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Entry  Wed May 2 10:44:17 2018, Alessio Berti, Peak at 0 mV in traces zero_peak_after_spike_removal_ch1.pngzero_peak_after_spike_removal_ch2.pngzero_peak_after_spike_removal_ch3.pngzero_peak_after_spike_removal_ch4.pngzero_peak_after_spike_removal_offset_correction_ch2.png
    Reply  Wed May 2 12:12:42 2018, Stefan Ritt, Peak at 0 mV in traces 
       Reply  Wed May 2 12:23:16 2018, Alessio Berti, Peak at 0 mV in traces zero_peak_after_spike_removal_ch2_1000_bins.png
          Reply  Fri May 4 11:35:20 2018, Stefan Ritt, Peak at 0 mV in traces Screen_Shot_2018-05-04_at_11.36.24_.png
             Reply  Tue May 8 12:15:54 2018, Alessio Berti, Peak at 0 mV in traces 20180508_drs4_drs_exam_1000_events_81_bins_linear.png20180508_drs4_drs_exam_1000_events_81_bins_log.png20180508_drs4_drs_exam_1000_events_23_bins_linear.png20180508_drs4_drs_exam_1000_events_23_bins_log.png
                Reply  Tue May 8 14:43:03 2018, Stefan Ritt, Peak at 0 mV in traces 
Message ID: 683     Entry time: Wed May 2 10:44:17 2018     Reply to this: 684
Author: Alessio Berti 
Subject: Peak at 0 mV in traces 

Hi,

we modified drs_exam.cpp to read all 4 channels from the DRS4 and apply directly the spike removal (taken from Osci.cpp) during the acquisition phase. For test purposes, we don't save the data showing spikes and we focus on the data not having spikes (even if at the end we end up having triple and quadro spikes which are not removed by the spike removal routine, but they are rare). With this modified program we wanted to characterize the noise of the DRS4, so we took 30000 events at 5GSPS, triggering on channel 1 with a 10 MHz sine wave with 100 mV_pp (trigger level set at 10 mV), while channels 2,3 and 4 were left open without any input.

We then took a look at the data and plotted the noise histograms for channels 2,3 and 4, which you can find attached (without offset correction, named zero_peak_after_spike_removal_ch*.png). For completeness, we also attached the plot from ch1 (the sine wave). The selections in time and amplitude we applied had the goal to remove the high oscillations in amplitude occurring in the first and last samples and to discard the quadro spikes we had in the data.

We see that there is a peak at 0 mV in all histograms from all channels and scanning through the data, we saw that indeed the value 0 mV is stored many times for each event, thus originating the peak we see in the histograms. We also applied an offset correction to the data (taking the average of the first three most occuring amplitudes) of channels 2 (as an example) and the problem seems to be only partially removed.

We also noticed that this peak at 0 mV is present also when we acquired the data from the DRS4 with DRSosc saving the data in binary format.

So we had the following questions:

- why is the DRS4 saving so many times the value 0 mV (exactly 0 mV)?

- is there any way (in our case through software, preferably at acquisition time) to solve this problem?

Thank you for the help and best regards,

Alessio & Davide

 

Attachment 1: zero_peak_after_spike_removal_ch1.png  10 kB  Uploaded Wed May 2 12:11:34 2018  | Show | Show all
Attachment 2: zero_peak_after_spike_removal_ch2.png  9 kB  Uploaded Wed May 2 12:12:18 2018  | Show | Show all
Attachment 3: zero_peak_after_spike_removal_ch3.png  9 kB  Uploaded Wed May 2 12:12:31 2018  | Show | Show all
Attachment 4: zero_peak_after_spike_removal_ch4.png  9 kB  Uploaded Wed May 2 12:12:45 2018  | Show | Show all
Attachment 5: zero_peak_after_spike_removal_offset_correction_ch2.png  8 kB  Uploaded Wed May 2 12:13:09 2018  | Show | Show all
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