| OCR Text |
Show ..". . ": .:.-,',. ;,. -.-.: ~ ~. ' ... ;" "~7' .-...:- by (2) For a gray body emitter whose emissivity is (1 = ((AI, T), the emitted radiation is (3) In the present case, therefore, if a burning particle of emissivity (1 and area Ae is radiating to a detector that subtends a solid angle of ~4>, the amount of radiation gathered by the detector in the wavelength band centered around A 1 is given by equation (3). Moreover, for a burning particle moving away from a fixed detector, Ae , T, ~4>, and, therefore, EAl are all functions of time. Only ~Ab which is a characteristic of the filter used, is not a function of time. Let Fl = F(AI) be the transfer function of the electronics hardware used to convert the light signal of equation (3) to a voltage signal 8 1 that can be measured, manipulated and stored in the data acquisition system. Fl includes the response of the various optical lenses, fibres etc. in the data path of the signal. It is not a function of time. Therefore (4) If the same analysis is repeated at another wavelength A2 yielding a voltage signal 8 2 we have (5) Taking the ratio R of the two signals and remembering that Ae and ~4> are the same, since the particle is the same, we get (6) The ratio is shown explicitly as a function of time as are the other important quantities in equation (6). Defining K, the calibration factor as (7) 6 |
