Apogee SS-120 Руководство пользователя - Страница 17

Просмотреть онлайн или скачать pdf Руководство пользователя для Измерительные приборы Apogee SS-120. Apogee SS-120 20 страниц. Spectroradiometer

MAINTENANCE AND RECALIBRATION

MAINTENANCE

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.

RECALIBRATION

The Clear Sky Calculator (www.clearskycalculator.com) can be used to determine the need for spectroradiometer

recalibration when spectroradiometer is used in Photon Flux Density mode. It determines PPFD 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 PPFD 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 PPFD measurements to calculated

PPFD values for a clear sky. If sensor PPFD 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 PPFD measurements are still different

after a second test, email

to discuss test results and possible return of sensor(s) for

recalibration.