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
