Review on Apera Instruments SX620 pH Pen Tester Kit: Accurate Results with 0.01 pH Accuracy, 3-Point Auto Calibration, and ATC by Josue Porter

I use this for several aquariums. Received yesterday, got some distilled water today to rinse the probe and opened the storage box with the pen. Please note that the package I ordered included the pen, storage solution, calibration solution and extra batteries. What, I'm glad I realized it was the extra batteries before trying to open the handle to install them, I still don't know how to open the handle. But I'm glad to know that the batteries and probe can be replaced. My first impression of the box was that this pen is very well made. I'm not familiar with laboratory or medical equipment, but as far as equipment and tools go, they are of good quality. The instructions were simple and clear enough. After a few minutes I was calibrated and tested various water samples and also checked the calibration pin again. I turned the pen off for a while, made a few adjustments, went back and retested the water sample and the pen passed the calibration. A few hours later when I retested the caibration I found it had grown by 1/10th. For now I am happy with my purchase and will continue to use this pen maybe a few times a week.