Apogee SQ-514 Руководство пользователя - Страница 15

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Immersion Effect Correction Factor

When a radiation sensor is submerged in water, more of the incident radiation is backscattered out of the diffuser

than when the sensor is in air (Smith, 1969; Tyler and Smith, 1970). This phenomenon is caused by the difference

in the refractive index for air (1.00) and water (1.33), and is called the immersion effect. Without correction for the

immersion effect, radiation sensors calibrated in air can only provide relative values underwater (Smith, 1969;

Tyler and Smith, 1970). Immersion effect correction factors can be derived by making measurements in air and at

multiple water depths at a constant distance from a lamp in a controlled laboratory setting.

Apogee SQ-500 series quantum sensors have an immersion effect correction factor of 1.25 (serial number 3734

and above) or 1.32 (serial numbers 0-3733). This correction factor should be multiplied by PPFD measurements

made underwater to yield accurate PPFD.

Further information on underwater measurements and the immersion effect can be found on the Apogee

webpage (http://www.apogeeinstruments.com/underwater-par-measurements/).

Smith, R.C., 1969. An underwater spectral irradiance collector. Journal of Marine Research 27:341-351.

Tyler, J.E., and R.C. Smith, 1970. Measurements of Spectral Irradiance Underwater. Gordon and Breach, New York,

New York. 103 pages