Automatic control method and system for temperature of beer fermentation tank

The invention relates to the technical field of beer fermentation and brewing control, and in particular, relates to an automatic control method and system for the temperature of a beer fermentation tank. The method includes the following steps: S1, taking an on-off valve as an actuator to control the refrigerant flow quantity; and taking a programmable controller as a controller of the on-off valve; S2, presetting the temperature required by the fermentation tank process and sampling the actual temperature of the fermentation tank; and S3, sampling and comparing the deviation between the preset temperature and the sampling temperature, calculating the opening degree of the on-off valve by a PID algorithm, then converting the analog quantity opening degree control signal into a digital quantity switching control signal, and then outputting the switching control signal to the on-off valve by the programmable controller to control the action of the on-off valve. Because the digital quantity switching control si