Mark Ito suggested this would be of broader interest, so I
am forwarding it to the group.
Basically Hall B is now monitoring some diagnostic signals from
the high sensitivity smoke detector network in Hall B, using
EPICS. There are 'chart recorder' outputs from the system which
can be accessed without disturbing its normal functioning.
This allows us to look for problems in parallel with the
certified building fire alarm system. If we can tolerate a false
alarm every now and then, we can set our alarm levels much lower
than the building systems and so potentially get much earlier
warning of incipient fires.
Since the message below, I put together a rudimentary alarm
handler which watches the VESDA system and the high voltage
systems. We have had about one week's operating experience with
this and it appears to be working well. One thing we observe
is VESDA trips during beam tuning into the hall; these are
very brief spikes in the output, sometimes firing 3 detectors
at once, obviously due to some electronic (not smoke) effect.
We have also seen alarms due to legitimate failures in the
high voltage systems. So everything appears to be working,
although there are details we don't quite understand.
CREDITS:
I was able to get the VESDA ADC's up and working in a week
or so, starting from almost zero EPICS knowledge, only because
of lots of patient help from Mike Vineyard on how to set up the
XYCOM 560's and read them out. Mike also showed me how to set up
the alarm handler. I benefitted from the work of Sasha Phillips
who already had automatically produced alarm handler configuration
files for the high voltage systems; I just tuned them a bit and
concatenated them into one big file for the run. Mark Ito helped
me at every point, in particular in fitting my code into the
production version of the Hall B slow controls software.
>Will,
>
>Why don't you post this to the slow controls mail list? Just send the
>message to clas_slow_control@jlab.org.
>
>-- Mark
>
>>
>> 15 February 1997
>>
>> Hello,
>>
>> The VESDA analog output is now displayed in the control
>> room on a slow controls screen. It looks a little funny
>> because some fonts aren't available for some reason, but
>> if there's smoke in the hall you'll see it on the screen.
>> I may change scales and make other small modifications,
>> but basically the system is in operation. I have currently
>> started it in one of the upper terminals in the control
>> room, visible when you enter the room.
>>
>> I have set the low level alarm at 1.0 volts, and the
>> upper level alarm at 1.5 volts. At the first level, the
>> bar plot turns yellow; at the second level, it turns
>> red. The building fire alarm rings at 8 volts, so we
>> have a possibility of a much earlier alert than before,
>> as long as people look at the display. We should discuss
>> where the best location is for this display. I would like
>> to always have it running, 24 hours a day, year round.
>>
>> - Will Brooks