A redox probe measures the oxidation power of pool water, which is related to the chlorine content. The higher the redox value, the higher the oxidation power and the more chlorine in the water.
You need to calibrate the redox probe a few times a year using a 468 mV buffer solution.
If stored at room temperature and away from light, the calibration solution can be used for up to two years.
If you don't have a bypass, you'll need to close the electrode hole during calibration with a dummy probe.
Important note: The redox value is not an absolute measure of chlorine, and the ideal redox value varies from pool to pool. You should adjust the chlorine content to 1 ppm free chlorine using a color meter. The redox value that you measure at pH 7.2-7.6 and 1 ppm chlorine is the ideal set point for your pool. In most cases, this is between 600 and 800 mV.