pH Meter and regulation


I'm new to Arduino and want to start with my first project.

I found already some information in the internet but I'm still not sure about everything.

The Idea:

First Step: What I want to do is a pH mesurement in a watertank.

Second Step: Adjust pH with pH down / pH up liquid ( acid / alkaline )

So I found different pH Meter Projects in the Internet I think I can use one of them for my project.

For the second step I need two peristaltic pumps to transport the acid / alkaline to the tank.

With the pH Meter projects there is also a program code, which I think is fine ?

The only thing I have to do is the control for the two pumps.

What do you think about this project ?
Could this work ?


You would want to have a pump to stir the tank.

Something to keep in mind is that pH electrodes drift and have to be re-calibrated all the time.
They can't be left in the tank all the time, but must spend most of their time in the storage solution.

That the electrode must be calibrated after certain time is clear

I don't understand the point with the electrode in the tank? Why can't it be left in the tank?

In the program text I want to make a control every hour with a second control after 15 minutes when the solution is adjusted

The pH electrode works by measuring the voltage generated by ions passing through the glass membrane in the bulb. Over time the ions (I think K+) leak through the glass and change the composition of the reference KCl solution inside the electrode. This is why you're meant to store the electrode in the KCl storage solution. The reference electrolyte can also be gradually poisoned by ions from the process fluid diffusing into the electrode.

There's an interesting writeup here:

Basically an ad for fancy process control pH electrodes.

Problems with reading drift and calibration will vary depending on the actual process chemicals and environment, and on the type of electrode you use. A cheap $40 e-bay electrode is not designed for continuous use. A fancier process control one is going to have a rated lifetime and all that, but cost a bit.

So how to deal with this problem ?

I mean in the Internet are several projects for ph mesurement. But in none of them a solution for this problem is mentioned ?


Well, it would be useful to know what your actual requirements are.

  • is it just a science project, or a practical application?
  • Is it okay to get started with something cheap and see how it goes? Or do you have to build a critical system of known verifiable precision and performance?
  • if practical, then for what? a pulp mill, or sewage treatment or what?
  • how long do you need to monitor? brewing beer might need a few hours; managing wine fermentation a few weeks, keeping your hot-tub pH set might mean running for months or years.
  • what is the process chemistry? Is it something benign like seawater? or is it fuming nitric acid with dissolved radium?

Thanks for the quick reply

So to answer your questions:

It's definitely a practical application

I think in the beginning it's okay to start with something cheap and look how it goes and if necessary spend more money

It's for a watering system for different plants / vegetables

So in fact I want to monitor and regulate as long the grow period is which means basically up to 3-4 months

But to resolve the problem with the ph Meter which can be left for a very long time in the solution a little DC Motor could help?

I mean, if I connect the PH Meter directly to a cable which is controlled by a little motor which can pull up and down , after every measurement I can pull the meter up

WHat do you think?

I know this post was last updated over a year ago, but I’m curious to see if you ever got your project working because I’m looking to create something similar.