In past winters, to measure snowfall, observers had to bring containers of snow inside houses every hour. After the snow turns into water, it is measured with a measuring cup, so the whole process can only be done manually. However, nowadays, with the continuous acceleration of meteorological modernization, weighing precipitation sensors have basically replaced manual observations. It can automatically measure snowfall according to weight, and can be set up in automatic observation stations in various regions to closely monitor snowfall conditions.
At present, the observations of solid precipitation by the Chinese Meteorological Department are mainly manual observations, which have many disadvantages such as poor timeliness and insufficient space-time density, and cannot comprehensively and continuously reflect the changes in the ice and snow process.
The rain gauge commonly used in the past is usually a tipping bucket rain sensor. This sensor is an instrument for automatically measuring precipitation. It is mainly composed of a water receiver, a filter funnel, a tipping bucket, a reed switch and a base. Precipitation passes through the water receiver, and then flows into the tipping bucket through a filter bucket. When a certain amount of rainwater flows into the tipping bucket, the tipping bucket is turned over to empty the water in the bucket, and the other bucket of the tipping bucket starts to receive water again. It is converted into a pulse signal by a dry reed switch and transmitted to the acquisition system. The measuring range of the instrument is 0 to 4mm/min.
Although digital transmission is realized, the tipping bucket rain sensor melts slowly when it encounters solid precipitation or mixed precipitation such as snow, hail, and sleet in a low-temperature environment in winter, which makes it impossible to monitor in time and needs to be covered and disabled. Human intervention is required to complete the observation.
The new weighing precipitation sensor is a fully automatic and all-weather precipitation observation instrument suitable for solid, liquid and mixed precipitation total and precipitation intensity measurement, which can provide more comprehensive and authoritative information support for meteorology.
The latest gravimetric precipitation sensors continuously record the total weight of the water reservoir with the precipitation accumulated in it by using a spring device or a weight balance system. It does not automatically pour water, has a fixed volume, and needs to reduce evaporation loss (add antifreeze and suppress evaporation oil), especially suitable for measuring solid precipitation.
The gravimetric precipitation sensor is designed based on the principle of load measurement technology. Through the rapid and corresponding measurement of precipitation for mass changes, it can output switching signals to connect to existing automatic weather stations, and can also be connected to other acquisition systems as smart sensors.
Specifically, the principle is to measure the amount of precipitation through the rapid response of the load element to the change in the quality of the water tank. The weighing type precipitation sensor is mainly composed of the water receiving port, the outer shell, the inner cylinder, the load element and the processing unit, the base assembly, the windproof ring, etc. components.
At present, there are two main measurement techniques used by weighing precipitation sensors:
Based on resistance strain measurement technology
The sensitive beam produces elastic deformation under the action of external force, so that the resistance strain gauge pasted on its surface also deforms accordingly. After the resistance strain gauge is deformed, its resistance value will change, and then the resistance change will be measured by the corresponding measurement circuit. Convert it into an electrical signal, and then get the quality of precipitation.
Vibrating wire measurement technique
This technology uses the string wire vibrating at a fixed frequency as the elastic component, and according to the corresponding relationship between the tensile force and the vibration frequency, the quality of the precipitation is obtained through the corresponding measurement circuit.
In general, the gravimetric precipitation sensor can effectively measure solid-state precipitation, and can solve the problems of poor timeliness, insufficient density and insufficient comprehensiveness caused by traditional manual observation of precipitation. It can be integrated into the existing automatic weather stations of various regional meteorological bureaus, and is in line with the development trend of intelligent weather sensors.
