Apogee SQ-300 Series Руководство пользователя - Страница 13

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13

MAINTENANCE AND RECALIBRATION

Moisture or debris on the diffuser is a common cause of low readings. The sensor has a domed diffuser
and housing for improved self-cleaning from rainfall, but materials can accumulate on the diffuser (e.g.,
dust during periods of low rainfall, salt deposits from evaporation of sea spray or sprinkler irrigation
water) and partially block the optical path. Dust or organic deposits are best removed using water, or
window cleaner and a soft cloth or cotton swab. Salt deposits should be dissolved with vinegar and
removed with a soft cloth or cotton swab. Never use an abrasive material or cleaner on the diffuser.
The Clear Sky Calculator (www.clearskycalculator.com) can be used to determine the need for quantum
sensor recalibration. It determines PPF incident on a horizontal surface at any time of day at any location
in the world. It is most accurate when used near solar noon in spring and summer months, where accuracy
over multiple clear and unpolluted days is estimated to be ± 4 % in all climates and locations around the
world. For best accuracy, the sky must be completely clear, as reflected radiation from clouds causes
incoming radiation to increase above the value predicted by the clear sky calculator. Measured values of
PPF can exceed values predicted by the Clear Sky Calculator due to reflection from the sides and edges
of clouds. This reflection increases the incoming radiation. The influence of high clouds typically shows up
as spikes above clear sky values, not a constant offset greater than clear sky values.
To determine recalibration need, input site conditions into the calculator and compare PPF
measurements to calculated PPF values for a clear sky. If sensor PPF measurements over multiple days
near solar noon are consistently different than calculated values (by more than 6 %), the sensor should be
cleaned and re-leveled. If PPF measurements are still different after a second test, email
to discuss test results and possible return of sensor(s) for
recalibration.