Underwater Quantum Sensor

The LI-192 Underwater Quantum Sensor measures PAR from all angles in one hemisphere. The LI-192 works in air or underwater at depths up to 560 meters. The measurements are cosine corrected and typically expressed as Photosynthetic Photon Flux Density (PPFD). For simultaneous measurements of downwelling and upwelling PAR, two sensors can be mounted on the 2009S Lowering Frame.

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Why choose the LI-192?

  • Designed for immersion
  • Rugged, corrosion-resistant sensors for use in fresh and saltwater environments
  • Ideal for oceanography, limnology, turbidity, and vertical profiling
  • Suitable for submerged and out-of-water measurements

How does it work?

The LI-192 uses a silicon photodiode and glass optical filters to create uniform sensitivity to light between 400 nm to 700 nm, which closely corresponds to light used by most aquatic plants and algae. A precision optical filter blocks light with wavelengths beyond 700 nm, which is critical for measurements in a water column, where the ratio of infrared to visible light may be high.

Cables and Accessories

The LI-192 is available with cable lengths ranging from 3 meters to 100 meters.

The 2009S Lowering Frame mounts one or two LI-192 sensors — one each for downwelling or upwelling radiation.

LI-192 Specifications

  • Absolute Calibration: ± 5% in air traceable to NIST
  • Sensitivity: Typically 4 μA per 1,000 μmol s-1 m-2 in water
  • Linearity: Maximum deviation of 1% up to 10,000 μmol s-1 m-2
  • Response Time: 10 μs
  • Temperature Dependence: ± 0.15% per °C maximum
  • Cosine Correction: Optimized for underwater and atmospheric use
  • Azimuth: < ± 1% error over 360° at 45° elevation
  • Operating Temperature Range: −40 °C to 65 °C
  • Detector: High stability silicon photovoltaic detector (blue enhanced)
  • Sensor Housing: Corrosion resistant metal with acrylic diffuser for both saltwater and freshwater applications. Waterproof to withstand approximately 5500 kPa, 560 meters (800 psi).
  • Size: 3.18 cm diameter × 4.62 cm height (1.25” × 1.81”)
  • Weight: 227 g (8 oz)
  • Mounting: Three 6-32 holes are tapped into the base for use with the 2009S Lowering Frame or other mounting devices
  • Cable: Requires 2222UWB Underwater Cable (available in 3, 10, 30, 50, 100 meter lengths)
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