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+ What quantum sensor should I purchase for my aquarium?
You should purchase the quantum sensor type that matches your aquarium light source the closest. We recommend the original quantum sensor (MQ-210) for supplemental electric lighting and sunlight. We recommend the full-spectrum sensor (MQ-510, SQ-520) for LED lights. Apogee 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, therefore, no post-measurement corrections need to be made. All other Apogee quantum sensors and meters can be used for underwater measurements, however, they need to have their respective immersion effect correction factor multiplied to their reading. For more information on underwater PAR measurements click here
+ 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. This 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 sensor is used with LEDs post-measurement correction factors need to be applied to achieve accurate readings.
+ 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 preprogrammed into the meter 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 preprogrammed into the meter so there is no need for post-measurement corrections for underwater measurements.
+ 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.
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 for my sensor?
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.
+ Are Apogee quantum meters waterproof?
The handheld meter is not waterproof, only the sensor and cable are waterproof.
Apogee MQ-510 Is The First Truly Underwater PAR Meter For Hobbyists - Jake Adams, Reef Builders
Dana Riddle Reviews the Apogee MQ-510 Quantum (PAR) Meter - Dana Riddle, Advanced Aquarist