US 7,321,428 B2
Process photometer
Robert N. Hunt, Steubenville, Ohio (US); Atul Khettry, Wheeling, W. Va. (US); and Matthew R. Vila, Wheeling, W. Va. (US)
Assigned to Bayer MaterialScience LLC, Pittsburgh, Pa. (US)
Filed on Dec. 22, 2004, as Appl. No. 11/21,202.
Prior Publication US 2006/0132779 A1, Jun. 22, 2006
Int. Cl. G01N 21/25 (2006.01)
U.S. Cl. 356—418  [356/414] 25 Claims
OG exemplary drawing
 
1. 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).