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Entry  Fri Mar 2 18:08:55 2018, Steven Block, ROI  
    Reply  Fri Mar 2 20:17:17 2018, Stefan Ritt, ROI  
       Reply  Fri Mar 2 21:05:48 2018, Steven Block, ROI  
          Reply  Mon Mar 19 16:22:42 2018, Stefan Ritt, ROI  
Message ID: 663     Entry time: Fri Mar 2 18:08:55 2018     Reply to this: 664
Author: Steven Block 
Subject: ROI  

Hello,

I have a question about how ROI works. From what I have read, it will only save data that ocurs some time [ta] dictated by the user after an event is triggered as well as a small time [tb] before the event. The technical manual seems to indicated that the deadtime assciated with operating in ROI mode can be reduced by the following factor: 

\frac{t_a + t_b }{\frac{N}{Sample Speed}} .

Where N is the number of points in the time window (ex. 2048 or 1024). Is it ok to describe this as:

\frac{N'}{N} 

Where N' is the number of samples in the ROI and N is the same as before.

For example, if I were running at 5Gsps (200ps between samples), only recording 1024 samples per event and I had an signal that lasted 2ns, that means the signal would last 10 samples. If I set the ROI to only save 20 samples around this signal, would my Deadtime go to:

\frac{10}{1024} * 30ns*1024 + 2\mu s = 2.3\mu s? (The second portion of this equation comes from a response I recieved earlier, but I just want to make sure I understand this concept properly)

I recognize that the caveat is that this would work only if the signal was detected during acquistion, which leads to my next question. If no signals were detected in the 1024*200ps time frame in ROI mode, would the DRS4 go dead for 32us (using the factor = 1 from above equation), or would it dump the earliest events in the buffer for the more recent ones until it detects a signal? 

Finally, I assume this functionality can only be utilized with custom electornics with the DRS4, not the evaulation/demo board, please let me know if this is the case. 

Best,

Steven

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