DRS4 Forum
  DRS4 Discussion Forum  Not logged in ELOG logo
Entry  Wed Nov 23 08:17:23 2016, Abhishek Rajput, Potential Incorrect Timing Calibration for DRS4 Data 
    Reply  Thu Nov 24 13:24:26 2016, Stefan Ritt, Potential Incorrect Timing Calibration for DRS4 Data drs.pdf
       Reply  Tue Nov 29 23:19:06 2016, Abhishek Rajput, Potential Incorrect Timing Calibration for DRS4 Data 
          Reply  Wed Nov 30 08:53:58 2016, Stefan Ritt, Potential Incorrect Timing Calibration for DRS4 Data 
             Reply  Fri Dec 9 04:17:46 2016, Abhishek Rajput, Potential Incorrect Timing Calibration for DRS4 Data 
Message ID: 580     Entry time: Fri Dec 9 04:17:46 2016     In reply to: 574
Author: Abhishek Rajput 
Subject: Potential Incorrect Timing Calibration for DRS4 Data 

Hello Stefan,

Many thanks for the explanations. You've cleared my confusion in this matter.  

Abhishek Rajput

Stefan Ritt wrote:

The inverter chain in the DRS4 is continously running in a ring. Once you get a trigger, it is stopped. This happens in any of the 1024 cells. The last cell which sampled a signal plus ne is called "trigger cell". In the previous diagram in event #1, the last cell sampling was "1", so the trigger cell is "2". In event 2 (red case), the trigger cell is 5. If you would run like this, you see only the part of the waveform BEFORE your trigger (since the DRS4 is continously sampling and is stopped with the trigger). In order to see the full peak of your waveform, you can apply some external trigger to shift the trigger position to the right. This is done in the FPGA reading out the DRS4 chip. If your peak is let's say 20 ns wide, and you delay your trigger by 30 ns, you see the peak plus 10 ns right of the peak.

Stefan

Abhishek Rajput wrote:

Hello Stefan,

Thank you for the excellent explanation and diagram. This part of the code is now much clearer to me.

My other questions pertain to the "trigger cell". Firstly, what precisely does this mean? Moreover, how does the "trigger cell" relate to the trigger time delay we can set in the DRS4 application? This is causing some confusion for me, because regardless of where you set the trigger time delay on the DRS4 application, there are still points on the waveform that are saved prior to the moment in time when a pulse exceeds some voltage threshold we set in the application. I get the impression that "trigger delay" and "trigger cell" are unrelated concepts, so any clarification you can provide would be greatly appreciated.

Abhishek

 

ELOG V3.1.4-80633ba