ELECTRO-CHEMICAL ELAPSED TIME INDICATORS

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Joe Gwinn 1 year ago

There was a question (from Larkin?) on non-electronic time delay components, and I recalled such a thing from the 1970s, when I considered using it to sequence an electromechanical gadget. Turned out to bet too complicated in that application, and went to a CMOS counter.

Anyway, the name came to me today, and it is still made.

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

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This uses mercury, but if I recall correctly, the 1970s original used silver. I think it was called a coulcell. The original company seems to be gone.

Joe Gwinn

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Jeff Liebermann 1 year ago

Sounds more like a timer than an elapsed time indicator. In the

1970's, we used Agastat pneumatic timers to generate fairly long time delays up to about 30 mins. The original technology was a piston and cylinder, with a controlled air leak.

Electro-Pneumatic timing relay:

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There are other companies that make the same type of timer:

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I suspect that someone had contrived a MEMS pneumatic timer, but I couldn't find one.

Agastat is now owned by TE Connectivity:

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john larkin 1 year ago

It's a form of mercury coulometer. That has a wikipedia page.

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Crash Gordon 1 year ago

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.

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

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Joe Gwinn 1 year ago

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.

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

Joe Gwinn

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ELECTRO-CHEMICAL ELAPSED TIME INDICATORS

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