Measurement
The SeaTech Transmissometer measures the beam attenuation coefficient in the red spectral band (λ = 660 nm).
Description
Light attenuation in seawater is due to suspended particles, coloured dissolved organic matter, and the water itself. The Transmissometer measures the intensity of a 660 nm laser at a distance of 25 cm. The degree to which this beam is attenuated (c) over the instrument’s 25 cm path length (r) is obtained by dividing the percent transmission (Tr) of light by the path length, where c = -Ln(Tr)/r. The output from the Transmissometer (0–5 Vdc) is an estimate of the percent transmission of light.
If the % reading is zero, it means the sensor output was zero volts. It is not possible to have a % value less than zero.
