymore