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Trigger Hardware Operations Safety and Tips
The primary safety issue with the trigger system is
the handling of trigger boards in the crates.
Although the trigger and DAQ crates operate on +-5V and +-12V, the
operating currents are running at >100A in some crates. Becuase the
power supplies need to be able to deliver this level of currents, it
will also happily drive large currents through accidental short
circuits due to improper operation, which will at least damage the
board and the crate backplane at the shorted areas with fair amount of
smoke, and may even cause a fire. Besides the obvious safety hazard
associated with this, the recovery from a damaged crate can be very
complicated, so that everyone performing the hardware operations
are expected to be following the guide lines very closely.
Precautions for Operation
- Think before you move
and move slowly. This is the most general principle
which applies to most hardware operations. Unlike some software tasks
(or video games which can restart after game over), one mistake here
can cause long delays of recovery or irrecoverable damage, or worst
still personnel injury. 'Swift' movement actually hardly saves you any
time and often causes you forgetting something or bumping/scraping on
something which takes more time to redo or fix. Before any major
movement, pause and ask yourself: "Is this what I really want to do ?"
- Check
crate power and
other activities. For any board insertion/extraction or
non-trivial touch to cabling etc., the crate power must be off before
such operations. Before turning on the crate, check activities around
the rack to make sure noone is working on the rack (e.g. at the back of
the rack). People working on non-trivial tasks around the crate other
than simple board insertion/extractions should unplug the crate power
cables.
- Get to know what you
are dealing with. Many accidents are results
of lack of awareness on the consequences of you actions. In our case, a
good knowledge of the crate infrastructure and the difference of
various types of boards, where they can go and where they should not is
a crucial defense against mistakes.
- Avoid
using brute force. Most tasks
can be accompolished with the right tools
and procedures without the need of brute force. Slips while exercising
excessive force is a common source of injury, besides the obvious risk
of equipment damage. Board insertion/ejection can be much easily done
from learning using the latches. In some cases where forces are needed
(e.g. some old boards don't have appropriate latches), it's generally
still possible to make sure the setup 'feels' right before applying
force.
- Resist temptation to
cut corners. Use the proper tools and equipment and
follow procedures. Reaching higher by standing on a chair with
wheels ? Carrying too many things to save a trip ? Conveniently leaving
things in an obviously unsafe position ? Can all be tempting to
save time, even though the risks are also clear.
- Do
not
'try/guess' on hardware. When not sure this is the right
place or procedure, it may be tempting to 'try'. The consequence can be
irrecoverable or easily cost more time to recover than to make sure
what you should be doing at first place.
- Take note of you activities. Write
down what you did systematically is
essential for all hardware operations. Take a note of what was the
settings before starting to change anything.
Trigger Hardware
( details to be added )
Trigger and DAQ
crates
For comments, suggestions and questions to this page,
contact Su Dong
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