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Need help with pH sensor

Discussion in 'Microcontrollers, Programming and IoT' started by techbud, Sep 12, 2019.

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  1. techbud


    Sep 12, 2019

    I'm using the E201-C pH probe, which outputs an analog voltage level corresponding to a pH value, like any other pH sensor. I am going through some trouble callibrating it, though. Here's what I'm doing and where I'm stuck at:

    -Since the board comes with an offset potentiometer, I short-circuited the BNC connector to simulate a pH reading of exactly 7, then adjusted the voltage output to 2.5V

    -Then, I removed the short circuit and immersed the probe into a pH 4 solution, and got a reading of 2.10V

    -Afterwards, I immersed the probe into a pH 8.1 solution, and the reading was 2.28V

    Now, here's the problem: from what I've read, an acidic solution should produce a voltage higher than the neutral one. The voltage values obtained here don't make much sense to me. Note: I'm cleaning the probe between one testing and the next one, and waiting even longer than the response time to measure the voltage.

    Any help would be much appreciated
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    For ph4 the reading should be near 3.07 V (reference). Did you compensate for temperature?
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