Calibrating a 10mOhm shunt is "easy".
What is your procedure to calibrate a 10 mOhm resistor in your lab?
At how many points between a low current and full scale current do you check for linearity?
Very interesting with your 4000A of multiple current sources.
With my two Agilent 6V / 100A PSUs I just can reach 200A.
Perhaps if you really interested in high accuracy high current stuff, you'd be better off getting LEM Ultrastab DCCT.
I'm late to this thread but acouple of people have asked "why 60mV" value for shunts. This is not the only value used, 75mV seems quite common in the UK, 50, 100 and 150mV are also seen. It's related more to the impedance of the matching meter than anything else. Most panel meters for use with shunts have a 1mA movement. A coil resistance of 60 Ohm is not unusual for a 1mA movement, and a lower value will allow for a series calibration resistor.
Perhaps if you really interested in high accuracy high current stuff, you'd be better off getting LEM Ultrastab DCCT.
They pop up on ebay from time to time to relatively cheap prices. I've got two with best linearity, Ultrastab IT-600S.
It is 1:1500 ratio CT, and with linearity spec <1ppm, offset error <20ppm and tempco <0.2ppm/K, so high chance that your measurements accuracy with these DCCTs will be limited by your burden resistor stability. There are also lower (and higher) current Ultrastab's with similar specs. Buying older Danfysik DCCT (model 867 is same as IT-600S) might save few $$.
CERN using these beasts to calibrate and maintain LHC superconductor magnet currents to ppm levels stability. You can find related research paper, covering their transfer and calibration apparatus.
But one big question is: How linear are these shunt resistors in real life?
That shunt is very interesting price, I wonder if this distributor can ship internationally to private customers..
Hi!
Always nice to help out fellow VoltNuts... I also ordered one Isabellenhütte resistor, got it this Thursday, very nicely packed in a plastic box from factory (what else to expect...)
Heavy beast, weighs almost 300g...
It has a stamped number on the solid copper base, perhaps unique serial number? or batch number at least...
Will put it in an aluminum box with four binding posts, high current binding posts will be 63A rated, Kelvin output will be a dual gold plated 19mm spaced version
Getting like a 0,25W TC=1ppm/K resistor is expensive enough, but 250W...
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Perhaps if you really interested in high accuracy high current stuff, you'd be better off getting LEM Ultrastab DCCT.
Thank you all for the good input.
The Ultrastab IT 600-S or the IT 405-S are too expensive and I have not found a good low cost source source.
But for now I bought one of the DANFYSIK Current Transducer ULTRASTAB 867.
May be this one will work for my purpose.
Type: 867-700I
Nominal current: 700A DC
Ratio: 1:1750
Output +/- 400 mA
I am surprised how difficult it is to make some precision current measurements, even at only 1A
...
Will put it in an aluminum box with four binding posts, high current binding posts will be 63A rated, Kelvin output will be a dual gold plated 19mm spaced version
Thanks for the heads up on the 300 gramm weight, I did not see that.
I ordered two of these Isabellenhütte resistors, too good of a deal to not take advantage of.
And I also wanted to put one in a box with binding posts and separate Kelvin output to good quality binding posts.
What gold plated bindings posts will you be using?
But why are you planning to have a "dual" output?
May be something to consider?
I would order a pair. Unfortunately, I know how much it costs to calibrate these. I remember the price was some 350-500 EUR each. And I'm sure everyone sees the 1K hour drift value, .2% for the .1% resistors. And they drift quite a lot, even if you don't use it near full load. I think our resistors never went above 20W load (8mOhm 50A) and the drift was still significant. But of course these were used a lot, hours every day.
That being said, they are excellent resistors. Make sure to cool it well. Bolting down to an aluminum extruded heatsink works quite well.
I would order a pair. Unfortunately, I know how much it costs to calibrate these. I remember the price was some 350-500 EUR each. And I'm sure everyone sees the 1K hour drift value, .2% for the .1% resistors. And they drift quite a lot, even if you don't use it near full load. I think our resistors never went above 20W load (8mOhm 50A) and the drift was still significant. But of course these were used a lot, hours every day.
That being said, they are excellent resistors. Make sure to cool it well. Bolting down to an aluminum extruded heatsink works quite well.
You are bringing up some good points.
Calibration.
Do you know how they are calibrated and what labs are capable of it to full current of 350A?
May be we can calibrate them ourselfs with the LEM / DANFYSIK sensors a few of bought?
Drift
Are you talking about a long therm drift?
Heaksink
I have been looking for a large heatsink already, that will fit with the resistor together, in to a nice aluminum box.
Linearity
I am really looking forward, testing these for linearity up to 100A, in comparison to the Danfysik / LEM. (may be 200A, if I hook my two agilent power supplies in parallel)
We were using a local Belgian cal lab, they were calibrated up to 50A, not to their full capability. I think I saw the invoice once, I'll try to recall what was the lab. They produced a very accurate reading, I think up to 7-8 digits. We sent our 3458A also there.
We were using these as a reference resistor, "gold standard", to calibrate the shunts built into the equipment we sold. The spec of our equipment was 0.03%, max current 50A. We were using the 2mOhm TK1 part, along with a bunch of other values for less current.
Drift is the long term drift. The datasheet specifies 0.2% drift @2000h, nominal load, 85 degrees. We were using it below maximum load (in fact below 2% load and almost room temperature) and it was causing issues with our spec. Like it drifted more than 0.03%, and we had to re-calibrate stuff. While the Arrhenius Equation would have suggested less drift, so careful, when trying to apply it. Also, these were used for 5+ years, so they had time to do initial drift. Might be, that some hysteresis or other physical phenomenon...