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Thread: PH1 and PH 2 probes / 2 different PH readings

  1. #1
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    PH1 and PH 2 probes / 2 different PH readings

    I just connected my second PH probe to my apex using the existing ORP port. I conducted the calibration using the 4 and 7 calibration fluid packs. When I placed the second probe in the sump (next to the first PH Probe), wow guess what, I got 2 different readings. The first probe was calibrated using the 7 low and 10 high calibration fluids. The PH 2 probe is reading 7.9 while the PH 1 probe is reading 7.7. Could it be the level of calibration fluids ie. 4/7 vs. 7/10. Both are lab grade. PH 2 probe is brand new. Ph 1 is a few years old.
    Anyone else experienced this?

  2. #2
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    Anyone else have this issue

  3. #3
    Frequent Visitor Scott.h's Avatar
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    Quote Originally Posted by lilchris View Post
    Anyone else have this issue
    How long has it been since you calibrated the first probe? Could there be any build up on the probe? You need to use the correct calibration solution for the range. If your ph is over 7 then you wouldn't want the 4-7 solution. I'm sure the difference lies there.

  4. #4
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    I recalibrated it last night. No build up from what I see. I used the 7 and 10 solutions for the probe in the tank and the 4 and 7 solutions for the probe in the reactor.

    Sent from my SM-G900V using Tapatalk

  5. #5
    Frequent Visitor Scott.h's Avatar
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    Quote Originally Posted by lilchris View Post
    I recalibrated it last night. No build up from what I see. I used the 7 and 10 solutions for the probe in the tank and the 4 and 7 solutions for the probe in the reactor.

    Sent from my SM-G900V using Tapatalk
    why are you using the 4 and 7 calibration solutions?

  6. #6
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    Because the ph in the reactor can drop below 7.0

    Sent from my SM-G900V using Tapatalk

  7. #7
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    Very Common

    Quote Originally Posted by lilchris View Post
    Because the ph in the reactor can drop below 7.0

    Sent from my SM-G900V using Tapatalk
    I have similar experiences with multiple pH probes. I actual had 2 APEXs on one tank so I had 4 pH probes in the same area. They were all cleaned and calibrated. But the reading varied by .1 across all of them. For example 8.2, 8.1, 8.3, 8.25. I was never able to get them within .05 of each other.

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