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Entry  Thu Apr 21 22:16:43 2016, Kyle Weinfurther, Negative fCellDT values from GetTimeCalibration() ch5.pngch7.pngch9.png
    Reply  Sat Apr 23 12:33:17 2016, Daniel Stricker-Shaver, Negative fCellDT values from GetTimeCalibration() 
       Reply  Tue Apr 26 09:54:16 2016, Stefan Ritt, Negative fCellDT values from GetTimeCalibration() 
Message ID: 511     Entry time: Sat Apr 23 12:33:17 2016     In reply to: 509     Reply to this: 512
Author: Daniel Stricker-Shaver 
Subject: Negative fCellDT values from GetTimeCalibration() 

Hi Kyle,

If I remember right the negative sampling width happens only for 498 and at high sampling speeds. It is described in a paper from Stefan:

http://arxiv.org/pdf/1405.4975.pdf

or

“Novel Calibration Method for Switched Capacitor Arrays Enables Time Measurements With Sub-Picosecond Resolution”( IEEE Transactions on Nuclear Science 61 (2014),Nr. 6, 3607–3617)

Kyle Weinfurther wrote:

Hello Stefan,

I am using four DRS4 v5 eval boards to digitize 16 channels of data. I have recently changed from saving the timing information of the waveform using GetTime() to GetTimeCalibration(). When changing over, I noticed that some values for fCellDT for cell 498 are negative. Over the 16 channels used, 4 of them have negative time bin widths for cell 498 while the other 12 channels are very close to 0 (in the ~10 ps range). One of the eval boards has no negative fCellDT whereas the other three boards have one or two channels with negative values.

Upon further inspection, I checked the time between samples of GetTime() and found the same results in cell 498. After finding this, I did a timing calibration again with CalibrateTiming() even though in a different post on the discussion forum you said it was valid for a wide range of temperatures and a long time (years). This still allowed the negative fCellDT values to persist.

Is this a common occurance? If so, is there a method to fix this issue? Is there a reason for cell 498 to have a small value for fCellDT? I searched the discussion forum and did not find anything relating to this issue.

Attached are a couple waveform traces using GetTime() zoomed in on cell 498.

Thanks,

Kyle Weinfurther

 

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