ATC Probe for 150-, 300-, 450-series metersATC Probe for 150 , 300 , 450 series meters Provides ATC for most current Oakton pH meters. What is ATC on a pH meter? Should I be looking for a meter that has this? ATC stands for Automatic Temperature Compensation this means the meter measures pH and temperature at the same time, then automatically calculates to correct for differences (e. g. if one sample is 20C and another is 37C) Features: Corrosion resistant stainless steel 30 K thermistor