Does anyone have measurements of the medical effects of power-line-frequency
current flowing in humans? Many years ago the IEEE Power Engineering Society
published data where the threshold was 200 milliamperes in power-line workers.
Thank you
Bob Schlentz
appro...@minn.net
Robert A. Macy wrote:
>From personal experience, 0.1mA is wa-a-a-ay too high!
Make it more like 10 uA
- Robert -
On Tue, 11 Oct 2005 18:03:19 +0100
gd...@ncht.trent.nhs.uk wrote:
With regard to whether Doug should be measuring Patient
Leakage from his
bedframe:-
I believe the bedframe is an Applied Part under the
definition of the
general standard 60601-1; ("AP = a part of the equipment
which in normal use
.....can be brought into contact with the patient ....")
ie: contact isn't
necessary for the device to perform its function, but
contact could happen
during use - which is the case for hospital bedframes.
Under the particular standard for electric beds
IEC-60601-2-38, "AP = all
parts of the bed which can intentionally or
unintentionally come into
contact with the patient..."). There is a diagram in the
edition we have
(1996) showing which areas of the bedframe are thus
included.
My interpretation is then that the bedframe should be
considered an AP and
so, as Doug says, it should be tested for Patient
Leakage. If it were not an
AP it would have to be tested for Enclosure Leakage
anyhow - in both cases
the limits for ac leakage are 0.1mA Normal Condition and
0.5mA Single Fault
Condition (though for Patient Leakage there are dc limits
too).
If you are measuring 0.1mA leakage through the specified
measuring device,
which simulates a patient impedance, then how low the
voltage is on the
earthed frame is kind of immaterial - it is the current
not the voltage that
the patient will feel. (The leakage likely has high
impedance origins which
are better modelled as a current source than a voltage
source).
Ged Dean
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