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Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

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Old 15th Dec 2018, 3:37 pm   #1
60 oldjohn
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Default What is this?

Anyone know what this is ? Marked The Wigston. Made from lacquered brass, copper and ebonite. Eight inches wide. This is 1000 ohms, 100ohms and 10ohms were available.


TFL John.
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Old 15th Dec 2018, 5:35 pm   #2
David Simpson
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Default Re: What is this?

Possibly a laboratory resistance standard. Regards, David
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Old 15th Dec 2018, 9:45 pm   #3
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Default Re: What is this?

Thank you David, looks like it has two electrodes they are tarnished, I think they may have been immersed in something.


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Old 15th Dec 2018, 10:08 pm   #4
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Default Re: What is this?

Very old, they were successors to Latimer Clarke, Muirhead & Co.

Lawrence.
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Old 16th Dec 2018, 9:21 am   #5
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Default Re: What is this?

Is it perhaps a very early thermocouple for (maybe) measuring the temperature of a liquid?
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Old 16th Dec 2018, 10:31 am   #6
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Default Re: What is this?

It couldn't be a thermocouple, which needs to be a junction of two dissimilar metals, at which a temperature difference occurs and a minute Voltage is generated.

https://en.wikipedia.org/wiki/Thermocouple

Just a guess could possibly be to provide the reference temperature of a laboratory standard thermocouple potentiometer bridge. The most accurate easily available reference temperature against which a thermocouple junction could be compared so as to measure the difference, is ice, into which the two tubes could be immersed. I think that ordinarily, a second thermocouple is immersed in ice and the difference in the minute voltage generated at the junction of the two is compared and brought into balance on a thermocouple potentiometer and the result read off on a scale.

Pure speculation on my part - I could be wide of the mark. (It won't be the first time!).

As it's marked '1,000 Ohms' does it measure that on a meter John?
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Old 16th Dec 2018, 4:22 pm   #7
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Default Re: What is this?

Hi David, I have taken some measurements, and the plot thickens! The brass piece is all one I can see where it soldered. The two copper rods are isolated from the brass. Copper rod to copper rod measures 1006 ohms @ 68F. So the black 1000 ohm resistor connects between the two copper rods.


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Old 16th Dec 2018, 5:36 pm   #8
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Default Re: What is this?

Some thoughts, the big brass can where the resistor is sits in oil at a set temperature measured by a thermometer down the middle hole. The ohms appear on the two sticking down legs, they look corroded because they would have had to be clean to make contact with the rest of the circuit and would probably have been dipped in mercury pots as part of a four wire measurement. Three wires in each pot including the brass legs.
 
Old 16th Dec 2018, 7:31 pm   #9
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Default Re: What is this?

I did wonder if the copper legs had been in Mercury, they are not actually corroded the coating looks like matt black paint but I am sure it is not it has a patina.


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Old 17th Dec 2018, 2:19 am   #10
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Default Re: What is this?

Is the cylinder part hollow as if something passed through it?
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Old 17th Dec 2018, 5:40 pm   #11
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Default Re: What is this?

Yes, hole is 16mm all the way through.

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Old 17th Dec 2018, 5:46 pm   #12
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Default Re: What is this?

I would guess that whatever is measured goes in the hole.
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Old 17th Dec 2018, 5:47 pm   #13
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Default Re: What is this?

My first thought was a resistance thermometer sensor (like a Platinum Resistance Thermometer) but while you might well get one specified to be 1k at 20 Celsius, the way it is worded on this device is rather odd.

It could still be that, to measure the temperature of some fluid through the central tube.
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Old 17th Dec 2018, 6:13 pm   #14
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Default Re: What is this?

Could it be intended that the brass 'pot' part (containing the standard resistor) is intended to be put in a heated water/oil-bath and the hole through the middle is for a thermometer to record the temperature ?
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Old 17th Dec 2018, 6:24 pm   #15
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Default Re: What is this?

The brass piece is isolated from the copper rods, the resistor is the black square that has 1000 ohms wrote on it. Please see #7


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Old 17th Dec 2018, 6:27 pm   #16
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Default Re: What is this?

Isn't the square black piece just a support?

I'd think the resistor (probably resistance-wire in a coil) is inside the brass can, probably with some sort of insulating/potting material like pitch between the resistor and the brass can.
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Old 18th Dec 2018, 12:08 am   #17
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Default Re: What is this?

I think you could be correct, that would be a more logical explanation. Possibly an oil cooled resistor? I do not know what is in the tank.
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Old 20th Dec 2018, 2:26 pm   #18
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Default Re: What is this?

Have a look here:

https://www.radioblvd.com/vintage_test_equipment.htm

and go down to "NBS Precision Oil-Filled Resistor Standards" where you'll see what I suspect is a slightly more-modern US version of something similar to what you've got.
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Old 20th Dec 2018, 9:19 pm   #19
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Default Re: What is this?

I think that is what I have, on investigating #4 I found that they were investigating and working on an ohms standard.


I still think the copper rods have been immersed in something, also there are no connectors like the one in the link.
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