The PCTRA078 sensor measure illuminance (lux), defined as the ratio between the luminous flux (lumen) through a surface and the surface area (m2).
The spectral response curve of a photometric probe is equal to the human eye, known as standard photopic curve V(λ).
The difference in spectral response between PCTRA078 and the standard photopic curve V (λ) is calculated by means of the error f'1.
The sensor is designed and constructed for outdoor installation for long periods. The photometric measurement for external use is used for the measurement of daylight in climatological and meteorological applications.
The sensor is based on a solid state sensor, whose spectral response corrected by filters to fit the response of the human eye. The typical spectral response curve is shown in the figure at the side.
The PCTRA078 is provided with a 50mm diameter transparent glass dome, in order to protect the sensor against atmospheric damage.
The cosine corrected response has been optained through both the PTFE diffuser and particular shapes.
The PCTRA078 excellent cosine response allows for use even when the sun elevation is low.