Simulated calibration sample for a spectrographic measurement sensor and method for use

#The invention of the present application relates in general to reference samples for calibration of spectrographic measurement sensors used to measure constituents of flat sheet products, for example webs of material as they are being manufactured, and more particularly, to a simulated reference sample for calibration of spectrographic measurements and a method for using a simulated reference sample. While the present invention is generally applicable for spectrographic measurement of a variety of materials including a wide variety of material webs, it will be described herein primarily with reference to spectrographic measurement of a paper web as it is being manufactured for which it is particularly applicable and initially being used.

#During the manufacture of flat sheet products, such as paper, plastic films, textiles, and the like, incandescent or blackbody light sources and corresponding sensors are used in measurement systems to measure constituents of a quickly moving, fluttering product web. For use with a web-manufacturing machine, measurement systems are often mounted on measurement platforms that support the light sources on one side of the web and the sensors on the other side of the web. Such sensors can also be configured in a reflection mode rather than a transmission mode. In reflection mode sensors, light sources and sensors are mounted on the same side of the web and may be mounted in a common housing. In any event, the measurement systems are scanned in a cross-process direction as the web moves relatively rapidly in a process direction. The scanning platforms are arranged so that they can move the light sources and sensors “off-sheet”, i.e., beyond at least one edge of the web product, so that an air gap is located between or adjacent to the light sources and sensors. While reflection sensors can be calibrated on-sheet, the light sources and sensors of both transmissive and reflective devices can be tested, serviced and calibrated while they are off-sheet.

#Spectrographic sensors (also known as spectroscopic sensors) are common measuring devices used for measurement systems associated with web-manufacturing machines. In these applications, spectrographic sensors measure radiation transmitted through a web at specific wavelengths or wavelength bands with measurements indicating the presence or absence of different materials and, if present, the amount of the materials within the web. Exemplary materials that the sensors may measure include water, polymers, cellulose and other components of the web. A common application is the measurement of the fraction of water by weight (percent moisture) in a moving paper web during manufacturing.

#The benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the illustrated embodiments and the appended claims, taken in conjunction with the accompanying drawings, wherein:

#FIG. 1 is a diagram illustrating a monitoring station of a paper web-manufacturing machine including the invention of the present application;

#FIG. 2 is a schematic diagram illustrating the internal structure of sensor elements of the monitoring station of FIG. 1; and

#While the present invention is generally applicable to any web manufacturing process, it will be described herein with reference to paper manufacturing for which it is particularly applicable and initially being used. Referring now to the drawings, in which like-referenced characters indicate corresponding elements throughout the drawings, attention is first drawn to FIG. 1 that shows a web monitoring station 100 of a paper web-manufacturing machine (not shown) with the station 100 including the invention of the present application. The paper-manufacturing machine produces a paper web 102 and the web monitoring station 100 includes a sensor system 104 comprising a light source housing 106 and a light detector housing 108. It is to be appreciated that both the source housing 106 and the detector housing 108, as illustrated, are mounted for conventional scanning back and forth across the web 102 in a cross-machine direction (CD), as shown by the arrows 110, using a measurement platform 111.

#Referring now to FIG. 2, mounted inside the source housing 106 is a lamp 112 having a filament 114 and a protective globe 116. The filament 114 may be a tungsten filament and may have a length of about 3.8 mm and a diameter of about 1.95 mm. The protective globe 116 may be formed of glass which may be covered with a reflective coating and may enclose a gas, such as halogen gas, as is conventional. Coupled to the lamp 112 are a power supply 118 and a light source intensity controller 120. The power supply 118 can be varied between, for example, outputs of zero volts and ten volts. The light source intensity controller 120 includes conventional electronics necessary to regulate and vary the voltage supplied by the power supply 118 to the lamp 112. Mounted inside the detector housing 108 is a spectrographic sensor 122. The spectrographic sensor 122 is connected to a system processor 124 that includes conventional electronic devices and systems needed for signal processing and other functions.

#The lamp 112 generates a broad bandwidth light or white light signal having a light intensity that is controlled by the level of the voltage applied to the lamp 112. The lamp 112 emits high energy density light including multiple infrared wavelengths onto a focal spot of about one centimeter in diameter at a controlled focal distance. The lamp 112 may be air-cooled using an air shroud (not shown) or otherwise cooled to increase lamp life and to reduce heat effects on the sensor system 104.