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Subject: Re: Fwd: Cosylab MicroIOC/BLM Calibration procedure confusion
From: Uwe Bonnes <bon@elektron.ikp.physik.tu-darmstadt.de>
To: Josh Stein <stein@aps.anl.gov>
Cc: tech-talk@aps.anl.gov
Date: Mon, 30 Apr 2012 22:10:01 +0200
    Josh> Calibration procedure confusion Date: Wed, 25 Apr 2012 12:02:08
    Josh> -0500 From: Josh Stein <stein@aps.anl.gov> To:
    Josh> tech-talk@aps.anl.gov

    Josh> Greetings all,

    Josh>   I have a question needing rapid response - hence my wasting
    Josh> tech-talk bandwidth instead of contacting Cosylab directly
    Josh> (which I will do also).  I have a Cosylab BLM system consisting
    Josh> of one of their MicroIOCS and a Bergoz detector. One of the
    Josh> procedures to follow when first using this system is a
    Josh> calibration involving setting two trimmer potentiometers.

    Josh>   In the (Cosylab) manual, they refer to setting the output of a
    Josh> particular detector 'side' to 10KHz - however all of the PVs for
    Josh> that device talk in "Counts". I'm not sure how to do a proper
    Josh> calibration when all the software returns are counts per
    Josh> time-slot.

Well, counts per seconds is frequency.

    Josh> For now, I just changed my time-slot to 1ms (about the longest
    Josh> duration possible) and adjusted the potentiometers to readback a
    Josh> value of (close to) 10 (figuring that 10 counts in 1ms = 10,000
    Josh> counts in 1 second).  This was pretty difficult - I feel as if I
    Josh> am dangerously close to an 'edge' of the trimmer pot and
    Josh> therefore in a non-linear region. Needless to say, I am not
    Josh> confident I have done this correctly.

There procedure is more like:

- Disable one channel, so the Bergoz doesn't work in coincidence, but delivery
each singel event
- Adjust the level for that channel so you have a noticable rate, e.g. the
10 kHz mentioned above. But "noticable rate" is more important than "exact
10 kHz", with no radiation on the detector.
- Reenable that channel, disable the channel and repeat for the second channel
- Reenable the second channel and measure

Measuring frequency for the setup is better done with a bigger integration
window like 100 ms, as values fluctuate less then.  As your setup can't do
that, perhaps add up 100-1000 time slots and their counts. But again,
"noticable rate" is more important than "exact 10 kHz".

    Josh> Does anyone out there have experience with this system? We have
    Josh> an opportunity today to do some experiments - hence my somewhat
    Josh> frantic email.

It seems you are on the right track. Good luck.

Bye

PS: Email me direct if there are more questions, as I am not on the list.
-- 
Uwe Bonnes                bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik  Schlossgartenstrasse 9  64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------

References:
Cosylab MicroIOC/BLM Calibration procedure confusion Josh Stein

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