Abstract: A portable fuel storage tank leak detection system for detecting fuel leaks from a fuel storage tank at a leak rate of 0.1 gallons per hour. The leak detection system provides for a probability of detection of at least 95% and a probability of false alarm of no more than 5%.

Abstract: A method is provided for determining and controlling feed water level in a steam generator of a nuclear power plant, whereby the water level sensor is calibrated in terms of the pressure drop across structural components in the feed water path. The water level differential pressure sensor is calibrated so that maximum water level is indicated as the level corresponding to the upper tap level plus the pressure drop across the foregoing structural components at maximum power plant power.

Abstract: An enclosure for handling hazardous material includes a sealable housing which is configured with a first air inlet connected to a bubble gauge and a second air inlet disposed inside the housing for air evacuation from the housing is connected to a pump for maintaining subatmospheric pressure in the enclosure and for drawing a stream of air inwardly through the first air inlet via the bubble gauge into the housing and out the second air inlet. A filter interposed in the stream of air leading to the second inlet. At least one glove port is formed in the housing and has a flexible relatively gas impermeable glove connected thereto. An air exchange port in the housing is operably connected to a sealed bellows which provides for changes in air volume within the enclosure which occurs from moving the glove within the enclosure under subatmospheric pressure.

Abstract: A spring assembly and an apparatus incorporating the same. The spring assembly includes a base block configured to be rigidly fixed to a frame. A pair of nominally identical spring rods is cantilevered from the base block in a first direction. Each rod has a length, a proximal end rigidly fixed to the base and a free distal end. The distal ends are configured to engage a linkage member to resist movement of the linkage member by axial deflection of said rods away from the first direction. The spring rods are each preferably characterized as substantially cylindrical in shape and formed from steel or other suitable spring material. A fulcrum preferably provides support to an intermediary portion of the spring assembly to adjust the spring force range. The spring assembly is preferably utilized in a liquid level indicator to indicate a height of a column of liquid in a vessel.

Abstract: A sensor for measuring properties of a fluid in a vessel, includes a sensor mount adapted to mount within a wall of a vessel; a sensor body extending substantially vertically from the sensor mount; and a plurality of sensors spaced vertically along the sensor body, whereby at least one of level, density, temperature and pressure of fluid in the vessel can be measured.

Abstract: Disclosed is a fluid level gauge for sensing the level of fluid in a dispenser. The level gauge includes an inlet port communicating with the fluid and a check valve in communication with the inlet port. The check valve includes a membrane which allows air to pass. The level gauge further includes a pressure sensor in fluid communication with the check valve. The fluid level gauge may be used in connection with a beverage dispenser.

Abstract: Method, system and program product are provided for monitoring coolant within a cooling system designed to provide system coolant to one or more electronics subsystems. The monitoring technique includes employing at least one pressure transducer to obtain multiple pressure measurements related to an amount of coolant within an expansion tank of the cooling system, and determining a rate of volume change of coolant within the expansion tank employing the multiple pressure measurements. Successive pressure measurements can be taken at a known time interval to determine the rate of volume change of coolant within the expansion tank. An automatic determination can also be made on the immediacy of action to be taken for service of the cooling system based on the rate of volume change of coolant within the expansion tank.

Abstract: The present invention comprises a novel level switch which may be employed to detect liquid levels within a process vessel. The level switch of the present invention is self validating so that manual testing is not required in order to ensure proper operation and switch calibration. The switch of the present invention may be easily introduced into existing process vessel designs as a replacement for prior art level detection switches with minimal or no retrofitting effort being required. The self validating level switch of the present invention may be connected to a Safety Instrumented System (SIS) such that process control including process shutdowns to avoid overfilling and low-fluid conditions may be accomplished.

Abstract: The invention relates to a method for determining the current filling level of a liquid, preferably a calibrating, quality control, or cleaning fluid, or waste water, in a container, for example of an analyzer, where an immersion pipe is dipped into the liquid in the container to be filled or drained. The immersion pipe is connected to a pumping device via a tube system. The pressure p in the tube system is measured and increased, starting from the ambient pressure p0, until a first discontinuous pressure change occurs at pressure p1 due to the liquid column in the immersion pipe being forced out of the pipe, and/or the pressure p in the tube system is decreased until the liquid column in the immersion pipe reaches a change in cross-section of the immersion pipe, which change is situated above the maximum filling level of the liquid, such that a second discontinuous pressure change occurs at pressure p2 due to the liquid column reaching the change in cross-section.

Abstract: The present liquid depth sensing system with its liquid identification capability provides an economical device which may be installed in a multitude of different applications to perform multiple quantity measurement and detection functions. The present system includes a miniaturized piezoelectric pneumatic pump, sized and adjusted to produce a consistent stream of bubbles from the outlet end of the dip tube in the purge system of the present invention. The small variations in pneumatic pressure in the system due to the cycling of each bubble working through the surface tension and viscosity of the liquid as the bubble leaves the outlet end of the tube are detected and converted to a voltage signal which is used to identify the liquid at the outlet end of the tube. The present system is extremely valuable for identifying contaminants in the tank, as well as for measuring the liquid quantity in the tank.

Abstract: An apparatus and method for monitoring a liquid level in a 4-20 mA closed loop system are provided. A process instrument and a measuring unit are powered for a predetermined time and power is provided by a battery.

Abstract: A dual-phase level monitoring (DPLM) instrument that provides continuous signals that enables determination of the location of the top surface of the lighter of two immiscible fluids (the product) and the hydrostatic pressure below the total fluid column of both immiscible fluids. By knowing the fluid specific gravities, the output signals are processed to yield the location of the air/product and liquid/liquid interfaces, and the depth of the lighter phase. The instrument is intended for use in groundwater monitoring wells with a light non-aqueous phase liquid (product) and tanks or vessels with dual-phase liquids and level monitoring and/or control issues. The DPLM instrument includes a first pressure transducer situated beneath the surface of the liquid with a greater specific gravity, which will typically be ground water. A level element with a float selected so as to be buoyant and float on the surface of the lighter fluid is positioned above the first pressure transducer.

Abstract: According to an exemplary embodiment, the present technique relates to a fuel sensor for determining operational fuel level (hnew) in a fuel tank (14). In the exemplary embodiment, an isolated airspace (44) is created. By monitoring the pressure conditions in the isolated airspace 44 as well as the pressure and temperature conditions in the remainder (42) of the tank (14), the operational fuel level (hnew) may be determined.

Abstract: An apparatus which indicates a level of a column of liquid in a storage vessel. A liquid level input assembly comprises flexible first and second sealing members which cooperate to form an enclosed chamber therebetween. The column of liquid applies a hydrostatic input force upon the first sealing member. The input force is translated through the first and second sealing members to a liquid measurement assembly to provide an indication of the height of the column. A leak indicating member is coupled to the enclosed chamber to indicate the presence of leaked liquid from the column through the first sealing member. Preferably, the first sealing member comprises a substantially planar diaphragm. The second sealing member also preferably comprises a substantially planar diaphragm, or alternatively preferably comprises a sealing ring. The liquid level input assembly can accommodate pressurized vessels and vessels that are vented to the surrounding atmosphere.

Abstract: A liquid level control system including a tank; a source of liquid in communication with the tank; a pressure fluid actuated valve for controlling the flow of liquid to the tank from the source; a pressure sensor disposed in the tank to monitor the hydrostatic pressure determined by the quantity of liquid in the tank. A source of pressure fluid is provided which is normally vented to the atmosphere. A pressure fluid amplifier is coupled to the pressure fluid actuated valve and to the source of pressure fluid. When the pressure sensor sensed an increase of pressure caused by an increase in the liquid level in the tank, the pressure fluid amplifier is effective to actuate the valve to close and militate against flowing into the tank to maintain the liquid at a predetermined level.

Abstract: A dedicated liquid level detection method having a sensor positioned into the casing of a groundwater well. The detector is in the form of an elongated thin film sensor tape that extends along the fill length of the well casing which detects the level, thickness and volume of both groundwater and any light or dense non-aqueous phase liquid that may be present. This is accomplished through the use of a conductive and hydrostatic resistive circuit measuring the level of liquids in a groundwater well at one hundredths of foot resolution or greater. Once the elongated sensor is installed, liquid levels can be gauged from the surface. The data is stored using a battery operated hand held digital display temporarily connected at the top well section casing. Since a sensor probe is not lowered into the well, cross contamination between wells is eliminated.

Abstract: A system and method for method for measuring the vertical level of fluid in a container is provided. According to one aspect of the invention, a method for measuring the vertical level of fluid in a container includes moving air downward along the inside of a bubble tube at an angle of about 5 degrees to about 85 degrees from vertical into the fluid. According to another aspect, the method includes injecting a mixture of air and steam into fluid in a container via a bubble tube. Aspects of the present invention further provide a differential pressure bubbler system that includes a bubble tube mounted to a tank at an angle of about 5 degrees to 90 degrees. Aspects additionally provide a bubble tube having a diameter of about 1 inch to about 6 inches. Further aspects include a bubble tube having pressurized air and steam inputs.

Abstract: The depth of a cryogenic liquid in a Dewar may be ascertained by inserting a measurement probe into the container. The measurement probe includes a hollow tube having a proximal end and an open distal end, a heater operationally connected within the tube and positioned substantially adjacent the distal end, a pressure sensor operationally connected within the tube and positioned substantially adjacent the proximal end, and a microcontroller in electric communication with the heater and with the pressure sensor. The distal end of the measurement probe is placed against the bottom of the container, liquid from the container enters the tube, and is evaporated by the heater. The gas pressure in the tube between the heater and the pressure sensor is increased, until the gas pressure in the tube is equal to the pressure exerted by the liquid in the Dewar.

Abstract: Apparatus and method for measuring the volume of a liquid in a fuel tank in a vehicle subject to varying external forces caused by movement or changes in the roll and pitch angles of the vehicle wherein the tank is mounted to the vehicle and subject to forces along the yaw axis of the vehicle. One or more tank load cells provides an output proportionally representing the load thereon. The load cells are placed between a portion of the tank and a portion of a reference surface of the vehicle and are sensitive along an axis that is substantially normal to the mounting surface and generally parallel to the yaw axis of the vehicle. A processor executes a derived relationship between the load cell output and the volume of fuel in the tank so as to convert the output signal from the load cell into output information representative of the volume of the fuel in the tank.

Abstract: A fuel pump module is liquid-tightly mounted in an opening of a vehicle fuel tank. The fuel pump module includes a residual fuel detector provided near the fuel tank. The residual fuel detector includes a diaphragm having a first diaphragm for receiving fuel pressure Pg by a head and atmospheric pressure Po, and a diaphragm portion for receiving atmospheric pressure Po and internal pressure Pi. The residual fuel detector detects the amount of fuel remaining in the fuel tank on the basis of these kinds of pressure Po, Pg and Pi. At the same time, the residual fuel detector detects the in-tank pressure Pt of the fuel tank on the basis of Po and Pi.

Abstract: Apparatus and method for correctly detecting the level of a processing liquid such as HPM in a processing tank in the event that any drift occurs in a detector is disclosed. A liquid level detecting apparatus (70) comprises a pressure sensor (73) operable to generate an output signal S0 which is maintained at a constant signal level until the level of HPM reaches a predetermined position M in the tank and rises in the signal level as the liquid level rises in the tank after reaching the predetermined position M, a determination circuit (93) for determining whether the liquid level reaches the predetermined position M and a liquid level detecting circuit (94) for detecting the liquid level. The output signal S0 from the pressure sensor is input to an amplifier (92). The liquid level detecting circuit (94) comprises a low-pass filter (97) which receives the amplified signal and generates an output pressure signal S4.

Abstract: A liquid-level measuring device measures the liquid level in a tank. This invention measures liquid level by measuring the pressure at the bottom of the tank. A pressure sensor is placed in the top sealed end of a pipe extending from above the top of the tank down to and open into the bottom of the tank. When the tank is empty the pressure is zero (relative to atmospheric pressure). As the liquid level of the tank rises from empty to full, the pressure rises according to the weight of the liquid. An electronic pressure sensor is used to measure the pressure. The output of the pressure sensor is amplified and sent to an operator display device.

Abstract: A water depth measuring method comprises steps of making a bundle of reference water column pressure measuring tubes of a U character form of the number of n≧2 at a same length with a water depth measuring tube in order to compensate for a total error of a water depth measurement; filling an amount of water into the reference water column pressure measuring tubes to form water columns therein; measuring the water pressure in the reference water column pressure measuring tube by a pressure transducer before measuring a water depth; subtracting previously known water column pressure values derived from the measured water pressure values to calculate total error values; calculating a total error based on the total error values, in which the total error was generated upon measuring of the bubble generating pressure in the water column pressure measuring tubes; subtracting the total error from the bubble generating pressure, dividing the calculated water column pressures by the water column pressure in the refe

Abstract: An apparatus and method for monitoring a liquid level in a 4-20 mA closed loop system are provided. A process instrument and a measuring unit are powered for a predetermined time and power is provided by a battery.

Abstract: A liquid level and weight sensor utilizes a pressure sensor of any type positioned at the base of the liquid or weight. A second pressure sensor is positioned external to the liquid or weight to measure the ambient pressure. Ambient pressure is subtracted from the total pressure indicated by the base positioned pressure sensor to determine the actual pressure exerted by the liquid or weight on the base positioned sensor. The actual pressure is then utilized in the calculation of liquid level or weight. The determination of liquid level requires that both the pressure and density of the liquid be known. When the density of the liquid is not known, a third pressure sensor is inserted in the tank at a known level above the first. The differential pressure and differential level are determinative of the liquid's density.

Abstract: An ALC circuit is turned on (S1), a nozzle is shifted to a sampling position (S2), and after the ALC circuit has been turned off (S3), the nozzle is allowed to start discharging air from its tip (S4). While the nozzle is being lowered, the inner pressure of the nozzle is monitored (S5, S6), and upon detection of an increase in the pressure, the discharging process of air and the nozzle lowering process are stopped (S7), while the monitoring of the magnitude of the pressure is continued (S8). When the magnitude of the pressure is being maintained within a permissible range of the change for a predetermined time, it is judged that the tip of the nozzle has come into contact with the true liquid level, and after a suction operation of a sample (S9), the nozzle is raised (S10).

Abstract: A self-regulating bubble tube assembly is used for determining the hydrostatic pressure exerted by fluids, such as drilling mud. The bubble tube assembly can be used to determine fluid level based upon said hydrostatic pressure and when bubble tubes are used in pairs can be used to determine a pressure differential that will indicate the density of the fluid. The bubble tube assembly comprises a flow of air directed through a diaphragm type pressure regulator. The pressure regulator output is connected to the bubble tube, which is partially submerged in the fluid, through a precision, in-line, flow limiting orifice. A feedback line from the bubble tube runs to one side of the diaphragm of the pressure regulator where the back pressure from the tube will regulate the output pressure from the regulator to maintain a pre-selected constant rate of air flow through the bubble tube.

Abstract: The present invention is a liquid depth sensing system utilizing the bubble tube or purge operating principle. In this system, a pneumatic tube extends downwardly into the liquid, and air (or other gas) passes through the tube to bubble from the lower end thereof. The air or gas pressure within the tube is equal to the head pressure of the liquid, thus allowing the liquid depth to be determined by measuring the air or gas pressure. Prior art systems are relatively bulky, maintenance prone, and require relatively high energy input due to the constant operation of the relatively large pneumatic pump motor and its high output pressure required due to the electromechanical pressure regulator installed downstream of the pneumatic pump. The present invention overcomes these deficiencies by using the pneumatic pump motor as the regulating device, by operating the motor only as required to produce only sufficient pressure for measuring the liquid depth.

Abstract: An improved pressure activated control apparatus is provided for sensing fluid pressure and triggering one or more switches in response to the fluid pressure, as desired. The apparatus is designed to be placed within a fluid of a reservoir. The apparatus includes a first resilient member, such as a pliable rolling diaphragm or bellofram, having an outer surface exposed to the fluid and responsive to the fluid pressure. The pressure activated control apparatus includes a second resilient member, such as a spring with a chosen spring constant, k, that provides a biasing force against the diaphragm that is opposite the fluid pressure. A transducer is operative to monitor changes in pressure of gases within the apparatus causes by movement of the diaphragm. A controller is responsive to the transducer and selectable fluid level thresholds to activate pumps and/or valves for adjusting the level of the fluid in the reservoir.

Abstract: A water depth measuring method comprises steps of making a bundle of reference water column pressure measuring tubes of a U character form of the number of n≧2 at a same length with a water depth measuring tube in order to compensate for a total error &Sgr;&Dgr;x of a water depth measurement; filling an amount of water into the reference water column pressure measuring tubes to form water columns ho1, ho2, . . .

Abstract: The present invention relates to a pressure housing for in-water pressure based systems and to a method for improving the life of the transducers and electronics of underwater systems by maintaining a humidity-free and clean environment around them by avoiding the entry of humidity, dust, or any suspended particles in the air during occasional data offloading and battery replacement in a humid and dust-laden field station; improving the ease of closing and opening of the pressure housing by the use of a novel arrangement thereby avoiding the use of conventionally employed cumbersome protruding and corrosion-prone locking devices such as screws, bolts, or clamps; and implementing reliable transmission of water pressure to the pressure port of the transducer, simultaneously minimizing the errors arising from dynamic pressure effects, preventing its chemical corrosion from saline water, and arresting bio-fouling in the vicinity of the pressure inlet.

Abstract: A measuring apparatus for measuring the volume of a contained fluid includes an exposure chamber adapted for exposure to head volume of a volume of the contained fluid. A displacement mechanism is connected to the exposure chamber such that the displacement mechanism is displaced in proportion to the amount of head volume in the contained fluid acting on the exposure chamber. A read mechanism is connected to the displacement mechanism. The read mechanism generates a signal corresponding to the amount of displacement of the displacement mechanism.

Abstract: A liquid level sensor 18 has sensor probes 20a to 21b, and a monitor unit 23. The monitor unit 23 has a probe potential difference detecting section 25 for detecting the output potential difference between sensor probes 20a, 20b, and the output potential difference between sensor probes 21a, 21b; and a liquid level determining section 26 for determining the level of the liquid from the result of detection. The monitor unit 23 has a bubbling detection pulse generator section 28 for detecting an occurrence of bubbling of a bubbling gas from the result of detection by the probe potential difference detecting section 25 and generating a pulse signal, and a pulse counter 29 for counting the number of pulses generated by the bubbling detection pulse generator section 28, thereby making it possible to grasp the number of bubbling periods of the bubbling gas.

Abstract: A method for determining the depth (DL) of a fluid contact level between a first fluid (F1), such as water, and a second fluid (F2), such as crude oil or natural gas, within the pores of an oil and/or gas bearing formation surrounding a borehole comprises measuring the phase pressure PF1 and PF2 of said pore fluids using a pressure probe assembly which is lowered to a depth (DP) above the depth of said contact level (DL) and determining the depth of said interface on the basis of the equation: D P - D L = P F1 - P F2 g ⁡ ( ρ F1 - ρ F2 )

Abstract: A system for monitoring the presence of deposits or buildup on the inside wall of a fluid-containing pipe comprises a pair of acoustic transmitters outside of the pipe and spaced apart along the length of the pipe and capable of transmitting an acoustic signal into the pipe wall, a pair of acoustic receivers outside of the pipe and spaced apart along the length of the pipe and capable of receiving an acoustic signal from the pipe wall, and a power source for causing the transmitters to transmit a signal.

Abstract: A liquid level and weight sensor utilizes a pressure sensor of any type positioned at the base of the liquid or weight. A second pressure sensor is positioned external to the liquid or weight to measure the ambient pressure. Ambient pressure is subtracted from the total pressure indicated by the base positioned pressure sensor to determine the actual pressure exerted by the liquid or weight on the base positioned sensor. The actual pressure is then utilized in the calculation of liquid level or weight.

Abstract: A system for indicating an amount of a process liquid contained within an interior of an ampoule. A first conduit is in selective fluid communication with the interior of the ampoule, and has a first opening configured for disposal below an upper surface of the process liquid. The first conduit introduces a carrier gas into the interior of the ampoule. A second conduit is also in selective fluid communication with the interior of the ampoule, and has a second opening configured for disposal above the upper surface of the process liquid. The second conduit receives the carrier gas from the interior of the ampoule. A pressure differential sensor is disposed between and is in selective fluid communication with the first conduit and the second conduit. The pressure differential sensor senses a pressure differential between the first conduit and the second conduit.

Abstract: The present invention is a liquid depth sensing system utilizing the bubble tube or purge operating principle. In this system, a pneumatic tube extends downwardly into the liquid, and air (or other gas) passes through the tube to bubble from the lower end thereof. The air or gas pressure within the tube is equal to the head pressure of the liquid, thus allowing the liquid depth to be determined by measuring the air or gas pressure. The present system may be applied to either open or closed liquid containers (e. g., fuel quantity indication), and may be adapted for use in the bottling industry.

Abstract: A well water level sensing apparatus using a pressurized air column in contact with the water at its distal end to derive a correlated value dependent upon the length of the air column which is converted for retrieving stored water levels from memory and displaying the retrieved water levels on a visual display. The water level sensing apparatus may be manually initiated or programmatically controlled for continual monitoring.

Abstract: Upward variations of a molten metal level in a container for melting metallic material shall be carried out by detecting variations of a liquid level inside a detector connected to a gas-pipeline, wherein a rise in the pipeline pressure causes the liquid level to move down. Communication is established by means of a gas-pipeline 13 for inert gas between that portion of a container for melting metallic material which is above a molten metal surface 15a and that portion of a detector 16 comprising a transparent tubular container 18 which is above a liquid surface 17a. Variations of the liquid level 17a inside the detector 16 due to a rise in the pressure inside the above-mentioned gas-pipeline 13 are detected as upward variations of the level of the molten metal surface.

Abstract: A well water level sensing apparatus using a pressurized air column in contact with the water at its distal end to derive a correlated value dependent upon the length of the air column which is converted for retrieving stored water levels from memory and displaying the retrieved water levels on a visual display. The water level sensing apparatus may be manually initiated or programmatically controlled for continual monitoring.

Abstract: A liquid level sensor 18 has sensor probes 20a to 21b, and a monitor unit 23. The monitor unit 23 has a probe potential difference detecting section 25 for detecting the output potential difference between sensor probes 20a, 20b, and the output potential difference between sensor probes 21a, 21b; and a liquid level determining section 26 for determining the level of the liquid from the result of detection. The monitor unit 23 has a bubbling detection pulse generator section 28 for detecting an occurrence of bubbling of a bubbling gas from the result of detection by the probe potential difference detecting section 25 and generating a pulse signal, and a pulse counter 29 for counting the number of pulses generated by the bubbling detection pulse generator section 28, thereby making it possible to grasp the number of bubbling periods of the bubbling gas.

Abstract: Apparatus and method for correctly detecting the level of a processing liquid such as HPM in a processing tank in the event that any drift occurs in a detector is disclosed. A liquid level detecting apparatus (70) comprises a pressure sensor (73) operable to generate an output signal S0 which is maintained at a constant signal level until the level of HPM reaches a predetermined position M in the tank and rises in the signal level as the liquid level rises in the tank after reaching the predetermined position M, a determination circuit (93) for determining whether the liquid level reaches the predetermined position M and a liquid level detecting circuit (94) for detecting the liquid level. The output signal S0 from the pressure sensor is input to an amplifier (92). The liquid level detecting circuit (94) comprises a low-pass filter (97) which receives the amplified signal and generates an output pressure signal S4.

Abstract: A watch, in particular a dive watch, having a movement (16) which is arranged in a watch case (12) and can be used to drive an hour hand (3) via an hour tube and a minute hand (4) via a minute tube in a fashion sweeping over a dial (1). Also present is a pressure detecting device for detecting the ambient pressure outside the watch case (12) and a display for representing the detected pressure values. There is arranged in the watch case (12) a mechanical pressure transducer to which the ambient pressure outside the watch case (12) can be applied and by means of which a mechanical depth measurement mechanism (17) of a mechanical display can be driven.

Abstract: An apparatus and method of for measuring fluid levels in a fluid tank (30) utilizing a no moving parts fluid level sensor (20). The apparatus comprises a hollow sensing tube (24) sealed to a pressure sensor (22). The pressure sensor (22) measures air column pressure as a function of hydrostatic pressure within the fluid tanks (30). By modifying the design of the hollow sensing tube (24) to incorporate at least 30% of the volume at its bottom end, the accuracy of the fluid level measurements may be increased by decreasing the meniscus level (34) deviation in the hollow sensing tube (24). Further, by adding a flexible diaphragm (62) to the bottom end that does not allow fluid to enter the hollow sensing tube (24), the accuracy of the fluid level measurements may be further increased by eliminating the meniscus level (34) altogether.

Abstract: Upward variations of a molten metal level in a container for melting metallic material shall be carried out by detecting variations of a liquid level inside a detector connected to a gas-pipeline, wherein a rise in the pipeline pressure causes the liquid level to move down. Communication is established by means of a gas-pipeline 13 for inert gas between that portion of a container for melting metallic material which is above a molten metal surface 15a and that portion of a detector 16 comprising a transparent tubular container 18 which is above a liquid surface 17a. Variations of the liquid level 17a inside the detector 16 due to a rise in the pressure inside the above-mentioned gas-pipeline 13 are detected as upward variations of the level of the molten metal surface.

Abstract: An ALC circuit is turned on (S1), a nozzle is shifted to a sampling position (S2), and after the ALC circuit has been turned off (S3), the nozzle is allowed to start discharging air from its tip (S4). While the nozzle is being lowered, the inner pressure of the nozzle is monitored (S5, S6), and upon detection of an increase in the pressure, the discharging process of air and the nozzle lowering process are stopped (S7), while the monitoring of the magnitude of the pressure is continued (S8). When the magnitude of the pressure is being maintained within a permissible range of the change for a predetermined time, it is judged that the tip of the nozzle has come into contact with the true liquid level, and after a suction operation of a sample (S9), the nozzle is raised (S10).

Abstract: A continuous liquid level measurement system is disclosed which is based upon a differential pressure measurement. The pressure of the liquid level to be measured is calibrated with a second pressure measurement of the pressure above the liquid in order to get a more accurate pressure measurement which is related in a predetermined manner to the level of the liquid. For instances in which the liquid to be measured is in a harsh environment, the invention provides for a means for mounting the sensitive pressure measurement devices remotely from the liquid.

Abstract: A pair of solid state pressure sensors are disposed near the bottom of a fuel tank vertically spaced with one a unit distance above the other. A third solid state sensor is disposed in the tank at the highest point under the upper wall. The apparent hydrostatic pressure is computed from the difference in pressure sensed by the highest and lowest sensors. The density is computed from the difference in pressure sensed by the pair of sensors near the tank bottom; and, the difference normalized for the vertical distance therebetween. The liquid level height is then computed from computed density and apparent pressure. The reserve volume of liquid fuel is then found for the computed height from a lookup table of values of liquid height and corresponding liquid volume.

Abstract: A flow meter for monitoring liquid flow at low or intermittent rates, such as waste water gravity flow from a reverse osmosis system. Water flow from the system enters a meter chamber vented to atmosphere. Water drainage from this chamber is adjusted to match the incoming water flow, and the level at which this occurs is determinative of the rate of waste water flow. Various ways are disclosed to adjust the rate of water drainage from the chamber, including the use of multiple drainage tubes.