Campbell SP-LITE Manuel d'utilisateur télécharger pdf (Page 7)

SP-LITE Silicon Pyranometer

The SP-LITE measures incoming solar radiation (sun plus sky radiation) with a photodiode

detector. Output from the photodiode is a current, which is converted to voltage by an

internal shunt resistor. The SP-LITE can be used in solar energy applications such as

plant growth, thermal convection and evapotranspiration.

1. General Description

FIGURE 1. SP-LITE Sensor without Leveling Fixture

The SP-LITE is used for measuring solar radiation. It measures the solar

energy received from the entire hemisphere – i.e. 180° field of view. The

output is expressed in Watts per square meter (W m

-2

The SP-LITE is designed for continuous outside use, and its calibration is valid

only for unshaded natural daylight – not for artificial light. It is most usually

used to measure solar radiation being received on the horizontal plane.

However, the SP-LITE can, if required, be used in an inverted or tilted

position.

1.1 Electrical Properties

The SP-LITE consists of a photodiode complete with housing and cable. The

circuit includes a shunt resistor for the photodiode in order to generate a

voltage output. The electrical specification of the sensor is determined by the

characteristics of the photodiode and resistor. The electrical circuit of the

pyranometer is shown in Figure 2, below.

The electrical sensitivity of the photodiode changes with temperature. A

nominal value for this change is 0.2% change per °C. Calibration is carried out

at 20 °C.

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Campbell SP-LITE Manuel d'utilisateur Page 7