Hi,
I've had my KHD running for a month. In the beginning I had to re-measure hoses and recalibrate the probe a couple of times to get the values ​​to match my Hanna Checker and Salifert test. Since then, everything has looked stable for about 3 weeks and I was going to go from measurement to control, but all of a sudden the measurement values ​​from KHD dropped from 6.5-6.9 to 5.6-5.9 while the values ​​with Hanna Checker are still around 6.5. Now I have recalibrated the probe and checked for air bubbles in the reagent hose but the values ​​are still 0.5 to 1.0 from Hanna Checker. What could it be due to?