Light extinction measuring fibre optic probe for pH measurement of watery solution

摘要

The fibre optic probe, or optode, includes two monochromatic light sources (1,2), a sensor head (5), optical fibres (3), and a light detector. One light source (1) is for a measuring ray (2) and the other is for a reference. These are connected to the fibres which carry light through the shafts (4) to a sensor head (5). The sensor head includes a concentration varying substance in fluid contact with colour variation reacting ion-based indicator. The sensitive layer is placed and secured over a prism or cylinder shaped casing with a plane parallel transparent surface material. The measuring light, after passing through the medium in which colour intensity is to be measured, is reflected back to another optical fibre (6) together with the reference light. This leads to a light detector (7) containing a photodiode where the relative light intensity is measured and converted for electronic output.