Amp meter / shunt  - Page 1
Forum section: electronics / projects

author: Liteace
author_rank: Regular Contributor
timestamp: November 26, 2018, 05:35:36 pm
content: Hello ALL. need a bit of advise, Ive, on the way to me an old server P.S it has 3 or 4 30 amp outputs that can be all joined together to produce about 100ish amps, I would like to if at all poss use an amp meter with shunt but how would I wire this up ?Thanks

author: rstofer
author_rank: Super Contributor
timestamp: November 26, 2018, 06:03:00 pm
content: For industrial applications, we use what are called '50 mV shunts'. For example, a 100A 50 mV shunt drops 50 mV when 100A flows. This is measured on a meter.https://www.amazon.com/Shunt-Portable-Out-0-50-0-100/dp/B01M0JJZI1

author: chuckb
author_rank: Frequent Contributor
timestamp: November 27, 2018, 03:35:29 pm
content: I had worked with 50 mV shunts for 20 years until I came across this installation restriction.There is guidance from shunt manufacturers that a shunt should not be run continuously above 66% current. We tested that guidance with a 400 amp 50mV shunt connected to 1" wide bus bars and passing full current. It reached well over 100 deg C and was discolored when were were finished. I'm sure the calibration of the manganin shunt was changed.If you have a 100 amp load I would use a 150 amp 50mV shunt.I found two links with this guidance -https://www.bluesea.com/products/9230/Analog_Meter_Shunt_-_100Ahttps://www.rammeter.com/media/bulletins/RamMeterInc_ShuntDiscussion1.pdfpage 2

author: rstofer
author_rank: Super Contributor
timestamp: November 27, 2018, 06:13:16 pm
content: As with most things in the electrical business, we need to derate. Operating a shunt at 66% makes all the sense in the world.

author: Liteace
author_rank: Regular Contributor
timestamp: December 03, 2018, 11:29:42 pm
content: This amp meter has not got to be 101% accurate, it will be glanced at every now and again to see what load is on the power supply, the power supply can deliver 130 amp and there's no way I'll be supping all of those, Ive also looked at thesehttps://www.google.es/imgres?imgurl=https%3A%2F%2Fi.ebayimg.com%2F00%2Fs%2FMTIwMFgxMjAw%2Fz%2FgGMAAOSwAvJXB2jH%2F%24_35.JPG%3Fset_id%3D880000500F&imgrefurl=https%3A%2F%2Fwww.ebay.com%2Fbhp%2Fac-ammeter&docid=ydOSyWtX60LaDM&tbnid=ZPebVklv4fNWPM%3A&vet=10ahUKEwjiz7T454TfAhWYSxUIHa3fCDAQMwitASgwMDA..i&w=300&h=300&bih=882&biw=1280&q=amp%20clamp%20digital%20panel%20%20meter&ved=0ahUKEwjiz7T454TfAhWYSxUIHa3fCDAQMwitASgwMDA&iact=mrc&uact=8something like that for DC voltage, what'd think ?Thanks

author: spec
author_rank: Frequent Contributor
timestamp: December 04, 2018, 12:52:48 am
content: Hi LiteaceI would have thought a current clamp meter would be ideal for your application. No wiring or shunt resistors to worry about. You can get current clamp meters for both AC and DC.(don't make the classic mistake: the clamp goes over just one wire, not two)

author: NiHaoMike
author_rank: Super Contributor
timestamp: December 04, 2018, 01:05:22 am
content: Quote from: chuckb on November 27, 2018, 03:35:29 pmCould it be possible to run the shunt at its rating by improving cooling, such as with a fan or by attaching heatsinks with an electrically insulating thermal epoxy?

author: 001
author_rank: Super Contributor
timestamp: December 04, 2018, 08:52:55 am
content: Quote from: NiHaoMike on December 04, 2018, 01:05:22 amWhat the reason of it? The sensor element is simple piece of manganin alloy. Pick one rated for large current. It is simply more fat wire

author: Liteace
author_rank: Regular Contributor
timestamp: December 05, 2018, 09:47:04 am
content: I need your help please Guy's, I dont really want exposed shunt sitting on the top of the unit me or someone else, more likely me with at some stage put something on it and short it all out, Im thinking of getting one of these, then I can have everything rubbered and short proof but I would if poss need help on what gauge to use with ithttp://www.chieful.com/pdf/Open/split/2--CS500EK1.pdfThanks

author: 001
author_rank: Super Contributor
timestamp: December 05, 2018, 12:57:57 pm
content: Do You REALLY need a shunt? You can use DC current clamp nowIt is the best way, since 50mv*100A=5W of heat for a long time

author: Liteace
author_rank: Regular Contributor
timestamp: December 05, 2018, 06:42:37 pm
content: Quote from: 001 on December 05, 2018, 12:57:57 pmNo, I hope not that why I looked at the hall effect current sensor but would need someones help as to what panel meter to use it with so its reasonably accuratesomething like:https://flexscada.com/product/hall-effect-current-sensor-ac-75a-dc-100a/Thanks