Camilla asked me to take some health check transfer functions on ZM4 and ZM5 since they recently had their coil drivers swapped for modified 100 Ohm output impedance drivers (91407). SQZ team had had to lower the COILOUTF filter bank gains from +/-1 to +/-0.08 due to saturations that they had been seeing after the driver swap.

I moved the COILOUTF gains into FM10 and called them drivercomp (accepted as ON in SDF). I then took health check transfer functions for ZM4 and ZM5 with their previous COILOUTF AntiLP filters on (which I believed to be the wrong filters). ZM4 looked good and was at a similar magnitude as before, but ZM5 is now lower in magnitude - 8% of what it used to be, which does line up exactly with the coil driver and gain change, but we would expect for both ZM4 and ZM5 to have reacted to these changes the same.

Settings
- ISI locked and tripped
- SUS in HEALTH_CHECK
- DAMP OFF
- COILOUTF FM6: zpk([0.9;211.883],[9.99;20.99]) (old, wrong?? compensation)
- COILOUTF FM10: gain(0.08)

ZM4
Data
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM4/SAGM1/Data/2026-08-05_1900_H1SUSZM4_M1_WhiteNoise_{L,P,Y}_0p02to50Hz.xml
r13101
Results
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM4/SAGM1/Results/2026-08-05_1900_H1SUSZM4_M1_ALL_TFs.pdf
r13102

ZM5
Data
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM5/SAGM1/Data/2026-08-05_1940_H1SUSZM5_M1_WhiteNoise_{L,P,Y}_0p02to50Hz.xml
r13103
Results
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM5/SAGM1/Results/2026-08-05_1940_H1SUSZM5_M1_ALL_TFs.pdf
r13104

Coil driver thoughts

These are actually our first two supensions with the HAM-A 100 Ohm output impedance coil drivers here at LHO (we have had a few with 1.2k Ohm output impedance). We discovered that we hadn't made of the modifications requested in IIET:30349 in 84454. I am pretty sure that the AntiLP filter modules in the COILOUTF filter banks should now go from zpk([0.9;211.883],[9.99;20.99]) to zpk([0.5;3174],[52.32;50.77]) (T2100410), but we don't have any other 100 Ohm CDs here to compare that to, and looking at LLO's filter banks for suspensions they claim have this modification for 100 Ohms, yet they still have the old compensation filters installed.

I did try to install the AntiLP filter that I believed to be the correct one, but doing that with the COILOUTF gains at +/-1 was definitelty not working. When there's some free time I'd like to try reinstalling the zpk([0.5;3174],[52.32;50.77]) filters but with the gain at the 0.08 that it was changed to? I don't see why we would need to do this since the 1.2k Ohm Coil Driver suspensions don't have this factor, but maybe I'm missing something that is specific to the 100 Ohm output impedance drivers.