Abstract: A method for determining the tendency of a non-woven web to curl, where the web has a machine direction (MD), a cross-machine direction (CD) and the web includes a wire side and a felt side. The method comprises determining a wire ratio which is the ratio of the number of fibers oriented in the MD to the number of fibers oriented in the CD, where the fibers are associated with the wire side of the web, a felt ratio which is the ratio of the number of fibers oriented in the MD to the number of fibers oriented in the CD, where the fibers are associated with the felt side of the web, and determining the wire to felt ratio which is a measure of the tendency of the web to curl.

Abstract: A sampling device for a batch or continuous pulp digester for reduction of pulp sampling errors such as during a digester "blow" and for improving a pulping process based on the obtained samples.

Abstract: A method is provided to monitor specific filtration resistance, total drainage resistance and drainage flow rate in a continuous on-line manner in the paper making process. It can be combined with the simultaneous measurement of streaming potential or zeta potential so as to enable optimization of the chemistry of the papermaking process.

Abstract: A procedure and apparatus for locating faults in the machine elements of a paper machine and in their functioning, wherein variations in the paper characteristics are continuously observed, the periodicity of the variations is recorded and the periodicity of the variations in the paper characteristics is compared with the periodicity in the functioning of the paper machine's machine elements. The apparatus comprises observation members (1-11) for observing the variations occurring in the paper characteristics; synchronizing pick-ups (43-53) disposed on machine elements (13-22) of the paper machine for observing the periodicity of the functioning of said machine elements; a recording means (40) for recording the periodicity of the variations in paper characteristics and the periodicity in the functioning of the machine elements; and a data processing unit (41) for comparing the periodicity of the variations in paper characteristics and that in the functioning of the machine elements.

Abstract: A drainage tester evaluates the reaction pattern of one or more reactions in a paper pulp furnish to predict behavior of the pulp on a paper line. The tester includes a mixing container in which an additive is mixed with the slurry under conditions that prolong the reactions in the container such that they take longer than the same reactions on a paper line. The mixer can also mimic the kinetic conditions (such as mixing by turbulence or passive diffusion) under which the additive is mixed with the furnish on the paper line. A test container has a screen bottom that separates furnish solid from slurry water by developing a pressure differential across the screen. An intermediate container is positioned between the mixing container and test container to provide a constant hydrostatic head on furnish transferred to the test container.

Abstract: A method and apparatus are provided for analyzing the elemental constituents of fluid streams in the cellulose pulp industry, such as liquid with dissolved solids for treatment of cellulose pulp or from the treatment of cellulose pulp, or liquid slurries including comminuted cellulose material. Continuous on-line elemental analyses are made of one or more such fluid streams, and at least the partial elemental make-up (either material, or of elements added for marking) of the streams determined. Then one or more processes for acting on the fluid streams are controlled to optimize the processes as a result of the analyses made. The invention is particularly useful in the continuous on-line analysis of black liquor utilizing prompt gamma neutron activation analysis, and controlling the operation of an evaporator or recovery boiler.

Abstract: Papermachine stock consistency is regulated while carried along a forming wire table. A variable draft vacuum box disposed beneath the forming wire to draw water from the wire carried stock is automatically adjusted in response to the summation of signals from several sources. A radioactive mass measuring gauge having a sensor head positioned beneath the forming wire downstream of the vacuum box provides a signal value indicative of the total mass carried above the sensor head. From this mass measuring gauge signal is deducted a value representative of the wire mass; the remainder representing the stock mass comprising a mixture of fiber and water. The quantity of fiber in the stock mixture, independent of the water, is determined by a dry basis weight measure of paper made from the stock. A signal value representative of the fiber basis weight is divided by the stock mass signal value to yield a consistency signal value.

Abstract: In a paper making machine, a strip of paper is caused to pass around part of the periphery of a rotary device comprising a plurality of cylindrical bodies arranged side-by-side across the width of the strip and each body has means for producing a signal representing the tension in the portion of the strip which controls the body, the thickness of the portions is also measured. From this data, control signals are produced representing the stress per unit of cross-sectional area of the portions of the strip and the paper making machine is controlled to keep the control signals constant across the width of the strip.

Abstract: A sensor, system and method for determining the various Z-directional properties of a sheet by measuring the caliper of a moving sheet of material at a plurality of pressures. The invention employs a caliper gauge and a set of pressure transducers that can measure and send signals indicative of the caliper as well as pressures exerted on the sheet. The signals are then digitized by an analog-to-digital converter and sent to a computer. The computer uses the compressibility data to construct a compression stress-strain diagram where the slope of the curve in the linear region of the curve is defined as the compression modulus of elasticity which can be empirically correlated to the tensile modulus of elasticity for various grades of paper. The tensile modulus of elasticity can be then used in various formulas to determine other Z-directional physical properties of the sheet, such as tensile strength, extensional stiffness and Scott bonding.

Abstract: A web rewet moisture actuator in which a plurality of air atomizing nozzles at spaced locations along a boom extending across the web are supplied with air under pressure by an air manifold on the boom and are supplied with water from a water manifold on the boom through respective proportional valve assemblies which permit flows therethrough in proportion to the magnitudes of control signals applied to the assemblies. A unit located downstream of the boom obtains a moisture profile across the web from which location and control signals are derived and fed to the valve assemblies to control the liquid flow through the valve assemblies in proportion to the magnitudes of the control signals.

Abstract: An apparatus and process is provided for testing the hardness of paper rolls. The apparatus includes a tester that is selectively moveable across a roll of paper. The tester includes an impact anvil which strikes the paper at a selected frequency and which determines the hardness of the paper roll based on forces encountered by the impact anvil. The tester further includes an encoder wheel for identifying relative positions on the paper roll at which each test is performed. The impact anvil and the encoder wheel are operatively connected to a computer which receives signals and calculates hardness at each of the plurality of positions tested. The computer provides output of data on the most recent traversal of a paper roll and on plural sequentially tested rolls to assess trends in the hardness of paper rolls produced by a particular machine.

Abstract: In the manufacture of stretchable webs such as creped tissue, nonwovens, and the like, in which the web is formed and thereafter wound onto a reel, basis weight control of the web on the reel is accomplished by measuring the speed and basis weight of the web prior to winding the web onto the reel and calculating the basis weight of the web on the reel. In response to this calculated value, either the upstream flow of material or the downstream speed of the web (reel speed) are adjusted to obtain the desired basis weight of the web at the reel.

Abstract: A method and system are provided for controlling the feed of comminuted cellulosic fibrous material (e.g. wood chips) to a continuous digester utilizing a chips meter of variable speed. A quality of the chips related to mass flow--preferably density--is continuously determined, preferably while the material is in free fall, not immersed in liquid. The speed of the material meter is controlled in response to the quality determined to provide a target mass flow of material from the meter to the digester. A nuclear type density gauge may be utilized having a source and a detector mounted on opposite sides of a chip chute, and above the level of liquid in a chip chute so that density is determined during free fall of the chips, not immersed in liquid. A level sensor may also be associated with the chip chute with a shield between the nuclear source and the level sensor. The chip meter speed is controlled in the range of about 0-16 rpm.

Abstract: A method and apparatus in the press section of a paper machine for regulating the axial linear-load profiles in its nip or nips (N.sub.1,N.sub.2,N.sub.3). The axial temperature profile(s) of the outer mantle(s) of a press roll or rolls (11, 13, 16, 17) is/are regulated. Thereby, the distribution of the diameter of the press roll in the axial direction is controlled on the basis of thermal expansion. Also thereby, the distribution in the transverse direction of the machine of the linear load in the press nip or nips (N.sub.1,N.sub.2,N.sub.3) formed by the press roll or rolls (11, 13, 16, 17) is affected. The temperature profile of the outer mantle(s) (11', 13',17') of the press roll or rolls (11, 13, 17) is regulated by a press felt or felts (10, 14, 18) running through the press nip or nips (N.sub.

Abstract: A method of foam forming of paper includes the steps of metering a controlled feed of fiber dispersed in an aqueous liquid into a dewatering device, wherein the consistency of the fiber dispersed in the aqueous liquid input to the dewatering device is between about 0.5 and about 7% by weight. A uniform continuous strand of semi-moist pulp is obtained wherein the consistency of the semi-moist pulp leaving the dewatering device is between about 8 and 30% by weight. A stream of a foamed aqueous admixture is obtained and introduced into a dispersing mixer having shearing action extending substantially throughout a zone substantially athwart the flow path of the uniform continuous strand and the foamed aqueous stream and forming a stream of dispersed fiber bearing aqueous foam. The dispersed fiber bearing aqueous stream is conducted to the inlet of a positive displacement pump.

Abstract: A method for determining bending stiffness of a moving sheet using an on-line sheet bending stiffness sensor. The sensor continuously bends the sheet as it is being manufactured and, based upon the force required to bend the sheet, the amount of bending and the tension applied to the sheet, the sensor determines a parameter indicative of sheet bending stiffness. The resulting parameter can be correlated with conventional destructive laboratory tests of sheet bending stiffness.

Abstract: The jet velocity along a slice opening of a papermaking machine is monitored at plural locations to provide a jet velocity profile. This jet velocity profile may be adjusted to more closely match a reference velocity profile for the jet. Preferably, microwave doppler-effect velocity sensors are utilized for sensing a jet velocity. In one specific embodiment of the invention, preamplifier and automatic gain control circuitry is used to minimize variations in the sensed signal due to changing conditions of the jet.

Abstract: Device for measuring the condition of a felt (4) in a paper machine and for reconditioning it, comprising a measuring head (7) provided with a suction chamber (7b) and a measuring surface (7a) to be positioned against the surface of the felt (4) and provided with suction holes (15) leading into the suction chamber (7b); a suction conduit (17) leading out of the suction chamber (7b) and communicating with a vacuum source (9) for sucking air and water through the suction holes (15) from the felt (4) into the suction chamber (7b) and for discharging water and air from the suction chamber (7b); and measuring means (18) for measuring the vacuum pressure in the suction chamber (7b). In the reconditioning and measuring device according to the invention, the measuring head (7) comprises two suction conduits (16, 17) for sucking water and air, respectively.

Abstract: In a flat bed, Fourdrinier-type, countercurrent washer for pulp, the opportunities for the development of foam are minimized by "wet" operation of the washer so that the pulp mat remains essentially full of liquid as it passes from each washing zone to the next. Special provision is also made for compensating for drainage at too slow a rate in one washing zone by bypassing some of the flow of washing liquid to that zone so that it is delivered to the zone upstream therefrom. An additional feature is the provision of controls over the flow of drained liquid from one or more of the receptacles therefor so that any solid particles floating on the top of that liquid in the receptacle are delivered to the countercurrent flow which ultimately reaches the evaporator.

Abstract: The invention provides multiple steam applicators which are used to distribute steam against a web during calendering. The invention includes a primary steam applicator located adjacent a side of the web to which steam is applied. The primary steam applicator has a manifold, a primary inlet valve, and a plurality of steam valves spaced along the primary manifold. Each steam valve regulates a steam flow distributed to a cross-directional section of the web. A secondary steam applicator is located adjacent the side of the web to which steam is applied. The secondary steam applicator has a manifold, a secondary inlet valve, and a plurality of steam valves spaced along the secondary manifold, each steam valve regulating a steam flow distributed to a cross-directional section of the web. A gloss sensor measures the gloss finish of the web.

Abstract: A method for measuring extremely low concentrations of non-aqueous constituents or chemicals in a water/matrix, including differentiating between pulp fines and extremely low concentrations of individual chemicals in a water/cellulose matrix such as occur in papermaking. The water/matrix is exposed to the near-infrared spectrum from 1000 to 2500 nm to produce a recorded voltage that is directly proportional to the absorption by the non-aqueous constituent. The amount non-aqueous constituent is determined from stored voltage values of incremental additions of the non-aqueous constituent.

Abstract: A system and process for continuously determining the strength of paper sheet material during manufacture includes a plurality of sensors for detecting proxies related to properties such as the strength of individual fibers, length distribution of fibers, quantity of fibers, distribution of fibers, orientation of fibers, number of bonds between fibers, and bond strength of fibers. For a given papermaking machine and paper type, multiple regression analysis is used to determine correlations between the measured proxies and laboratory tests of paper strength. Then, during operation of a papermaking machine, changes in the proxy measures are used to indicate paper strength and to adjust operation of the papermaking machine based upon changes in the strength of sheet material being produced.

Abstract: An apparatus and method for suppressing flutter of a moving web manufacturing operation to include a sensor for sensing the pressure of air in a region proximate the web, which sensor generates a pressure signal representative of the air pressure, a signal processor, connected to receive the pressure signal and to derive therefrom a negative feedback suppression signal phase-shifted to attenuate the air pressure, and an air modulator, positioned to modulate the air in the region proximate the web, which modulator receives the suppression signal and modulates air in response thereto so that flutter is attenuated. The modulator can be a speaker placed in an air supply duct, and in another embodiment it is placed directly in a web pocket.

Abstract: The stack reflectance is predicted from an on-line, wavelength dependent measurement of the sheet reflectance and the on-line measurement of the sheet opacity at a wavelength interval. The stack reflectance Rst is then used to predict and/or control stack color, preferably by using the parameter K/S=(1-Rst.sup.2)/2 Rst where K is the dye absorption coefficient and S is the dye scattering coefficient.

Abstract: The present invention relates to a method of qualitative and quantified monitoring of the instant local physical state of a substantially incompressible fluid material such as a liquid or pasty substance (for instance slurry or pulp) and a device for carrying out this method and the various applications and uses resulting from the working of the method and/or device for the automatic control of said physical state. The invention is also directed to the various equipment and systems provided with at least one such device.

Abstract: The invention relates to a process for wetting a paper web in a calendering step by using water-containing microcapsules in the surface structure layer of the paper web, said microcapsules being ruptured in the calendering step whereby water is released. The invention also relates to microcapsules comprising a water-impermeable shell and an interior substantially comprising water, and having a diameter of 0.1 to 100 .mu.m and a shell thickness of 0.01 to 5 .mu.m.

Abstract: In a method and apparatus for making a dry sheet-like sample of solid particles from a suspension, a part of the suspension is sampled by a sampling unit as it flows through a pipe or while it is retained in a storage tank, then the sampled suspension is stirred by supplying a compressed air and then dewatered by filtration with vacuum, thereby forming a wet sheet-like intermediate sample of solid particles deposited on a filter. Subsequently, the filter and the intermediate sample deposited thereon are conveyed by an overturning conveyor unit to a drying station while being turned upside down, thereafter intermediate sample is removed from the filter by a sample removing unit, and finally, the wet sheet-like intermediate sample is dried with heat and pressure whereby a dry sheet-like final sample is obtained.

Abstract: A method to control the opacity of sheet formed of nonwoven material involves providing a computer with a steam pressure measurement from each of two steam heated palmer bonders. One pressure sensor from the first bonder drum and one from the second bonder drum provide signals used to control steam pressure and thus temperature of each bonder drum's surface. A signal indicating temperature of the surface of each drum and a measurement of speed are also collected by the computer/controller. The fundamental control signal is provided to the computer from an opacity sensor device which is compared to an opacity aim and then steam pressure to the bonder drum is adjusted to minimize any error signal between opacity aim measured opacity.

Abstract: A method of detecting counterfeit paper currency includes applying a test solution having an initial color to an area of a paper currency to be tested. After waiting for a predetermined time period, the color of the test area is compared with a predetermined standard to determine if a reaction has taken place, whereby on the application of the test solution to a counterfeit paper currency the net result will be a color change from its initial color to a black coloration and for a genuine paper currency there will be no immediate change in its initial color.

Abstract: When a paper web is coated on paper machine the surface temperature is controlled at or below a temperature determined by an equation (1) given below, in order to obtain a coated paper having an evenly coated layer. ##EQU1## where T: surface temperature of the paper web (.degree.C.)m: wet value of the paper web (g by weight)v: viscosity of the coating composition (cps)x: x=40 or 35 with 35 being the preferred form of the equation.

Abstract: In the manufacture of stretchable webs such as creped tissue, nonwovens, and the like, in which the web is formed and thereafter wound onto a reel, basis weight control of the web on the reel is accomplished by measuring the speed and basis weight of the web prior to winding the web onto the reel and calculating the basis weight of the web on the reel. In response to this calculated value, the downstream speed of the web (reel speed) is adjusted to obtain the desired basis weight of the web at the reel.

Abstract: A testing device for determining the amount of liquid having been doctored through the Fourdrinier fabric or wire at the wet end of a Fourdrinier-type paper machine. Included is a pick-up for insertion beneath the foil blades of the paper machine, having an opening for insertion into the stream of the liquid being doctored from the pulp. A container is connected in liquid communication with the pick-up. A weir is positioned within the container to divide the container into a collection well upstream from the weir and a discharge well downstream from the weir. The container includes a still well positioned in liquid communication with the collection well. A proximity sensor is provided, and positioned with respect to the still well to sense the level of liquid in the still well. A microprocessor controlled display is provided for receiving a signal from the proximity sensor and displaying a flow rate based on the level of the liquid in the still well.

Abstract: A method for controlling high-speed sheetmaking machine after abrupt process changes and during start-up periods and the like, includes operating a scanning sensor to periodically traverse back and forth across a sheet in the cross direction to detect values of selected sheet property along each scan while the cross-directional width of each scan is controlled to be substantially less than the width of the sheet being scanned.

Abstract: A system and process for continuously determining the strength of paper sheet material during manufacture includes a plurality of sensors for detecting proxies related to properties such as the strength of individual fibers, length distribution of fibers, quantity of fibers, distribution of fibers, orientation of fibers, number of bonds between fibers, and bond strength of fibers. For a given papermaking machine and paper type, multiple regression analysis is used to determine correlations between the measured proxies and laboratory tests of paper strength. Then, during operation of a papermaking machine, changes in the proxy measures are used to indicate paper strength and to adjust operation of the papermaking machine based upon changes in the strength of sheet material being produced.

Abstract: The method and apparatus automate the observation of the dry line on the wire of the Fourdrinier paper machine on whose visual observation by eye the conventional control of the paper machine is based. In the invention, the position of the dry line and its such values which deviate from normal, and the quantities which express its form, are reproduced to the operator repeatedly. In order to carry out this, it is formed as one essential feature of the invention, the image of the plane of the wire with an opto-electric camera and the electric, discrete image information is transmitted into a computer. While the conventional observation of the dry line is based on reflections from the pulp surface which are brighter than the other surface, these, however, disturb an instrumental observation and check an interpretation of the result of observation.

Abstract: A system and process for controlling the displacement of a thickness regulating member which regulates the basis weight of a sheet being formed from fluid material. The displacement of the thickness regulating member is determined by measuring the forces which slice rods exert on the thickness regulating member.

Abstract: An apparatus and method for determining the frequency and amplitude of flutter of a moving web in a web manufacturing operation, is shown to include a sensor for sensing the pressure of air in a region proximate the web and for generating a pressure signal reflective of the air pressure and a signal processor, connected to receive the pressure signal, for determining the amplitudes and frequencies of the flutter from the pressure signal and for generating an indication signal representative of the flutter amplitude and frequency.

Abstract: A method for monitoring and/or controlling a liquid/solid separation process is described. The method utilizes photodetectors to view the surface of the composition being dewatered, and correlate the corresponding signals from the photodetectors to dryness values.This is a continuation of application Ser. No. 122,976, filed Nov. 19, 1987 now abandoned.

Abstract: A sensor and a method for determining the basis weight of coating material on a substrate is described. The determined basis weight is insensitive to changes in the amount of substrate material underlying the coating. Signals from the sensor may be used in the control of a coating mechanism to provide a coating having a uniform basis weight.

Abstract: The invention relates to a method of active attenuation of machine directon pressure pulsations in the stock fed into the headbox (10) of a paper or board machine in such a way that the pressure pulsations in the stock are measured and the water flow to be fed into the stock is controlled on the basis of the results of the measurement. The volume available for the stock flow is controlled by means of water flow changes. Pressure variations achieved by volume variations are arranged substantially in opposition to the pressure variations to be attenuated thus attenuating the pressure variations in the stock. The invention also relates to an apparatus for carrying out the above method. The apparatus comprises a sensor (6) or a set of sensors, on the basis of whose output signal/signals a regulator (7) has been arranged to automatically control the water flow to be fed into the stock by an adequately fast valve arrangement (1) moved by the controlling element (2) of the regulator (7).

Abstract: The maximum amounts of the retention-influencing variable stock components which can be added are determined as a function of a predetermined degree of flocculation and typical values of the stock suspension with the aid of a mathematical relationship, and control signals for metering retention aids are derived from the amounts so that the greatest possible retention can be achieved without exceeding a set-point for the degree of flocculation.

Abstract: A method and device for determining the strength of a sheet material, such as paper, utilizing floc size and the variability of the local basis weight of the sheet. The force required to deflect the moving sheet out of a nominal position, the distance the sheet is deflected by said force and the average tension applied to the sheet may also be utilized in the above determination of sheet strength.

Abstract: A method for controlling high-speed sheetmaking machine after abrupt process changes and during start-up periods, includes operating a scanning sensor to periodically traverse back and forth across a sheet in the cross direction to detect values of selected sheet property along each scan while the cross-directional width of each scan is controlled to be substantially less than the width of the sheet being scanned, the progressively increasing the width of the scan until each scan encompasses the full width of the moving sheet.

Abstract: The method of dispersing a material containing waste paper by means of a dispersion apparatus and a dewatering machine, renders possible performing the material dispersion operation at essentially constant specific dispersion work even when encountering fluctuations of the raw material to be dispersed and of the dispersing process itself. For this purpose there is provided a regulating system which, with the aid of measured values or magnitudes derived from the dispersing process and predeterminate processing relationships, controls the addition of diluting water to the material to be dispersed at a location upstream of the dispersion apparatus.

Abstract: A method of and apparatus for adjusting the impact angle of a doctor blade are provided to at least partially offset negative effects of doctor blade wear. For example and not by way of limitation, in papermaking machines for making creped tissue paper, a negative effect of progressive doctor blade wear is progressive diminution of machine-direction tensile strength of the paper, all other operating factors being constant. That is, machine-direction tensile strength of the paper is inversely related to doctor blade wear which wear is, generally speaking, directly related to operating time. This progressive lessening of the paper's machine-direction tensile strength can be at least partially offset or compensated for by adjusting the impact angle of the doctor blade.

Abstract: The present invention concerns a method in a paper machine for the measurement of air penetrability or permeability of fabrics penetrable by air, in particular of a wire or felt. In the method, the fabric penetrable by air such as a wire is passed over at least one roll, where a positive pressure is formed at an inlet side of the fabric with respect to the roll when the fabric runs and in an inlet nip formed between the moving fabric and a face of the roll, and a negative pressure is formed at an outlet side of the moving fabric with respect to the roll in an outlet nip formed between the moving fabric and the roll face. The positive pressure and negative pressure depend up on the permeability of the fabric penetrable by air. According to the method, at least one device is mounted below the fabric penetrable by air such as a wire, this device being sealed relative to the moving roll face so that an at least partially closed pressure space is formed between the device, the roll face, and the fabric.

Abstract: This invention is directed to a filtration simulator. More specifically, this invention is directed to a Dynamic Filtration Simulator (DFS) and method of determining the interaction and effect on liquid flow of additives to paper stock in a papermaking machine, which comprises:(a) admixing one or more additives to be tested with paper stock in a slurry tank to form an aqueous paper stock slurry;(b) pumping said slurry from step (a) to a filtration means comprising permeable filter material, the interior of said filtration means being in fluid communication with an exit pipe which is in fluid communication with said slurry tank, whereby aqueous slurry permeates said filter material to form a permeate and said permeate flows through said exit pipe back to said slurry tank;(c) measuring the pressure and volume flow of the aqueous paper stock slurry into the filtration means; and(d) measuring the pressure and volume flow of the aqueous permeate.

Abstract: In a headbox system for a papermaking machine with an adjustable distribution of the fiber stock suspension or pulp over the web width, the flow in the delivery slice is controlled in such a way that, across the web width, also the distribution of the fibers in respect of fiber orientation and quantity has a desired profile. For this purpose, the flow of the fiber stock suspension is controlled such that in the event of a change in the distribution of the fiber stock suspension across the web width, the horizontal component of the flow direction in the delivery slice remains, at all locations, always in the predetermined machine direction and thus transverse flows are avoided and the flow rate in the delivery slice has a predetermined profile.

Abstract: A method for measuring the permeability of pervious sheet material is disclosed; the measurement is based on the flow rate of water ejected at a given pressure between 2 and 1000 kPa through a nozzle pressed against one surface of the sheet material whose permeability is to be measured.

Abstract: A method of testing security papers with respect to the positions of a safety thread and water marks to detect errors in the paper is performed by a linewise scanning of a finished paper web. The web has at least two point like measuring marks inserted into it in addition to the water marks, whereby impulses which are originated from these measuring marks are evaluated and the sheet width and the sheet distortion are calculated by comparing the x-y positions of the individual measuring marks with each other. The measuring marks are sharpe edged and rich in contrast. The given edge impulse is evaluated.