ABSTRACT
Chromatic optical monitoring of various conditions may be regarded as having focussed upon the use of two classes of systems – optical fibre and camera systems. Both systems have broadly similar structures (Figure 2.1), each of which involves an illumination source whose output is directed onto a sensor element where the light is modulated before transmission to a chromatic optical detector. The detector output is processed to produce chromatic parameters (e.g., H, L, S; Chapter 1) which indicate the condition of the sample. Examples of optical fibre and camera monitoring units are shown in Figure 2.2a and b, which have been deployed for monitoring the condition of the liquid digestate at a biodigestion processing site Rallis et al. (2005). This indicates the different arrangements with each system – the optical fibre system has an optical probe which is immersed into the liquid, whilst the camera system is nonintrusive and addresses the liquid remotely.
