If you have a home weather station, you may be aware of a radiation shield covering the temperature and humidity sensors. In this experiment, the Instrument Choice scientists demonstrate the function of a passive solar radiation shield by collecting temperature data from a logger protected by a radiation shield and then comparing results to a logger that recorded temperature data when placed in direct sunlight.
Video: What is the Function of a Solar Radiation Shield?
About Radiation Shields
The function of a radiation shield is twofold:
- First and foremost, radiation shields protect the temperature sensor of a weather station against both direct and indirect heat radiation sources.
- The second function is to shield the temperature (and humidity, if applicable) sensor against wetting during rain or fog events.
Both heat radiation and sensor wetting will lead to inaccurate temperature readings. However, if you completely shield the sensors, the result will be inadequate ventilation, which also produces inaccuracies. The design of radiation shields must find a balance between the requirements of protection while permitting adequate airflow.
Figure 1 Example of a solar radiation shield
Although designs will differ slightly, figure 1 (above) is an example of a typical passive solar radiation shield. Such shields comprise several (usually) white stacked plates made from UV-stable plastic. These plates cover and surround the temperature and humidity sensors while facilitating airflow.
The Experiment
For this experiment, we selected two data loggers, one to collect temperature information under the protection of a radiation shield, and the other we will expose to direct solar radiation.
Required Materials
- Two EL-USB-1 temperature data loggers.
- A solar radiation shield.
Method
- Set up the two data loggers to record temperature readings at one-minute intervals.
- Place one logger (EasyLog USB 1 - Shield ) within the solar radiation shield.
- Place the second logger (EasyLog USB 2 – No Shield) on concrete, in direct sunlight.
- Leave both loggers for several hours to collect temperature information.
- After several hours, compare collected temperature information against official government temperature information collected from the nearest weather station.
Results
Figure 2: Comparison of a shielded logger, exposed logger, and the actual temperature readings.
Results showed that the shielded logger (EasyLog USB 1 - Shield) recorded temperatures that followed verified actual temperatures closely. The unshielded temperature logger (EasyLog USB 2 – No Shield) experienced temperatures much higher than official readings, which our scientists attributed to direct (unprotected) solar radiation.
Conclusion
Our experiment indicates that radiation shields work to ensure consistent and accurate temperature readings by adequately shading a weather station's sensors, and permitting adequate ventilation.
Want more information on solar radiation shields and how to protect your weather station? Speak with an Instrument Choice Scientist! We're here to help! Call 1300 737 871 or email customer-service@instrumentchoice.com.au.