max. depth 350m

The LI-193 Spherical Quantum Sensor measures photosynthetically active radiation (PAR) underwater from all directions at depths up to 350 meters. This sensor is useful for studies of phytoplankton, which uses radiation from all directions. The measurement is referred to as Photosynthetic Photon Flux Fluence Rate (PPFFR) or Quantum Scalar Irradiance.

The LI-193 uses a diffusive sphere to direct light through glass optical filters to the silicon photodiode. The filters create uniform sensitivity to light between 400 and 700 nm, which closely corresponds to light used by most aquatic plants and algae. The angular response of a typical LI-193 is slightly lower in the direction of the cable connection. When mounted, the low response is usually not significant due to the small proportion of upwelling radiation compared to the total.

Technical data:

  • Pressure resistance: 350 dbar
  • Absolute calibration: 5 % in air
  • Sensitivity: typ. 4 μA per 1,000 μmol/s m² in water
  • Linearity: max. deviation of 1% up to 10,000 μmol/s m²
  • Response time: 10 μs
  • Temperature dependence: ± 0.15% per °C maximum
  • Azimuth: < ± 1 % error over 360° at 45° elevation
  • Operating temperature: -40°C…65°C
  • Principle: Quantum sensor
  • Used for: CTD75M, CTD90, CTD90M, CTD115M

>> Show data sheet here