The utility model discloses a PID
temperature control circuit applied to a microbial culture monitor. The PID
temperature control circuit comprises a
PID controller and a PID
control circuit, the
PID controller is used for receiving target temperature, incubation frame bias temperature and PID
control parameters issued by the upper computer, receiving temperature parameters, sent by the PID
control circuit, of all incubation frames in real time, conducting PID operation on the temperature parameters, outputting PWM adjusting signals to the PID
control circuit according to operation results, and adjusting the temperature of the incubation frames by changing the output quantity of the PID control circuit. And the output power of the heating component or the refrigerating component is adjusted. The three-state buffer can buffer and isolate signals, prevent
noise from interfering with the
PID controller, protect the sensitive PID controller from being damaged by a rear-end circuit, and prevent residual output signals of the PID controller from influencing turn-off logic. In emergency, the output of the PID controller is
cut off according to the emergency
stop signal, so that the power switch device is quickly closed, the
power output of the
temperature control load is stopped, and the emergency stop function is realized.