APOGEE - MQ-510 - PER Meter Full Marine Spectrum

Ensuring appropriate light levels for underwater photosynthesis

Photosynthetic radiation is essential for the growth of 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 in this range.

How it works

PAR (Photosynthetically Active Radiation) is the source of energy necessary for photosynthesis, created by photons in the wavelengths of 400 to 700 nm. The energy source, PAR, is expressed in units of photosynthetic photon flux density (PPFD), µmol m-2 s-1. PAR can be measured from sunlight and electrical light sources to ensure that corals are receiving the correct light or photons for optimal health. The PAR requirements of corals vary greatly due to the different depths and water conditions in which they naturally exist. Information on the specific PAR needs of corals can be found by asking a professional aquarist to get involved with a local reef club and through articles such as Photosynthesis and Photoadaptation by Sanjay Joshi.

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 389-692 nm ± 5 nm. The sensor is available attached to a portable meter that provides a digital readout (MQ-510), with USB communication and custom software (SQ-520), and in multiple analog outputs for use with a data logger or voltmeter.

original sensor

A less expensive option that is excellent for all light sources except most LEDs, where post-metering correction factors must be applied to obtain accurate readings. The original quantum sensor has a spectral range of 410-655 nm. The sensor is available attached to a handheld meter that provides a digital readout (MQ-210) and in multiple analog outputs for use with a data logger or voltmeter.

Ready for underwater use

All models of Apogee underwater meters and sensors (MQ-210 and -510, and SQ-420 and -520) automatically correct for the immersion effect or have an immersion adjustment, allowing the user to perform excellent underwater measurements right out of the box. The sensors feature a waterproof sensor head that is potted solid for a complete seal and to ensure there are no hollow cavities for water to enter and cause measurement errors.

Underwater PAR Measurements

Quantum 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 has been calibrated in the air is used to make measurements underwater, the sensor reads low.

This phenomenon is called the immersion effect and occurs because the refractive index of water (1.33) is greater than that of air (1.00). The higher refractive index of water causes more light to be backscattered (or reflected) from 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, causing the sensor to read low. When this effect is not corrected for, underwater measurements are only relative, making 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 (mostly the shape) make the effect of greater immersion for the new sensor. Underwater PAR measurements collected using a full spectrum sensor can be corrected by multiplying by 1.32; measurements taken 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 through the meter firmware. Additionally, the SQ-420 and SQ-520 have a "Dip Setting" which applies the immersion effect correction factor to sensor readings via ApogeeConnect software. These sensors do not need post-measurement corrections applied to their measurements.

Data Logging Capabilities

The MQ-210 and -510 meters store up to 99 manual measurements. In record mode, the meter will take a measurement every 30 seconds. Every 30 minutes, the meter will average the sixty 30-second measurements and record the average value. The meter can store up to 99 averages. The SQ-420 and -520 USB sensors have internal memory capable of storing 10,000 user-specified periodic measurements which can be downloaded to a computer, however, the built-in daily total can only be viewed by downloading the data to a computer. Downloading data to a computer requires the AC-100 communications cable (a standard USB cable will not work) and Apogee- AMS software.

Typical Applications

Canopy PPFD measurements in outdoor environments, greenhouses and growth chambers, and reflected or under-canopy (transmitted) PPFD measurements in the same environments. Quantum sensors are also used to measure PPFD in aquatic environments, including saltwater aquariums where corals are grown.

Assembly

The AL-120 Solar Mounting Bracket with Leveling Plate makes it easy to mount the collector on a mast or pipe. The AL-100 Solar Collector Leveling Plate is designed to level the collector when it is sitting on a flat surface or mounted on a surface.