Low gain on the HEPI pier interface D080521
It is quite surprising to see that the HEPI L4C signals don’t overshoot +/-100 counts on the ADC (attachment 1) when the actuators are not driven.  After checking that all elements of the readout chain were turned on, we measured the L4C gain of one HEPI pier interface D080521. The gain is 22 and a 0.1V input offset gives 3600counts on the ADC as expected.
After comparing calibrated spectra of the HEPI L4Cs (on top of the piers) with spectra of the ISI L4Cs (stage 1), the HEPI L4Cs spectra don’t look wrong.
L4C gain in D080521 seems low.