Tech Specs

The Meter is a robust, general purpose, ten wavelength device for measuring spectral reflectance from liquids (e.g. milk), flat objects (e.g. leaves) or solids (e.g. soils, produce).

The circuit has an on-board lithium battery charger (designed for a 3.7V 18650 Li battery), current-controlled pulsed LEDs to illuminate the sample, as well as an optional hall effect sensor, contactless temperature sensor and temp/pressure/rh sensor (BME280).

Key Features
  • 10-wavelength output not affected by ambient light
  • Robust and field-ready
  • Connects to Survey Stack (Our-Sci's open-source software) to collect, share, and display results
  • Connects to any Android device wirelessly using Bluetooth or wired USB On The Go
  • Includes a wall charger and an internal 3400 mAh battery
  • Fully open source and modifiable

Designed for use with:
  • liquids in 5 mL or 0.7 mL square cuvettes
  • liquid colormetric measurements (example: pH change)
  • cell density (940 nm)
    • examples: milk fat concentration; spectral properties of juices, wines, etc.
  • soil or other bulk solids
  • soil carbon estimation (requires calibration)
  • soil color estimation
  • solid objects (fruits, veggies)
  • spectral signatures for nutrient estimation (requires calibration)
  • leaves or other flat objects
  • NDVI (greenness) in leaves
  • relative carotenoids, anthocyanins, or other color-related compounds

Default Output
  • Reflectance at all wavelengths (normalized from 0 - 10,000)
  • Chlorophyll fluoresence and any fluorescence with excitation <700 nm and flurorescence >700 nm
  • NDVI (greenness) in leaves

Sensor Detail
Reflectance hardware:
  • 10 wavelength (nm): UVB - 365; Visible - 385; 450; 500; 530; 587; 632; Far Red; NIR - 850; 880; 940
  • 2 detectors (nm range): 300-700; 700-1100

  • Additional Sensors:
    • Temperature (full range: -40 - 85 C, accuracy within 0 - 65 C: +/- 1C)
    • Relative Humidity (range: 0-100%, accuracy: +/-3%)
    • Pressure (range: 300-1100 hPa, accuracy: +/-0.25%)
    • VOCs (range: 0 - 500 IAQs, accuracy: +/- 15%)
    • Audio jack for additional inputs / outputs. Examples include soil senseors, moisture sensors, etc.

  • 13.9 cm x 5.2 cm x 4.6 cm
  • 3D printed PETG
  • Temperature resistant up to 60° C / 140° F

All instruments come individually calibrated to reduce instrument-to-instrument variation, as well as variaton by time and by temperature.

For long-term shifts in signal intensity, users may easily recalibrate. If you're working with several machines that you would like calibrated to the same standard, please contact

All of our products are open source

To build this devices yourself, you will need the following documentation: