PR721 series precision digital thermometer adopts intelligent sensor with locking structure, which can be replaced with sensors of different specifications to meet different temperature measurement needs. The supported sensor types include wire-wound platinum resistance, thin-film platinum resistance, thermocouple and humidity sensors, which can automatically identify and load the type, temperature range and correction value of the connected sensor. The thermometer is made of aluminum alloy as a whole, with IP64 protection class, which can be used reliably in harsh environments.