The meters are used to measure acidity and alkalinity of liquids.
With two points calibration function, it will prompt pH calibration solution when you calibrate the meter.
You need only immerse the pH electrode into standard solution and press [CAL] key, then the meter will be calibrated automatically.
When measure the sample solution, you need freeze reading temporarily for ease of recording.
Waiting for a stable reading, press [HOLD] key, then the meter will hold the value.