Apogee PAR-FAR sensors combine two photodetectors that measure photosynthetically active and far-red radiation. The PAR sensor is the same as the Apogee model SQ-500 full-spectrum quantum sensor and is designed to measure photosynthetic photon flux density (PPFD, 400-700 nm). The far-red sensor is a quantum sensor that measures photons in the 700-760 nm range.
A domed diffuser promotes self-cleaning to minimize errors from dust and debris. 0-40mV output, SDI-12 version available (S2-441).
Pigtail-lead sensors feature on IP68, marine-grade stainless-steel cable connectors attached directly to the sensor head to simplify sensor removal for maintenance and recalibration.
The S2-141 PAR-Far Red Sensor is also available as a package with a microCache Bluetooth micro-logger at a special introductory price.
Above: Spectral response of PAR detector (blue) and Far Red detector (red) compared to defined response of plants to radiation (dashed).
|Output (sensitivity):||0.01 mV per μmol m⁻² s⁻¹ (PAR)
0.02 mV per μmol m⁻² s⁻¹ (Far Red)
|Calibration Factor (reciprocal of sensitivity):||100 μmol m⁻² s⁻¹ per mV (PAR)
50 μmol m⁻² s⁻¹ per mV (Far Red)
|Calibration Uncertainty:||± 5%|
|Output Range:||0 to 40 mV (PAR)
0 to 20 mV (Far Red)
|Measurement Repeatability:||Less than 1%|
|Long-term Drift:||Less than 2% per year|
|Non-Linearity:||Less than 1% (up to 4000 μmol m⁻² s⁻¹) (PAR)
Less than 1% (up to 1000 μmol m⁻² s⁻¹) (Far Red)
|Response Time:||Less than 1 ms|
|Field of View:||180°|
|Spectral Ranges:||389 to 692 nm ± 5 nm (PAR)
700 to 760 nm ± 5 nm (Far Red)
|Directional (Cosine) Response:||± 2% at 45°; ± 5% at 75° zenith angle|
|Temperature Response:||Less than 0.1% per °C|
|Housing:||Anodised aluminium body with acrylic diffuser|
|Operating Environment:||-40°C to 70°C; 0 to 100% relative humidity|
|Dimensions:||30.5mm diameter, 36.6mm height|