A temperature and humidity sensor is an instrument that can simultaneously measure and control temperature and humidity signals, and achieve LCD digital display. It can also set and display the upper and lower limits of temperature and humidity through buttons, so that the instrument can automatically start the fan or heater according to the on-site situation, and automatically adjust the actual temperature and humidity of the tested environment. The action indication is output through two normally open contacts, truly making the instrument more intelligent and adaptable to complex and ever-changing on-site situations, thereby achieving the goal of effective protection of equipment.