Abstract: In a coating apparatus for supplying a mixed solution of a resist solution and a thinner onto a wafer from a nozzle, the nozzle is connected to a mixed solution supply pipe, and the resist solution and the thinner are supplied to the mixed solution supply pipe from a resist solution supply pipe and a thinner supply pipe respectively through a junction pipe. The diameter of the junction pipe is set smaller than those of other supply pipes, whereby the resist solution and the thinner can be mixed efficiently in the junction pipe, and as a result the wafer is coated with the mixed solution so that a uniform film thickness can be obtained within the surface of the wafer.

Abstract: A wire coloring method and a wire coloring apparatus are provided. The wire coloring apparatus 1 has a coloring portion 10, a colorant-supplying portion 11, and a control unit 12. The coloring portion 10 has a mixing tank 23. The mixing tank 23 mixes first to fourth colorants B,R,Y,BL supplied from the colorant-supplying portion 11. The coloring portion 10 colors an outer surface 5a of an electric wire 3 with the mixed colorant in a mixing tank 23. The colorant-supplying portion 11 has a first to fourth adjusting valves 26,27,28,29 to increase and decrease flow rates of the first to fourth colorants B,R,Y,BL to the mixing tank 23. The control unit 12 controls opening ratios of the first to fourth adjusting valves 26,27,28,29.

Abstract: The invention relates to a method and an apparatus for measuring a coating from paper or board. The measurement is carried out by one detector at different times or by two detectors simultaneously. IR radiation directed at the coating and radiation emerging from the coating are chopped synchronously in blocks. A wavelength band sensitive and insensitive to the absorption are bandpass filtered and measured in both the MIR and NIR region. The absorption strength is measured in a digital signal processing block by comparing the radiation sensitive to absorption to the radiation insensitive to absorption, and the amount of each coating component is determined in the digital signal processing block on the basis of the absorption strength.

Abstract: A particle measurement configuration measures the particle concentration in a liquid or gaseous medium by way of a particle measuring instrument. In order to avoid erroneous measurements or damage to the particle measuring instrument, a measuring cell is provided which measures temperature or pressure or pH of the medium. A system controller shuts off a valve if threshold values are exceeded and it prevents the particle measuring instrument from being operated outside a predefined specification.

Abstract: The invention relates to a method for electrically controlling a flow of material, wherein a single- or multi-component, essentially polymer-based material (1), such as plastics, elastomer or the like, is charged electrically (I) and sprayed (II) in an electrical field (E) to a three-dimensional mould (2)/target (3). The method of the invention makes use of the mould (2)/target (3) set at an electric potential and provided with two or more treatment blocks (Li) to be set at voltage levels different from each other, especially for coordinating the courses of sprayed material particles and the electrical field (E) affecting the same, in such a manner that each section/area of the mould/target surface forms a material layer of desirable thickness in the spraying cycle (II). The invention relates also to an apparatus operating in accordance with the method.

Abstract: A method of controlling the content of a chemical bath includes the steps of: determining a replenishment condition for the chemical bath; defining a unit of the replenishment condition; establishing a pacing factor corresponding to a replenishment volume of a replenishment medium per unit of the replenishment condition; and defining a replenishment threshold corresponding to the product of a predetermined number of the defined units of the replenishment condition and the pacing factor. The rate of continued replenishment of the predetermined constituent of the chemical bath is determined in response to the replenishment condition, which may be elapsed time, ampere-hours (or coulombs), number of product loads, product surface area, or line speed over time. The method replenishes constituents as they actually are consumed. It also prevents depletion (or buildup in the case of decanting a by-product) and the associated time delay related to detection and correction.

Abstract: There is described a medical image recording apparatus, which records a medical image on a recording medium based on image data. The apparatus includes an ink-jetting head to emit ink particles onto the recording medium and a controlling section to control the ink-jetting head, so that a total amount of the ink particles per unit area, emitted by the ink-jetting head and adhered onto the recording medium, is maintained at substantially a constant value even if density of a solid-tone image area varies within density range D. With respect to at least one of combinations of values k1, k2 selected under conditions of 0≦k1<1, 0<k2<1.0, and k1<k2, the density range D fulfils the equation of Dmin+k1(Dmax−Dmin)≦D≦Dmin+k2(Dmax−Dmin), where, Dmax is a recordable maximum-density, and Dmin is a recordable minimum-density.

Abstract: A method of applying a treating liquid to a porous body (11), in particular a pre-baked carbon component of an aluminium production cell, such as an anode block, a cathode block or a sidewall. In this method first the body (11) to be treated is inserted, with its part to be treated facing up, in the treating chamber (12). At least one sealing member (13) is then applied to the body so as to isolate a space (14) in an upper part of the treating chamber (12) around the part of the body to be treated from a lower part (15) of the treating chamber around a bottom part of the body which is not to be treated. Next, treating liquid (10) is supplied to the upper part (14) of the treating chamber to cover the part of the body to be treated with the treating liquid and applying a vacuum to intake an amount of the treating liquid into pores in the part of the body to be treated. Then the body (11) is freed from the sealing member(s) (13), and removed from the treating chamber (12).

Abstract: The present invention relates to a method of and a device for optimizing at least one coating material at at least one point of a substrate surface to which the coating material is applied. The method, which is carried out with the corresponding device, comprises at least the following steps: a) applying said at least one coating material to said at least one point of the substrate surface, b) curing said at least one coating material at said at least one point of the substrate surface, and c) determining the state, especially the curing and/or yellowing and/or gloss, of said coating material at said at least one point of the substrate surface, possessed by said coating material as a consequence of steps a) and b).

Abstract: A method for making an aerogel film includes the steps of performing a gelation reaction of a metal alkoxide on a substrate to prepare a substrate with a wet-gel film, and converting the wet-gel film into an aerogel film by a supercritical or sub-critical drying process of the substrate with the wet-gel film, wherein the degree of gelation of the wet-gel film is controlled to be a predetermined value at the start of the supercritical or sub-critical drying process. Aerogel films having uniform qualities are produced by the supercritical or sub-critical drying process in one lot.

Abstract: In a coating apparatus for supplying a mixed solution of a resist solution and a thinner onto a wafer from a nozzle, the nozzle is connected to a mixed solution supply pipe, and the resist solution and the thinner are supplied to the mixed solution supply pipe from a resist solution supply pipe and a thinner supply pipe respectively through a junction pipe. The diameter of the junction pipe is set smaller than those of other supply pipes, whereby the resist solution and the thinner can be mixed efficiently in the junction pipe, and as a result the wafer is coated with the mixed solution so that a uniform film thickness can be obtained within the surface of the wafer.

Abstract: An apparatus for measuring the concentration of developer in a liquid printer, the apparatus includes a housing, a developer film forming device installed in the housing for forming a developer film, and a sensing device including a light source unit for emitting colored light corresponding to a range of wavelengths for which the light transmissivity is relatively low to a developer film of a selected color developer, and a photodetector installed corresponding to the light source unit and receiving the light emitted by the light source unit and transmitted through the developer film. Thus, a thin developer film is formed and the concentration of developer is measured by emitting light in a range of wavelengths for which the selected color developer has a relatively low light transmissivity to the developer film. The affect by the toner mixed with other color is relatively less and the concentration of developer can be measured close to the actual concentration although the developer is contaminated.

Abstract: A device for measuring the concentration of a developer liquid for a liquid-type printer, including a container having a discharge portion, first and second rotary members rotatably installed in the container with a predetermined space, and a supply portion for supplying the developer liquid containing toner particles and liquid carrier into the space between the first and second rotary members. A concentration detector is provided for detecting the concentration of the developer liquid by emitting light onto the developer liquid flowing along the space between the first and second rotary members, and receiving the light passed through the developer liquid. In the concentration measuring device, the space between the first and second rotary members can be adjusted to be smaller, and the concentration of a developer liquid having a low light transmittance can also be measured.

Abstract: A sensor and a method for determining the basis weight of a coating material containing latex 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: A sensor and a method for determining the coating weight of a coating material containing silicone on a substrate is described. The determined coating 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 weight.

Abstract: A substrate treating method and apparatus are disclosed which are capable of heating a substrate in a stable atmosphere including the vapor of a treating liquid, without permitting the vapor of the treating liquid to condense on the substrate. The vapor of the treating liquid is mixed with a diluting gas to form a treating vapor mixture. At this time, the flow rate of the diluting gas is adjusted so that the partial pressure ratio of the vapor of the treating liquid in the treating vapor mixture increases with the passage of time. This treating vapor mixture is transmitted to a treating chamber. The treating chamber includes a substrate support table heated to a predetermined temperature.

Abstract: An image forming apparatus having an improved developer density detecting device for detecting density of a liquid type developer without using an optical sensor. Density of the liquid type developer is detected based upon viscosity of the liquid type developer, which is obtained by sensing pressures, for example, of the liquid type developer sent by a pump and flowing through a developer circulating pipe and applying pressure data obtained by sensing pressures to a predetermined formula. The viscosity can also be obtained by dropping a steel ball, or moving a steel ball, through the liquid type developer and measuring an induced current in a coil based on movement of the steel ball. The viscosity can also be obtained by measuring torque of a device rotating with the liquid type developer.

Abstract: An image forming apparatus having an improved developer density detecting device for detecting density of a liquid type developer without using an optical sensor. Density of the liquid type developer is detected based upon viscosity of the liquid type developer, which is obtained by sensing pressures, for example, of the liquid type developer sent by a pump and flowing through a developer circulating pipe and applying pressure data obtained by sensing pressures to a predetermined formula. The viscosity can also be obtained by dropping a steel ball, or moving a steel ball, through the liquid type developer and measuring properties based on movement of the steel ball. The viscosity can also be obtained by measuring torque of a device rotating with the liquid type developer.

Abstract: An apparatus for measuring the concentration of a liquid developer of an image processor includes: a housing; a rotating roller disposed inside the housing, a driving source for rotating the roller; a developer supplier for supplying the developer to the roller such that a developer film can be formed as the roller rotates, and a sensor for sensing an amount of light transmitted through the developer film by directing light to the developer film and receiving the light transmitted through the developer film.

Abstract: A sensor and a method for determining the basis weight of a coating material containing CaCO.sub.3 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: A system for applying a suspension of uncooked starch particles in water to a web on a forming wire includes a source of such suspension and a source of dilution water, an application die positioned transversely of the web with an internal manifold opening into a downwardly opening die slot through which material flows from the manifold as a falling curtain onto the web. The die has a plurality of transversely spaced inlets leading into the manifold to define transversely spaced application zones across the web. The suspended starch and water are applied from the manifolds through control valves into the inlets by means of which the consistency or concentration of the starch may be varied at positions representing the application zones across the web to provide a desired strength profile to the dried web.

Abstract: A method of applying a starch sizing to a forming web on a paper machine, such as in the form of a curtain on a fourdrinier machine, employs a suspension of uncooked particulate starch and water which is applied, as a suspension, to the inlet of a downwardly opening die positioned over the forming web and applied at a consistency of between about 2 to 10% onto the surface of the web as a free falling curtain, the impact velocity of which is controlled to a rate sufficiently low to prevent distortion of the web on impact. Improved drainage is achieved by heating the suspension to a temperature less than about 150.degree., to prevent the cooking of the starched particles. The curtain may be applied to the web at fourdrinier table consistencies as low as about 2% and still obtain starch retention rates of about 80%.

Abstract: A plant for preparing and feeding a coating composition to a coating head for paper or the like includes a plurality of hoppers, each hopper being intended to receive and deliver one ingredient of the composition. The plant further includes a premixer tank which is fed by the hoppers and mixes and homogenizes the formed composition and a homogenizing tank, fed by the premixer tank, having a high-speed stirrer for shearing the composition. A buffer capacity is directly and continuously fed by the homogenizing tank and connected to the coating head, wherein the buffer capacity preferably has a volume and an attached level detector for determining when the composition in the buffer capacity is below a predetermined level. A set of controllers attached to the level detector control the delivery of components from the plurality of hoppers.

Abstract: A spray booth includes an outer enclosure in which the temperature and humidity of a fluid (such as air) is not controlled and a fluid handling unit within this enclosure, which circulates and controls the temperature and humidity of a smaller volume of the same fluid (air) to develop an environment suitable for application of coatings to desired substrates. In use, fluid is drawn from the outer enclosure into the inner, fluid handling unit in order to clean and modify the temperature and humidity of the fluid being handled, conditioning it to be delivered to the region of limited size which is established for receiving the substrate to be coated.

Abstract: A system for MOCVD fabrication of superconducting and non-superconducting oxide films provides a delivery system for the feeding of metalorganic precursors for multi-component chemical vapor deposition. The delivery system can include multiple cartridges containing tightly packed precursor materials. The contents of each cartridge can be ground at a desired rate and fed together with precursor materials from other cartridges to a vaporization zone and then to a reaction zone within a deposition chamber for thin film deposition.

Abstract: A method of measuring gas component Concentrations of special material gases for semiconductor, and a semiconductor equipment are provided. The method and apparatus can be incorporated in a gas pipe line system in an inline manner, and measure the component and concentration of a gas flowing through a gas pipe line or a gas with which the gas pipe line system is filled, thereby eliminating any erroneous connection. In the method of measuring gas component concentrations of special material gases for semiconductor, as means for attaining the objects, an infrared gas detector is disposed in a gas pipe line between a gas cylinder containing a special material gas for semiconductor and a semiconductor producing section, so that the gas component and concentration are measured in an inline manner. An apparatus for supplying special material gases for semiconductor is also provided.

Abstract: A sensor and a method for determining the basis weight of a coating material containing CaCO.sub.3 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: A method is described of determining a sensitivity parameter of a toner monitor that forms a part of an electrostatographic recording apparatus having a development station that includes a mixture of a toner material in a toner developer composition wherein concentration of the toner material in the composition tends to change with use of the apparatus in making copies or prints. The method comprises providing in the development station a known weight or concentration of toner material as an initial condition of weight or concentration of toner material. The toner monitor generates a first signal representing a first output voltage of the toner monitor for the initial condition of weight or concentration of toner material. The electrostatographic recording apparatus is operated in a recording mode wherein the predetermined weight or concentration of toner material in the development station is reduced by a predetermined amount.

Abstract: In accordance with the present invention a toner concentration and temperature sensing apparatus is provided for use with a developer container adapted to retain a quantity of developer material, the developer material including varying concentrations of magnetic carrier material and toner material. The toner sensing apparatus includes a micro controller device for controlling a sensing head to selectively generate a magnetic field within the developer container according to a first set of parameters stored in the micro controller. A preselected portion of the developer material is compressed by the magnetic field and a signal is generated across the sensing device and determining the resistance thereof. The signal across the sensing device varies as a function of the concentration of the toner. The micro controller converts the observed signal into a toner concentration value based on a second set of stored parameters.

Abstract: An apparatus for controlling the concentration of toner within a developer material of carrier and toner. The apparatus having a magnetic roll for transporting a combination of carrier material and toner particles, a donor roll for transporting toner particles from said magnetic roll to a photoreceptor transfer zone, the magnetic roll and the donor roll each having a voltage applied thereto. A sensor measures the dynamic current between the magnetic roll and the donor roll and generates a signal as a function thereof. The dynamic current between the magnetic roll and the donor roll is a function of the concentration of the toner particles and the carrier material. As a result of the sensor output signal toner particles are added to the developer sump to maintain proper triboelectric properties within the developer unit.

Abstract: An apparatus for processing a layer on a workpiece includes a source of reactant fluid, a reaction chamber having a support for the workpiece and a fluid delivery apparatus for feeding an input fluid into the reaction chamber with the input fluid being utilized to process the material. An infrared sensor is adapted to cooperate with the fluid delivery apparatus for sensing the concentration of a component of the input fluid. The infrared sensor includes an infrared light source positioned to direct a beam of infrared light at an infrared light detector through the input fluid. The infrared light detector produces an electrical output signal indicative of the amount of light received by the detector and therefore not absorbed by the input fluid.

Abstract: An image recording apparatus includes a toner supplying unit for supplying fresh toner to a toner chamber via a toner supplying passage; a toner collecting unit for collecting toner which remains on a photosensitive medium after an image on the photosensitive medium is transferred to a sheet of paper, and for supplying the collected toner to the toner chamber via a toner collecting passage; a toner ratio detecting unit for detecting whether or not a ratio of the collected toner to the fresh toner relating to a quantity of to toner contained in the toner chamber is greater than a maximum allowable ratio; and a toner quantity control for it for allowing the toner supplying unit to supply free toner to the toner chamber when the ratio relating to the quantity of toner contained in the toner chamber is detected to be greater than the maximum allowable ratio.

Abstract: An improvement for a container disposed in a printing machine is disclosed. The container is adapted to dispense toner and capable of maintaining a quantity of toner therein. The improvement includes a sensor for sensing that the quantity of toner in the container is less than or equal to a predetermined quantity. The sensor is located in and isolated from the container by an isolating arrangement, the isolating arrangement preventing forces applied to the container from being transmitted to the sensor. In the preferred embodiment, the isolating arrangement includes a mechanism for damping movement of the sensor with respect to the container to decouple substantially the sensor from the container.

Abstract: Continuous process for recovering the overspray of aqueous coating agents during spray application by collecting it in an aqueous washing liquid which is continuously circulated in a circuit (A) to the spray booth, where the solids concentration of said washing liquid is maintained within the range of 1-1.5 wt.-%, whereby a part of the washing liquid containing overspray is fed to a first ultrafiltration circuit (B) in which the solids concentration of the circulating liquid is maintained within a range of 8-15 wt.-%, a part of the circulating liquid from ultrafiltration circuit (B) being fed to a further ultrafiltration circuit (C) in which the solids concentration of the circulating liquid is maintained approximately constant within a range between 35 wt.

Abstract: In an image forming apparatus, a toner concentration sensor senses the concentration of a toner contained in a developer which is stored in a developing unit. A toner concentration controller controls a toner replenishing member in response to the output of the toner concentration sensor, thereby replenishing the toner from a toner container to the developing unit. Despite that a single toner concentration sensor is located in a position relatively close to a replenishing position, the apparatus insures stable image quality by effecting toner concentration control in harmony with the balance of toner in the entire developing unit.

Abstract: An "L" shaped element having horizontal and vertical sections, is submerged in the liquid toner concentrate such that the horizontal section is totally submerged while the vertical section is submerged proportionally to an amount of the liquid toner concentrate. A voltage source is connected to the "L" shaped element. A second element is placed in close proximity to the horizontal section of the "L" shaped element and is also totally submerged in the liquid toner concentrate. Next, a third element is placed in close proximity to the vertical section of the "L" shaped element. The current flowing from the horizontal section of the "L" shaped element through the liquid toner concentrate to the second element is proportional to the concentration of solid. By measuring the current flowing from the vertical section of the "L" shaped element through the liquid toner concentrate to the third element and dividing by the current in the second plate, the volume of the liquid toner concentrate can easily be calculated.

Abstract: A method for detecting a fluidity of powder includes the steps of: (a) making the powder come into contact with a surface of a piezoelectric element which is parallel with an oscillating direction of the piezoelectric element that generates traverse wave oscillations; (b) detecting electrical characteristics of the piezoelectric element under a condition of resonance; and (c) detecting the fluidity of the powder in accordance with a change in the electrical characteristics with respect to a reference value.

Abstract: An apparatus for controlling thickness of a coated film of paint on a continuously moving sheet member. A paint in a paint pan is picked up through a gap h.sub.PA formed between a pickup roll and an applicator roll, part of the paint is attached to the applicator roll and delivered to a sheet as a supply flow rate q.sub.A. The film thickness coated on the sheet is controlled in accordance with a model equation: M={(q.sub.A -q.sub.L)'.gamma.'C}/LS which has evaluated a difference between the supply flow rate q.sub.A and a leak flow rate q.sub.L not transferred onto the sheet, remaining on the applicator roll and escaping through a gap h.sub.AS (.XI. is the specific gravity of the paint, C the concentration of a solid content of the paint and LS a moving speed of the sheet).

Abstract: A method and apparatus for monitoring and controlling reactant vapors prior to chemical vapor deposition (CVD). The reactant vapors are monitored at full concentration without sampling as they are transported to a CVD reactor. Contaminants detected cause a process controller to switch the transport path to direct reactant vapors to a system pump.

Abstract: A toner monitor which measures the magnetic permeability of the developer mix uses a coil around the toner monitor so that when energized with a DC current, the coil acts as an electromagnet to align the developer mix in a consistent fashion at the monitor. The permeability of the mix is measured and the DC current to the coil is inhibited allows the measured sample to fall away or be moved away from the sensor by mixing augers or paddles. When current to the coil is once again restored, another sample is captured and aligned with the monitor. Information concerning the permeability of the developer mix is used to control replenishment of the toner.

Abstract: A system controls the concentration of toner in developer in an electrophotographic printer. Toner is applied on a test patch on a charge-retentive surface in a manner consistent with a desired toner density on a test patch, and the actual toner density on the test patch is measured. The charge applied to the charge-retentive surface is then adjusted in response to the measured actual toner density to obtain the desired toner density on a subsequent test patch. The change in charge applied to the charge-retentive surface is used to detect a shortage of toner in the developer.

Abstract: Adhesion apparatus for applying a hydrophobic treatment to a semiconductor wafer comprises a tank housing a treating agent of liquid HMDS and a process chamber into which a mixed gas consisting of a vaporized HMDS coming from the tank and a carrier gas is supplied for applying a hydrophobic treatment to a wafer surface. A supporting table on which the wafer is disposed during the hydrophobic treatment is provided within the process chamber. A heater and a cooling water passageway are housed in the supporting table for controlling the wafer temperature. A concentration measuring section for measuring the HMDS concentration in the waste gas is connected to the discharge pipe of the process chamber. The concentration measuring section is connected to a CPU serving to derive a temperature control signal from the measured value of the HMDS concentration. The temperature control signal is transmitted to a temperature control section.

Abstract: A toner concentration detecting circuit detects a toner concentration of a two-component developer composed of toner and a carrier by detecting a change of magnetic permeability of the two-component developer. The detecting circuit is used in a developing device of an image recording apparatus. The toner concentration detecting circuit includes a sensor for sensing a change of a magnetic permeability of the two-component developer, a waveform corrector, a counter connected to a control CPU and a gate signal generating circuit connected to the control CPU so that a gate signal is sent to the counter.

Abstract: The present invention relates to apparatuses and methods for measuring and controlling the amount of multiple coating materials applied to a substrate, and in particular to an apparatus and method for monitoring and regulating the amount of multiple coating materials containing different compositions applied to a substrate, such as paperboard. The coating measurement is insensitive to changes in both the amount of substrate as well as in the amount of an interfering component associated with the substrate.

Abstract: A recirculating coating liquid supply system for continuous delivery of a supply of coating liquid to a coating apparatus includes a holding tank carrying coating liquid mixture, a main feed line having an intake at the holding tank and a discharge at an applicator trough associated with the coating apparatus. A branch of the main feed line discharges into the holding tank. The system also includes a return feed line having an intake at the applicator trough and a discharge at the holding tank. Pumps are associated with both the main feed line and the return line and a viscometer is connected to measure the viscosity of the coating liquid mixture flowing through the main feed line. Viscosity adjustments are made by infusing measured quantities of coating liquid base or coating liquid thinner into the main feed line.

Abstract: In an image forming method using an electrophotographic process, an amount of toner to be supplemented for maintaining a desired image density is estimated in response to input data which are a ratio of reflection densities produced by an optical sensor responsive to a pattern for control and an estimated toner consumption signal. Toner supplement control is executed on the basis of the result of estimation. The method sharply responds to a change in environment due to aging and a change in the kind of documents to thereby insure stable image density, compared to a conventional method relaying on an optical sensor or a toner sensor.

Abstract: A self calibrating system for measuring concentration of a material carried in a fluid medium. The system has a flow cell means for measuring the transmissivity of a fluid medium passing therethrough, a first means for delivering a first fluid containing material carried in fluid medium, and a second means for delivering a clear dispersant fluid.

Abstract: This invention relates to a toner density control method for an image recording apparatus including the steps of: obtaining, as a sensitivity of a toner density sensor, a change amount in output voltage of the sensor with respect to that in control voltage for controlling a strength of the magnetic field generated by the sensor; calculating a ratio of the sensitivity of the sensor to that of a standard toner density sensor, thus obtaining a correction value; discriminating which one of plurality of ranges bounded in accordance with operational results of a value of the output voltage of the standard toner density sensor and the correction value of the output voltage of the sensor belongs to, and changing a replenishing amount of the toner on the basis of a discrimination result, and relates to an apparatus for practicing the method.

Abstract: A developing unit comprises a magnet roller, a stirring roller, a carrying screw, a toner density sensor, and a sensor level adjusting device. When feeding or exhausting the developing powder, the rollers and screw are driven at a slower or faster rotary speed than the speed given when developing an image. After the supply of the developing powder is terminated, the rotary speed of the rollers and the screw is changed to the speed given for developing an image. After a certain time is elapsed, the adjusting device serves to start the level adjustment when the sensor produces a stable output.

Abstract: A toner concentration detecting device for detecting a toner concentration of a two component developer including a differential transformer which is connected with a phase detecting circuit. A variable capacitance diode is connected between the primary coil and the secondary coil and a variable resistor is provided to supply the variable capacitance diode with a DC voltage to vary the capacitance of the diode. The variable resistor and DC voltage are located at a remote location from the transformer.