Patent ID: 7321428

Claim:
A process photometer comprising a) an insulated compartment maintained at a relatively constant, elevated temperature which houses: (1) a source of chopped radiation directed to a focal point, (2) a means for detecting the chopped radiation's phase and generating a phase pulse, (3) an output optical fiber to convey the chopped radiation from the focal point to a remote sample, the fiber having one end supported by (4) a connector which holds the supported end of the optical fiber stationary at the radiation focal point, (5) a rotatable filter wheel having at least one filter for a radiation wavelength band modulated by each material being monitored, (6) means for rotating the filter wheel a regular, pre-determined distance at regular, pre-determined time intervals, (7) a return optical fiber to relay radiation modified by a material being analyzed from a remote sample cell to a filter on the filter wheel, (8) a radiation detector for radiation which has passed through a filter on the filter wheel, (9) a preamplifier for low noise amplification of output from the radiation detector, (10) a lock-in amplifier for synchronized detection of output from the preamplifier with chopped radiation phase pulse, (11) a means of converting the analog output from the lock-in amplifier to a digital signal, (12) means for maintaining a relatively constant temperature in compartment a), and (13) means for securing the components housed in compartment a) in the insulated compartment in a manner such that they are held in proper position, and b) a non-insulated compartment which houses a power supply, and c) a means for controlling movement of the filter wheel which may be located in the insulated compartment, in the non-insulated compartment or external to both compartments a) and b).