pH and EC sensors


A few comments on these sensors:

  1. They are NOT meant to be in the water for extended periods. I have noticed (depending on fertilizer, etc) drift from my Hanna Instruments HI98129 after a few days of continuous use.

  2. If not in the grow tank they must be kept wet.

  3. There is an adjustment potentiometer on the pH PCB. Put the pH probe into a standard and adjust to correctness. Generally, you will be in the 5.5 to 6.5 pH range during use so you ‘may’ be able to do a single point adjustment with a standard around there.

  4. Its good to have a instrument to compare you system to, so purchasing a combo meter like the Hanna HI98129 would be useful. If you do, you can just not purchase the EC and pH ones on the BOM until a better solution arrives and just periodically monitor the water.


I found this on Amazon. Hanna claims that the probes are “HI 991404 and HI 991405 have been designed for continuous,
high accuracy pH, EC/TDS and temperature measurements.”. While not cheap, they are less expensive than alternative continuous duty probes. I just ordered one to ‘hack’ it up.


DFRobot also has a PH sensor with an industrial probe, which can be used continuously. It sells either the kit or just the probe, for people that already have the circuit from the scientific one (the one in the PFC BOM).

I have read some good reviews on this E201WM EC industrial probe, and it is compatible with the DFRobot EC sensor circuit. The problem is that DFRobot doesn’t sell only the circuit and doesn’t have a kit with this probe. We would have to buy both the kit and the separate probe.

But since I don’t have neither these nor the BOM DFRobot ones nor the Vernier ones (I’m using normal portable sensors), I can’t really tell which is the best option.


Im working on a new probe for the SqRoot design. It will be a continuous immersion design (with periodic maintenance) and the hardware/software will be offered in a configuration for FC1.0. Should be done in a month or so.


An update on my varriant of a ph/ec probe. hardware is completed, software is in process. will need testing for a month and it should be ready to go. target price will be $150 to $200 USD.


Added source available at Hardware is available for pre-order, shipping end of July.


I would love to understand how your electronic part works. I’ve looked at your github repository, but can’t find neither the schematic nor the bom.

Is this information available somewhere ?

Greetings Community - Lighting PCB

This plantcubed link does not work


Does anyone have a cheap solution for continuous measurement of pH of aeroponics nutrient solution. Or at least a handheld tester from eBay.
The yellow one is not good enough. My stopped functioning ~OK when I mistakenly put it in water with a pH-granulate with reading pH 1.