Abstract: An apparatus (50, 100, 150) for sensing a surface level (20) of fluid (12) includes a generally cylindrical central conductor (16, 102, 152) for connection to a pulse signal source (26) with a reduced diameter end (28, 104, 154) and an opposite end (24, 124, 168); a generally tubular outer conductor (14) concentric with the central conductor for connection to the pulse signal source and having one open end (32) adjacent the central conductor reduced diameter end and an opposite open end (18) adjacent the central conductor opposite end, the central conductor and the outer conductor forming a transmission line for pulse signals generated by the pulse signal source and a cavity (C) between an interior wall surface of the outer conductor and an exterior surface of the central conductor; a non-metallic seal (54) mounted at the outer conductor open end for sealing the cavity, the central conductor reduced diameter end extending through a central aperture (52) formed in the seal; a circuit board (58) for mounting th

Abstract: A device utilizes micropower, impulse radar and time domain reflectometry to determine the dielectric constant of a fluid. An electrically conductive probe preferably in the form of a transmission line, is inserted at least partially into the fluid. The device includes a signal generator that generates an impulse signal that is propagated along the probe. The time that it takes for the signal to reach the end of the probe is determined. The time of travel of the signal along the probe is then used to determine the dielectric constant of the fluid.

Abstract: A method and apparatus (10) for sensing a surface level (24) of fluid (12) in a tank (14) having an electrically conducting pickup tube (20) extending through a wall (16) of the tank (14) and into the fluid (12) includes a time domain reflectometry circuit (40) connected to the tube (20) for generating an incident pulse (68) that travels down the tube (20) and a portion of which is reflected at the surface (24) as a reflected pulse (70, 72) which travels back along the tube (20) and is sensed by the circuit (40). The circuit (40) utilizes the elapsed time between the generation of the incident pulse (68) and the receipt of the reflected pulse to determine the position of the surface (24) relative to a reference point. The robe (20) forms a transmission line with one of a plate (48), an outer tube (110) and a return tube (130).

Abstract: A method and apparatus (10) for sensing a surface level (24) of fluid (12) in a tank (14) having an electrically conducting pickup tube (20) extending through a wall (16) of the tank (14) and into the fluid (12) includes a time domain reflectometry circuit (40) connected to the tube (20) for generating an incident pulse (68) that travels down the tube (20) and a portion of which is reflected at the surface (24) as a reflected pulse (70,72) which travels back along the tube (20) and is sensed by the circuit (40). The circuit (40) includes a microprocessor (92) which utilizes the elapsed time between the generation of the incident pulse (68) and the receipt of the reflected pulse to determine the position of the surface (24) relative to a reference point and the amount of the fluid (12) in the tank (14) and indicate the amount of fluid at a display (106). The tube (20) forms a transmission line with one of a plate (48), an outer tube (110) and a return tube (130).

Abstract: This invention is a lightweight, portable, quickly assembled, wide band, discone antenna for high frequency ground wave communication. The disk portion of the antenna is formed of telescoping spokes and the cone portion is formed of separate retractable wire elements. Disassembled, the antenna can be carried in a backpack. It can be assembled in less than ten minutes to achieve non-fading, non-line-of-sight communication.

Abstract: A toner mass developed control system for use with electronic printers or copiers provides for the measurement of toned photoconductor reflectivity and bare photoconductor reflectivity. The standard control ratio is modified by characterizing the particular sensor unit in use and by taking into account the reflectance from both photoconductor and toner in the toned patch reflectivity measurement. These factors together with a modification for photoconductor reflectance degradation enable accurate control in high optical density development and with highly reflective color toners by altering the control ratio in accordance with these factors.

Abstract: A patch sensing toner concentration control method and apparatus is provided in which the optical density of reproduction output can be changed without changing the quantity of toner that is deposited on the photoconductor's test patch area. The test patch area receives toner as the patch area passes through a developer station under the influence of a patch development electrical field or vector. Light that is reflected from a bare photoconductor area is compared to light that is reflected from a toned test patch area. The ratio of these two reflected light intensities is used to control the addition of toner to the developer station. Optical density of the reproduction output is changed by changing the toner concentration in the developer station. The toner concentration control method and apparatus of the invention is constructed and arranged to require a fixed or constant ratio of light reflection as an indication of proper toner concentration, independent of the absolute value of toner concentration.

Abstract: This describes a vibrating probe for measuring electrostatic surface potential. A multilayered piezoceramic bender element assembly is provided with a multilayered shield surrounding the bender assembly on all sides except for one opening window. The conductive sense element of the bender assembly is located in the window and is positioned near the surface to be measured. The bender assembly includes a conductive layer sandwiched between a drive piezoceramic layer and a feedback piezoceramic layer. The feedback piezoceramic layer is coated (on the side opposite to the inner conductive layer) with the conductive sense element and with a separate conductive area for connection to a drive oscillator. The multilayered shield is comprised of inner and outer conductive layers sandwiching an insulator. A circuit is provided whereby the sensed signal floats on a high voltage signal applied to the conductive layers of the shield.

Abstract: A toner concentration control test cycle in which a developed test area is formed on a photoconductor charged to a dark charge level. The optical reflectivity of the developed test area is sensed and the result used to replenish toner if indicated. During the test cycle, the magnetic brush bias potential is altered to produce development of the test patch in the gray area with the level of dark charge held constant at a predetermined nominal level. An electrostatic probe and associated circuitry are provided to maintain dark charge at the nominal level during the test cycle.

Abstract: Factors affecting copy quality are continuously adjusted during copying in accordance with the actual charge on the photoconductor relative to a fixed reference potential. The photoconductor, carried on a moving, partially exposed, constant potential conductive support, is sensed by a probe. The probe supplies a signal as a function of the potential on portions of the photoconductor and the conductive support passing by the probe. A circuit converts the probe signals into digitized values representing the current photoconductor potential relative to the support. The digitized values adjust copier parameters to compensate for deviations of photoconductor potential from predetermined desired values.

Abstract: A system for checking copy quality variables within the image area of an electrophotographic machine. During a test cycle, quality is checked by producing sample test areas within the photoconductor image area ordinarily used for producing copies. Reflectance measurements are made on the sample test areas and compared to a dynamically floating reference achieved by a reflectance measurement from a cleaned portion within the image area of the photoconductor. The testing circuit is balanced so that the same reflectance voltage should be generated whether the single reflectivity-sensing device is viewing a sample test area or a cleaned reference area. The system checks for quality variables such as toner concentration, image voltage, and an abnormally low reflectance photoconductor and provides a partial check on its own fault-free condition during periods when it is not in use.