[modeleng] Re: In case anyone is looking for me
- From: "Dud.One" <dud.one@xxxxxxxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Sun, 6 May 2007 11:45:43 +0100
fitted with Transmitters !, is that so we can find our family member whilst
they wander
around and away from the rest of the family , must remember to take my
handie on shopping trips from now on
for a spot of DF'ing the missing family member .
sorry just had to say it .
dont worry over it too much Alan , just keep well away from welders , motors
should be fine unless your leaning on them when they are running , but at
usual operating distances you should be fine , one other item to be careful
with which does not always spring to mind in the workshop is the Instant Gun
Type Soldering Irons , this affected a friend of mine about 6 months ago ,
so he binned it , you should be able to sense any changes to your pacemaker
, well before it becomes a danger or a problem .
Dave
----- Original Message -----
From: <peter.chadwick@xxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Sunday, May 06, 2007 10:52 AM
Subject: [modeleng] Re: In case anyone is looking for me
> Hi Alan,
> I've been away and out of email access, so couldn't answer before.
>
> Sorry to hear about the problems, but without the electronics, it could be
> worse!
>
> Pacemakers have to have, by law or at least EC Directive, immunity to EMC
> to EN45501 for implantable devices. Peripheral devices have to be able to
> operate in fields of up to 10V/m (EN60601-1-2) if they are life support,
> and most pacemakers are done ona risk assessment basis. However,
> manyfacturers are very careful about it. The biggest problems can come
> form strong very low frequency fields below 15Hz, and a nasty source that
> has been quoted but without any actual figures, are electric locomotives
> in Belgium and Sweden, where the electrification is 16-2/3Hz. Thyristor
> controlled locos running slowly, can, it is claimed, put out very strong
> VLF magnetic pulses which get picked up on the sensors, and through the
> low pass filters. This is where the problem with security gates and
> welders comes in. Incidentally, pacemaker cases are made out of titanium,
> electron beam welded. Pacemakers have very expensive sealed feedthroughs
> incorporating low pass filters, cutting off around 20kHz. 4 leads
> filtered, in a unit about 4mm diameter and the same long, hermetically
> sealed.
>
> Microwave Ovens. If you can get 2.4GHz at 10V/m around the pacemaker, you
> have something more to worry about than the pacemaker! As far as ham radio
> is concerned, you can get advice from the pacemaker manufacturer. The big
> ones are Medtronic, St. Jude Medical, Guidant (which is now Boston
> Scientific) and ELA/Sorin. You've probably got either St Jude or Medtronic
> - they're the biggies in this field. (The year before last, Medtronic's
> CRM - Cardiac Rhythm Management - group showed profits of $26million!)
> Both of them have head offices in Minnesota, which is probably where you
> can the most definitive data for ham radio from - they do have a fair
> number of hams working for them. I may be able to get a contact name for
> SSt Jude in Sweden and for Medtronic in Minneapolis.
>
> As far as ham radio is concerned, a lot depends on the installation. If
> you ran 400 watts plus to a long wire terminating in the shack or to a
> dipole running over the house, there could be a problem. With what's
> called 'good husekeeping' keeping antennas well away from the house - 30
> feet or more - shouldn't offer a problem. EN60601-1-2 does ctually give
> some separation distance, but I don't have it here at home.
>
> Test done by Georgia Tech in the US back in the late 80's (aricle in RF
> Design magazine) showed that no pacemaker tested that had been made after
> 1980 fell over until the field strength was such that the pateient would
> be cooking first.......additionally, I'm told by the manufacturers,
> pacemakers are arranged these days so that in the event of untoward EMC
> conditions, they fall back into a steady 60 or so beats per minute pacing
> mode, althugh this is mandated by the FDA or under the EC's Active Medical
> Implants Directive.
>
> You might ask hw I know all this. For my sins, I'm the Chairman of ETSI
> (European Telecommunications Standards Institute) ERM_TG30 (EMC and Radio
> Matters Task Group 30) and our responsibility is standards for medical
> wireless telemetry. Incidentally, pacemakers will soon have transceivers
> in them, working in the 402 - 405 MHz band. High power for the transmitter
> is 1 milliwatt and the antenna gain and body losses are such that you're
> lucky to get 25 microwatts when measured outside the body........Even so,
> some poeple have raised concerns about the SAR (Specific Absorption Rate).
> So I have a fair amount to do with pacemaker manufacturers - Zarlink have,
> in the past, made the chips for pacemakers, and still do some special
> surge protection devices for defibrillators, which discharge somewhere
> between 800 and 1200 volts from a 1 microfarad capacit into the heart.
> Ouch! These days, we are manufacturing radio transceiver chips for
> implanted medical devices..... as well as for hearing aids and wirel;ess
> endoscopes.
>
> Hope this helps
>
> Peter Chadwick G3RZP
>
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