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Re: [IP] Static Electricity

On 11 Oct 00, at 3:29, email @ redacted wrote:

> I've written to MIT specialists the following:
> We have a medical infusion pump motor running on Eveready 357 batteries. The 
> motor turns a camshaft in short click spurts.  Some users of this pump think 
> that static electricity can temporarily disable it. They believe it is 
> specificaly the motor. They claim an engineering recomendation to wrap the 
> equipment in clothes dryer static guard sheets. Do you have any proof  or 
> contraindications as to the efficacy of this safeguard?

Without samples of the systems I don't think the "MIT specialists" can do 
much more than a guess or opinion.  My experience with the MiniMed in high 
magnetic and RF fields has been that no failures have been encountered.  
The couple of times that my pump have been "zapped" (gone into alarm mode 
and lost all basals, history and had to be reset by removing the batteries) 
have all been in environments where there was a low RF/magnetic field and 
no static electricity (warm, comfortable days with no static crackle when 
you touch things). In the wintertime my office is so dry that static 
electricity is a problem with the computers, but my MiniMed has survived 
two winters without a problem.  

 I'd be more inclined to consider a software problem, like an interrupt 
signal being missed (maybe an edge dectector circuit not quite ready to 
read the pulse that it just got) and the safety systems recognizing that a 
problem exists and then just defaulting to shut everything down.  The 
problem is not too repeatable, and it probably is dependent upon personal 
differences (if it's the static thing that varies widely between individuals, 
and if it's the software then it may depend on the exact state of basal 
rates, history, bolus activity and time of day).  It's very hard to 
troubleshoot this kind of problem too, because all the details needed to 
determine what is going on are hard to duplicate...

I don't thinks the static guard sheets will hurt anything though.  If the 
problem is static related they may help...  and then there's option #3 - a 
combination of static electricity causing the missed pulse which confuses 
the software...  Ain't technology grand?

Rev. Randall Winchester
WD4HVA (email @ redacted)
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