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Measure PAR, PPF, and PPFD measurements from all light sources.

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.

Full Spectrum Quantum Sensor

The new SQ/MQ-500 Full Spectrum quantum sensors feature a new detector that provides accurate measurements under all light sources, including LEDs, right out of the box.

  Original Apogee Quantum Sensor

The original SQ/MQ-100, SQ/MQ-200, SQ/MQ-300, and SQ-400 series quantum sensors are great for for measuring all light sources except certain LED colors, where post-measurement correction factors need to be applied to achieve accurate readings.


Click for full screen    About Dr. Bruce Bugbee

Click for full screen    About Dr. Bruce Bugbee


Apogee quantum sensors are used to measure incoming PPFD in outdoor environments, greenhouses, growth chambers, and aquariums. The Original Quantum Sensor (SQ/MQ-100, SQ/MQ-200, SQ/MQ-300, and SQ-400 Series) are excellent for all light sources except most LEDs, where post-measurement correction factors need to be applied to achive accurate readings. The SQ/MQ-300 series provide spatially-averaged measurements, which are useful in settings where light is non-uniform. The Full Spectrum Quantum Sensor (SQ/MQ-500 Series) is ideal for use under all light sources, including LEDs, right out of the box.

Spectral Response
The Original quantum sensor has a spectral range of 410 to 655 nm. The Full Spectrum quantum sensor has a spectral range of 389 to 692 nm ± 5 nm. The improved spectral response increases the accuracy of LED measurements. The spectral responses can be be seen in the graph below (click to enlarge).
Original & Full Spectrum Quantum Sensor Spectral Response.

To ensure accuracy each sensor is carefully calibrated in controlled conditions and traceable to NIST reference standards. The Original sensors are pre-calibrated for either sunlght or electic light sources. The Full Spectrum sensors are pre-calibrated for all light sources.

Durable Design
Apogee quantum sensor heads are potted solid and contain no internal airspace. The sensors are fully submersible and suitable for use in all climate conditions.

Excellent Cosine Response
Sensors are cosine-corrected to maintian their accuracy when radiation comes from low zenith angles. The sensors measure PPFD with a cosine response accurate within ± 5 % at 75° zenith angle.

Self-cleaning Head
The Original quantum sensors feature a patented dome-shape head that quickly sheds water, dirt, and other debris. This reduces maintenance and maximizes performance in the field.

Sensors are available with several outputs including: USB, pigtail leads to be connected with most dataloggers, or with a handheld meter.

Warranty and Support
All Apogee products are backed by an industry-leading four year warranty and outstanding customer support.

Sensor Applications/ Featured Projects
  technical information
Technical Information
  using your sensor
Using Your Sensor

spec sheets
Spec Sheets
SQ 100, 200, 300 Series
MQ 100, 200, 300 Series


SQ 100, 300 Series
SQ 212, 215, 222, 225
SQ 214, 224
MQ 100, 200, 300 Series


software download
Software Downloads
*If your SQ-420 sensor has a serial number less than 1258 click here for update instructions.*
ApogeeConnect USB PC Software

ApogeeConnect USB Mac Software


deep red LEDs plants
The MQ-200 is often used by reef keepers to measure the PAR output of their electric lights to ensure proper specimen health. pink LEDs
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
17. PPFD to Illuminance Calculator