Patent ID: 7001067

Claim:
A method of measuring temperature in a furnace comprising: providing a combustion gas stream containing water vapor and carbon dioxide, wherein the combustion gas stream is semi transparent to wavelengths of infrared radiation, positioning a pyrometer having a lens tube and an optical head comprising a single objective lens in a fireside port of the furnace, with a line of sight intersecting a passage of the combustion gas in the furnace and able to view at least forty feet of unobstructed interior of the furnace from one furnace wall short of an opposite furnace wall; providing a photometer circuit connected to the optical head for detecting wavelengths of infrared radiation produced by water vapor contained in the combustion gas stream as it passes the line of sight; measuring the infrared radiation produced by water vapor contained in the combustion gas stream through the single objective lens in the fireside port of the furnace, converting the infrared radiation to an electrical signal; providing the lens tube with a cooling means comprising a inner concentric tube; wherein the cooling means is capable of aspirating the objective lens; utilizing a cooling gas between the lens tube and the inner concentric tube to cool the lens tube; providing a watertight electronics enclosure mounted to the lens tube for housing electronic circuitry; providing a power supply circuit; providing a scaling circuit mounted within the electronics enclosure and connected to the photometer circuit for scaling the electrical signal; scaling the electrical signal to maximize signals generated by infrared radiation which is semi-transparent to the combustion gas stream; providing an output circuit connected to the scaling circuit for receiving a 0 to 2 milliamp analog output signal and producing an output voltage signal; and providing an output means connected to the output circuit for displaying the output voltage signal as a temperature measurement; providing the watertight electronics enclosure with an analog thermometer; measuring the temperature in watertight electronics enclosure with the thermometer; and utilizing a cooling means comprising a vortex cooler and coolant to maintain a temperature of below 130 F in the watertight electronic enclosure.