The following contains brief information on Apogee quantum sensor and meter technical information. For complete technical information please view the manual.
An ideal quantum sensor would give equal emphasis to all photons between 400 and 700 nm and would exclude photons above and below these wavelengths. The response of such a sensor is shown in the adjacent graph (black). The most accurate way to measure this radiation is with our spectroradiometer, which costs less than $4000.
Original Quantum Sensor
Full Spectrum Quantum Sensor
A "cosine corrected" sensor is designed to maintain its accuracy when radiation comes from different angles. For quantum sensors this is important for measuring scattered light, typical in under-canopy measurements. Apogee quantum sensors achieve this through the curvature and optical qualities of the convex lens.
Our long term tests indicate that the cosine errors between completely sunny and heavily overcast days are less than 0.5 percent. Cosine errors between the summer and the winter solstice are also less than 0.5 percent.
Use Under Different Light Sources
Applicable for models SQ/MQ-100, SQ/MQ-200, SQ/MQ-300, and SQ-400 Series.
This table shows the quantum sensor's output under varying light sources. The sensor's spectral response, the spectral output of electric lamps, and these errors are all constant -- allowing the user to calculate the correct output for each light source.
For example, if the MQ-100 Quantum Sensor set to electric lamps is used in sunlight and a value of 1,500 μmol m-2 s-1 is given, the actual light is 1,665 μmol m-2 s-1.
In a controlled environment with multiple lamp types (such as a mixture of MH and HPS), a more precise percent error can be determined when the amount (%) of each type of light present is known.
Increasing temperature decreases the output of most silicon photodiodes. This quantum sensor was calibrated at 20 C. It reads 0.6 percent high at 10 C and 0.8 percent low at 30 C. This temperature error is insignificant for most applications.
The output of all radiation sensors tends to decrease over time as the detector ages. Our measurements indicate that quantum meters should be recalibrated every 3 years.
Do not attempt recalibration without a radiation standard.
Visit our recalibration section for info on how to request an RMA to send in your quantum sensor for recalibrating.