CVNetters,
Thanks to all who shared their tips on monitor shielding with me. Because
I received almost as many requests for a summary as I did tips, I conclude
this is a common problem. Here are the tips I received; I have attempted
to delete redundant ones.
Ken Britten
UC Davis Center for Neuroscience
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>From fraser@NSMA.Arizona.EDU Tue Apr 2 06:01 PST 1996
From: Fraser Wilson <fraser@NSMA.Arizona.EDU>
To: khbritten@ucdavis.edu
Ken,
OCLI (Santa Rosa, CA) manufacture coated glass shaped to fit
monitors. Attaching a grounded wire to the rim of the glass knocks down
the monitor radiation such that there is no perceptible artifact with a
video stimulus. It is expensive, though. I don't have OCLI phone number
right now, but I will look it up and pass it on. Please let me know if
you hear of some good alternatives.
Good luck,
Fraser Wilson
Neural Systems, Memory & Aging
327 Life Sciences North Building
College of Medicine
University of Arizona
Tucson, AZ 85724-5115
Phone: (520) 626-2374
FAX: (520) 626-2618
Email: fraser@nsma.arizona.edu
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>From rabolt@xs4all.nl Tue Apr 2 06:51 PST 1996
From: "Rene A. Bolt" <rabolt@xs4all.nl>
Subject: Re: CVNet - query on monitor shielding
How large does the screen have to be? You can buy glass screens with an
antireflecting coating, which is also conducting - these are used for
'upgrading' monitors, and are conducting in order to 'dump' static
elictricity; they can be grouded as well. They should be available in
17" size. If this is large enough (you might use a metal shielding, and
use this as a transparent window in the shielding), it might also be
affordable. A 14-15" version is about 100 Dutch Guilders, I think a 17"
version might be about twice this. Unfortunately, i have no specs
available. Many computer suppliers will have these screens available.
Sincerely,
Rene A. Bolt
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From: poirson@cns.NYU.EDU (Allen Poirson)
To: khbritten@ucdavis.edu
Subject: Displays
Hi Ken-
Have you considered generating your image elsewhere
and projecting it to the place you want? This solves
problems for the fMRI guys. (I'm not yet up on the devices
they use).
Good luck,
Allen
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>From oph001@service1.uky.edu Tue Apr 2 08:40 PST 1996
To: khbritten@ucdavis.edu
Subject: Re: CVNet - query on monitor shielding
>
>I might suggest what I have buildt, and that we were building many years ago
>as well : distinctly low tech - a 1 inch deep salt water aquarium! Simply
>build a plexiglass window sandwich with about a 1 inch central cavity. Fill
>that with salt water and ground the water. Presto, a transparent electrical
>shield.
>
>Elmar T. Schmeisser, Ph.D.
>Ophthalmology, Kentucky Clinic
>voice: 606/323-6730 FAX: 606/257-6718
>alternate e-mail: oph001@ukcc.uky.edu
>http://www.uky.edu/Medicine/Departments/Ophthalmology/ophthalmology.html
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>From bullers@violet.berkeley.edu Tue Apr 2 11:27 PST 1996
To: khbritten@ucdavis.edu
Subject: monitor shielding
Ken
I offer chicken wire as a low tech solution.
Mark Bullimore
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>From r.jacobs@auckland.ac.nz Tue Apr 2 16:33 PST 1996
To: khbritten@ucdavis.edu
From: r.jacobs@auckland.ac.nz (Rob Jacobs)
Subject: Monitor Shielding
To Ken Britten
The people using the VERIS system (including ourselves) routinely record
nanovolt potentials from flickering stimuli of about 100cd/sqm produced on
a VDT viewed from as close as 30cm.
We and others use an earthed conductive "cone" (made of aluminium foil on a
cardboard substrate in our case) between the monitor and the patient. The
small end of the cone is large enough for the patient to look through and
the large end of the cone is the outside diameter of the screen. This
means that there is nothing between the patient and the screen to reduce
luminance.
Hope this helps.
Rob Jacobs, Norhani Mohidin, Maurice Yap
Rob Jacobs email r.jacobs@auckland.ac.nz
Department of Optometry and Vision Science fax +64 9 308 2342
The University of Auckland phone +64 9 3737 599 xt 6019
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>From jnelson@ln.nimh.nih.gov Tue Apr 2 18:04 PST 1996
From: jnelson@ln.nimh.nih.gov (Jerry Nelson)
To: khbritten@ucdavis.edu
Subject: monitor shielding
Ken,
Be sure to reflect your answers to the Net--big common problem
here.
For magnetic shielding away from the screen, there is of course
mu metal in convenient strips, even pressure-sensitive adhesive-
backed from e.g., McMaster-Carr 908/329-3200.
I would be pleased to discuss optimizing the recording electronics
with you -- no one in Desimone's lab shields the monitor --
but you probably know most of the generalities I can tell you.
Getting the principles applied effectively can require a
willingness to tear down and rebuild a setup (oh no!!),
and the rebuilding has to be done with a no-panic, no-rush
attention to detail and craftsmanship. (It may just look like
Al foil to you, but... )
Best wishes with all this,
--jerry
Jerry Nelson, Ph.D.
Lab Neuropsychology
NIMH / NIH Bldg 49 1B80
49 Convent Drive MSC 4415
Bethesda, MD 20892
jnelson@ln.nimh.nih.gov
tel 301/496-5625, ext 224
tel+FAX home: 703/448-4543
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>From NPARRY@fs1.mci.man.ac.uk Wed Apr 3 01:07 PST 1996
From: Neil Parry <nparry@fs1.mci.man.ac.uk>
Organization: M.R.I (University of Manchester)
To: khbritten@ucdavis.edu
Dear Ken,
For several years I have been using earthed Pilkington K-glass to
reduce electrostatic interference from my monitors. It's
ion-implanted on one side to make it conductive. I don't have
the technical specs here but the light transmission is as good as or
better than you quote, and the impedence is similar. Optical
quality is pretty good. It's designed as low heat loss glazing
material, although I don't know if its available in the US.
Let me know if I can help more. Good luck.
Neil.
DR NEIL PARRY
Clinical Vision Scientist,
MANCHESTER ROYAL EYE HOSPITAL
email: nparry@fs1.mci.man.ac.uk
phone: +44 161 276 5571
fax: +44 161 273 2028
smail: Vision Science Centre
Manchester Royal Eye Hospital
Oxford Road
Manchester M13 8WH
UK
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>From fraser@NSMA.Arizona.EDU Wed Apr 3 08:44 PST 1996
From: Fraser Wilson <fraser@NSMA.Arizona.EDU>
Ken,
You were interested in obtaining treated glass for shielding
amplifiers from CRTs. This is old address, but the products work:
Optical Coating Lab
2789 North Point Parkway
Santa Rosa, CA 95407-7397
(707) 545-6440
Fraser Wilson
Neural Systems, Memory & Aging
327 Life Sciences North Building
College of Medicine
University of Arizona
Tucson, AZ 85724-5115
Phone: (520) 626-2374
FAX: (520) 626-2618
Email: fraser@nsma.arizona.edu
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From: "Curtis L. Baker" <curtis@spot.vision.mcgill.ca>
To: khbritten@ucdavis.edu
Subject: shielding
Hi Ken,
I have never had any problems of pickup from my monitor on a recording
setup, which I could not eliminate by re-arranging the grounding, even at a
short (30 cm) viewing distance. However, I have never had to deal with
search coils, which I gather are a greater problem.
A lot of consumer-grade anti-glare shields for monitor screens now
also have some electromagnetic shielding, for those worried about getting
cancer from their computers - have you tried any of those ?
Another very low-tech approach might be to use copper or aluminum
window screen - unless you are using very high spatial frequencies, this will
cause very little image attenuation, especially if outside the focal plane of
the animal.
Curtis Baker
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>From rpinter@maxwell.ee.washington.edu Wed Apr 3 12:25 PST 1996
Date: Wed, 3 Apr 1996 12:25:27 -0800
From: Robert Pinter 3-2186 <rpinter@maxwell.ee.washington.edu>
To: khbritten@ucdavis.edu
Subject: shielding film.
| This material has proven useful in insect vision physio. setups, and
is fairly thin. The company is
Tecknit, EMI Skhielding Div.; 320 N. Nopal St. Santa Barbara, ca 93103
-Bob Pinter
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>From larry@vis.caltech.edu Wed Apr 10 13:11 PDT 1996
From: larry@vis.caltech.edu (Lawrence Hugh Snyder)
To: khbritten@ucdavis.edu
Subject: monitor shielding
Hi Ken. We've found that a "Anti-Glare Radiation Filter" made by 3M
model number AF250XXL works well. (For 19" to 21" monitors).
They don't give specs on resistance, but claim "blocks 99.9% of ELF/VLF
E-field radiation", which probably doesn't mean a damn thing, BUT
it seems to do the trick quite nicely -- no problems recording with
the monitor face sitting 20" or so from the monk. Try
CDW
1020 East Lake Cook Road
Buffalo Grove IL 60089
larry snyder
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