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'[EE] Murcury Time Totalizers'
2007\05\14@125235 by Pete

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Doh, repost under [EE]


I've seen these things on quite a bit of older equipment, "Time
totalizers" consisting of a glass tube filled with a murcury bubble that
moves maybe an inch over 5000 hours. For instance the one at the bottom
of this page:

http://www.surplussales.com/Meters/MtrTime.html

I'm curious, do they still make them? How do they work anyway?

- --
http://petertodd.ca
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2007\05\14@130743 by David VanHorn

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> I've seen these things on quite a bit of older equipment, "Time
> totalizers" consisting of a glass tube filled with a murcury bubble that
> moves maybe an inch over 5000 hours. For instance the one at the bottom
> of this page:
>
> http://www.surplussales.com/Meters/MtrTime.html
>
> I'm curious, do they still make them? How do they work anyway?
>

I'd be surprised if anyone makes them anymore, ROHS compliance would
be an issue.

They work by electroplating the mercury across the bubble. You feed
them a small constant current.

2007\05\14@133225 by Pete

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On Mon, May 14, 2007 at 01:07:41PM -0400, David VanHorn wrote:
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Probably very true.

> They work by electroplating the mercury across the bubble. You feed
> them a small constant current.

Ahh, so basically the current transports the murcury ions from one
surface of the bubble to the other? Hence why you can put one in
reverse, and the bubble goes backwards?

So what's the bubble actually made out of?

- --
http://petertodd.ca
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2007\05\14@134542 by David VanHorn

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> Ahh, so basically the current transports the murcury ions from one
> surface of the bubble to the other? Hence why you can put one in
> reverse, and the bubble goes backwards?

Right, and IIRC you can run them much faster than normal, maybe 10x,
to facilitate resetting them.

> So what's the bubble actually made out of?

That stuff in the middle of Happy Fun Ball?   Damifino.

2007\05\14@142928 by Walter Banks

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The bubble is a generally a small amount of a salt solution. The rate is
current dependent.

spam_OUTpeteTakeThisOuTspampetertodd.ca wrote:

{Quote hidden}

2007\05\14@183219 by Vitaliy

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Walter Banks wrote:
{Quote hidden}

I'm intrigued. So, how is the thing actually used? Once the bubble gets to
one side, the current stops?

Vitaliy

2007\05\14@185016 by Peter P.

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Vitaliy <spam <at> maksimov.org> writes:

> I'm intrigued. So, how is the thing actually used? Once the bubble gets to
> one side, the current stops?

No, the electrode is 'eaten' and that is not reversible because usually a gas
bubble forms and cuts the current. But normally technicians invert the device in
its socket when it is near the end marker and then you have another 1000 hours
to go. This can be repeated a number of times before the device fails. The
device can be killed by passing too much current. If a gas bubble develops (and
it will) then it's dead. The bubble can be seen against a strong light (the
'salt' solution is black or yellowish-dark, the bubble is clear and usually
elsewhere than where the salt solution is). Also afaik the 'slat' is HgCl2 . Not
very healthy but a tiny amount. I could be wrong on this though.

Peter P.



2007\05\14@185158 by David VanHorn

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>
> I'm intrigued. So, how is the thing actually used? Once the bubble gets to
> one side, the current stops?


I don't think they have an output, or that anything actually happens at the end.
They are mainly for logging power-on hours.

2007\05\14@192316 by Mike Harrison

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On Mon, 14 May 2007 18:51:57 -0400, you wrote:

>>
>> I'm intrigued. So, how is the thing actually used? Once the bubble gets to
>> one side, the current stops?
>
>
>I don't think they have an output, or that anything actually happens at the end.
>They are mainly for logging power-on hours.

Things like these are pretty much obsolete as nowadays any pretty much any equipment that needs to
log power-on hours will have a processor and therefore be able to do it in software. And if not, a
low-end PIC etc. can do the job cheaply and easily.



2007\05\14@211123 by Pete

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On Mon, May 14, 2007 at 10:50:07PM +0000, Peter P. wrote:
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Interesting... Mercury chloride is probably not too hard to obtain,
although as you say it is very toxic stuff. The mercury again is easy to
get, especially in the tiny quantities needed.

Be an interesting experiment to try to make one of these myself.
Probably won't be accurate, but it will work.

Mind you... would it have been Hg2Cl2 instead? According to wikipedia
that is used as a reference electrode for it's stability and accuracy.
Decomposes upon exposure to UV light, but then again they are encased in
glass which IIRC filters UV light.

- --
http://petertodd.ca
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2007\05\14@213829 by David VanHorn

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> Interesting... Mercury chloride is probably not too hard to obtain,
> although as you say it is very toxic stuff. The mercury again is easy to
> get, especially in the tiny quantities needed.

Di-Methyl mercury is the really fun stuff.
It also blows through latex gloves like they aren't there.

2007\05\14@230201 by Jinx

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> Di-Methyl mercury is the really fun stuff.
> It also blows through latex gloves like they aren't there

Saves you money then, not having to bother buying latex gloves.....

2007\05\14@234514 by Pete

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On Mon, May 14, 2007 at 09:38:28PM -0400, David VanHorn wrote:
> > Interesting... Mercury chloride is probably not too hard to obtain,
> > although as you say it is very toxic stuff. The mercury again is easy to
> > get, especially in the tiny quantities needed.
>
> Di-Methyl mercury is the really fun stuff.
> It also blows through latex gloves like they aren't there.

I've heard of that stuff... A single drop's enough to kill ya, but it
takes a few months before you start to get sick...

Definetely a poison to consider if you are an aspiring supervillian,
although Polonium 210 is so much more sophisticated... Takes care of
Russian dissidents, AND static cling!

- --
http://petertodd.ca
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2007\05\15@074836 by Peter P.

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David VanHorn <microbrix <at> gmail.com> writes:

> Di-Methyl mercury is the really fun stuff.
> It also blows through latex gloves like they aren't there.

What has that got to do with this ? The electrolyte is likely HgCl2 because it
is likely one of the few mercury salts which is soluble in water (or alcolhool -
more likely). The quantity used is very small, I'd say about 0.8*10^-6 ml (0.8
picoliters). Breaking that thing will more likely cause a stupid panic than real
damage. Total volume is about 0.1mm dia x 25 mm length -> ~160 picoliters
(0.00016  ml). Anyway the normal way to check it is to see that it has about 10
kOhms of DC resistance and/or passes a few uA of current when connected to a
voltage source of about 12 V through 100 kOhms. Another sign for a damaged unit
is that it has two bubbles or none (bubble past the visible part of the tube).

Peter P.


2007\05\15@134251 by Gerhard Fiedler

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Peter P. wrote:

> I'd say about 0.8*10^-6 ml (0.8 picoliters).

Just nit-picking... Isn't

0.8 * 10^-6 ml
= 0.8 * 10^-9 l
= 0.8 nl
= 800 pl ?

> volume is about 0.1mm dia x 25 mm length -> ~160 picoliters (0.00016  ml).

Here I get

(((0.1/2)^2 * pi) * 25) mm^3
= 0.2 mm^3
= 0.2 * 10^-6 l
= 0.2 * 10^-3 ml = 0.0002 ml
= 0.2 ul
= 200 nl
= 200'000 pl

(Using milli=10^-3; micro=10^-6; nano=10^-9; pico=10^-12.)

Gerhard

2007\05\15@160758 by Peter P.

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Gerhard Fiedler <lists <at> connectionbrazil.com> writes:

> (Using milli=10^-3; micro=10^-6; nano=10^-9; pico=10^-12.)

Caught. Those were nanos not picos. Anyway it's a thousandth of a drop or less.
So it won't kill you.

Peter P.


2007\05\20@180608 by Peter P.

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Final calculations (reviewed):

bubble (likely HgCl2 solution):

 0.1mm dia, 0.1mm long -> 0.000785 mm^3 ~> 800 pl

mercury total, approx (incl bubble):

 0.1mm dia,  25mm long ->    0.196 mm^3 ~> 200 nl

Peter P.


2007\05\20@184251 by Gerhard Fiedler

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Peter P. wrote:

> mercury total, approx (incl bubble):
>
>   0.1mm dia, 25mm long -> 0.196 mm^3 ~> 200 nl

About a third of the volume of a 1608 (0603) resistor.
About 2.6 mg mercury -- less than in most CFLs (4...8 mg).

Gerhard

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