The weather can be simply defined as the state of atmosphere. There are numerous factors that can influence the weather conditions or the atmosphere. It is almost impossible to predict the weather conditions but with technology, it has been made possible. Weather stations have been specially designed for this purpose. As the state of atmosphere is directly related to the air temperature and pressure, knowing the air temperature as well as pressure can give us powerful insight about the weather around us.
We all know that a weather station is not a single device, but it is a collection of many small tools to form a larger unit. It consists of various sensors and gadgets that work together but in specialized ways in order to transmit proper and accurate data of the weather variables. It is not really easy for common people to understand the main working principle of these units.
So that you can be more familiar with the device, it is quite important for you to know the various equipment of a weather station and also the way they work. We have tried our best to explain to you this mechanism in a very simple and less technical manner.
Thermometer is the basic unit of a weather station. It works as a temperature sensor and transmits the data to the main console. Usually, a weather station consists of wireless indoor and outdoor thermometer, by the help of which it is actually possible for you to peek out from underneath the warm covers, reach over to the console and check your room temperature, as well as the outdoor temperature.
Type and Working Principle
The temperature sensor of a weather station can be of three types:
- Thermocouples: These are made by joining two different types of metals that can create a voltage when temperature differs from the reference temperature, based on the electromagnetic force that is generated at the combination junction of the two metals.
- Thermistors: These use a thermally active resistor that is made of metal oxides, which has been encased in glass or epoxy. The resistance output varies according to the temperature. Usually more accurate Thermistors can vary linearly.
- PTD probes: These are basically made of pure metal, usually platinum. The temperature increases with increase in the electrical resistance of the metal. Even a small positive change will signal a 1 degree increase in the temperature.
Like any other thermometer, the temperature sensor in the weather station senses the type of temperature of the surrounding atmosphere and converts it into a proper and understandable data. In addition to the inside thermometer housed in the console of the weather station, right there beside you, there is another temperature sensor outside, which transmits data to the main unit.
It works like a main device that receives the data at one end and allows it to be virtually visible at the other end. The unit works typically at the range of around 30 meters or 100 feet. Some sensors run on batteries and some work on solar energy. The outdoor temperature sensor works more accurately if it is housed inside a good radiation shield.
Hygrometer is the humidity sensor. As moisture plays a very important role in weather, it is necessary to be updated with the humidity present in the air. A weather station can contain different types of hygrometers.
The hygrometer is usually placed besides the temperature sensor. Basically the hygrometer in the weather station, which is used to measure the relative humidity, is a type of capacitor. This sensor consists of a dielectric polymer layer with a thin metal electrode, through which water molecules are absorbed from the air. This finally causes a change in the capacitance and indicates certain change in the relative humidity. The dew point is calculated by correlating the relative humidity and temperature sensed by the hygrometer and thermometer, respectively.
Barometer is used to measure the barometric pressure or atmospheric pressure of the air.
The electronic pressure sensor or the electronic barometer in the weather station sensor unit measures the pressure using a force collector to determine the strain due to an applied force over a particular area. When mechanical strain is applied, the change in electrical resistivity of a semiconductor or metal is measured. The voltage output or the data is in the form of analog, which is then converted to digital that is displayed in the console.
Anemometer is the sensor that transmits the data for wind direction and wind speed. There are three types of anemometers; Cup anemometer with wind vane, propeller anemometer and sonic anemometer.
Type and Working Principle
- Cup anemometer with wind vane: It comes with three cups like structure that measures the wind speed. The additional wind vane is for measuring the direction of wind. The vane is designed in a way that it always points against the direction of the wind and transmits an analog voltage signal that is directly proportional to the angle of azimuth.
Whereas to measure the wind speed, the three cups are designed in such a way that one of the three cups is always at a 45° angle to the wind. In this manner all the three cups are faced towards the wind. Though there are also some with four cups, but are less reliable. The voltage output is then finally scaled to the actual wind speed according to the size of the cups and the overall diameter of rotation.
- Propeller Anemometer: This anemometer comes with a vane and a propeller, which work together to transmit the data for wind speed and direction. In this, the propeller is forced by the wind vane to face towards the wind, which results in producing the data of the direction that the wind is coming from, as well as the data for the maximum wind speed.The output for direction is received in an analog voltage signal that is directly proportional to the angle of azimuth. The wind speed is finally measured by a four-blade propeller with the frequency of the rotation that is directly proportional to speed of wind.
- Sonic anemometer: This type of anemometer uses ultrasonic waves in order to transmit the wind data. The sonic anemometer sticks up high above in the air like antennae, which are several inches apart from each other. The wind that passes through the spaces either speeds up or slows down the ultrasonic waves. This way, the changes in the ultrasonic waves are record by the anemometer and the data for wind speed and direction are finally transmitted to the display.
Rain gauge is the rain sensor that calculates the amount of rainfall and transmits the data. There are various types of rain gauges but the mostly used is the one with tipping bucket technology.
In the tipping bucket rain gauge, the gauge has an 8-inch rain collector that offers high precision accuracy by measuring every .01 inch of precipitation, each time the bucket shaped rain collector is tipped and the rain is collected. It also consists of insect and debris meshes in order to keep the gauge clean and free.
Many of the high quality weather stations are also able to provide the data for various additional weather variables that are calculated using the data provided by the common outdoor sensor system as well as the indoor sensors, so reports and forecast are displayed based on the outputs transmitted to the console. The mechanism is complex and so is the weather station.