Hello, I've been reading a few articles on 2-Terminal and 4-Terminal Current Sense resistors, here are those articles:


https://www.koaspeer.com/fundamentals-of-current-sensing-resistors/
https://www.digikey.com/en/articles...nt-measurement-part-1-current-sense-resistors

https://www.thin-film.com/wp-content/uploads/2020/11/Current-Sensing-2-Terminal-vs.-4-Terminal.pdf

I have also looked a few FPGA Evaluation boards to see what they do. Some use 2-Terminal for very high currents and currents that are fast changing, all others they use 4-terminal devices.


I would like to know what others think of 2-Terminal and 4-Terminal current sense resistors. Which style do you use?


Thank you

 

It depends on what is important. If a simple two-wire measurement yields values that are good enough, then why do anything more? If a two-wire measurement doesn't yield values that are good enough, then you need to do something more and a Kelvin connection is the obvious first step. But, even with that, it may or may not be good enough and, if not, then additional factors have to be taken into account and mitigated against.

At the end of the day, it comes down to what level of performance is actually needed. If your design doesn't deliver that level of performance, then it's not good enough. But, if you design something that is complete overkill, that is quite possibly not good enough, either -- are people really likely to pay $100 for your system when a $10 system would provide results that are completely acceptable?

 

W is fairly correct. What sort of accuracy and repeatability does your application require?? The four terminal scheme is used so that none of the voltage sensing conductors carry any load current, because that would affect the repeatability of the measurement. In a switching power supply that is quite important, while in many applications it does not matter at all. Where my requirement is to accurately measure current I always use the separate connections for measuring the shunt voltage. Good quality current shunts always have the separate gage circuit connections. But where my current sense measurement is only to know ON/or OFF, a two terminal shunt connection is adequate. And usually cheaper.