DIY EC Probe

A DIY EC probe is pretty much essential considering the extremely high cost of buying one. After a bit of experimentation i've found a solution that works extremely well, gives accurate readings and costs less than $15. The video below explains exactly how to build your own.


Hi Hugo,

Those will work just fine.

Hi. Can i use any standard 2-wire EC probe with your circuit ? If so, what cell-constant should i look for ?


Also, can you provide any schematic for the EC shield ? On its webpage, i see a link for Documentation and Schematic, but only find the documentation - not Schematics.




I have one of your Ultimate Shield, How do you tune the probe to the board? I see the are 4 pots but aren't they for pH and ORP?




HI Practical Maker,

I have seen many EC probes that use carbo contacts set in resin. Have you experimented with tose. I hear that carbon probes do not suffer from buildup on the contacts. Do you know if that is true?



I have not experimented with carbon contacts as of yet. They should perform better (I've heard good things about graphite).

Hello, nice work!! Im trying make one just like you did. Can you tell me what is the thickness of the wire NiCr you use.



Hi Ricardo,

I'm not sure what thickness it is. I never checked the thickness when I ordered it. To be honest I don't think it matters the thickness, but rather how close to exactly 1cm apart you can get them.

@Robert. The EC doesn't need tuning. Basically the frequency changes whenever the conductivity changes and the code corrects based on calibration values.

@Zeeshan, Yes, and standard 2 wire EC probe should work. The SHIELD on the shield is for hooking up a mesh around the probe ti get more consistent readings.

I'll be getting the schematic up shortly.

As for the cell constant that depends on what salinity you're looking to measure. If you're looking to measure high salinity go with a cell constant of 10.

Thank You Very Much. I needed this very badly, instructions were great and appriciate the EC build instructions

What's your technique for soldering the nichrome wire to your hookup wire? I can't get solder to flow on the stuff even if I drench it with a flux pen.

I twist them together really tight (inline not the 90 degree twist).

hiya quick question can i connect the telephone cable to a BCA connector?

@Luis, yes you could hook it up to a BNC connector. You'll have to find bnc plug to hook onto the wire end of the sensor, but then it could easily be hooked up to a bnc connector.

Hey Andrew, nice and simple tutorial. The probe works great, such a simple simple item to make.

One question though: where does the 1.9% temp compensation factor listed in the documentation come from? From what I see 10% NaCL(aq) is around 2.14% and 10% KCL(aq) is 1.88% so something around 1.9 - 2% makes sense, but for a solution like sugar syrup (making maple syrup?!) it's upwards of 5.64%!! Other solutions can be even higher from the ref. material I have...

Thanks again for this, it's been a great money saver :)

The 1.9% compensation factor comes from saltwater (IIRC... I'd have to locate the docs again). Do you have any reference material? It would greatly help a lot of people (and me too!) to have some kind of reference temperature compensation slopes. Glad you like it!

Would titanium wire work?

It would work, but I'm not sure how much corrosion you'd get. If you try it make sure to report back your results!

From what I understand, titanium doesn't corrode. I'm not sure though if it's more reactive. I've tried it and I'm getting unstable results. There's too many fluctuations in frequency. Once calibrated to get salinity, I start off with 34 ppt and will go up to 37 after a few hours. I'm not sure if this is because I used titanium, or because I used reef safe adhesive instead of electrical tape. Also, if I was to use a mesh, do you think that would help in getting more stable results? How far apart should the mesh be from the wires? Thanks.

I'd probably look at replacing the electrical tape with shrink tubing, perhaps even tubing that heat a heat activated sealant.

Hi Doug, Great minds think alike! I've actually been experimenting with heat shrink tubing that has sealant in it and it works very nicely. I'll get a new video/instructions up soon!


i am trying to use this probe in interface with an arduino. It should be a fairly simple circuit, but I am confused on where the ground connection should be if I am supplying 5v from the arduino and plugging the other into the analog input pin. Input is appreciated!

Hi Katelyn,

You'd also need the EC Shield to plug the probe into.

hey could u please upload an entire schematic+ how to interface it with d arduino coz i am a bit confused how u did dat


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