Abstract: A method of controlling the opacity of the exhaust of the combustion of solid fuel and air in a furnace comprises measuring the opacity of the exhaust. The amount of air and the direction (i.e., increase or decrease) entering into the furnace is changed. The opacity of the exhaust is measured again. The later measured value of opacity is compared to the earlier measured value. The amount of air entering into the furnace is controlled based upon the comparison.

Abstract: A method of measuring the amount of substance associated with a material in the presence of a contaminant comprises choosing a first band of radiation which lies outside the absorption band of the substance but within the absorption band of the contaminant. The first band is directed at the material; a first detector is positioned to receive the radiation after impinging the material. The first detector converts the radiation received into a first electrical signal. A second band of radiation, which is chosen to lie within the absorption band of the substance, is also within an absorption band of the contaminant. The second band is directed at the material; a second detector is positioned to receive the radiation after impinging the material. The second detector produces a second electrical signal in response to the radiation received. The second electrical signal is subtracted from the first electrical signal.

Abstract: In an apparatus for the measurement of the thickness of a sheet through the use of air bearings, the apparatus has a stationary housing, a member in the housing capable of being extended in a direction substantially perpendicular to the sheet, and a fluid ring bearing capable of directing fluid to impinge the member in a substantially omnidirection which is substantially perpendicular to the direction of extension of the member.

Abstract: An apparatus to measure select properties such as color, brightness or gloss, of a moving sheet, is insensitive to flutter in the sheet. The apparatus comprises a housing to one side of said sheet. A source is located in the housing; the source is capable of emitting a beam of electromagnetic radiation which is aligned to impinge the sheet. The radiation is selected such that it is capable of being absorbed and being reflected by the select properties of the sheet. A collector is also located in the housing; the collector is capable of receiving a portion of the beam reflected from the sheet. A detector capable of measuring the select properties of the sheet based upon the radiation received by the collector is also provided. The housing is held at a constant distance from the sheet by a stream of fluid from the housing directed to impinge the sheet in a direction substantially perpendicular to the sheet. A standardization member is to the other side of the sheet.