On Fri, 03 Feb 2017 13:39:02 -0500, wrote:

On Fri, 03 Feb 2017 09:32:07 -0800, Jeff Liebermann
wrote:
In a previous life, I tried to design a "warranty timer" into a
product. Actually, it was suppose to accumulate and display the
amount of time that the unit had been powered on to help establish
maintenance intervals. In previous products, a mechanical
counter-timer was used, but for this version, it was deemed too big
and expensive.
http://www.alliedelec.com/images/products/Small/70132720.jpg
I found a company that made an electrochemical equivalent. It was
housed in a glass cylinder, similar to a common 3AG glass fuse. Inside
was some chemical solution. When a few volts of DC was applied,
electrolytic action caused one end to slowly turn dark, thus
indicating the amount of time that the DC was applied. Sorry, but I
couldn't find the vendor or an equivalent online. When the required
maintenance was performed, the indicator would be replaced as it could
not be reset.

Something like a coulometer???

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...


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558