This project belongs to the field of metrology science and technology.
The standard humidity generator is a device that generates standard relative humidity and standard dew point atmosphere. It is an essential equipment for measuring and calibrating various humidity instruments. At present, humidity generation equipment at room temperature and general precision has become relatively common at home and abroad, but high-end standard humidity generation equipment at high precision, high temperature, low temperature, low pressure, etc. is still very lacking, but social needs are very urgent. Based on this, this project has developed this set of wide-temperature variable pressure standard humidity generator. Its main technical indicators are as follows

1. Humidity occurrence range: 3%RH96%RH (-50℃90℃)
2. Humidity uncertainty: U ≤ 0.5%RH at 0℃90℃ (k =2);
   U ≤ 1.0%RH (k =2) at-50℃0℃;
3. Dew point occurrence range: -70 ℃ DP ~88℃DP
4. Dew point uncertainty: 0.05℃DP~ 0.1℃DP (k =2)
5. Sample gas flow rate: 5~30 L/min.
   Main technological innovation contents:
   1) A unique saturator pressure and flow linkage control device has been designed, which can stabilize the saturator pressure fluctuation within 0.01% of the reading for a long time in a wide flow range and a wide pressure range.
   2) A unique structure of stacked disk saturator and an external controllable temperature presaturator with bypass are designed to produce 100% saturated moisture under wide temperature, water surface/ice surface, and wide flow conditions. Ice clogging occurs.
   3) Through the special design and operation of the device, a method to determine the uncertainty of saturation of the saturator is found.
   Main advantages:
   The humidity generation range is particularly wide, with high accuracy, and can change temperature, voltage and humidity at the same time. It is currently the only device in China that can generate standard relative humidity and high temperature dew point at low temperatures and low pressures. The operation is fully automatic, safe and reliable. The overall technical indicators are in line with the international advanced level of similar devices, laying a foundation for better carrying out humidity transfer in Shanghai and East China.
   Promotion and application situation:
   After the successful development of this generator, as the highest humidity standard device in East China, it provides measurement transmission for precision dew point meters of many measuring institutions in Shanghai and East China, ensuring the unity of humidity measurement values.
   Humidity measurement at low temperatures and low pressures is the main function of radiosonde. Previously, only a few national laboratories such as NIST in the United States and NPL in the United Kingdom had humidity calibration capabilities at low temperatures and low pressures. After being put into use, this device has provided measurement and calibration for low-temperature humidity instruments such as radiosonde. It is currently the only equipment in China that can provide simulation of high-altitude low-temperature and low-pressure conditions to calibrate humidity sensors. It is important to improve my country's high-altitude meteorological and ground detection level, and it is of great significance to respond to global climate change and disaster reduction and meteorological disaster prevention and reduction.
   Since the device was put into use, a large number of low-temperature, high-temperature and high-precision humidity instruments have been detected, solving the humidity measurement and calibration problems of many companies such as Shanghai Changwang and Shanghai Baosteel. Users have spread all over East China provinces.