I'm new to the world of ph and ec/tds, but in my opinion dont rely on a factory pre-calibration. I calibrated before first use and indeed it needed adjustments. I have recalibrated every 2 weeks or so, and while nothing has drifted too far, I have had to adjust a bit the low setting.

Also make note of which solution yours came with so you can buy the proper calibration fluid for EC/TDS. Some use 1500ppm solution, others use an EC rated solution.
MisterE Reviewed by MisterE on . Someone please explain... Can someone please explain the purpose of Ph buffers. Do you need them? Why are there specific amounts? Do they correlate with Ph up/down or IS ph up/down a buffer in its own? I bought a hanna 4 in one combo gro check. It came calibrated already but included Ph 4.01 and Ph 7.01 solutions for calibration? What are these packets? Do I need them? They are 20 mL each. Are these one time applications? Can I use them more than once? How do you store it if you can use it more than once because they Rating: 5