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PH measurement — Parallax Forums

PH measurement

RS_JimRS_Jim Posts: 1,753
in Propeller 1
Hi,
Has anyone used a Prop1 for PH measurement?
Jim

Comments

  • kwinnkwinn Posts: 8,697
    There have been several PH projects posted in the past. Basically you need to amplify the probe signal, use an ADC to measure the signal, and write or download the code to convert the measurement to PH.

    See:

    https://forums.parallax.com/discussion/82338/ph-sensor

    https://forums.parallax.com/discussion/71895/ph-sensor-w-adc-w-stamp

    https://www.emesystems.com/OLDSITE/OL2ph.htm
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    You could also use a test strip and read it using Parallax's ColorPAL.

    -Phil
  • Duane DegnDuane Degn Posts: 10,588
    edited 2020-08-03 20:42
    I used to do a lot of pH measurements and I have a stack of old electrodes. pH electrodes have a limited life similar to the way a battery cell has a limited life.
    To accurately measure pH, you really need to purchase a new electrode one or two times a year. At least this is what I had to do when measuring lots of solutions with a pH around 2. (Extreme pH values wear out an electrode faster than normal.)

    pH electrodes need to be calibrated pretty much each time they're used. To get a good calibration, you should use a pH buffer solution above and below the pH you want to measure. For measuring pH 2 solutions I used buffers at 1.68 and 4.01 (IIRC).

    The pH electrode needs to be connected to an appropriate amplifier in order for produce a voltage level capable of being read by normal ADC chips.

    I looked into building my own pH meter once and found it a very involved project. I have a pH meter (but no good electrode presently) but I wanted to make my own in order to connect it to data logging equipment.

    If I needed to measure pH now, I'd probably purchase pH paper. They make lots of different variations of pH paper. You can get very precise readings by using pH paper with a limited range.

    I should add I haven't researched this topic in about ten years.

  • Duane DegnDuane Degn Posts: 10,588
    edited 2020-08-03 20:55
    You might want to look at this. You still need an electrode but the module should convert the signal to something a Propeller could read.

    Edit: This one looks like it comes with an electrode and buffer solutions.
    It looks like these things may be sold separately.


  • RS_JimRS_Jim Posts: 1,753
    My Thought was to continusly monitor the H2O moving thru the pool filter and add muratic acid as needed to keep the PH at the correct leval. The makeup water here is high in PH and requires a cup or more acid a day.
    Jim
  • frank freedmanfrank freedman Posts: 1,975
    Considered this for a hot tub as well. PH marginally controlled due to high alkalinity. Total hardness makes balance near impossible. At least for the hot tub we can go with a water softener it looks like.
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