Apera ph20 problem

I’m having trouble calibrating my ph pen. When I calibrate 7, rinse off, hold calibrate dip in 4 go to hit button and it says error 1. I’ve taken batteries out, whole 9 yards. Anyone have same experience? Or know a solution?

Also need a recommendation on a good cheap under $20 tds meter off Amazon, one with the option that temp doesn’t effect reading

Might be bad test solution. Here’s what the manufacturer says:

Er1 will usually appear on the screen when users dip the probe into the wrong calibration solutions. For example, for pH calibration, the 1st point calibration must be 7.00 pH. If users dip into 4.00 or 10.01 for the 1st point calibration, Er1 will appear to remind you that it’s not the correct calibration solution. If you are pretty sure you are dipping into the correct solution, but the Err1 still comes up, it could be caused by either of the following reasons:

  1. The calibration solution is contaminated or expired, thus not holding a correct standard value. Users need to replace new calibration solutions.
  2. After 1st point calibration, you turned the meter off and turn it back on for the 2nd point calibration. In that case, you need to start with 7.00 pH again, and then 4.00 or 10.01. Therefore, a good practice would be to do the 2nd point calibration right after the 1st point (7.00 pH) without turning off the meter.
  3. The pH probe of the meter loses its sensitivity due to long-time use or long-time dry storage. To solve this problem, soak the pH probe in the storage solution overnight, and then do the calibration again.
  4. Check if there is a small air bubble inside the glass bulb sensor. If you find it, simply shake the meter several times until the air bubble disappears. The existence of the air bubble inside the glass bulb will cause significant inaccuracy to the measurements.

If you have confirmed that it’s none of the above reasons, try setting the meter back to factory default (refer to your instruction manual), and then perform the calibration again starting from pH 7.00. After that, if Er1 still comes up, it’s possible that the pH probe of the meter is not working properly. Users can contact us or the retalier for return or replacement service.

  1. Parameter Setting
    6.1 Setting Schedule
    6.2 Parameter Setting
    When turned off, long press (POWER/MEAS) to enter setup → short press (POWER/MEAS) to switch
    P1-P2→ Short press (CAL), parameter flashing→short press (POWER/MEAS) to choose,
    short press (CAL) to confirm parameter selection→Long press (POWER/MEAS) to switch off.

The second part is in the manual, about resetting it. I hope that helps! :v:


I have this TDS pen, and it does automatic temperature adjustment:

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Cool deal. Read that different temperature of exact same water will read different

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As @elheffe702 pointed out, one has to do the pH 7.0 then the pH 4. Out of order, turning off, or repeating will give an “er” msg.

I’ve also found that if you short push the calibration button before the meter has settled down with a constant smiley face, it’ll give the “er” msg. Forcing you to shut it off and start from scratch.

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It’s finicky, but I still think it’s a great meter. Mine sat in storage for about 6 months, in KCl, but it had all dried up/crystallized. I took it out, soaked it in some fresh solution for about an hour, then checked, and it was still reasonably calibrated. I recalibrated it anyway, but I was impressed.

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I replaced my ph20 with the ph60 because mine did the same thing. The ph20 I have is still accurate but I get the error message also. I sprung for the more expensive one because the probe is replaceable. The way I see it, ph is the foundation of a successful grow and is an area I don’t want to guess at.


I’ll probably do the same if/when my ph20 fails.

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That’s why I upgraded to the pH60—> replaceable probe. Oh, and the backlight.


Yeah, no backlight is sometimes a pita.

Mine read that after storing in distilled water for extended period. After soaking a couple days in storage solution worked fine.