2.2 Components of a Flame Atomic Absorption/Emission Spectrometer System
2.2.4 Chopper
A chopper is a device that splits a single beam of radiant light into two directions. A chopper is a circular-shaped device split into quarters (refer to the figure below). Opposing quarters of the chopper are open (contain no material as in the left-hand side of Figure 2-2) while the other quarters of the chopper contain a mirrored surface (as in the right-hand side of Figure 2-2) in order to direct the light to the sample cell (as shown in Figure 2-1). The chopper rapidly spins in the beam of light, directing the light by reflection as the mirror interacts with the light or by allowing the radiation to pass as the empty portion of the chopper moves past the beam of light. Thus, choppers split the beam of light with respect to time (as opposed to space where two adjacent mirrors would direct the light in two different directions). If the chopper spins faster than the fluctuation of noise in the source signal, an accurate measurement of the background noise can be obtained and corrected for in the sample readings. The positions of the chopper and the resulting beam of radiation are illustrated in Figure 2-2.
Figure 2-2 A Chopper, a Device used to Split Source Light with Respect to Time.
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