DaveB, JimB, CoreyG, RickS

We recently discovered that the PDA DC and PDB DC readouts on the MEDM screens were about a factor of ten lower than they had been.

After some investigation today, we found  that the gains in the filter modules had been changed from -1 to -.116 and -.108 respectively on March 18th.  The safe.snap file has the -1 values.

Not knowing why or how they changed, we changed them back and the MEDM screen now has the normal appearance, with the "DC" signals about 5 times the "AC" values.

The voltages measured on the inputs to the ISS Servo module in the LVEA, from which the "AC" and "DC" output signals are derived, are about 1.7 V, same as the "AC" values on the MEDM screen.

The servo seems to be functioning normally.

Note for operators:  The ISS varies the amount of light diffracted out of the PSL beam such that the "AC" output of the selected photodetector matches the "requested" REFSIGNAL value.  Thus in the attached photo, the PD A Output AC value of 1.67V equals the requested -1.67 V (opposite sign).

Photos attached:
Left side of PSL ISS screen.
Filter module before making the changes today.
Filter modules after making the changes today.
Matlab script for the "Cali-mean" F1 filter.  Note the gain of -4.91999.