40A current shunt - Page 1
Forum section: electronics / testgear

author: maginnovision
author_rank: Super Contributor
timestamp: February 08, 2019, 09:09:30 am
content: Does anyone happen to know of a ready made device like keysights 34330A 30 A Current Shunt but 40A capable? Going to need to calibrate a power supply and it wants .1% or better. Or should I just buy one of the terminal block style shunts that have the required accuracy and run the wires myself?

author: coromonadalix
author_rank: Super Contributor
timestamp: February 08, 2019, 09:54:51 am
content: Try to use the same specs shunt 1mv/amp0.001 ohms at 50 amps, gives 50mv, at 2.5 watts of powerUse a power shunt resistor, and build a nice little box to put it in it.some modelshttps://www.digikey.com/en/product-highlight/r/riedon/precision-dc-current-shuntsPersonally i would use fixed resistors values, i use 100 amps clamp meters once in a while, but always have to zero it ... (thats normal) and sometimes they are picky if i have some inductives loads near by .....And with a shunt i simply add it in serial for ac / dc circuits, i have an 0.001 ohms 0.25% precision 10 watts who do the job prefectly, in a small vented box, costed 75$ usd at the time, now sold for 20$ lollmy 2 cents

author: joeqsmith
author_rank: Super Contributor
timestamp: February 08, 2019, 06:57:49 pm
content: I assume that 0.1% is the entire error budget including the meter you plan to use with the shunt. I am not aware of a plugin shunt like the one you show that would do what you are asking.

author: Fungus
author_rank: Super Contributor
timestamp: February 08, 2019, 07:01:15 pm
content: Two 20A shunts in parallel?

author: maginnovision
author_rank: Super Contributor
timestamp: February 08, 2019, 07:10:05 pm
content: The manual specifies a .1% shunt and a 4.5 digit meter so I think it's just the shunt for the .1% not total measurement error. This is their shunt. I was considering just shorting the output and measuring from this but there is no spec for it, just the value. Maybe I'll buy one of the high spec busbar types and make some cables for it.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 09, 2019, 04:33:10 am
content: That makes more sense. I would just buy a good shunt, or see of anyone near you will loan one out if it's a one time measurement.

author: threephase
author_rank: Regular Contributor
timestamp: February 09, 2019, 10:58:21 am
content: I have only seen the Keysight shunt and shunts from Omicron in the style you have indicated. Omicron stop at 32A, but they are an horrific price for what they are.As the others have done, I just buy a current shunt to suit and house it in a small case, or if I am feeling really good at the time, I cut the box down to a smaller size and can achieve something similar to the Keysight shunt.Kind regards

author: beanflying
author_rank: Super Contributor
timestamp: February 09, 2019, 11:14:03 am
content: Going way back into the Arc I had a shunt made and calibrated by a local lab. Wasn't cheap but it was accurate.There is one option you can consider buying a cheap and nasty evilbay 50 or 100A shunt then buying say a 0.01-0.05% 5-10A shunt from a known source. Then use the good one one to get a number on the cheapy with reasonable confidence and or trim it into shape.The other option is one I have used before is making Kanthal shunts. Two brass bussbars with multiple lengths of wire between, one end fixed and the other locked with brass grubscrews for adjustment. Same transfer using a known better shunt to set it from.

author: Fungus
author_rank: Super Contributor
timestamp: February 09, 2019, 11:21:29 am
content: Quote from: beanflying on February 09, 2019, 11:14:03 amMeasuring a current shunt isn't difficult if you have a couple of good multimeters?Fine adjustment of the shunt? Use emery paper.

author: beanflying
author_rank: Super Contributor
timestamp: February 09, 2019, 11:27:51 am
content: Commercially the big ones are made under resistance then filed across the bars into trim.Using wire and screws was easier than the strip option to make home brew adjustable ones as drilling holes was easier than cutting slots and you can go up or down then trim excess wire later if you want. Using Kanthal has a fairly well known set of specs so you would always be close for a start.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: February 10, 2019, 12:51:53 am
content: https://www.burster.de/en/calibration-instruments/calibration-and-precision-resistors/

author: threephase
author_rank: Regular Contributor
timestamp: February 10, 2019, 09:56:47 am
content: @Neomys Sapiens - They look like good quality units covering a good range, I suspect they come at some price though?

author: maginnovision
author_rank: Super Contributor
timestamp: February 10, 2019, 05:23:18 pm
content: Quote from: threephase on February 10, 2019, 09:56:47 amI saw a thread mentioning 400 euro. I emailed them but no response yet.

author: HighVoltage
author_rank: Super Contributor
timestamp: February 10, 2019, 10:24:32 pm
content: Quote from: threephase on February 10, 2019, 09:56:47 amThe BURSTER 1240 are very reasonable in price at around Euro 260 each.They are very reliable as well.Here I show a few of them:https://www.eevblog.com/forum/metrology/low-ohm-precision-resistor-standard-and-testing/msg1063840/#msg1063840

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: February 11, 2019, 12:01:33 am
content: I can't say, because the two which I have came to me second hand - one cheap and one essentially free (a project refugee).And the Burster catalogue which I have that shows pricing is from mid-80s.But very reliable and well build.