| Products > Test Equipment |
| Measuring 100A DC current |
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| Njk:
Consider a welding machine Hall sensors (available as spare parts). Something like that |
| geggi1:
If you want to measure DC very accurate look into fluxgate current sensors. As far as i know it is only Lem and Danisense that sell these. https://danisense.com/flux-gate/ https://www.lem.com/en/fluxgate-current-sensors They are expensive but you can get precision down to hundreds of percentage. |
| Hydron:
Old ultrastab sensors (i.e. what was suggested above) go for pretty cheap on eBay. They have a current output of a specified ratio to the measured current, and you can always just use a bench meter in current mode (even with autoranging) to measure the output if you don't have some precision resistors better than the internal meter shunts. If you have a decent meter with a scale function then you can even get direct readings. |
| Martin72:
I find the idea of using Danisense or Ultrastab quite charming. We have both for our ZES LMG power analyzers, they are accurate. And we had an LEM converter built into a case plus supply, plus huge terminals - as a current transformer for currents up to 2500Adc..... |
| Stray Electron:
--- Quote from: Martin72 on June 07, 2024, 11:27:13 am --- --- Quote from: gaminn on June 07, 2024, 07:58:37 am ---Hopefully I will be able to screw in some banana sockets (and they will not melt...) instead of that 8-32 screws to make my measurements easier. --- End quote --- Banana sockets are not designed for such high currents, which is why most power supplies that deliver 20A and more also have regular terminals. At higher currents, contact resistances can no longer be neglected. I really hope that if you “drive” currents over 10A, you no longer do this with normal banana cables... --- End quote --- X2. Adding additional wires and sockets to the shunt is going to wreck the accuracy of the circuit! The resistance of a 100 Amp 50 mV shunt is only 0.0005 Ohms. And the OP going to add wires to it! What is the resistance of your wires? And the resistance of the sockets? No where near as low as that of the shunt, I can guarantee. The math: OMG! With a 50 Mv 100Amp shunt; every millivolt represents 2 amps of current! So millivolts x2 equals the current in amps. How much simpler could the math be? If you use a 150 amp 50 mV shunt then millivolts x3 equals the current in amps. And if you (the OP) takes a look at the various brands of shunts being sold you'll see that the better ones have four terminal connections, two large ones for the high current circuit and two smaller terminals for the voltage metering circuit. It forms a four wire Kelvin connection and the theory behind it is exactly the same as that for very accurate power supplies and very accurate meters and very accurate electronic Standards. The OP is very naive is he thinks that a 200 Amp shunt from Alibaba is going to be anywhere near as accurate or the size or will dissipate as much heat as a good quality 100 Amp American shunt! Chinese products simply aren't made that way. If you look at the shunts on Ebay, you can easily find shunts that are rated for 0.25% accuracy and that are made by companies like Weston, Fluke, and Simpson, that actually build meters and understand how measurements are supposed to be taken. Specs for many of the US and Canadian made ones are online and you can look up their tolerance and have some degree of faith that they will actually meet their spec, unlike anything made in China today. |
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