Abstract: A method and apparatus for measuring a level of a material in a tank includes providing a stepped frequency microwave signal to an antenna of a transmitter and receiving in the antenna a received signal from a surface of the material at the level to be measured. A measuring signal containing ranging and calibrating signals is processed in even and odd sample sets input to contiguous narrowband filters formed digitally in a processor using DFT and other algorithms to form true in-phase and quadrature outputs. These outputs are combined and further processed using an interpolation algorithm to isolate ranging and calibration frequency components and to accurately measure the distances represented by such components. The calibration distance associated with the calibration frequency component is compared to a known delay line length and any determined error is used to correct the ranging distance associated with the ranging frequency component.

Abstract: An apparatus for fuel level display systems comprises a fuel level sender providing a fuel level signal, a short period filter for filtering the fuel level signal through a short time constant filter, a long period filter for filtering the fuel level signal through a long time constant filter, a signal selector for selecting the long period filter output if the fuel level is above a trip point and for selecting the short period filter if the fuel level is below the trip point, and a display device for displaying a level of fuel in the tank in response to the selected signal.

Abstract: An apparatus and method for measuring the water level at the bottom of a storage tank, the water level being the product-water interface between product and water within the storage tank. The apparatus includes a sensor assembly which is located at the tank bottom. The assembly has a plurality of measurement sensors arranged in a housing having slots for product and water to enter and leave the housing. Each measurement sensor is an open-circuited co-axial transmission line with a probe at its open end which functions as a monopole antenna. In preferred embodiments, the transmission lines are quarter wavelength open-circuited coaxial transmission lines. Each probe is located at a different distance from the tank bottom to cover a measurement range. The transmission lines are excited with signals which are reflected by the probes.

Abstract: A system such as one for detecting when a hydraulic fluid system adapted to a turf care machine, has developed a leak and to warn the machine operator of such a leak before an appreciable amount of hydraulic fluid is allowed to leak from the system. The system includes a reservoir for holding a quantity of hydraulic fluid. The reservoir is connected via a connecting tube or hose to an expansion tank mounted adjacent to the reservoir. The expansion tank includes a fitting having an elongated tube extending down into the expansion tank. The end of this tube is maintained substantially below the level of hydraulic fluid in the expansion tank during operation of the turf care machine to which it is attached. As the machine is operated, the hydraulic fluid expands with rising temperature, and the connecting tube communicates the expanding fluid to the expansion tank. When operation of the machine is discontinued the hydraulic fluid contracts as it cools.

Abstract: A detector for detecting the level of oil in an oil reservoir is disclosed having particular application for use in a lubricating system of a gas turbine engine in order to determine a malfunction of an oil-fuel heat exchanger. The device uses an electrically actuated level sensor within the oil reservoir connected to a first electrical circuit having an outlet junction at which is applied a voltage U.sub.1 which varies with the level of oil in the reservoir, and a second circuit having a second outlet junction at which is applied a voltage U.sub.2 which decreases as the oil level decreases, but which does not increase as the oil level increases. A comparison circuit connected to the outlet junctions of the first and second circuits compares the difference between the voltages U.sub.1 and U.sub.2 to a predetermined reference voltage U.sub.0 and, if the difference exceeds this reference voltage, provides an output signal to actuate a visual indicator.

Abstract: A method and apparatus of determining the fill fraction of a liquid in a spacecraft in weightless space is disclosed. A small motion is introduced about the center of mass of the spacecraft undergoing steady spin and/or thrust, and resulting spacecraft oscillations are sensed. The measured frequency, amplitude and phase of the spacecraft oscillations are compared with counterpart values predicted for possible liquid quantities by a nonempirically computed model of spacecraft dynamics.

Abstract: A method of measuring and indicating a level of natural gas fuel in a storage tank of a motor vehicle, comprising the steps of determining a temperature of the natural gas, determining a pressure of the natural gas, retrieving from a look-up table, responsive to the determined temperature and pressure, a signal representative of a percentage that the tank is full of the natural gas, determining a gauge command responsive to the signal, and driving the gauge according to the determined command.

Abstract: A bottom referencing fuel tank sender assembly has a first bracket and a second bracket which are slidable relative to one another. The second bracket is biased against the floor of the tank and carries the sender assembly. Both brackets are meal pressings, with the guides for guiding the relative movement being formed by the material of the brackets themselves.

Abstract: An ink jet pen supply cartridge having a spring biased ink bag with a visual indication of remaining ink quantity. The spring-bag reservoir tends to collapse laterally as the ink supply decreases due to differential pressure exerted thereto. The spring-bag is contained in a rigid cartridge and a pair of flexible tape members are cemented or welded, one to each side of the spring-bag, and extend generally parallel toward a narrow end surface of the cartridge at which they overlap and can be viewed through a window. The overlapping relationship of the tape members provide ink quantity indicia which change as the spring-bag collapse draws them past each other.

Abstract: A point liquid level monitoring system includes a sensor removeably mounted to a liquid level device. The sensor is designed to direct a microwave signal from a transmitter through a window in the liquid level device. In one embodiment, the microwave signal is reflected off a surface in the device opposite the window and collected by a receiver. In another embodiment, the microwave signal is collected by a receiver mounted onto a second window opposite the first window through which the microwave signal is transmitted. When liquid is present in the liquid level device at or above the level of the transmitter and receiver, the microwave signal is attenuated as it passes through the liquid. Sensor electronics compare the received signal to a predetermined threshold level and provide an output indicating the presence or absence of liquid at the transmitter/receiver level.

Abstract: A circuit apparatus for providing increased apparent resolution in digital signal processing systems includes a comparison circuit receiving an N bit digital input signal and the N most significant bits of an N+M bit output signal. The comparison circuit compares the two signals and provides a control output in response to the comparison. An N+M bit counter increases or decreases a count value which is the output signal in response to the comparison, whereby the output signal has an apparent resolution 2.sup.M better than the resolution of the input signal.

Abstract: A lubrication management system controls the lubricant quantity in multiple refrigeration compressor lubricant sumps. A buoyant member is placed in the lubricant, where a float portion and a magnetically conductive portion rise or fall together. The sensor further includes a displacement transducer producing a variable electrical signal through a resonant frequency shift. The displacement transducer, in proximity with the magnetically conductive portion of the buoyant member, transforms motion of the magnetically conductive portion to changes in resonant frequency shift in proportion to the position of the magnetically conductive element relative the displacement transducer. The system also includes circuitry for receiving the signal and comparing the signal to an adjustable set point, from which the circuitry determines whether an output for signalling a need for additional lubricant is necessary.

Abstract: An apparatus for determining the pressure distribution along a limited distance comprises a plurality of pressure sensors arranged at predetermined distances to each other and connected to an evaluation circuit, the pressure sensors being arranged, in particular embedded, in/at a preferably round rope-type body of elastomeric material, the body being surrounded by a non-elastic, however in radial direction deformable cover in fixed connection thereto. The apparatus may be advantageously used as a filling level indicator in a bin or for various other purposes.

Abstract: An ultrasonic level measuring system includes a transducer mounted on the bottom of a pipe which launches acoustic pulses up through the pipe wall into the water. The pulses are reflected from the water surface and received by the transducer along with pulses reflected by the pipe wall and reverberations within the pipe wall. The system has a monitor mode in which a variable threshold for the reflected pulses is set by dividing the time after a trigger pulse into time bins and automatically establishing a threshold level for each time bin. In a signal search mode, the time bin containing the liquid level is identified from a histogram recording reflected pulses which exceed the threshold levels for the various time bins. In a normal operating mode, foreground calculations precisely calculating the liquid level in the identified bin alternate with background calculations which reassess the identification of the time bin containing the liquid level.

Abstract: A device for monitoring the level of salt in a brine tank. The device includes a housing and a circuit within the housing connectable to an electric power source. An indicator is connectable to the circuit for indicating the existence of a first electrical state and a second electrical state. An actuator member is provided having a first position wherein the indicator member indicates the first electrical state and a second position wherein the indicator member indicates the second electrical condition. A biasing member having a predetermined force biases the actuator member towards the first position. A surface member is provided for resting on the upper surface of the material in the tank, the surface member having a weight greater than the predetermined force of the biasing member and a density greater than water.

Abstract: Two embodiments of a molten metal gauging and control system using a fixed position capacitance sensor and methods therefor are disclosed. The first embodiment discloses a molten metal gauging system, the output of which can be used by various different external control systems to adjust the flow of molten metal appropriately. The second embodiment discloses a molten metal gauging and control system that comprises the molten metal gauging system of the first embodiment in conjunction with a tapered pin positioner system as the element to control the flow of molten metal.

Abstract: A jet level sensor used for controlling the liquid level in a tank such as a fuel tank. The sensor includes a nozzle and receiver supported within a bracket so that the nozzle and receiver and the associated conduits are freely rotatable with respect to the bracket. A manifold is coupled to the receiver for providing a plurality of output pressure signals indicative of the liquid level within the tank. The sensor is connected to a system which includes a main inlet valve and redundant relay valves which are fluid pressure responsive and which shut off responsive to the absence of a pressure signal from the sensor when the liquid within the tank reaches a predetermined desired level. Also provided are shut-off valves connected to be responsive to a tank and nozzle failure over-pressure condition at the inlet or within the tank.

Abstract: A liquid level monitor for sensing the level of liquid in a tank or vessel, typically an automobile radiator, employing a probe with a light emitting diode and phototransistor mounted inside an enclosure, the enclosure having a transparent lens through which light can pass, and the lens having a prism configuration which diffuses or alters stray light which occurs by reflection off an interior core wall of the vessel and prevents the diffused or dispersed light from rendering the phototransistor conductive and possibly leading to a false indication or reading of liquid level. The light emitting diode is electrically excited with a high-intensity, short duration pulse, which improves the sensitivity of the monitor.

Abstract: An add-on liquid overflow shut-off valve for a tank. The device is used to ensure that a holding tank is not overfilled and provides a fail safe way to prevent spillage when pumping into a holding tank. The device provides a warning indicator when the holding tank is near full. The device also has a fail safe switch which will turn off air to a pump when the holding tank is full and also blow a whistle to indicate the tank is full. The device uses a diaphragm which operates on a pressure differential. When the pressure is increase past a spring set point, the diaphragm raises a plate that activates a switching valve which shuts off air supply to an air pump and blows a whistle.

Abstract: An apparatus is provided which includes a reaction cartridge having a plurality of reaction wells having different reagents disposed thereon, at least one well adapted to receive a sample, a well containing particles adapted to bind to the sample and which have the capability of being separated from cells which are not bound to the separation particles and at least one fluorophore adapted to bind to a specific type of cell in the sample, and a wash area adapted for washing a probe. An image forming device is provided to detect images which indicate whether specific reactions have occurred in each of the reaction wells. The apparatus also includes a mechanism for dispensing and aspirating liquids including a mechanism for detecting liquid levels. The device further includes logic for analyzing the information received from the image detection apparatus and processing the information to generate a visual indication of the results of the assays being performed.

Abstract: A sensor assembly is provided for determining the level of liquid, such as fuel, in a tank such as a motor vehicle fuel tank. A mounting bracket has a support end adapted to be supported from the tank and also has a distal connection end. A liquid level sensor has lower and upper ends and a resistor element extending therebetween, and is connected to the connection end of the mounting bracket by a shaft. A torsional spring is disposed around the shaft, and biases the liquid level sensor from a retracted position and toward a deployed position. In the retracted position, the sensor assembly is insertable through an access hole in the tank. In the deployed position, the upper end of the liquid level sensor is disposed generally above the shaft and the resistor element is disposed generally vertically to provide the greatest resolution possible with both linear and angular sweep floats.

Abstract: A liquid level sensor has a liquid sensing element carried on the end of a curved probe which is inserted into a liquid-holding chamber. The probe can be rotated to properly locate the sensor within the chamber. A threaded nut locks the curved probe in position to maintain the sensor in the proper position.

Abstract: A water level measurement system for use with a pressurized power plant boiler comprises a tubular pressure vessel for attachment to one end of the boiler such that the water level in the pressure vessel is the same as in the boiler. The pressure vessel has a central rod-like conductor which together with the vessel forms a coaxial RF waveguide. A pair of spaced reference discontinuities are provided in the conductor above the maximum level of the water, so that an RF pulse injected into the waveguide is reflected successively by both discontinuities and the surface of the water. The level of the water can then be determined independently of changes in the dielectric constant of the vapor above it, from the ratio between the time intervals between the first and second reflected pulses and between the first and third reflected pulses. The conductor is mounted at the top of the pressure vessel by way of a pressure seal and a ceramic insulator.

Abstract: An electronic timepiece having functional hands includes indicating hands for indicating the time such as hours and minutes, a detection unit for detecting the information other than the time and an indicating part for indicating the information detected by the detection unit. The detection unit includes a first functional hand and a second functional hand for indicating mutually relevant information data.

Abstract: A stereolithographic system for automatically generating three-dimensional objects on a layer by layer basis by alternately forming layers of medium over previously formed layers of the object and selectively solidifying successive layers of medium at a surface of a body of the medium whereby the object is formed from a plurality of solidified and adhered layers. The surface of the body of medium is maintained at a desired working surface, for example by detecting its level and relatively adjusting it and the working surface so that they coincide.

Abstract: A device is disclosed to measure the level of material within containers, in particular containers in which free-flowing materials having different dielectric constants, for example water and oil, are collected. The device includes a sensor, which is arranged electrically nonconductively fashion on an outer side of the container and forms part of an electric capacitor, and an electrically conducting complementary plate, which is arranged on the inside of container opposite the sensor and spaced therefrom, which, forms another part of an electric capacitor.

Abstract: A small-sized electronic device with depth gauge includes a pressure sensor for measuring a present water pressure and outputting a pressure value. A memory stores the pressure data. A dive time measuring circuit measures a dive time interval. A mean depth calculator receives the pressure data and dive time interval and in response thereto outputs a mean depth value which is displayed on the device.

Abstract: A liquid level sensor system for a tank includes a stillwell having a transducer assembly positioned in the bottom of the stillwell. A guide conduit surrounds a flexible plastic coated wire bus which extends through a sidewall of the tank and which connects the transducer assembly to an indicator assembly located outside the tank. The conduit includes an end cap which secures the wire bus within the conduit. Installation and removal of the transducer assembly and wire bus is accomplished at a location outside the tank by removing the end cap and pulling or pushing the transducer assembly through the conduit by means of the wire bus.

Abstract: A system (10) and methods of use for determining the level of a body of liquid (16), e.g., a chemical, in a storage tank, irrespective of the specific gravity of that liquid. The system (10) comprises a pressure transducer (22) and an elongated tubular, flexible sheath (24). An operating liquid (26) of lower specific gravity than the body of liquid (16) is disposed within the sheath (24). The transducer (22) is also disposed within the sheath adjacent the bottom end. The sheath (24) is immersed in the body of liquid (16) so that its top end (28) is above the liquid's surface. The pressure applied to the sheath (24) by the liquid (16) causes the sheath to collapse to a minimal internal cross sectional area, whereupon the operating liquid migrates up the sheath to form a very thin column (44). The operating liquid forming a pool (46) is located at the top of the very thin column (44). Thus, the sheath expands outward adjacent the surface (16A) of the body of liquid to retain that pool.

Abstract: A liquid level sensor for detecting a level of an electrolyte where: a pair of resistance films are formed on an insulating substrate: a plurality of electrodes are intermittently mounted on the resistance films in the longitudinal direction; the resistance films are soaked in the electrolyte in the vertical direction along the longitudinal direction; the liquid surface is detected from the variation of the resistance value of the resistance films caused by the short-circuiting of pairs of the electrodes in the electrolyte. The exposed surface of the resistance film is covered by a moisture-resistance film. The result is that undesirable change of resistance value of the resistance film caused by being moistened can be reliably prevented.

Abstract: A method and apparatus determines a quantity of liquid in a tank when at least one liquid sensor is inoperative. In a first embodiment, a plurality of tables are stored in memory which are grouped by identities of the possible inoperative sensor or sensors. One group of tables is selected based on the identified inoperative sensor or sensors. Then, that one group of tables is accessed, and the quantity of liquid in the tank is calculated based on the readings of the operative sensors. In a second embodiment, a first plurality of tables stores quantity readings for each sensor as if all sensors are operable. A second plurality of tables includes one table for each possible configuration of inoperative sensor or sensors. When the inoperative sensor or sensors are identified, one particular table in the second plurality is accessed and a quantity amount is then added to the liquid quantities determined from the first plurality of tables to provide a total liquid quantity in the tank.

Abstract: A storage installation capable of storing a variety of materials includes a shielded level sensing device disposed entirely externally of the container. The sensing device includes an elongated strip of metal which is associated with shielding circuitry for electrostatic protection of the strip. The sensing metal strip serves as a capacitor component in an oscillator circuit which is arranged so that the electrostatic field emanating from the sensing strip will change oscillator amplitude in proportion to the level to be sensed of material in the container. Detected changes in amplitude of the oscillator circuit produce a DC level proportional to the level of the oscillator amplitude, which in turn may be processed to indicate the level of material within the storage container.

Abstract: According to this process: the position in respect of height of the "molten metal (2)/liquid slag (3)" interface (M) is continuously determined. Further the position of an isotherm (IS) located at the "liquid slag (3)/powder layer (4)" interface is continuously determined by automatically controlling the position of a thermocouple (8) on this isotherm and by measuring the displacements of this thermocouple.By comparing the position in respect of height of the molten metal/liquid slag interface (M) with the position in respect of height of the isotherm (IS), the thickness and thus the variations in thickness of the liquid slag are continuously deduced.

Abstract: An electrode for level detection includes a detection electrode including conductor portions and resistor portions arranged and formed one after the other in a level change direction. An insulating coating layer is formed on either each conductor portion or each resistor portion. The insulating coating layer may be of a film having a property to repel a liquid to be measured.

Abstract: An activating mechanism is disclosed for an indicator. The mechanism includes a mounting bracket which may be connected to a container. A force transmitting member is slidably received by the bracket and extends through the container wall. The actuator is collapsible to be slid through an opening formed in the container wall. Through lever action, the actuator engages and moves the force transmitting member.

Abstract: Method and apparatus for monitoring the water level in the ground in which a casing hole is formed in the ground by driving a solid rod into the ground which compresses the ground material to form a compacted but porous wall for the casing hole. The rigid rod is withdrawn and a perforated tubular member of lesser diameter than the inner diameter of the casing hole is inserted into the casing. The water level rises within the tubular member and a dip-stick is inserted into the top of the tubular member to measure the water level. The dip-stick or the tubular member has a stop to limit the insertion distance of the dip-stick.

Abstract: A self-contained, submerged aparatus for monitoring the height of a liquid in a wetwell includes a tube defining an upright conduit, a first chamber at the bottom of the conduit and communicating with it, a second chamber adjacent the first chamber and separated from it by a first impervious non-rigid membrane, the second chamber being defined in part by a second impervious non-rigid membrane in contact with the liquid in the wetwell. The second chamber contains a first liquid to which the membranes are inert, and the first chamber contains a second liquid to which the first membrane is inert. Pressure from the liquid in the wetwell exerted against the first membrane is transmitted to the second membrane and causes the second liquid to rise in the tube. The top of the tube is vented to the atmosphere, and a plurality of electrical terminals disposed at spaced locations lengthwise of the tube are provided for producing a signal which is a function of the height of the second liquid in the conduit.

Abstract: An isolation fluid control device and water cup for use in an automated, random-access, isolation fluid-based, analytical instrument. The cup, in operation, contains two immiscible liquids. The cup is provided with inlets and outlets, and additionally comprises a liquid level control structure and structure operable to permit passage of one liquid therethrough to the substantial exclusion of the other liquid.

Abstract: A method for contactless measuring the values of magnitudes which relate to an electrically conductive material in solid or liquid form, for instance such magnitudes as the distance of the conductive material from a given point, linear dimension(s) of a body that incorporates such material, the electrical conductivity value of the material, and the temperature of the material. In accordance with the method, an electromagnetic field, generated with the aid of a constant current which flows through at least one field generating coil, is caused to penetrate at least partially into the material. The supply of current to the at least one coil is discontinued subsequent to the magnetic field having penetrated the electrically conductive material to an extent sufficient for the intended magnitude to be measured.

Abstract: A method and an apparatus for determining the thickness of a layer of a first liquid above an interface formed by the first liquid and the second liquid underlying the first liquid in a subterranean formation. The apparatus includes an elongated metal rod having a sharpened distal end. An electrode is provided adjacent the sharpened distal end to indicate when the interface formed by the two liquids has been reached. A lengthwise running elongated slot is provided in the outer surface of the body of the metal rod and contains an indicator strip. The indicator strip is adapted to undergo a color change upon contact with the first liquid. By measuring the length of the indicator strip which has undergone a color change, the thickness of the layer of the first liquid can be determined.

Abstract: An apparatus and method for determining the level of material within a rotating cylindrical vessel are disclosed in which a rigid member means on the interior of the rotating vessel is fixedly secured to a rod having a longitudinal axis parallel to the rotational axis of the rotating vessel, and wherein the rod extends through one end wall of the vessle to the exterior at which it is fixedly secured to an indicator means. The rigid member means within the vessel is capable of resting at the top surface of the material within the vessel. As the level of material within the vessel is raised or lowered the rigid member means will rotate, thus causing an equal rotation of the rod and the indicator means on the exterior of the vessel. By monitoring the position of the indicator means, the level of material within the vessel can be determined.

Abstract: A level indicator for blood reservoirs, in particular of medical apparatus, having a level-responsive component to be provided on the wall of the blood reservoir is provided with an oscillator set to an operating frequency of greater than or equal to 50 MHz and having integrated into its circuit the level-responsive component which, when a preset limiting value is passed, changes the phase condition or amplitude condition decisive for the oscillation of the oscillator.

Abstract: A radar probe including several individual scanning antennas is mounted in the wall of the furnace above the loading surface and performs a two-dimensional scanning of the entire loading surface.

Abstract: A device for measuring displacement comprises a pair of sensor elements of which output voltage changes stepwise in dependency upon displacement of a measurement object, a differentiating circuit for detecting time points at which the output voltage of the pair of sensor elements suddenly changes, and a counter for counting the sudden change time points of the output voltage detected by the differentiating curcuit.

Abstract: A small electronic device having a depth gauge is provided. An electronic device includes a pressure sensor which produces a signal corresponding to a depth. A first memory stores decompression data while a second memory stores residual nitrogen time. The first counter counts a dive time while a second counter counts a surface interval time. A calculating circuit calculates non-decompression time limits based upon the depth information and decompression data. A decompression management circuit determines when the decompression time limit has exceed and calculates the decompression dot profile and output decompression dive data. A second calculating circuit calculates repetitive dive non-decompression time limits based upon the previous the dive depth, dive time interval surface time interval and the residual nitrogen time. The control circuit receives each bit of information and causes a displayed display information either simultaneously or independently.

Abstract: The level of the surface of a bath of molten metal beneath a fluid layer of slag in a metallurgical vessel is measured by a detector which is moved through the slag layer into the metal bath and then withdrawn. To improve accuracy and to avoid the need for a separate measurement the detector used comprises an oxygen concentration sensor which emits signals indicating the boundary between the molten metal and the slag, whereby the height of said boundary is determined.

Abstract: A capacitive sensor is described having an element which traverses the outside of a container of liquid to ascertain the vertical locations of liquid interfaces in the container. The sensor uses an oscillator whose amplitude or phase is a function of the capacitance of the element.

Abstract: A storage installation which is capable of storing a variety of materials, both conductive and non-conductive, includes a level sensing device disposed entirely externally of the container for the material such as to the exterior of the walls thereof. The sensing device includes an elongated strip of metal preferably copper or brass cut to the length of the container when arranged in a vertical direction therefor and applied to the exterior of the container by suitable adhesive material. The sensing element serves as a capacitor component in an oscillator circuit which is arranged whereby the electrostatic field emanating from the sensing strip will change the oscillator amplitude proportional to the level of the material in the container. The detected changes in amplitude in the oscillator circuit will produce a DC level proportional to the level of the oscillator amplitude. The DC level in turn will be processed by a remote indicator circuit to drive a readout meter, bar graph or digital unit.

Abstract: The castable fish/depth finder has a display unit, rod and reel, transducer and conductors establishing electrical continuity from the display unit to the rod and reel, and therefrom to the transducer. The conductor from the rod and reel to the transducer additionally functions as mechanical means for conventional casting by an onshore fisherman of the transducer to a particular section of a body of water. The presence of fish in such particular section and the water depth is ascertained and indicia therefor is displayed on a screen of the display unit.

Abstract: A device is provided for detecting the ullage level and flow in a vessel by detecting the presence of a solid or liquid material in proximity to a microwave detector. The device may be mounted to the side of the vessel or suspended inside the vessel so as to bring the microwave sensor into proximity with the surface of the contents of the vessel. A microwave bridge circuit may be used to detect a change in either the amplitude or phase of a signal reflected by the material within the vessel compared to a reference signal tuned to either the presence or absence of the anticipated solid or liquid material. In one embodiment, the reflected material signal is compared to the signal from a sample chamber containing the material to be detected. The device can reliably detect the level of multiple interfaces for various materials having distinct electric or magnetic properties.