FYI

 

From: markel...@gmail.com [mailto:markel...@gmail.com] On Behalf Of Mark
Littlejohn
Sent: Tuesday, 17 July 2012 10:09 AM
To: Owen Byrnes
Subject: Re: [bmelist] Re: Laproscopic instrument testing with an HiPOT
insulation tester

 

Pregnant Women and HiPOT testing

 

I need to declare that I have a vested interest in this as a manufacturer,
however I have some references and data that may be useful as guidance for
Biomeds.

 

I usually don't reference Wiki but it is fairly accessable
http://en.wikipedia.org/wiki/Spark_gap which says in part-


"Health hazards


Exposure to an arc-producing device can pose health hazards. In a closed
space such as a classroom or home, the continuous arc formation of an
open-air Jacob's Ladder will ionize oxygen and nitrogen, which then re-form
into reactive molecules such as  <http://en.wikipedia.org/wiki/Ozone> ozone
and  <http://en.wikipedia.org/wiki/Nitric_oxide> nitric oxide. These
<http://en.wikipedia.org/wiki/Free_radicals> free radicals can be damaging
to the  <http://en.wikipedia.org/wiki/Mucous_membranes> mucous membranes of
people near the spark gap. Plants are also susceptible to ozone poisoning.

These hazards are not present when the arc is formed outdoors since the
heated ionized gases will rise up into the air and dissipate into the
atmosphere. Spark gaps which only intermittently produce short spark bursts
are also minimally hazardous because the volume of ions generated is very
small.

Arcs can also produce a broad spectrum of wavelengths spanning the visible
light and the invisible ultraviolet and infrared spectrum. Very intense arcs
generated by means such as  <http://en.wikipedia.org/wiki/Arc_welding> arc
welding can produce significant amounts of ultraviolet which is damaging to
the retina of the observer. These arcs should only be observed through
special dark filters which reduce the arc intensity and shield the
observer's eyes from the ultraviolet rays."

 

I have not been able to find any references to XRay generation, except
perhaps in reference to TV CRT's where you accellerate electrons at approx
25kV over approx 400mm, which is noted that it can produce low level soft
Xrays. However health risks would be only elevated over the background
radiation after long term continuous exposure.

 

 The voltage outputs of the HiPOT 150 tester is 4.34kV @ 120MegOhms and 1kV
@ 33MegOhm yielding currents of approx 30uA which is well under the Applied
Part Leakage Normal Condition (BF 100uA) and also Mains on Applied Part
leakage (BF 500uA). These currents are sufficiently low for monitoring
equipment used in labour wards, and that the current path of the HiPOT (if
used with the wrist strap) should not involve the Uterus.

 

 

There is higher peak currents available from the discharge of the stray
capacitance. This stray capacitance and static discharge is always present
(especially in cars, new carpets etc) and naturally occuring static charges
can be up to 20kV (note the ESD protection for MOS devices). The wrist strap
discharges static build up in the stray capacitance through a 1MegOhm
resistor (as per the standard for ESD). 

 

 

Mark Littlejohn
ElectroLAB P/L
129 Ala Moana Rd
East Kurrajong NSW 2758
Ph    61  2  4573 0591
Fax   61  2  4573 0592  

 

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