What it this device? - Page 1
Forum section: electronics / testgear

author: nikonoid
author_rank: Regular Contributor
timestamp: July 03, 2017, 01:17:53 am
content: 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

author: Nusa
author_rank: Super Contributor
timestamp: July 03, 2017, 02:40:48 am
content: Intriguing. What is that glass-tube looking component on the back of the precision dial? Can we get a close-up?

author: nikonoid
author_rank: Regular Contributor
timestamp: July 03, 2017, 02:49:26 am
content: It is a wire wound resistor (10 Ohm). Same value as most of resistors in the box.

author: Nusa
author_rank: Super Contributor
timestamp: July 03, 2017, 02:55:47 am
content: Ah, the glass look was an illusion. Thanks.

author: nikonoid
author_rank: Regular Contributor
timestamp: July 03, 2017, 03:17:25 am
content: Resistors appear covered with epoxy, probably for humidity protection. So I guess that explains the glass look.Sent from my iPhone using Tapatalk

author: WastelandTek
author_rank: Frequent Contributor
timestamp: July 03, 2017, 03:25:35 am
content: please don't scrap that for the binding posts

author: Vgkid
author_rank: Super Contributor
timestamp: July 03, 2017, 03:37:30 am
content: They are used in systems that use strain gauges in a bridge setup.

author: nikonoid
author_rank: Regular Contributor
timestamp: July 03, 2017, 03:52:39 am
content: Quote from: WastelandTek on July 03, 2017, 03:25:35 amI 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

author: nikonoid
author_rank: Regular Contributor
timestamp: July 03, 2017, 03:54:21 am
content: Quote from: Vgkid on July 03, 2017, 03:37:30 amWould that be to emulate strain gage?Sent from my iPhone using Tapatalk

author: Vgkid
author_rank: Super Contributor
timestamp: July 03, 2017, 05:33:51 am
content: Quote from: nikonoid on July 03, 2017, 03:54:21 amCorrect. 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.

author: Vgkid
author_rank: Super Contributor
timestamp: July 03, 2017, 06:19:35 am
content: Quote from: nikonoid on July 03, 2017, 03:17:25 amIt would either be epoxy, or a wax coating.

author: ebastler
author_rank: Super Contributor
timestamp: July 03, 2017, 06:44:21 am
content: Quote from: nikonoid on July 03, 2017, 01:17:53 amThese 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.htmlEDIT: 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.