> For the complete documentation index, see [llms.txt](https://mapir.gitbook.io/daq/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mapir.gitbook.io/daq/daq-u/daq-u-user-manual.md). # DAQ-U User Manual The DAQ-U is a modular, radiometrically calibrated USB-C spectroradiometer. Its internal spectrometer records the ambient light spectrum from **340 – 1010 nm** as **135 measurements** (one every 5 nm) in absolute irradiance units (**W/m²·nm**), streaming to a connected computer at up to **10 Hz**. Use it to calibrate [MAPIR multispectral camera](https://www.mapir.camera/pages/multispectral-cameras) images, measure ambient light sources, or measure object reflectance. The DAQ-U contains the same radiometrically calibrated light sensor as the [DAQ-M](/daq/daq-m/readme.md) (Bluetooth) and [DAQ-E](/daq/daq-e/daq-e-user-manual.md) (Ethernet). All three speak the same protocol and produce the same `.daq` data file, so downstream processing is identical regardless of which model you use — the DAQ-U is simply the USB-C variant.

The DAQ-U with the Sunshine cap installed

The DAQ-U is externally powered over USB-C and has no battery or internal memory. Plug it into any Windows or Linux computer (including embedded devices such as a Jetson or Raspberry Pi) and stream measurements live.

The DAQ-U connects and is powered over USB-C

## Radiometric Calibration Every DAQ-U ships with a unique, per-unit radiometric calibration certificate ([view an example](https://cdn.shopify.com/s/files/1/0878/4732/files/daq-u_example_calibration_certificate.pdf?v=1783033670)). When you connect the sensor, Chloros automatically downloads that unit's calibration data (gain, dark offset, and cap correction) from the MAPIR Cloud and applies it to every measurement — even raw recordings are calibrated automatically at processing time. After the factory calibration the DAQ-U spectrometer never needs to be recalibrated. Because the measurements are absolute and repeatable from unit to unit, any radiometric differences in overall light intensity and spectrum are corrected for. When the spectrometer log is used with images of our [reflectance reference targets](https://www.mapir.camera/collections/calibration-targets), the resulting calibrated pixel data is in units of percent reflectance, and multispectral indices such as NDVI stay consistent and comparable across different locations and times. ## Caps The DAQ-U accepts optional snap-on caps that adjust the light path to the sensor: * **Sunshine Cap** — a white glass cosine corrector that diffuses incoming light for accurate ambient / downwelling irradiance measurements. This is the default cap assumed by Chloros and is used when recording the ambient light spectrum to correct Survey3 and LATTICE images. It also reduces light intensity, allowing measurements of bright sources such as direct sunlight without over-saturating the sensor. * **Field-of-View Caps (15° / 30° / 45° / 60° / 90°)** — narrow the sensor's angle of measurement so you can more accurately measure reflected light from a defined region or target in front of the sensor. A narrower cap measures a more selective area.

The DAQ-U caps, from left: Sunshine, 90°, 60°, 45°, 30°, 15°

{% hint style="info" %} Whichever cap is installed, tell Chloros which one you are using so it applies the correct per-cap correction profile. {% endhint %} ## Measurement Modes A single DAQ-U measurement produces several kinds of data at once: | Mode | Output | Description | | ------------------- | ----------------------------------------------- | ------------------------------------------------------------------------------ | | Spectroradiometer | Spectral Irradiance Power (W/m²·nm) | Research-grade ambient light spectrum used to correct Survey3 / LATTICE images | | Spectrophotometer\* | Percent Reflectance (%) | Measures object / target reflectance | | Irradiance Sensor | Total Irradiance Power (W/m²) | Total power across the full 340 – 1010 nm range | | Colorimeter | CCT (K), CRI, XYZ, xy, uv | Color data derived from the spectral measurement | | PAR / Lux Meter | Photometric Illuminance (lux), PPFD (µmol/m²/s) | Light levels for plant growth and human perception | \*Reflectance is calibrated against a scan of a white reference target, or by using a second DAQ sensor for the ambient reference (see [Using Multiple DAQ-U](/daq/daq-u/using-multiple-daq-u-together.md)). ## Capturing Data To record light measurements, connect the DAQ-U to a computer with USB-C and use one of the Chloros capture methods described in [Capturing Light Sensor Data](/daq/daq-u/capturing-light-sensor-data.md): {% content-ref url="/pages/5VvuwnXpoi5UhTziBEo0" %} [Capturing Light Sensor Data](/daq/daq-u/capturing-light-sensor-data.md) {% endcontent-ref %} Each recording is written to a self-describing `.daq` file (an SQLite database) that embeds the device model, sensor ID, installed cap, the per-unit calibration that was applied, a UTC timestamp with nanosecond precision, the integration time and frame-averaging settings, and the full spectrum along with the derived total power, PPFD, lux, and color metrics. ## Specifications | Specification | Details | | --------------------------------- | ------------------------------------------------------------- | | Dimensions (without cap) | 36 x 20 x 12 mm (1.4 x 0.8 x 0.5 in) — L x W x H | | Dimensions (with Sunshine cap) | 42 x 20 x 12 mm (1.7 x 0.8 x 0.5 in) | | Weight | 8.13 g (9.22 g with Sunshine cap) | | Operating Temperature | 0 °C – 60 °C (32 °F – 140 °F) | | Spectrometer Calibration | Radiometric (W/m²·nm) | | Calibration Certificate | Per-unit PDF (downloaded via Chloros) | | Wavelength Range | 340 – 1010 nm | | Number of Wavelength Measurements | 135 | | Wavelength Measurement Width | 5 nm | | Wavelength Resolution | 20 nm – 50 nm | | Wavelength Accuracy | 3 nm | | Repeatability (peak) | 1 nm | | Measurement Power Range | 20 – 150,000 Lux (PPFD: 0 – 2,000 µmol) | | Signal to Noise Ratio | 250:1 @ max. power & average of 40 | | Dynamic Range | >1000:1 | | Linearity | 99% | | Integration Time | Auto or Manual (4 ms – 500 ms) | | Streaming Rate (maximum) | \~10 Hz (adjustable via integration time and frame averaging) | | Field of View | <180° (Sunshine Cap); 15° / 30° / 45° / 60° / 90° (FOV Caps) | | Diffuser Type | White Glass Cosine Corrector (optional Sunshine Cap) | | Power | USB-C only (no internal battery) | | Memory | None (streams over USB-C) | | Interface | USB-C (USB Serial) | | Software | Chloros (Windows, Linux) | ## In the Box * 1x DAQ-U spectroradiometer * 1x USB-C cable (1 m) * 1x Radiometric calibration certificate (digital — downloaded via Chloros) Caps and the optional tripod mount are sold separately.