Apogee SQ-514 Руководство пользователя - Страница 16

Просмотреть онлайн или скачать pdf Руководство пользователя для Аксессуары Apogee SQ-514. Apogee SQ-514 20 страниц. Quantum 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 upward-looking 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 upward-looking 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 abrasive material or cleaner on the

diffuser.

Although Apogee sensors are very stable, nominal accuracy drift is normal for all research-grade sensors. To

ensure maximum accuracy, we generally recommend sensors are sent in for recalibration every two years,

although you can often wait longer according to your particular tolerances.

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).

to discuss test results and