Jeff Liebermann wrote:
On Tue, 14 Feb 2017 11:42:15 -0500, "Michael A. Terrell"
wrote:

Jeff Liebermann wrote:
On Mon, 13 Feb 2017 23:30:17 -0500, "Michael A. Terrell"
wrote:

Jeff Liebermann wrote:
Sorta. The timer was basically a miniature electroplating bath, which
used a the current flow to move ions of something, from one end of a
glass cylinder to the other. A coulomb is 1 amp for 1 second and can
count both electrons and ions, as in the bath.
http://www.electrolytics.org/faradaysLaw.html
I have a box buried somewhere with the project notes which might have
the data sheet. Meanwhile, I think I may have found the patent, or
rather a later patent as the one I used was in about 1976:
https://www.google.com/patents/US6198701
I'll dig through the citations later...

http://oakbluffclassifieds.com/Funny-Listings/Very-Funny/Curtis-elapsed-time-indicators-520LNA-115-240-indachron-picture-3.jpg

Bingo:
http://download.siliconexpert.com/pdfs/2010/11/28/5/7/11/117/crts_/manual/120-pc.pdf
That's it except the one we were using was the PCB mounted model,
something like the 620PC model:
https://rcfreelance.com/IC/MS3311-3/
Curtis Instruments is still around. The mercury coulometer product
does not appear on their web site, but is mentioned in the company
history at:
http://curtisinstruments.com/?fuseaction=Company.Anniversary

Thanks much.

You're welcome. I have heard they stopped making them, after some
old ones caught on fire and did a lot of damage.

I don't see what might have burned. They were very low power.
According to the data sheet, 4uA at 5V for the model 120PC. My
guess(tm) is that the mercury used in the indicator was deemed
environmentally incorrect.

It would interesting to resurrect the idea, but using something less
hazardous, in order to build a warranty timer. Offering a warranty by
hours of use, instead of years after manufacture, would be an
attractive sales gimmick.


It was the AC versions that were reported to have caught fire, just
like some of the modular IEC power connector/line filters when the
European made film capacitors failed. Certain brands of these modules
are replaced in every piece of equipment by some people who collect old
test equipment.


--
Never **** off an Engineer!

They don't get mad.

They don't get even.

They go for over unity! ;-)