What it this device?

[nikonoid]

I bought this "millivolt source" very inexpensively on eBay mainly to salvage low EMF tellurium copper binding posts. This seemed 5 times cheaper than buying new.

In fact it turned out to be a precision voltage divider that is still spot on and usable down to microvolts.



On the inside it is full of precision wire wound resistors.




I can also see connectors marked Br1, Br2, Sw1 and Sw2 and it might be a bridge of some sort. Even after partially reverse engineering circuit diagram I still cannot figure out how to use them.

The device seemed to be made by James Biddle, but I cannot find anything similar from James Biddle online.

Would anyone know what it is? Are there any documents available? Thanks.








Sent from my iPhone using Tapatalk

[Nusa]

Intriguing. What is that glass-tube looking component on the back of the precision dial? Can we get a close-up?

[nikonoid]

It is a wire wound resistor (10 Ohm). Same value as most of resistors in the box.

[Nusa]

Ah, the glass look was an illusion. Thanks.

[nikonoid]

Resistors appear covered with epoxy, probably for humidity protection. So I guess that explains the glass look.


Sent from my iPhone using Tapatalk

[WastelandTek]

please don't scrap that for the binding posts

[Vgkid]

They are used in systems that use strain gauges in a bridge setup.

[nikonoid]

please don't scrap that for the binding posts

I like old equipment and this piece it in meticulous shape. If I can figure out a good use for it, I definitely will not scrap it.


Sent from my iPhone using Tapatalk

[nikonoid]

They are used in systems that use strain gauges in a bridge setup.

Would that be to emulate strain gage?


Sent from my iPhone using Tapatalk

[Vgkid]

They are used in systems that use strain gauges in a bridge setup.

Would that be to emulate strain gage?

Correct. It us used to divide the excitation voltage down to a level used to simulate the output of the strain gauge. That way, it can be read by whatever is being used to interpret the output.

[Vgkid]

Resistors appear covered with epoxy, probably for humidity protection. So I guess that explains the glass look. 

It would either be epoxy, or a wax coating.

[ebastler]

The device seemed to be made by James Biddle, but I cannot find anything similar from James Biddle online.
Would anyone know what it is? Are there any documents available? Thanks.

These guys (apparently an importer/distributor) have a large selection of old Biddle and Megger manuals online, altough they might not go quite as far back. Any indication of a model number on your device?

http://www.biddlemegger.com/cgi-bin/webshop.cgi?config=megger&uid=jeuwukkl149906390058&command=link--MeggerManuals.html


EDIT: Ah, just made out the catalog number on the Biddle tag in your first photograph -- 603020, right? In which case they unfortunately don't seem to have the manual online. I wonder whether this device was originally made by Megger, as Biddle was apparently their US distributor. That might explain the bolted-on Biddle name tag. There are some other documents on that web site for similar model numbers, which refer to Megger instruments.