Detectors:

The detectors are used to convert a light signal to an electrical signal that can be suitably measured and changed into a result. The detectors used in most of the instruments generate a signal that is linear in transmittance that is they respond linearly to radiant power falling on them. The transmittance values could be changed logarithmically into absorbance units by an electrical or mechanical arrangement in the signal read out device. There are three categories of detectors that are used in modern spectrophotometers.  These are elaborates in the following paragraphs.