Review on Optimized 0-14 pH Electrode Probe with BNC Connector, 300cm Cable - Suitable for PH Meter Monitor Controller Test Sensor, Ideal Replacement Kit for Aquariums, Hydroponics, Plants, Pools, and Spas (pH Electrode) by Lance Foster

There is a QR code for the video in the user manual. The website has expired and is now loading with the usual crappy shadow web ads. Luckily, it also had written instructions to follow when calibrating. It was only 0.01 from the factory and I adjusted it accordingly. It had a good stable reading for over 24 hours and is now fluctuating wildly between 5 and 11. I double checked the readings with the strips, they were all the same at 7.8 so I think the sensor passed out after a day . Get something else that might still have some sort of manufacturer support.