Review on 🔵 Ultimate Accuracy VIVOSUN TDS Tester 3-in-1: TDS EC & Temperature Meter - High Precision Digital Water Quality Analysis (Blue) by Chuck Chen

Since these are "cheap" pens, I bought two at once. Mainly because your counter never dies at a good time. In this case it was good that I bought two. The first showed 44.9F. Press the button to switch to Celsius scale and it will show 23.0°C. Hmmm? So I change it to another one as the second device seems to be reading accurately. According to the instructions, the device can be calibrated. However, do not offer any guidance on how to perform the calibration. It is also not specified which calibration solution should be used. It is stated to have been calibrated at the factory. All in all a decent device. Unfortunately, new doesn't mean working these days. Definitely test it somehow. Even a replacement for the shelf ;)