Ok guys got me a digital ppm and ph meter and wanted to make a quick guide on how to calibrate them so for anyone who gets one in the future. Things you'll need, dig ppm meter, calibrations solution 342 ppm most come with the screw driver to calibrate and small container to hold your solution for testing So i poured my solution into my jar, set my ppm meter in, let it sit for bout 15 mins, took the reading as you see it was at 492 ppm. On the back is where you have to stick the screw driver in and calibrate it to the correct ppm. and botta bing botta bang there ya have it. easy as pie. then rinse your meter off with tap water and good to go.