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Old 13th Jul 2020, 9:02 am   #1
vinrads
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Default What is it ? [elapsed time indicator]

I found this in a load of components given to me , any idea ,Mick.
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Old 13th Jul 2020, 9:20 am   #2
lesmw0sec
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Default Re: What is it ?

Possibly a temperature checker?
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Old 13th Jul 2020, 9:21 am   #3
Cobaltblue
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Default Re: What is it ?

Looks like an elapsed hour/time meter we used to use a similar device at work 4 decades ago.

this is a similar device

http://oakbluffclassifieds.com/Funny...indachron.aspx

Spec of similar device https://docs.rs-online.com/b953/0900766b8001a8fe.pdf

Cheers

Mike T
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Old 13th Jul 2020, 9:23 am   #4
G6Tanuki
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Default Re: What is it ?

It's an "Elapsed time" indicator - - when fed by the specified (DC) voltage the silver 'blob' moves along the scale by some sort of electrolytic action.

The blob moves _very_ slowly - the gear I reall these being used in would typicallly see 60,000 hours of operation before the blob reached the end.
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Old 13th Jul 2020, 10:25 am   #5
SiriusHardware
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Default Re: What is it ?

I wonder how they ever tested these?
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Old 13th Jul 2020, 10:46 am   #6
Radio Wrangler
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Default Re: What is it ?

Reverse current reverses the action. Different resistor values/different voltages scale the time factor. Some had a diode fitted internally to make them less nobble-able.

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Old 13th Jul 2020, 11:04 am   #7
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Default Re: What is it ?

Agreed- elapsed time indicator, a pleasingly quaint piece of electrochemistry. Mercury is made to migrate s-l-o-w-l-y from one side of the indicator bubble to the other by a DC current in the order of micro-amps. There was a simple equation for running current that allowed the scale to be calibrated in multiples of hours. A wee while back, there was a thread on the Cossor CDU 150 oscilloscopes where some military personage seemingly saw fit to order their retrofit with one of these indicators and just a few years later another military personage decided that they were a serious hazard and needed to be removed post-haste with all sorts of mortal trepidation. It's the mercury that worried people, being made of thin glass didn't help, I suspect that they are now verboten and absent from supplier catalogues for some time now.

Hang onto it as an interesting curio, or pass it on to an interested party!
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Old 13th Jul 2020, 11:06 am   #8
Outrun_uk
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Default Re: What is it ?

Saw these fitted in ex-rental VCR’s.
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Old 13th Jul 2020, 12:22 pm   #9
Maarten
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Default Re: What is it ?

Philips fitted them in some early production models N1500 and possibly CD100 to better track warranty failures and maintenance intervals.
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Old 13th Jul 2020, 1:07 pm   #10
G6Tanuki
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Default Re: What is it ?

I'm familiar withthem being fitted in 1970s mainframe-computer hard-disk-drives [the ones about as big as a fridge, with the platter-stack removable from the top, and a storage capacity of a massive 500 Megabytes].

Also seen them fitted in some similar-era UPS gear, arranged to only 'log' time when the thing was running on batteries/generator.
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Old 13th Jul 2020, 3:12 pm   #11
vinrads
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Default Re: What is it ?

Quote:
Originally Posted by Radio Wrangler View Post
Reverse current reverses the action. Different resistor values/different voltages scale the time factor. Some had a diode fitted internally to make them less nobble-able.

David
When I tested it it did read as a poor diode ,and the resistance read about 600k ohms . so it's a time elapse device . not much use in old radio's . Thank's Mick.
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Old 13th Jul 2020, 3:55 pm   #12
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Default Re: What is it ?

I have seen the odd one in various instruments over the years.
They had a rating like a battery so that after passing a certain amount mah the bubble got to the end. After that some cheeky engineers used to turn them round and run them back the other way.
When you fit one you choose the resistor to make the duration as long as you want within reason.

You want to see just how complicated and expensive the things those indicators replaced were...
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Old 13th Jul 2020, 4:17 pm   #13
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Default Re: What is it ?

A similar device was fitted to Canon CX engine laserprinters (the original HP Laserjet, etc). A timed pulse of current (meaning a certain charge) was fed through the device for each page printed. Therefore a tiny (and constant) amount of the 'silver' (actually mercury I think) was plated from one end to the other for each page. The unit acted as a page counter.
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Old 13th Jul 2020, 5:53 pm   #14
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Default Re: What is it ?

Hitachi video recorders used them. I was completely puzzled by them and just could not understand how they worked! J.
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Old 13th Jul 2020, 8:01 pm   #15
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Default Re: What is it ?

Yes, elapsed time indicators. They were fitted in the back of Telequipment D53S and DM53A storage 'scopes.

Les.
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Old 13th Jul 2020, 9:00 pm   #16
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Default Re: What is it ? [elapsed time indicator]

We were fitting identical ones in the military stuff we were developing at Plessey in the early 1970's. I did liberate one to fit in my EL3302 to measure head use (specified at 500 hours) but it never worked. I think I have another NOS example in my collection of old electronic stuff, but haven't seen it for ages and no longer have the info for calculating appropriate resistor values.
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Old 13th Jul 2020, 10:39 pm   #17
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Default Re: What is it ? [elapsed time indicator]

Quote:
Originally Posted by SiriusHardware View Post
I wonder how they ever tested these?
Relatively easily, since movement is proportional to the milliampere hours passed through the device, at any reasonable current.
For example one milliamp for a hundred hours would have the same result as one hundredth of a milliamp for ten thousand hours.

The contents were usually mercury that was moved from one end of a sealed chamber to the other end by electrolytic action. With anything other than flat smooth DC, the response was to the AVERAGE current and not to the RMS current.

These elapsed time indicators were made in several formats, some the size and shape of a small fuse, easily replaced or turned around, and others with wire ends to be soldered in place when tamper resistance was required.
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Old 14th Jul 2020, 12:51 am   #18
jamesperrett
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Default Re: What is it ? [elapsed time indicator]

Fostex fitted them to their E series tape machines back in the late 80's to measure head hours (IIRC).
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Old 14th Jul 2020, 10:20 am   #19
G6ONEDave
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Default Re: What is it ? [elapsed time indicator]

First one that I saw was in a Granada ex rental vcr. It was the same dimensions as a 1.25" fuse but with a plastic body, standard fuse end caps and that mercury indicator. It was mounted quite prominantly near the preset tuner bank.
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Old 14th Jul 2020, 6:52 pm   #20
duncanlowe
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Default Re: What is it ? [elapsed time indicator]

I have seen similar devices but non electronic / electrical. A tube of ink, that gradually creeps up a paper indicator. I came across it as a way of indicating the end of life of an inline water filter, I think the time was 12 months. Mind you after 3 years and repeated requests to sort it out, and the ink having spread way further than the indication line, the filter was still in place. Indication is one thing, doing something about it quite another.
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