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Photosynthetic radiation is essential for the growth of the photosynthetic organisms such as corals. The wavelength range from 400 to 700 nm is PAR (Photosynthetically Active Radiation) or PPFD (Photosynthetic Photon Flux Density). Apogee quantum/PAR sensors are calibrated to measure the number of photons of light across this range.

How It Works
PAR (Photosynthetically Active Radiation) is the energy source required for photosynthesis, created by photons in the wavelengths of 400 to 700nm. The energy source, PAR, is expressed in Photosynthetic Photon Flux Density (PPFD) units µmol m-2 s-1. PAR can be measured from both sunlight and electric light sources to ensure corals are receiving proper light or photons for optimal health. PAR requirements of coral varies greatly due to different depths and water conditions they naturally exist in. Information on specific coral PAR requirements can be found by asking a professional aquarist becoming involved in a local reef club and through articles such as Photosynthesis and Photoadaptation by Sanjay Joshi. Apogee Underwater Quantum/PAR meters and sensors accurately measure an aquariums range of PAR to give a better understanding of aquarium lighting, for more details on underwater PAR measurements click here.

Full-spectrum Sensor
Features an improved detector that provides excellent measurements under all light sources, including LEDs, right out of the box. The full-spectrum quantum sensor has a spectral range of 389 to 692 nm ± 5 nm seen in graph to the left. The sensor is available attached to a hand-held meter that provides a digital readout (MQ-510), with USB communication and custom software (SQ-520), and in multiple analog outputs to be used with a datalogger or voltmeter.

Spectral Response

Original Sensor
A lower-cost option that is excellent for all light sources, except most LEDs, where post-measurement correction factors need to be applied to achieve accurate readings. The original quantum sensor has a spectral range of 410 to 655 nm seen in graph to the right. The sensor is available attached to a hand-held meter that provides a digital readout (MQ-210) and in multiple analog outputs to be used with a datalogger or voltmeter.

Ready for Underwater Use
All Apogee Underwater Quantum Meters and Sensors models (MQ-210, MQ-510, SQ-520) have the immersion effect correction factor preprogramed in the firmware or sensor software allowing the user to make excellent underwater measuremnts right out of the box. Sensors feature a waterproof sensor head that is potted solid for a complete seal and to ensure it has no hollow cavities for water to penetrate and cause measurement errors.

Datalogging Capabilities
The MQ-210 and MQ-510 meters record up to 99 manual measurements. In logging mode the meter will make a measurement every 30 seconds. Every 30 minutes the meter will average the sixty 30 second measurements and record the averaged value. The meter can store up to 99 averages. The SQ-520 USB sensor has internal memory capable of storing 10,000 user-specified periodic measurements that can be downloaded to a computer.

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

   

Need help choosing a sensor?

  Technical Information
Technical Information
Find software, articles, manuals, FAQs, technical support, and more.
 
 
What is the difference between the MQ-200 and MQ-210 / MQ-500 and MQ-510?
 
The only difference between the MQ-200 and MQ-210 is the MQ-210 has the immersion effect correction factor already applied to the firmware so there is no need for post-measurement corrections for underwater measurements. Similarly, the only difference between the MQ-500 and MQ-510 is the MQ-510 has the immersion effect correction factor already applied to the firmware so there is no need for post-measurement corrections for underwater measurements.
 
What type of Quantum Sensor do I need?
 
Apogee Instruments produces two types of quantum sensors.

The Full-spectrum Quantum Sensor (MQ and SQ-500 series) has a spectral range of 389 to 692 ± 5 nm. The Full-spectrum quantum sensor provides excellent measurements under all light sources, including LEDs, right out of the box. The Full-spectrum quantum sensor is the best option for LED and multiple light applications.

The Original Quantum Sensor (SQ-100, MQ and SQ-200, SQ-300, and SQ-400 Series) have a spectral range of 410 to 655 nm. The Original Quantum Sensor works great for most single light, non-LED, and sun applications. When the original quantum sensor is used with LEDs post-measurement correction factors need to be applied to achieve accurate readings.

 
Which Original Quantum Sensor model do I need?
 
All Original Quantum Sensors (SQ-100, MQ and SQ-200, SQ-300, and SQ-400 series) use the same detector. The model number you need depends on which output is compatible with your datalogger and if you are measuring a sun or electric light source. Model numbers are listed below with their output and calibration:
SQ-110 0 to 800 mV 0 to 4000 µmol m-2 s-1 Sunlight Calibration
*To use a voltmeter connect the positive lead of the voltmeter to the red wire of the SQ and negative lead of the voltmeter to the black wire of the SQ. To get the unit µmol m-2 s-1 multiply the mV reading by 5.0. Voltmeters with mV setting attain the resolution.
SQ-120 0 to 8000 mV 0 to 4000 µmol m-2 s-1 Electric light calibration
*To use a voltmeter connect the positive lead of the voltmeter to the red wire of the SQ and negative lead of the voltmeter to the black wire of the SQ. To get the unit µmol m-2 s-1 multiply the mV reading by 5.0. Voltmeters with mV setting attain the resolution.
MQ-210 Sensor attached to a handheld meter with digital readout Electric calibration
 
Which Full-spectrum Quantum Sensor model do I need?
 
All Full-spectrum Quantum Sensors (MQ and SQ-500 series) use the same detector. The model number you need depends on which output is compatible with your datalogger. Model numbers are listed below with their output:
SQ-500 0 to 40 mV 0 to 4000 µmol m-2 s-1
*To use a voltmeter connect the positive lead of the voltmeter to the red wire of the SQ and negative lead of the voltmeter to the black wire of the SQ. To get the unit µmol m-2 s-1 multiply the mV reading by 100.0. Voltmeters with mV setting attain the resolution.
SQ-520 USB/software 0 to 4000 µmol m-2 s-1
MQ-510 Sensor attached to a handheld meter with digital readout 0 to 4000 µmol m-2 s-1
 
Do I need to apply an immersion effect corretion factor to my meter/sensor measurements?
 

The MQ-210 and MQ-510 meters are designed for underwater PAR measurements, and already apply the the sensor's immersion effect correction factors to the meter readings through firmware.

The SQ-520 has an "Immersion Setting" that applies the immersion setting to the sensor's readings through the ApogeeConnect Software.

All other Apogee meters and sensors will need to have their measurements multiplied by their respective immersion effect correction factor when used to take underwater measurements. Additional information can be found here.

 
What is the immersion effect/ immersion effect correction factor?
 

When a quantum sensor that was calibrated in air, such as Apogee's, is used to make underwater measurements, the sensor reads low. This phenomenon is called the immersion effect and happens because the refractive index of water (1.33) is greater than air (1.00). The higher refractive index of water causes more light to be backscattered (or reflected) out of the sensor in water than in air (Smith, 1696; Tyler and Smith, 1970). As more light is reflected, less light is tansmitted through the diffuser to the detector, which causes the sensor to read low. Without correcting for this effect, underwater measurements are only relative, which makes it difficult to compare light in different environments.

The Apogee full-spectrum quantum sensor (model SQ-500) is more spectrally accurate than the original quantum sensor (model SQ-120), but the unique optics (mainly the shape) cause the immersion effect to be larger for the new sensor. Underwater PAR measurements collected using a full spectrum sensor can be corrected by multiplying by 1.32; measurements collected using an original Apogee sensor should by multiplied by 1.08.

For details on how these multipliers were determined, read the white paper on Apogee's Immersion Effect Correction Factors for Quantum Sensors.

 
Can I use a voltmeter wih my sensor?
 
Voltmeters can be used with the SQ-110, SQ-120, or SQ-500.

To use a voltmeter connect the positive lead of the voltmeter to the red wire of the SQ and negative lead of the voltmeter to the black wire of the SQ. Voltmeters with mV setting attain the best resolution.

SQ-100 series: To get the unit µmol m-2 s-1 multiply the mV reading by 5.0.

SQ-500 series: To get the unit µmol m-2 s-1 multiply the mV reading by 5.0.

 
How do I correct for spectral errors of my Original Quantum Sensor?
 
Apogee has done extensive research to help custometers make acurate PAR readings, which can be found here.
 
What quantum sensor should I purchase for my aquarium?
 
You should purchase the quantum sensor that matches your aquarium light source the closest. We recommend the MQ-210 or SQ-420 for supplemental electric lighting and sunlight. We recommend the MQ-510 or SQ-520 for LED lights. Apogee does offer meters and sensors, models (MQ-210, MQ-510, and SQ-520), that are ready out of the box for underwater measurements. These underwater meters and sensors are preprogrammed with the immersion effect correction factor, so no post-measurement corrections need to be made. All other Apogee quantum sensors and meters need to have their respective immersion effect correction factor multiplied to their reading. For more information on underwater PAR measurements click here.
 
Are Apogee quantum meters waterproof?
 
The handheld meter is not waterproof, only the sensor and cable are waterproof.
 

spec sheets
Specification Sheets

 

 


Photos

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

 


Videos

Why do I need a PAR-Quantum Meter?

 

In-depth Look at PAR-Quantum Meters


Apogee Quantum Sensors are recommended and sold by some of the biggest names in the aquarium industry:

Aquarium Specialty, Bulk Reef Supply, Premium Aquatics

 

Models


Models listed below are designed for underwater use and already correct for the immersion effect throught firmware or software. For complete quantum sensor selection visit Original Quantum Sensor and Full-spectrum Quantum Sensor, these sensors can still be used underwater but require post-measurement correction to get absolute underwater PAR values.