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Tue Aug 19 19:14:17 2008
C1:IOO-MC_RFAMPDDC, which is a PD at the transmission port of the MC, was not recording sensible values.
So I tracked down the problem starting from the centering of the beam on the PD.
The beam was hitting the PD properly. The DC output BNC on the PD provided +1.25V output when the light was
falling on the PD. The PD is fine.
The flat cable from the PD runs to the IOO rack and fed into the LSC PD interface card.
The output from the interface card is connected to a VMIC3113A DAQ card, through cross connects.
The voltages on the cross connects were ok.
The VMIC3113A was controlled by an EPICS machine (c1iool0). So it provides only a slow channel.
By looking at C1IOOF.ini and tpchn_C1.par, I figured that C1:IOO-MC_RFAMPDDC is using chnnum=13639 in the RFM
network and it is named C1:IOO-ICS_CHAN_15 in the .par file. So it is reading values from the ICS DAQ board.
Actually nothing was connected to the channel 15 of the ICS board and that was why C1:IOO-MC_RFAMPDDC was reading
nothing. So I took the PD signal from the cross connect and hooked it up to the Ch15 of the ICS DAQ through
the large black break out box with 4-pin LEMOs. Now C1:IOO-MC_RFAMPDDC reads the DC output of the PD.
I also put an ND filter in front of the RFAMPD to avoid the saturation of the ADC. The attenuation should have been done
electronically, but I was too lazy. Since the ND filter changes the Stochmon values, someone should remove it and reduce the
gain of the LSC PD interface accordingly.