Review on Accurate and Reliable VIVOSUN Digital PH Tester Pen for Water Testing by Johnny Pigao

Seems so simple mine must be crazy. Ordered a pH meter to test plants working in a DWC facility. Did the calibration and that's when he started to stagger. After calibration, it was set to 8.78 every time I turned it on. It also showed a standard test fluid of 7.0 at 7.50 (after calibration). in less than 24 hours it is completely unusable. It won't settle before or during use, and I can't recalibrate it because you have to use their ridiculous three-person testing method with pre-provided powders to calibrate it, and they just send one set of powders to calibrate. Either ship each tester with multiple calibration kits or make a product that can be manually adjusted to a standard liquid. Really disappointed with this product. Usually happy with Vivosun.