[Hps-ecal] ecal hv

[FX]

This is very low current, so it's not dangerous. I am not sure about safety
rule however.
On Dec 3, 2014 8:23 AM, "Gabriel CHARLES" <charlesg at ipno.in2p3.fr> wrote:

> Am I allowed to measure high voltage with a standard voltmeter if they
> can measure up to 400V?
>
> Le 2014-12-03 06:35, Stepan Stepanyan a écrit :
> > OR, we could first measure voltage right at the output of the
> > distribution
> > module and see if it is different from the set value.
> >
> > Stepan
> > On 12/3/14, 6:16 AM, Nathan Baltzell wrote:
> >> Yes, we cannot rule out the distribution modules yet.
> >> One option to test that is to move a "bad" HV module to a different
> >> distribution module.
> >> -Nathan
> >>
> >>
> >>
> >>
> >> On Dec 3, 2014, at 12:18 AM, Stepan Stepanyan <stepanya at jlab.org>
> >> wrote:
> >>
> >>> Nathan,
> >>>
> >>> Are you sure this is the problem of the slot/channel on the
> >>> mainframe/board or the distribution
> >>> module. We should find a way of measuring voltages. perhaps before
> >>> and
> >>> after the distribution
> >>> modules in the racks (may be tricky, we can ask electronics group for
> >>> help).
> >>>
> >>> Regards, Stepan
> >>>
> >>> On 12/2/14, 9:00 PM, Nathan Baltzell wrote:
> >>>> Dear Everyone,
> >>>>
> >>>> This evening we realized another problem probably due to the ECal HV
> >>>> supply.
> >>>>
> >>>> First, we see gains from cosmics that are 30/40% higher on all
> >>>> channels in
> >>>> certain HV groups, while all channels outside those groups are
> >>>> within few-%.
> >>>> Those high-gain groups are isolated to the left half of the
> >>>> calorimeter, on both
> >>>> top and bottom, and occur every other HV group.
> >>>>
> >>>> One hypothesis is that it is due to motherboards, since left-top and
> >>>> left-bottom are
> >>>> from one manufacturer, while right-top and right-bottom are from
> >>>> another.  But I
> >>>> think we ruled that out as the primary cause out by using LEDs:
> >>>>
> >>>> Swapping calorimeter channels from one HV mainframe channel to
> >>>> another,
> >>>> while keeping everything else constant (including, of course, the
> >>>> voltage demand
> >>>> and readback settings), resulted in large changes in measured LED
> >>>> signal amplitude
> >>>> consistent with cosmic gains for these low/high-gain groups.
> >>>>
> >>>> It may also be worth noting that these high-gain HV groups are on
> >>>> mainframe
> >>>> channels 3,5,7,9,11 for the modules in both slots 0 and 8.  When
> >>>> plotting for ECal
> >>>> geometry the correspondence with mainframe channel is not obvious,
> >>>> due to
> >>>> mappings and relocation of one dead channel to another slot.
> >>>>
> >>>> So it seems the large variations in cosmic gains for certain HV
> >>>> groups must be due
> >>>> to the HV supply and nothing to do with the calorimeter.  One
> >>>> question is what to do in
> >>>> the short term for 2014 running.  We can try moving the modules to
> >>>> open slots, or
> >>>> just reseating them, both possible tomorrow.  Or measure voltages
> >>>> directly at the
> >>>> calorimeter and adjust accordingly, ignoring mainframe's readback.
> >>>> Or just correct
> >>>> with gains, which could require some channel-dependent thresholds
> >>>> for data
> >>>> acquisition.
> >>>>
> >>>> - Nathan
> >>>> _______________________________________________
> >>>> Hps-ecal mailing list
> >>>> Hps-ecal at jlab.org
> >>>> https://mailman.jlab.org/mailman/listinfo/hps-ecal
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> >
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>
> --
> Gabriel CHARLES
> Institut de Physique Nucléaire d'Orsay
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