Ametek Land 4200, Руководство пользователя

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Page 3
User Guide Model 4200 Dust & Opacity Monitor
3 Theory of Operation
3.1 Theory
When a beam of light crosses a medium containing smoke or dust particles some
of the light is transmitted and some is lost due to scattering. The fraction which
is transmitted is called the transmittance and the fraction which is lost is the
opacity.
In the early days of emissions measurements, the opacity of the smoke leaving
a stack was measured by the Ringelmann method in which a trained observer
makes a visual estimate of its appearance.
Modern methods for opacity measurement still use the darkness of the stack
gases (their opacity) to measure the amount of smoke present.
The Land Model 4200 uses a high intensity LED light source to project a beam of
light across the stack; the amount of light lost in crossing the stack is the opacity
and this can be related to the amount of dust and smoke present as described in
Section 3.2.