Yes, I also belive that your equipment has no patient leads and that the enclosure leakage was performed as part of the power supply. If in doubt regarding the enclosure leakage, best is to ask the power supply manufacturer for a complete report.
Why are you using UL544 power supply? This standard is becoming obsolete soon! There are many power supplies out there evaluated to UL2601-1 which is harmonized with IEC 60601-1. Best Regards At 15:35 24/03/2000 EST, [email protected] wrote: > >Most esteemed colleagues, we are looking for your professional opinion on a >UL 544 leakage limit (I think you will find this interesting): > >1. This particular product uses a UL 544 evaluated direct plug in power >supply with outputs to the patient care equipment. In this case it is a >diagnostic unit that sends an audible tone to headphones (audiometer). The >plug in power supply Conditions of Acceptability indicate the outputs are >"not evaluated for patient leads" (i.e. applied parts"). > >2. Table 42.1 of UL 544 specifies leakage limits. "patient connection" >footnote "a" references testing of "patient leads (applied parts)" >connections. There is no written definition for "patient leads" or "applied >parts" in UL544. > >As such NFPA 99 supplements UL 544 as it draws from the NEC and NFPA 99 >(referenced in UL 544): > >NFPA 99 defines the US definition of "Patient Lead" = "A deliberate >electrical connection that can carry current between an appliance and >patient. It is not intended to include adventitious or casual contacts such >as a push button, bed surface, lamp, hand held appliance, etc." > >3. As the headphones of this audiometer are clearly not "deliberate >electrical connections" we conclude these are not "patient leads (applied >parts)" which would not fall under the limits for "patient connection" limits >per 544. The applicable limits would be as defined under "enclosure or >chassis" "grounded " or" double insulated".... Now be careful not to jump to >a conclusion yet..... You might say "enclosure or chassis?", but if you >examine this, you will find the footnotes reference UL 544's Enclosure >definition: > >"Enclosure = That external portion of an appliance that serves to house or >support component parts, or both. Enclosure of patient care equipment likely >to be contacted by a patient include, for example, bedside monitors, bed >frames, dental chairs, and examination stands." > >Our conclusion: Due to the US definition of "patient leads (applied parts)", >the earphones of an audiometer (patient care equipment) are subjected to the >leakage current limits for "enclosure or chassis", and not the limits of >"patient connection". For this particular application, we conclude that based >on the C of As, the output of the power supply has already been evaluated for >"enclosure or chassis" leakage limits. > >Your Thoughts??? > >Drew > >PS: If you care to look, CSA supports this position in that 50uA is related >to "cardiac tissue" limits only. See Appendix A of CSA 22.2 125 (500uA). > >------------------------------------------- >This message is from the IEEE EMC Society Product Safety >Technical Committee emc-pstc discussion list. > >To cancel your subscription, send mail to: > [email protected] >with the single line: > unsubscribe emc-pstc > >For help, send mail to the list administrators: > Jim Bacher: [email protected] > Michael Garretson: [email protected] > >For policy questions, send mail to: > Richard Nute: [email protected] > > > Peter Merguerian Managing Director Product Testing Division I.T.L. (Product Testing) Ltd. Hacharoshet 26, POB 211 Or Yehuda 60251, Israel Tel: 972-3-5339022 Fax: 972-3-5339019 e-mail: [email protected] website: http://www.itl.co.il ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
