Re: MicroR inst, NaI question

[Wes Van Pelt <VanPeltW@idt.net>]

Les Slaback wrote:
 
> Question:  What is the change in the NaI PM technology that has reduced the
> power draw so much that these portable MCAs work on just a few batteries?
> It used to be that you needed a separate, wieghty battery pack.
> 

Les and All,

I believe PM tubes have not changed...they never have drawn much
current.  The old battery packs were large and heavy because they had to
produce about 1,000 volts (and very low current).  It would take 667
individual cells in series to make 1,000 volts.

My guess is that today they use a few D cells and a DC to DC electronic
converter to get 1,000 volts. The trick is to keep the voltage very
stable.

Regards,
Wes
-- 
Wesley R. Van Pelt, Ph.D., CIH, CHP                KF2LG
President, Van Pelt Associates, Inc.     
Consulting in radiological health and safety.
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