Apogee S2-441 Manual del usuario - Página 15
Navegue en línea o descargue pdf Manual del usuario para Accesorios Apogee S2-441. Apogee S2-441 19 páginas. Par-far sensor
MAINTENANCE AND RECALIBRATION
Blocking of the optical path between the target and detector can cause low readings. Occasionally, accumulated
materials on the diffuser of the sensor can block the optical path in three common ways:
1. Moisture or debris on the diffuser.
2. Dust during periods of low rainfall.
3. Salt deposit accumulation from evaporation of sea spray or sprinkler irrigation water.
Apogee Instruments sensors have a domed diffuser and housing for improved self-cleaning from rainfall, but active
cleaning may be necessary. 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 cloth or cotton swab. Salt
deposits cannot be removed with solvents such as alcohol or acetone. Use only gentle pressure when cleaning
the diffuser with a cotton swab or soft cloth, to avoid scratching the outer surface. The solvent should be allowed
to do the cleaning, not mechanical force. Never use an abrasive material or abrasive cleaner on the diffuser.
Although Apogee sensors are very stable, nominal calibration drift is normal for all research-grade sensors. To
ensure maximum accuracy, recalibration every two years is recommended. Longer time periods between
recalibration may be warranted depending on tolerances. See the Apogee webpage for details regarding return of
sensors for recalibration (http://www.apogeeinstruments.com/tech-support-recalibration-repairs/).
To determine if a specific sensor needs recalibration, the Clear Sky Calculator (www.clearskycalculator.com)
website and/or smartphone app can be used to indicate 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 PPFD can exceed PPFD
predicted by the Clear Sky Calculator due to reflection from thin, high clouds and edges of clouds, which enhances
incident PPFD. 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 for a clear sky. If sensor PPFD measurements over multiple days near solar noon are consistently
different than calculated PPFD (by more than 6 %), the sensor should be cleaned and re-leveled. If measurements
are still different after a second test, email
possible return of sensor(s).
The Clear Sky Calculator does not calculate far-red photon flux density, but it can be approximated from PPFD
returned from the calculator. The ratio of far-red photon flux density to PPFD on clear days near solar noon is
typically within the range 0.20 to 0.22.
to discuss test results and