> For the complete documentation index, see [llms.txt](https://3dpaws.comet.ucar.edu/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://3dpaws.comet.ucar.edu/building-3d-paws/building-the-core-instruments/radiation-shield.md). # Radiation Shield ### How the Sensors Work The radiation shield houses integrated environmental sensors to ensure accurate readings: * **Temperature:** Temperature measurements are provided by the **SHT31D**, **MCP9808**, and **BMP390** sensors. The SHT31D and MCP9808 use precision semiconductor temperature-sensing elements whose electrical characteristics change predictably with temperature, enabling accurate, linear temperature measurements without a separate thermistor component. The BMP390 also measures temperature internally, providing a supplementary temperature observation as part of its pressure compensation system. Using three temperature sensors enables measurement verification, quality control, and improved confidence in reported environmental conditions. * **Relative Humidity:** Relative humidity is measured by the **SHT31D** using a moisture-sensitive polymer sensing element. As the amount of water vapor in the air changes, the capacitance of the sensing element changes proportionally, allowing the sensor to determine relative humidity. * **Atmospheric Pressure:** Atmospheric pressure is measured by the **BMP390** barometric pressure sensor. The sensor uses a micro-electromechanical (MEMS) silicon diaphragm that flexes in response to changes in atmospheric pressure. These microscopic deflections are detected by piezoresistive elements embedded within the diaphragm and converted into highly accurate digital pressure measurements. **Wiring**:\ All three sensors connect via **I2C** (shared SDA/SCL lines) to minimize wiring complexity. The radiation shield’s passive ventilation design protects sensors from direct sunlight, precipitation, and debris while maintaining airflow for precision. ### Instruction Slides for Wiring the Sensors {% embed url="" %} ## Assembling the Radiation Shield The radiation shield is a passively ventilated enclosure that protects temperature, humidity, and pressure sensors from environmental interference while maintaining airflow for accurate measurements. Its multi-plate design minimizes exposure to direct sunlight, precipitation, and debris, while allowing ambient air circulation. The shield reduces radiative heating and thermal inertia, ensuring sensors measure true ambient air conditions rather than artificial microclimates. ### Instruction Slides for Assembling the Radiation Shield {% embed url="" %} ### Tutorial Video for Assembling the Radiation Shield This video demonstrates the entire assembly of the instrument. There is only one video in this particular playlist. {% embed url="" %} --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://3dpaws.comet.ucar.edu/building-3d-paws/building-the-core-instruments/radiation-shield.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.