Principle of relay action when pH acidity meter controls acid additionAs follows:

Add acid, set the high point, and connect the output switch signal to the high point (HIGH) relay. When the pH value of the incoming water is greater than the HIAL value, the status of the high point relay starts the acid adding pump, and the pH value changes positively. When the acid is added to HIAL, a Hb value is set to prevent the dosing pump from frequently operating. When the pH continues to drop to the (HIAL-Hb) value, the high point relay will activate and the acid adding will stop. Subsequently, the incoming water was continuously replenished, and the pH value increased in reverse. When the pH reached the (HIAL Hb) value, the high point relay did not activate, but only activated when the pH reached HIAL, continuing to add acid.