Make New Entry, Make Followup Entry
User name brads
Log entry time 18:17:27 on October 21, 2009
Entry number 296017
This entry is a followup to: 296014
keyword=NIM MPS signal quality to Moller DAQ is marginal (fixed for FADC Moller DAQ)While working with the FADC Moller DAQ I noted the leading edge of MPS signal to the FADC DAQ sucked (Figure 1; 250us/div). Followed problem upstream to output of the P7126 NIM-ECL module in old Moller DAQ. Figure 2 shows the leading edge of the NIM output on that module (time scale zoomed to 2.5us/div).
That module gets its MPS input from the Counting House through a long patch cable. Figure 3 shows the wild leading edge of the (allegedly) NIM pulse coming down from upstairs -- this is interacting with the P7126 NIM-ECL module to give the stuttering pulse in Figure 1.
Checked upstairs and the signal looked somewhat marginal coming right out of the upper output on the MPS fiber<->NIM converter. There are two outputs on that converter unit. The second output had a cable plugged into it, but seemed to be dead. I have no idea if that is 'normal' or if the converter unit is dying...
FWIW, the MPS pulse was fine on Aug. 7 (the last time I looked at it on a scope down at the FADC Moller setup).
Meagan took a look at the Compton system in the Hall and tells me it looks OK there. Perhaps the output she was looking at ran through a module that handled a marginal input better than the P7126 on our end?
After talking with Sasha we decided to leave the old Moller setup alone for
now. I decided to clean the signal up for the FADC DAQ by running it into a
gate-and-delay generator and using its leading edge to construct a clean
500us long MPS pulse for my system. Figure 4 shows the (leading edge) input
to the GDG along with the leading edge of the output. Figure 5 shows
alignment of the trailing edges of the original and 'fixed' MPS signals are
aligned to within 100ns (on a 500us wide pulse). The time axis is 200ns/div.
A copy of this log entry has been emailed to: rom, brads, gen, glamazdi, camsonne
Figure 1: Full MPS pulse at the FADC Moller DAQ
Figure 2: Leading edge of MPS signal after P7126 NIM-ECL
Figure 3: MPS signal from CH going to (old) Moller
Figure 4: Leading edge of old (pink) and new (yellow) MPS pulse to FADC DAQ
Figure 5: Trailing edge of old (pink) and new (yellow) MPS pulse to FADC DAQ
