The NM-HUMI700 Standard Ventilated Dry-Wet Hygrometer is designed based on the principle of the dry-wet hygrometer. It consists of two temperature sensors, one for dry bulb temperature measurement and the other for wet bulb temperature measurement. The wet bulb temperature sensor is wrapped in a cloth soaked in water. The evaporation amount of the wet bulb surface of the humidity temperature sensor depends on the atmospheric relative humidity, and the heat required for this evaporation causes the wet bulb temperature to drop. By integrating the dry bulb temperature, wet bulb temperature, and the current atmospheric pressure, the relative humidity value is calculated using the humidity formula. The motor drives a fan to ventilate the surfaces of the dry and wet temperature sensors, maintaining a relatively constant wind speed on the sensor surfaces, making the humidity measurement more stable and accurate.