Shopping Help: Kelvin / 4 wire Shunt Resistor for 30Amp load - Page 1
Forum section: electronics / testgear

author: jnz
author_rank: Frequent Contributor
timestamp: October 13, 2015, 10:37:04 pm
content: I'm looking for some opinions on shunt resistors. I have a Fluke 28-II, and some 0-30Amp @ 14.5V loads I want to measure. I need about 2% accuracy or so... Lower better, higher wouldn't really hurt anything, but it's nice to have goals.I'd like a resistance value of .001 or .01 or .1 or something that makes the resulting voltage drop instantly readable as Amps. I was looking at this:http://www.rc-electronics-usa.com/buy-current-shunt.htmlbut I'm not sure what the difference is to other options in practical terms.Someone told me to double my amp rating for whatever I buy (if I need 50, buy 100).Thoughts on what works well? Where to buy?Thanks guys

author: nctnico
author_rank: Super Contributor
timestamp: October 13, 2015, 11:12:58 pm
content: I just built a shunt using this shunt resistor:http://www.digikey.com/product-detail/en/TGHGCR0050FE/TGHGCR0050FE-ND/1817155There are other values as well but my scope has the ability to adjust the scaling so no problem using a 5m Ohm resistor.

author: jnz
author_rank: Frequent Contributor
timestamp: October 13, 2015, 11:43:30 pm
content: I like that. I don't really care about the price, and $25 is fine, but any more than that and I'll grumble.

author: MarkL
author_rank: Unknown
timestamp: October 14, 2015, 02:25:29 am
content: Not sure what country you're in, but here's another option for $12. 0.5% accuracy, reads 1mV per amp:http://www.allelectronics.com/make-a-store/item/snt-50/50-amp-shunt-50mv-50a/1.htmlThey have other ratios too:http://www.allelectronics.com/make-a-store/category/385100/meters-panel/shunts/1.htmlThe CSA100-100 you initially picked out also looks good to me, but maybe a little overkill.

author: LaurentR
author_rank: Frequent Contributor
timestamp: October 14, 2015, 03:51:24 am
content: Keysight 34330A?http://www.keysight.com/en/pd-1000000543%3Aepsg%3Apro-pn-34330A/30-a-current-shunt?cc=US&lc=eng

author: jnz
author_rank: Frequent Contributor
timestamp: October 14, 2015, 03:42:39 pm
content: Yea, I'm sure there is no magic on these, main thing I was curious about is the accuracy.There is going to be a derating for current as it heats up, but likely a change in actual resistance as well right?I was also running into the curiosity of that even with my new Fluke meter, is 1mV per Amp reliable to measure? Can I be assured that a 1Amp/1mV reading is reliable? Or does the accuracy scale along with the current, so that at 1Amp I have a 20% accuracy, and as it comes up into a reading of 30Amp or so I get closer to my 1-2% goal.This is what I think someone tried to explain to me as to why you'd buy a much larger shunt than you need (to keep it from heating up) but as you do that, typically the resistance goes down and then see my concern above about actual resolution...

author: Gyro
author_rank: Super Contributor
timestamp: October 15, 2015, 09:43:32 am
content: You could also check out ebay - there are loads of shunts these days to go with LED/LCD panel meter modules, but should meet your accuracy requirements. Note that a lot of them are 75mV for rated current.