# DAQ-U User Manual The DAQ-U is a USB-C light sensor that requires a connection to a computer to stream and record light measurements. An internal spectrometer records the changing ambient light spectrum (every 5nm, 340 - 1010 nm) to assist with calibrating [MAPIR multispectral camera](https://www.mapir.camera/pages/multispectral-cameras) images, measuring ambient light sources or for measuring object reflectance. The optional (recommended) DAQ-U Caps allow you to slide on various adapters that adjust the light path to the light sensor. Caps which narrow the angle of light measurement allow you to more accurately measure defined regions in front of the sensor. Caps that include a white glass diffuser reduce the ambient light intensity, allowing measurements of bright light sources, such as direct sunlight, without over-saturating the sensor. The relative radiometric calibration keeps the wavelength to wavelength measurements consistent regardless of the intensity of the changing ambient light. After the factory calibration the DAQ-U spectrometer never needs to be recalibrated. The DAQ-U relative illumination spectrometer is not calibrated for irradiance (W/m^2) so it cannot measure the *amount* of light intensity (power) change. When the spectrometer log data is used with images of our [reflectance reference targets](https://www.mapir.camera/collections/calibration-targets) the resulting calibrated pixel data will be in the units of percent reflectance. As the ambient light changes, any radiometric differences are corrected for, meaning multispectral indices such as NDVI are maintained. Radiometric differences in the overall light intensity and spectrum are calibrated and comparable across different locations and time. --- # Agent Instructions: 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: ``` GET https://mapir.gitbook.io/daq/daq-u/daq-u-user-manual.md?ask= ``` The question should be specific, self-contained, and written in natural language. 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.