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PAR, PPF, PPFD measurements from sun or electric light sources.

Measures photosynthetically active radiation in µmol m-2 s-1

Photosynthetic radiation is essential for the growth of all photosynthetic organisms such as plants, algae, and corals. The wavelength range from 400–700 nm is called PAR (Photosynthetically Active Radiation) or PPFD (Photosynthetic Photon Flux Density). Apogee quantum sensors are calibrated to measure the number of photons of light across this range. Sensors are available with both sunlight and electric light calibrations, and are fully epoxy-potted for use in all conditions, even underwater. Quantum sensors are available in single sensor or multi-sensor “line quantum” models that provide spatially-averaged measurements useful in settings where light is non-uniform (i.e. under plant canopies).

Click for full screen    About Dr. Bruce Bugbee

Click for full screen    About Dr. Bruce Bugbee

Installed as a standard feature in growth chambers from industry leaders Conviron, Biochambers, Environmental Growth Chambers, and Percival Scientific. Quantum sensors are used for incoming PPFD measurement over plant canopies in outdoor environments or in greenhouses and growth chambers, and reflected or under-canopy, transmitted, PPFD measurements in the same environments.
Potted solid sensor head contains no internal air space, and is fully submersible and suitable for use in all climate conditions. Sensors have been subjected to unprecedented extreme accelerated aging tests, and are designed for continuous PPFD measurement in indoor or outdoor environments. Apogee sensor testing eliminates any weaknesses or design flaws.
Quantum Sensor
Spectral Error Reduction
Sensor head features unique blue diffuser to reduce spectral error to less than 5% for sunlight and common electric plant lights, and less than 10% for LEDs. You can read more about using our quantum sensors with various light sources in our Knowledge Base.

Sunlight or Electric Pre-Calibrations
Each Apogee quantum sensor is carefully pre-calibrated to NIST standards in carefully controlled conditions. Sensors are pre-calibrated to sunlight or electric calibrations.

Self-cleaning Head
The patented dome-shape head quickly sheds water, dirt, and other debris, reducing maintenance and maximizing performance in the field.
  Excellent Cosine Response
Sensors measure PPFD with a cosine response accurate within ±5 % at 75° zenith angle.
Sensors come in several outputs that are readily compatible with most dataloggers, or can be used with an attached handheld meter.
  Warranty and Support
All Apogee products are backed by an industry-leading four year warranty and outstanding customer support.


Additional Information
Applications Quantum Sensor Applications / Apogee Featured Projects Technical information Apogee Instruments Quantum Sensor Technical Information
Instructions Using Your Apogee Instruments Quantum Sensor Spec sheets Spec Sheets: SQ Series Sensors, SQ-420 USB Quantum Sensor, MQ Series Meters
Owner's Manual: SQ-100 and SQ-300 Series, SQ-212, SQ-215, SQ-222, and SQ-225 (Amplified), SQ-214 and SQ-224 (4-20 mA), SQ-420, MQ Series
Software: SQ-420 PC Version, SQ-420 Mac Version Coming Soon
Visit our knowledge base for more information


Application Information
1. Daily Light Integral: Measuring Light for Plants
2. Aquarium Applications
3. Comparisons in Quantum Sensor Output for Different Light Sources
4. Amplified Sensors Explained
5. Apogee Meter Tips and Troubleshooting
6. When to Recalibrate: Clear Sky Calculator
7. Using the Clear Sky Calculator
8. Light Intensity Measurements for Light Emitting Diodes (LEDs) - correcting for errors
9. Economic Analysis of Greenhouse Lighting: Light Emitting Diodes vs. High Intensity Discharge Fixtures
10. Analysis of Spectral and Cosine Errors in Quantum Sensors
11. Spectral Errors from Four Commercial Quantum Sensors Under LEDs and Other Electric Lights
12. Converting from μmol m-2 s-1 to footcandles
13. Converting from μmol m-2 s-1 to Lux
14. Converting from μmol m-2 s-1 to mol m-2 d-1
15. Converting from μmol m-2 s-1 to Einsteins
16. Sample datalogger programs



The MQ-200 is often used by reef keepers to measure the PAR output of their electric lights to ensure proper specimen health. Apogee Instruments Quantum 

Sensors are fully waterproof