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Problem with leakage current

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Chris Jones

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Mar 8, 1999, 3:00:00 AM3/8/99
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Hello,

I'm a computer tech at a hospital. I'm working with our BioMed people
to try and find a solution to a problem.

We have a system for doing EEGs that uses a standard IBM compatible PC
and Monitor for the data collection and review.

My BioMed people tell me the Federal Regs say leakage current on a device
that could come in contact with a patient cannot exceed 300 microAmps. The
monitor is leaking 290 microAmps by itself. The PC, amplifiers, and other
devices combined are well with in this limit. Only the monitor is way out
there. If we can find a monitor that is leaking less than 100 microAmps I
think we would be OK.

Do any of you know of a large monitor, 17 to 21 inch, that is designed
to have low leakage current? Or have you dealt with this situation some
other way? Any suggestions would be apprecitated.

Thanks,

Chris Jones
Work: clj...@jpmc.org
Home: clj...@ionet.net

Michel

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Mar 9, 1999, 3:00:00 AM3/9/99
to
Chris, you might end up having to use an isolation transformer.

Take care, Michel.

Ian Molesworth

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Mar 10, 1999, 3:00:00 AM3/10/99
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Chris Jones wrote:

Hi Chris

I am reading your posting on a 17 inch LCD monitor - how about that as a
solution?

Ian Molesworth


Frank Miles

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Mar 10, 1999, 3:00:00 AM3/10/99
to
In article <36E67185...@logica.com>,

Ian Molesworth <moles...@logica.com> wrote:
>
>> We have a system for doing EEGs that uses a standard IBM compatible PC
>> and Monitor for the data collection and review.
>>
>> My BioMed people tell me the Federal Regs say leakage current on a device
>> that could come in contact with a patient cannot exceed 300 microAmps. The
>> monitor is leaking 290 microAmps by itself. The PC, amplifiers, and other
>> devices combined are well with in this limit. Only the monitor is way out
>> there. If we can find a monitor that is leaking less than 100 microAmps I
>> think we would be OK.
>>
>> Do any of you know of a large monitor, 17 to 21 inch, that is designed
>> to have low leakage current? Or have you dealt with this situation some
>> other way? Any suggestions would be apprecitated.
>
>Hi Chris
>
>I am reading your posting on a 17 inch LCD monitor - how about that as a
>solution?
>
>Ian Molesworth
>

As soon as you upgrade, or get a new piece of equipment, or perhaps
wire things differently, you (or your patient!) could be in trouble.

If your EEG input amplifiers aren't isolated, then you should upgrade
them. Possibly no more expensive than a 17" LCD monitor. Then you
can have complete freedom on the other side of the isolation barrier
to use any PC, monitor, whatever, and your patient will be in a
safer situation!

-frank


Eisner Safety Consultants

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Mar 10, 1999, 3:00:00 AM3/10/99
to
I assume your EEG is Certified to a 601-1 based standard such as UL 2601-1
or CSA C22.2 No 601.1 or IEC 601-1 or EN60601-1. If that is the case you
may want to consider using IEC 601-1-1 (Medical Electrical Systems
standard). There are several solutions to your problem. The most commnon
is to use a medical grade isolation transformer.
To find out more please contact me directly at:
ttrav...@earthlink.net
Leonard Eisner, P.E.
Product Safety & CE Mark Consultant

>I'm working with our BioMed people
>to try and find a solution to a problem.
>

texu...@md3.vsnl.net.in

unread,
Mar 20, 1999, 3:00:00 AM3/20/99
to

Hello,


I don't know monitor manufacturers will publish leakage currents on their
specifications.Anyway you can check this thing with one company who is
specialised in Medical monitors


Clinton Electronics Corporation
Minnesota USA
Tel: 612-753-8452
e-mail: HRdi...@aol.com

Regards


SRI

In article <7c224g$me4$1...@ionews.ionet.net>,


"Chris Jones" <clj...@ionet.net> wrote:
> Hello,
>

> I'm a computer tech at a hospital. I'm working with our BioMed people


> to try and find a solution to a problem.
>
> We have a system for doing EEGs that uses a standard IBM compatible PC
> and Monitor for the data collection and review.
>
> My BioMed people tell me the Federal Regs say leakage current on a device
> that could come in contact with a patient cannot exceed 300 microAmps. The
> monitor is leaking 290 microAmps by itself. The PC, amplifiers, and other
> devices combined are well with in this limit. Only the monitor is way out
> there. If we can find a monitor that is leaking less than 100 microAmps I
> think we would be OK.
>

> Do any of you know of a large monitor, 17 to 21 inch, that is designed
> to have low leakage current? Or have you dealt with this situation some
> other way? Any suggestions would be apprecitated.
>

> Thanks,
>
> Chris Jones
> Work: clj...@jpmc.org
> Home: clj...@ionet.net
>
>

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AlliedInco

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Mar 20, 1999, 3:00:00 AM3/20/99
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Hi, There are two easy solutions to your problem. One: Buy a medical grade
monitor, relatively expensive but current leakage would be acceptable. Two:
Isolation transformer, economical solution which is also applicable to nearly
any piece of equipment. I am surprised your BMETs didn't know this.
Unfortunately there are many varieties of BMETs. Look for the CBET after the
name to get a certified tech. Hope this helps. e-mail me if you need further
assistance.

Kenneth R. Foster

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Mar 21, 1999, 3:00:00 AM3/21/99
to
> Isn't the solution to use an isolation amplifier as preamplifier for the EEG
> electrodes? The leakage current from the amplifier into the patient will be
> very small. You need that for electrical safety reasons in any event.

Or am I missing something?

> "Chris Jones" <clj...@ionet.net> wrote:
> > Hello,

> > We have a system for doing EEGs that uses a standard IBM compatible PC
> > and Monitor for the data collection and review.
> >
> > My BioMed people tell me the Federal Regs say leakage current on a device
> > that could come in contact with a patient cannot exceed 300 microAmps. The
> > monitor is leaking 290 microAmps by itself. The PC, amplifiers, and other
> > devices combined are well with in this limit. Only the monitor is way out
> > there. If we can find a monitor that is leaking less than 100 microAmps I
> > think we would be OK.

--
Kenneth R Foster
Department of Bioengineering
University of Pennsylvania
220 S. 33rd St.
Philadelphia PA 19104-6392
215-898-8534
fax 215-573-2071
Chair, EMBS Committee on Man and Radiation 1997-
Faculty Associate, Ware College House
*****************************************************************************
SSIT Website: http://www4.ncsu.edu/unity/users/j/jherkert/
COMAR website http://homepage.seas.upenn.edu/~kfoster/comar.htm
Blurb for latest book http://homepage.seas.upenn.edu/~kfoster/book.htm
Recent Papers http://homepage.seas.upenn.edu/~kfoster/papers.htm

AlliedInco

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Mar 26, 1999, 3:00:00 AM3/26/99
to
Actually the patient leads to the preamp were originally elertomagentically
isolated vis an isolation transformer. Modern units use optical isolators.
There are two kinds of leakage to be concerned with regarding ECG units:
patient leakage and chassis leakage. From the original message I concluded the
PC was permitiing unacceptable leakage. That is chassis leakage and can be
corrected by an isolation transformer.

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