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Apogee Underwater Full Spectrum Quantum Meter MQ-510

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The MQ-510 quantum meter is designed for underwater PAR measurements and already applies the sensor's immersion effect correction factor to the meter readings through firmware. The meter provides excellent measurements under all light sources, including LEDs. The meter consists of a waterproof quantum sensor attached via waterproof cable to a handheld meter. The waterproof sensor incorporates a blue-enhanced silicon photodiode and custom optical filters with a rugged, anodized aluminum body with acrylic diffuser. The underwater quantum sensor is typically used in salt water aquariums where corals are grown. Note: The handheld meter is not waterproof, only the sensor and cable are waterproof.

The meter has a sample and log mode, and will record an integrated daily total in mol m-2 d-1. Sample mode will record up to 99 manual measurements. Log mode will power the meter on/off to make a measurement every 30 seconds. Every 30 minutes the meter will average the sixty 30 second measurements and record the averaged value to memory. The meter can store up to 99 averages, once full it will start to overwrite the oldest measurement with new ones. An integrated daily total will be recorded from the 48 averaged measurements (making a 24 hr period). Sample and log measurements can be reviewed on the LCD display or by downloading the data to a computer, however, the integrated daily total can only be viewed by downloading the data to a computer. Downloading data to a computer requires the AC-100 communication cable (a standard USB cable will not work) and ApogeeAMS software.

Underwater PAR Measurements

Quantum sensors (often called PAR sensors) are increasingly used to measure photosynthetic photon flux density (PPFD, units of µmol m-2 s-1) underwater, which is important for biological, chemical, and physical processes in natural waters and in aquariums. When a quantum sensor that was calibrated in air 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, 1969; Tyler and Smith, 1970). As more light is reflected, less light is transmitted 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 be multiplied by 1.08*.

*The MQ-210 and MQ-510 Underwater Quantum Meters already apply the immersion effect correction factor to the meter readings througt the meter firmware. Additionally, the SQ-420 and SQ-520 have an "Immersion Setting" that applies the immersion effect corection factor to the sensor readings through the ApogeeConnect Software. These sensors do not need post-measurement corrections applied to their measurements.
How It Works
To ensure an aquarium specimen is receiving proper light, or photons, aquarium lighting can be tested for quantum or PAR outputs. PAR is the energy source required for photosynthesis, created by photons in the wavelengths of 400 to 700 nm, and can be measured from both sunlight and electric lighting sources. The energy source, PAR, is expressed in Photosynthetic Photon Flux, PPF, units µmol m-2 s-1.
Datalogging Capabilites
The meters (MQ-200 and MQ-500) include datalogging capability and can store up to 99 manually recorded measurements. In automatic mode, measurements are made every 30 seconds and averages are stored every 30 minutes. Daily totals are also calculated for the past 99 days. The USB sensor (SQ-420) has an internal memory capable of storing 10,000 user-specified periodic measurements that can be downloaded to a computer.
Refined Spectral Response
The improved spectral response of the MQ-500 increases the accuracy of LED measurements making it ideal for use with both natural and electric light sources.
Cosine Response
This cosine-corrected sensor is designed to maintain its accuracy when radiation comes from low zeith angles. The sensors measure PPFD with a cosine response accurate within 
± 5 % at 75 ° zenith angle.
Rugged Design
Head is potted-solid making it submerisble and suitable for use in all climate conditions.
Reliable Accuracy
To ensure accuracy each sensor iscarefully calibrated in controlled conditions and traceable to NIST reference standards.
Warranty and Support
All Apogee products are backed by an industry-leading four year warranty and outstanding customer support.
How is the MQ-500 different from previous Apogee quantum sensors?
The MQ-500 is a full spectrum quantum sensor with a spectral range of 389 to 692 nm ± 5 nm, which can be seen in the graph below. This improved spectral respose increases the acuracy of LED measurements.
Calibration Uncertainty ± 5 %
Measurement Range 0 to 4000 µmol m-2 s-1
Measurement Repeatability less than 0.5 %
Long-term Drift (Non-stability) less than 2 % per year
Non-linearity less than 1 % (up to 4000 µmol m-2 s-1)
Response Time less than 1 ms
Field of View 180°
Spectral Range 389 to 692 nm ± 5 nm (wavelengths where response is greater than 50 % of maximum)
Spectral Selectivity less than 10 % from 412 to 682 nm ± 5 nm
Directional (Cosine) Response ± 5 % at 75 ° zenith angle
Azimuth Error less than 0.5 %
Tilt Error less than 0.5 %
Temperature Response -0.11 ± 0.03 % C -1
Uncertainty in Daily Total less than 5 %
Detector blue-enhance silicon photodiode
Housing anodized aluminum body with acrylic diffuser
IP Rating IP68
Operating Environment 0 to 50 C; less than 90 % non-condensing relative humidity up to 30 C; less than 70 % non-condensing relative humidity from 30 to 50 C; separate sensors can be submerged in water up to depth of 30 m
Meter Dimensions 126 mm length; 70 mm width; 24 mm height
Sensor Dimensions 24 mm diameter; 37 mm height
Mass 100 g (with 5 m of lead wire)
Cable 2 m of shielded, twisted-pair wire; additional cable available; santoprene rubber jacket
Warranty 4 years against defects in materials and workmanship

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