Hacked Gadgets Forum

January 21, 2008


at 5:16 am. Filed under Complex Hacks, DIY Hacks, Electronic Hacks



I have never had the need (and probably never will) for a device that could measure the amount of salts in a solution, but I found the circuit to be very interesting. This EC TDS PPM Meter project provides all the information you need to make your very own.


"TDS is the measuring of the amount of salts in a solution. For alot of applications the amount of salt is indicitive of the levels of other stuff in a solution. TDS/PPM meters sold for gardening and aquariums figure the amount of salt in Parts Per Million by measuring the Electrical Conductivity of the solution under test. So a PPM/TDS meter is a EC meter that converts the EC value into PPM values.

There were alot of design considerations such as needing to pass a minimum amount of current and voltage thru the solution while keeping a good s/n ratio. But most most important it had to use stuff i had laying around the house and be pretty accurate.

The circuit outputs a DC voltage equal to the EC value of the solution being tested. So like 4v on the meter means an EC of 4, 2v means EC of 2, .5V = .5 EC blah blah. To convert EC value to PPM just multiply by 500, so like 4 EC = 2000PPM, .5 EC = 250PPM. Also the output can be connected to an A/D converter without alot much grrrrr."


Thanks Momo


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11 Responses to “DIY EC TDS PPM Meter”

  1. RB Funk Says:

    TDS (Total Dissolved Solids) is used to measure the “strength” of coffee. Strength as amount of coffee in suspension not taste. Taste has a whole nother set of measurements.
    I should build this one up so that I don’t have to buy another meter for when I drop the one I got.

  2. Shadyman Says:

    Wow, now THAT article title is alphabet soup.

  3. Alan Parekh Says:

    A bit of acronym soup I guess… 🙂

  4. Bryan Says:

    This is what i have been looking for. Thank you

  5. Tech News » Blog Archive » Make Your Own Salinometer. Why? Ask Not Why. Says:

    […] EC TDS PPM Meter project [via Hacked Gadgets] […]

  6. Gareth Rolles Says:


    I saw with great interest your circuit for EC/TDS Measurement. I am currently working on my own project for automating hydroponic nutrient mixing. I have all the experience necessary on the software side but unfortunately I have no experinece on the electronics side. I was wondering would it be possible for me to purchase an assembled EC/TDS and a PH board from you.


    Gareth Rolles

  7. jason Says:

    i will add a pic and display and there you have a stand alone unit

  8. david dicks Says:

    hello i am also looking for a pic controller for ph and tds for hydroponic growing
    thanks david

  9. david dicks Says:

    hello it has to be a very low cost unit i am able to help my email is eandaindustries@aol.com

  10. Alan Parekh Says:

    Hi David,

    The plans are here. It would be very cheap to build.

  11. Ramises Magallanes Says:

    what rectifier is used in this project? please reply

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