# Resistivity measurment using four point probe and arduino

I want to build an arduino project to measure the resistivity of semiconductor sheet by using four point probe method. I understand how the probe works in principle. it is just four equally spaced linearly arranged pins, a const. current is supplied through external pair of pins and voltage across the middle two is measured. I want to do same using arduino, since professional equipment is expensive. I don't want it to be as accurate as pro gear, it is more of a proof of concept project. but I don't understand where to start from, like how would I control the cc power supply using arduino and how to read micro volt voltages. I want to collect data through labVIEW or Mathematica and plot it. I'd be really thankful if anyone points me in the right direction.

This may be of interest, You could add Arduino with a 16/24 bit ADC.
http://www.kerrywong.com/2011/08/14/accurate-milliohm-measurement/

I have seen designs use an LM317 to create a constant current of 100ma not sure how good they sare

Hi,
Interesting. I have seen this done in the lab but I was never involved..

This is a good perspective (LINK)

Some Arduino Constant Current discussion HERE

But, if you can measure the current, and do math, you don't really have to have a precisely-controlled constant current, right?

It's mathematically convenient to have a nice constant current. I measure the resistance of, say, a 20 amp circuit breaker by using my high current variable supply to put 10 amps through it and then separately measure the voltage across the terminals. 0.1 V = 0.01 ohms for example.

Let us know how this works out...

317 seems to work ok. Depends on a lot of factors but I would imagine pumping 100mA through some semiconductors would be a bad idea.