Dear Alice, thank you for forwarding this anonymous quote. I have some
questions to ask your anonymous friend. You see, I am in Africa. I have
FACScan in the "field" and the power here eats up a lot of equipment.
Everyone recommends a UPS. I use the FACScan plugged to a 220 to 110
tranformer and then a UPS. Everyone recommends this. Does he have any
specific UPS recommendations for my situation? What is the best way for me
to prevent damage to my equipment. This is late because I am
afraid I already had some. This person can e-mail me directly if he/she
feels comfortable doing so.
Jose A. Stoute
USAMRU, Kenya
email: stoutej@africaonline.co.ke or stoutej@wrsmtp-ccmail.army.mil
_______________________ Reply Separator _______________________
Subject: line conditioners
Author: Alice.L.Givan@dartmouth.edu (Alice L. Givan) at wrsmtp-ccmail
Date: 1/5/98 5:42 PM
With regard to my query about voltage line conditioners, I have had mixed
replies about how necessary they are. The people who replied all have them (in
one configuration or another), but some remain sceptical about whether they
actually do anything important or are just insurance (so that service engineers
can't blame voltage fluctuations if something goes wrong???).
I am appending here comments from a service engineer --- that seem to me to be
particularly helpful.
Cheers,
Alice Givan
Quote:
The information I will give you is generic and based on my personal
experience with ALL medical equipment, both therapeutic and diagnostic.
First off, any systems not required for life support should NOT be plugged
into emergency power. This is especially true in areas (like the southeast)
where thunderstorms frequently occur. The reason for this is the trouble
"Emergency Power" generators cause with microciruitry/computers. Most of the
items on Emergency Power are huge inductive (they have motors, compressors, and
require lost of voltage and current to run) devices. As all of the air
conditioners, freezers, air handlers, pumps, elevators, and any other devices
needed for emergency operation start to run after a short power interruption,
they all "grab" for power and cause a power struggle/surge. You've probably
heard the term "transients"...The result is large power spikes, some which will
destroy electronic devices, especially those which are normally used in
households, like a PC. Most manufacturers will install some kinds of voltage/
line conditioners in their main instruments, but not in the PC's they use. PC's
were never designed for industrial use, and those that are have protection
installed and are much more expensive.
The other main cause of power problems in any institution is construction.
Most hospitals, universities, and growing companies are constantly evolving and
changing within or expanding. Unfortunately, most contractors don't give a hoot
about your instruments. They want to stay on their time schedule for completion
of the project and often "stuff occurs"...power shutdowns, interruptions, and
finally-they use power tools! These are also large inductive devices and put
"noise" on the power lines, usually only if they are sharing a circuit, like
working in the next room, or possibly in the same wing of a building. AND, if
you're located in the lab, and X-ray is next door...that new CAT scan system
may
draw more power than the older system that was in there...You may see problems
after a modification/alteration. You can create the same problem in your own
lab
by installing one of the huge tub or refrigerated centrifuges next to your PC
or
cytometer. It draws plenty of current and puts noise on the line. That is the
reason we (BD) ask for a dedicated line.
The BEST device to have installed on any systems not required for life
support is a "drop-out box". It's cheap and opens the circuit if there is a
power outage. The only way to power the system up again is to manually reset
the
cicuit by pressing a button. It's VERY easy. The best thing is that the system
is shut down ONE time, even if you're gone to lunch or a meeting. The greatest
damage done to any elecronic device is when it is swtched Off-On-Off-On-Off due
to a power failure. It is the worst kind of fluctuation a system can face. This
is not to be confused with a GFI (Ground Fault Interrupter) which you will
usually find in your bathroom or anywhere you use electricity near water, which
is grounded to Earth through the water system and the shortest path to ground.
The GFI measures the difference in potential between The Positive (Black) and
Neutral (White) lines of the circuit and trips if there is an imbalance. This
is
useless in a lab with saline, body fluids, chemicals, etc., dripping
everywhere.
Almost every instrument will have some small amount of current leakage which
will cause a GFI to trip.
Then there is the line conditioner, which is the most popular type of
protection device. It will compensate for "brownout" conditions and catch some
of the slower noise spikes. Anyone who says their line conditioner will remove
ALL line noise or spikes is lying. It's almost impossible. The best thing is a
line conditioner AND a dedicated line. And you STILL won't have drop out
protection, unless you buy a conditioner with one included (or install one of
those, too.).
The more expensive option is a "UPS" (Uninterrupted Power Supply), which
employs the use of a huge DC battery in conjunction with a line conditioner.
The
AC is created by a "chopper" circuit or some other method of creating AC from
DC. They also won't run very long, because something like a laser or motor uses
a lot of current. I DO NOT recommend this option. The cost vs. benefit isn't
worth it.
With regard to imaging systems, I can tell you for sure that the frame
grabber cards on an imaging system are VERY sensitive. The boards are about
$2000.00 a piece. They will die if you look at them the wrong way... In our
product line, the frame grabber cards we use are about $25000.00 and I can
tell you they will blow when there are unfavorable power conditions as well. We
installed a universal power supply in that system, and it handles line
conditions pretty well. I can at least tell you we haven't blown any
cards...yet.
I apologize for going on so long about a boring subject, but it is one we
wrestle with almost daily. It is usually an intermittant problem, adding to the
frustration for everyone involved.
unquote.
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