Review on VIVOSUN 0 05Ph Accuracy Readout Temperature by Lindsay Law

Not factory calibrated. It reads a mistaken pack of 6.86 ph buffer solution as 6.50 ph. look at my photo I also tested a glass of water 3 times within an hour and got 3 different readings. First time it showed: 5.52ph Second time: 5.69ph Third time: 5.72ph It might not seem like much but there can be a BIG difference depending on what you're doing for need an accurate pH value. . I bought this because my 2 year old brand "Jellas" worked properly. But it still gives the same reading (6.2 ph) as a week ago on the same water. I also don't like the sizing style. I've only seen the type so far where you turn the little screw on the back and dial in to read what the buffer should be. How do I know that what is pre-programmed into the memory circuit is correct? What if I only have a pack of 4.0 and 6.86 parts buffer solution? Does that mean I can't calibrate if I don't have all three? Not cool. I like to calibrate with just one or two levels of calibration if that's all I have at the moment. I will try another brand.