The DH-3020 low-temperature constant temperature bath adopts the world's first advanced fluorine free refrigeration system. A low-temperature experimental instrument developed for scientific research, biology, medicine, chemical engineering and other departments with high requirements for constant temperature accuracy. It has the characteristics of making the temperature in the tank uniform and intelligent temperature control more accurate. Equipped with an over temperature alarm system to ensure instrument safety, power off protection function, automatic delay of three minutes, cold liquid in the tank can be drawn out, and experimental containers outside the cooling machine can also be used for calibration purposes in the manufacturing of ordinary thermometers and other temperature measuring instruments.