Oil tank is a tool widely used in chemical industry, petroleum, medicine and biology. It is a place with controllable cold and heat and uniform temperature for experiments and tests in physical chemistry, metrology, universities, electronic instruments, scientific research institutions and other fields. The control system of the constant temperature tank adopts PID automatic control and LED digital display, and its external circulating pump can output the constant temperature liquid in the tank to the outside and rub the second constant temperature field.