Re: ELECTRO-CHEMICAL ELAPSED TIME INDICATORS

On Mon, 16 Dec 2024 17:34:12 -0600, Crash Gordon <uucp@crashelex.com>
wrote:

On 12/14/2024 1:29 PM, Joe Gwinn wrote:

Curtis coulometers are analog Elapsed Time Indicators (ETIs) which use
an electro-chemical plating process to integrate current over time.

>
I have a box of these squirreled away in a box someplace.
(Unfortunately I have a *lot* of boxes)
>
There was a paper card underneath the tube that you would slide to
"zero" the meter.  And when it hit the end of the scale, the tube could
be removed (like little fuse clips) and flipped over to count more.
ISTR that if you allowed the electrolyte "bubble" to get all the way to
either end of the tube the device was ruined.

I sorta recall that detail. 

I did a design with such  device in the late 1970s, and when the
design was done, I turned to my business partner and said that there
was no way this would work in the real world because it was far too
hard to come up with any plausible design.  I started over, and
designed the CMOS replacement in a day or two.  And it worked just
file in the field.

The accuracy of the device was proportional to the accuracy of the
current you passed through it.

Yes, but not a big problem in my application..

Joe Gwinn