If you want to improve your Bluelab pH product’s accuracy and longevity, you’ll need to get into the habit of regular cleaning and calibration.

Luckily, the easy-to-follow calibration process is the same for all Bluelab pH meters and pens.

After cleaning your pH probe, you’ll need to calibrate it with pH calibration solutions at two reference standards - 4.0 and 7.0 pH. Once calibrated, you can start measuring pH again immediately. You’ll need to recalibrate whenever you clean your pH probe and when your meter alerts you that a calibration is needed.

https://bluelab.com/usa/bluelab-ph-4-0-calibration-solution-500ml-1