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Entry  Thu Jan 14 21:49:37 2016, Chris Thompson, Triggering of DRS4 in the fastest sampling mode OR_mode_selected.jpgAND_mode_selected.jpg20ns_per_div.jpg
    Reply  Fri Jan 15 08:09:00 2016, Stefan Ritt, Triggering of DRS4 in the fastest sampling mode edge.png
Message ID: 476     Entry time: Fri Jan 15 08:09:00 2016     In reply to: 475
Author: Stefan Ritt 
Subject: Triggering of DRS4 in the fastest sampling mode 

Hi Chris,

if you ever used an oscilloscope, you might be familar with the button controlling the riger in respect to "risign edge" vs. "falling edge". I copied the same for the DRS software. So just click on that button:


and you will get what you want. Also the AND/OR gets reversed this way. If you select rising edge (default), the AND will be made if both signals are ABOVE the threshold, that's why it does not work for you. If you select falling edge, the AND will be made if both signals are BELOW the threshold. For negative pulses you need falling edge.


Chris Thompson wrote:

I am attempting to use the DRS4 to measure the timing resolution of a pair of SensL silicon photomultipliers (SiPM). In order to do this I need to trigger the DRS4 only when there is a coincidence between the two input signals, and hopefully make histograms of the relative detection times of each detector.

There are two completely separate issues. (1) I think this may just be a labelling error. In the first image (OR_mode_selected) one can clearly see two pulses which are very similar. In this mode, both signals are present, and are always present. I think this should be the "AND", not "OR" of the two signals. Contrast this with the second image where I have selected "AND_mode". Clearly only one signal is present, and either signal trigges an event, so this should be "OR", not "AND"

The second issue is, for me, much more serious. I want to sample the leading edge of this event in order to determine its "time". The little "T" at the top of each image is, I believe the "trigger point" in the first two images. However, this is well after the part of the signal I am interested in. The first two images were at 2 GigaSamples/sec. The third is at 5 GigaSamples/sec. Clearly the event I am interested in processing is over by then. At the lower sampling rate, I can see well before the "T", but at the higher one I can only see after the "T". I had built an external "coincidence circuit" and the "external trigger mode" hoping to to circumvent this issue by using very long cables to delay the signals inut to the DRS4, But even then I have not been successful in getting the to work.

I am using version 5.0.3 on a PC as the version released after that did not work.

I hope some can help!

Chris Thompson


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