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Thermometer: is used to measure the temperature the mercury-in-glass type, which consists of a uniform-diameter glass capillary that opens into a mercury-filled bulb at one end. The assembly is sealed to preserve a partial vacuum in the capillary. If the temperature increases, the mercury expands and rises in the capillary. The temperature may then be read on an adjacent scale.
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Stevenson screen: is a box designed to hold weather-measuring instruments such as thermometers. It is kept off the ground by legs, has levered sides to encourage the free passage of air, and is painted white to reflect heat radiation, since what is measured is the temperature of the air, not of the sunshine.
- Wet & Dry Thermometer: also known as a hygrometer In physics, any instrument for measuring the humidity, or water vapour content, of a gas. A wet and dry bulb hygrometer consists of two vertical thermometers, with one of the bulbs covered in absorbent cloth dipped into water. As the water evaporates, the bulb cools, producing a temperature difference between the two thermometers. The amount of evaporation is then measured.
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Max & Min Thermometer: is designed to register the maximum or minimum temperature attained. A mercury-in-glass clinical thermometer, for example, is a maximum-reading instrument in which a trap in the capillary tube between the bulb and the bottom of the capillary permits the mercury to expand with increasing temperature, but prevents it from flowing back unless it is forced back by vigorous shaking.
Data Logging
Data logging is the automatic recording of data for later use. Where a computer is used, sensors usually collect the data via an interface box and the data is then stored in a computer. Many modem interface boxes have the ability to store data themselves. Data can then be analysed later. In order for the data logging system can work, it requires sensors. Data can be set to record over a certain period of time and frequency can be set to which measurements are made, also the measurements will be more accurate because there is no human error.
Advantages Of An Automatic Weather Station
- The automatic station can be set to take readings over a certain period of time so you can even take readings when you are not there e.g in the middle of the night you will still be able to take readings while you are in bed
- The frequency with which the data is logged can be changed
- The electronic signals can be relayed through communication lines (by radio or through the telephone wires) so the sensors can be situated anywhere in the world.
- There is no room for human error when collecting the data so the results will be much more accurate
- Results can be displayed immediately on screen as graphs making it much easier to analyse the results.
Sensors
A data logging system requires sensors to work sensors include analogue and digital sensors and can be passive or active devices. Sensors act as input devices into the computer, a sensor simply monitors some physical quantity such as pressure, rate of flow, humidity e.t.c and it turns this into analogue or digital electrical outputs.
Temperature: the temperature sensor gives an analogue signal which is converted via an analogue-to-digital converter to a digital signal, which is then stored by the microprocessor.
Wind Speed: an anemometer measures wind speed by using an optical sensor to generate a binary digital signal each time it rotates. The wind speed is recorded in kilometres per hour.
Wind Direction: the wind direction is detected on a grey code disk. As the wind vane rotates, three optical sensors read the disk and generate a three bit binary pattern. Each pattern represents one of the eight wind directions
Rainfall: rainfall is measured using a tilting bucket as the bucket fills with water, it starts to tilt. When it is full the bucket tips the water out and brings another bucket into position ready to collect more water. An optical sensor detects the number of tips and this digital signal is passed to the microprocessor.
Daylight and Sunshine Hours: Sunshine is detected by a special diode. The signal from this is then passed to microprocessor after it is converted from an analogue to digital signal. The digital signal is then used by microprocessors to determine sunrise and sunset and also measure sunshine hours
Additional Sensors: additional sensors measure atmospheric pressure and relative humidity these may also be connected to the system.
Analogue and Digital
The principle feature of analogue representations are that they are continuous where as Digital representations consist of values measured at discrete intervals also computers are unable to read non-digital format this is why an analogue to digital converter is needed to read the data.
Results
Most of the weekly data that has been recorded with 21 readings 3 readings, each day however the rainfall has only been recorded with one reading at the end of the day.
The temperature has been recorded in degrees Celsius and the highest temperature is 16 C and the lowest is 3.02 C.
The rainfall has been recorded in mm with one reading each day the lowest amount of rainfall is 0 mm and the highest is 4 mm
The wind speed is measured in m/s the highest speed 20.11 m/s an the lowest is 1.53 m/s
The humidity is measured in percentage the highest humidity is 75% the lowest is 23%
The day log temperature has been recorded at a set time of every 30 minutes the temperature is recorded in C.
The highest temperature is 19.2 C and the lowest is 4.36 C
