Step infusion is a common brewing method in many microbreweries. It means the mash temperature would increase and keep in various stage. Take a example. There are four stages for step infusion.
Stage 1: 30-35℃ for 30 minutes
Stage 2: 55-65℃ for 30-60 minutes
Stage 3: 65-68℃ for 30-60 minutes
Stage 4: 76-78℃ for 10 minutes

For PID control, you need to set up target temperature before every stage and control the time by yourself. That is to say, before stage 1, you should set target temperature 30-35℃. Then wait the mash being heated to 30-35℃. After that, calculate the time to keep the mash under 30-35℃ for 30 minutes. Next, set the target temperature of stage 2, 55-65℃ and wait the mash being heated to 55-65℃. The following process will be similar with sage 1. The whole procedure must require a brewmaster staying there always.

For PLC control, it makes the brewing much easier as you can input the temperature and time in advance for all of stages. Therefore, the mash can be heated, kept under target temperature automatically. Before lautering, you do not need to do anything. For your better understanding, I attach a picture. Please kindly check.

Current: display the actual temperature;
Set: input target temperature;
HY: adjust temperature reaction sensitiveness; You can set it to 0.1. It means the burner or steam boiler would start to heat mash when the actual temperature is lower 0.1℃ than target temperature. Of course, it is not good for burner or steam boiler to start and close frequently. So some customers do not like so sensitive temperature reaction. In this case, you can set HY to 1. when the actual temperature is lower 1℃ than target temperature, the burner or steam boiler will start to heat mash. It is very flexible.
Set: input time you want to keep under target temperature;
Remain: Count down time once the actual temperature reaches target temperature.