My Shunt collection (uCurrent Passive???) - Page 1
Forum section: electronics / testgear

author: Gyro
author_rank: Super Contributor
timestamp: February 02, 2016, 09:40:36 pm
content: While I had the camera out I thought I might share my Current Shunt collection...One of my pet peeves is the voltage burden of current ranges - it seems particularly ridiculous on high spec Bench DMMs. Probably the reason that Datron didn't include current ranges on theirs.Anyway I now have a set of external shunts spanning 1mOhm to 1k which I can use on my Datron 1045 10mV range (1mV burden if necessary, reduced to 3 1/2 digit resolution). The shunts are un-fused (voltage burden again) and diode clamped where possible, so completely unsuitable for high-energy circuit use. All shunts are 4 wire Kelvin sensed.The details, easy one first:- 1mOhm: This is an old AVO shunt I picked up from Stewart of Reading's bargain section many years ago. It's specified as <2% up to 150A, good enough.- 10mOhm: A de-rated (to 10A) 20A metal plate shunt from RS components. Original spec 1%, I was able to bring it within 0.01% by paralleling a 1R resistor.- 100mOhm: A 4 terminal wire-wound resistor, I think originally from a piece of AVO test gear (not an AVO 8 ). Measured 0.0993R on a freshly calibrated 34401A, close enough and nothing sensible I can do to increase the value.- 1R: A nice big 4 terminal wire-wound that I got in a bag of precision resistors (198x vintage), I suspect also from Stewart of Reading bargain basement. Spec'd as 0.05%, measured 1.0004R on the 34401A! At this point overload protection with inverse pair 3A diodes becomes possible. A nice resistor and this seemed the best way of protecting it from harm (and prompted the other ones).- 10R-1k: Recently completed, now we're within switch contact territory. The 10R wire-wound is within 0.01%, the 90R and 900R from the same bag are spec'd at 0.05%, need to check after they've recovered from soldering. Protection is by 1A inverse pair diodes (checked for <1nA leakage forward and reverse at 200mV). The current and voltage taps are independently switched to avoid contact resistance errors.Photo's are attached. Hopefully this will be food for thought for someone - potentially someone with an excess of diecast boxes and time on their hands!Edit: I just about have overlap with my Picoammeter now (tops out at 4.5nA with fresh battery), but not with any degree of accuracy.

author: Vgkid
author_rank: Super Contributor
timestamp: February 02, 2016, 10:35:04 pm
content: I believe that the blue(teal) resistor is made by a company called Kelvin Industries. I believe that they were bought by vishay a long time ago.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 03, 2016, 02:53:09 am
content: Nice collection!

author: Mickle T.
author_rank: Frequent Contributor
timestamp: February 03, 2016, 06:58:47 am
content: Quote from: Vgkid on February 02, 2016, 10:35:04 pmNo. The blue(teal) resistor is made by a company called Mann Components Ltd. (Ayton Road, Wymondham).

author: Gyro
author_rank: Super Contributor
timestamp: February 03, 2016, 11:06:20 am
content: Many thanks for the feedback guys.I've attached a closeup of the 1R resistor to help the debate, I don't recognize the logo myself.I'd forgotten it was spec'd as tight as 0.01%, or that it was as old (and stable) as 1979. I really must start noting these things downbeforeI assemble them.Edit: Sadly I haven't managed to turn up anything for either Mann or Kelvin Industries for type 4N/C. It would be nice to confirm the Tc and especially power rating for peace of mind.Edit2: I suddenly remembered I had seen some same colored resistors in the Datron, on checking they have the same logo and the BOM in the manual identifies them as Mann, also taken over by Vishay (well spotted Mickle T. and thanks also to Vgkid).

author: Vgkid
author_rank: Super Contributor
timestamp: February 03, 2016, 03:07:50 pm
content: Quote from: Mickle T. on February 03, 2016, 06:58:47 amThanks for that Mickle. I was trying to go from memory, i had some stuff gathered online about that company on my home computer. Reminds me to put my 7065 on ebay.