QUESTION:
My customer wishes to place a RISC System/6000 and associated
peripherals (7013,7012,7010,6091,7210,7209,7208, etc.) near a heavy
MRI research area. Consequently, the machines would be very close to
some powerful magnets. I cannot find any magnetic tolerances published
for the RISC System products. Can you please find out what is
considered a normal magnetic operating environment for RISC System
equipment, especially the disk and tape?
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Please try to find out the answers to the following questions:
1) How much EMR do the magnets produce (I think this is measured
in gauss)?
2) How far away from the magnets will the RISC/6000 hardware be?
3) Will there be any shielding (e.g. - lined windows) between the
magnets and the RISC/6000?
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QUESTION:
The MRI supplier has stated that the fringe field from the magnet is not
expected to exceed the room walls surrounding the magnet (i.e. the
RISC Systems and optical disk, magnetic disks, CD, etc. would be just
OUTSIDE those walls). The .5 gauss line is expected to fall right on
the partitions of the MRI room. The customer wants to know at what
point he should be concerned.
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A: We do not test for magnetic field susceptibility. However, there are
some data available as to the effects of certain magnetic field levels
on system components.
Display
-------
The display is the system component that would probably react first to
the lowest magnetic field levels before effects are observed on any other
system component. Several outside studies have shown that levels where
distortion from AC magnetic fields first become noticeable are 10 mG and
16 mG for VGA and EGA displays, respectively.
A field level of 500 mG will probably cause some waviness on the display.
However, this distortion can probably be reduced by repositioning the
display to minimize its alignment with the H-field lines.
Data Storage Media
------------------
On the other hand, a much higher magnetic field is required to directly
alter data bits on a hard-file. Storage Engineering in Austin has dealt
with one vendor who specified his file's susceptibility to DC magnetic
fields at 10 G.
It is unlikely that 500 mG will directly alter bits on any data storage
media.
System CPU
----------
Since we do not test H-Field susceptibility, it is harder to assess the
MRI unit's effects on CPU operation. Any effects would probably appear
somewhere along the 40 dB range between the 10 mG and 10 G levels
discussed above.
It should be considered that RS6000s have operated in relatively
uncontrolled environments and that fields from appliances spaced 1" away
can greatly exceed 100 mG. Moreover, we are not aware of any CPU
failures that have been conclusively attributed to magnetic fields.
If a RS6000 failure is suspected to be caused by H-fields, the system
should be moved and an attempt made to repeat the failure.
Solutions for verified H-field failures are usually either to shield
the susceptible component or to permanently move the RS6000 further
from the H-field source.
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This item was created from library item Q621896 CBTXG
Additional search words:
APR93 ASSOCIATED CBTXG HARDWARE IX MAGNETIC PERIPHERAL PRODUCT RISC
RISCOHW RISCSYSTEM S6000 TOLERANCES
WWQA: ITEM: RTA000029731 ITEM: RTA000029731
Dated: 04/1996 Category: RISCOHW
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