Abstract: A technique that is usable with a well includes disposing a distributed temperature sensor in a conduit that traverses a region of the well. The region contains at least two different well fluid layers. The technique includes circulating a fluid through the conduit and using the distributed temperature sensor to observe at least one temperature versus depth profile of the fluid. Based on the observation, the depth of a boundary of at least one of the well fluid layers is determined.

Abstract: A fluid level indicator for determining the level of fluid in a container includes a dipstick that is entered into the fluid in the container and withdrawn from the fluid, a billet of thermochromic material having a reference temperature, a billet length extending along a portion of the dipstick, and a fluid level range marking on the dipstick along the length of the billet.

Abstract: To detect the volume of gas remaining in a gas bottle or a fixed tank of a system for supplying liquefied gas as fuel for a combustion engine, a positive temperature coefficient (or PTC) probe (16) is placed in the gas feed line (12) between the gas source and the combustion engine. The PTC probe (16) detects the change of phase, from the liquid phase of the liquefied gas to the gaseous phase, in the feed line (12) and delivers an electrical signal to an electronic circuit that triggers a visual or audible signal in response to the detection of the phase change.

Abstract: A system for determining the position of a gas/liquid interface of a fluid in a tank having a probe and a controller. The probe has silicon diodes arranged linearly on a substrate. The controller applies power to each of the silicon diodes to make a determination of whether a fluid in which the silicon diode is immersed is a liquid or a gas based on a rate of transfer of heat from the silicon diode to the fluid. A method for determining the phase of a fluid in which a sensor is immersed includes the steps of immersing the sensor in a fluid and increasing power applied to the sensor. The value of a thermal transient of the sensor is then measured and the phase of the fluid is determined based on the measured value of the thermal transient.

Abstract: The invention relates to a superconducting level measuring apparatus for liquid hydrogen in liquid hydrogen vessels, in particular vehicular tanks, a superconductor (1) based on magnesium diboride MgB2 being arranged vertically or inclinedly to the vertical in a liquid hydrogen vessel (5), and a controllable heat source (2) being arranged on the upper region of the superconductor (1), the superconductor (1) being electrically contacted with a controllable current source (3) as well as a voltage measuring apparatus (4) and the level being measured by measuring a voltage. The MgB2 material is preferably employed as a filament wire. Continuous level measurements of high spatial and temporal resolution can be implemented in uncomplicated fashion. The level measuring apparatus and the method are also suitable for level measurement of liquid neon.

Abstract: An improved single threshold liquid level sensor is disclosed which provides a signal to indicate a level of liquid within a container. The sensor uses a small amount of power, has low-weight, utilizes small space and utilizes a single hot and cold thermocouple junctions being spaced along a line extending either in the direction in which the liquid level may vary or in the perpendicular direction in which the liquid may move.

Abstract: A control device includes a control unit and an evaluation unit that is configured to generate a control signal by which the control unit is impinged upon. The control unit is provided with a voltage source and a reference resistor that can be connected in series to a sensor resistor whose value depends on the temperature thereof. An output voltage of the voltage source drops on the sensor resistor and the reference resistor in the connected state. The reference resistor is dimensioned in such a way that the maximum power loss of the sensor resistor lies in the specified value range of the sensor resistor.

Abstract: An apparatus for measuring a volume of liquid within a vessel is described. The apparatus includes a plurality of devices each having electrical properties that are dependent on a temperature of the device, a constant current source coupled to the plurality of devices, and a unit configured to output a signal based on an amount of voltage at by the plurality of devices. The amount of voltage is based on a number of the plurality of devices immersed in the liquid, and a number of the plurality of devices not immersed in the liquid.

Abstract: In many applications, where the level of a liquid needs to be monitored (and possibly controlled), it is not necessary to provide a continuous (analog) liquid level signal, but limit sensing to one (or two) discrete levels over a small level range. In this case, a ceramic substrate sensor with discrete thermistor/heater pairs provides necessary information to control the level of the fluid. Protection of the substrate from liquid (and potential contaminants) is accomplished by coating the surface with an inert glass (“glaze”) layer and/or polymer layer (e.g., “Parylene”). Packaging of the coated substrate is accomplished by protective base, epoxy, and slosh shield. Cost can be significantly reduced over a prior art multiple thermocouple based sensor design, since discrete electronic components are avoided or reduced. Also, the number of pins, and therefore electrical connections, can be significantly reduced.

Abstract: The present invention deals with determining the level of fluid in a container. Typically, a beverage container containing a liquid will absorb heat energy from the surrounding environment at a greater rate than a gaseous component in the headspace of the beverage container. Thus, as the liquid is drawn from a beverage container a greater headspace results. If a thermometric measuring device is employed along the height of the beverage container the volume may be determined by observing the difference in the temperature along the height of the beverage container. In practice, a beer keg may exhibit a difference of as much as 9° Fahrenheit on the exterior surface of the beer keg when measured at the headspace as opposed to the area where the liquid is present in the beverage container.

Abstract: A liquid level indicator, suitable for determining the level of a volatile liquid within a container, includes temperature sensors spaced vertically apart from each other. A processor processes the outputs of the temperature sensors and produces an indication, such as an audible indication by an audible alert device, when liquid level is detected. The determination of liquid level can be by one or more of various temperature processing techniques, including difference in temperature between temperature sensors, and/or difference in temperature over time at one or more of the temperature sensors.

Abstract: A conductance probe is provided for adapting in a device having a container for holding a fluid therein. The a conductance probe is installed therein for providing a conductance signal indicating whether it is in contact with the fluid. The conductance probe features a conductance probe cleaner having a temperature sensitive element arranged on a tip thereof that is responsive to a change in the temperature of the fluid, for wiping the conductance probe to keep deposits from building up thereon. The scope of the invention includes any and all bi-metal configurations using temperature changes to create probe cleaning. The device may be a boiler or other suitable device having a heating element for boiling water contained therein. The temperature sensitive element is arranged on a metal tip of the conductance probe so as to move axially when wiping the same.

Abstract: The present invention provides a liquid level detection device for detecting the liquid level height of liquid fuel in a chamber, which has an inner space connected with the chamber. The liquid level detection device comprises: a heater, which is configured in the inner space of the liquid level detection device, and is used to heat the liquid fuel in the inner space; at least one temperature sensors, which are configured in the inner space of the liquid level detection device, and is used to measure the temperature of the liquid fuel in the inner space; and, a liquid level calculation device, which receives the temperature signals of the liquid fuel measured by these temperature sensors, and calculates the temperature variation rate of the liquid fuel, and converts into the liquid level height of the liquid fuel in the chamber according to the temperature variation rate.

Abstract: A device for measuring at least one of a level and a temperature of a liquid in a container includes a resistor arrangement adapted to be immersed in the liquid. An immersed length of the resistor arrangement in the liquid corresponds to the level of the liquid in the container. The resistor arrangement includes upper, middle and lower temperature-dependent elongated resistor elements connected in series or in parallel. Each resistor element has an uniform resistance per unit length along a length thereof. The upper and lower resistor elements are shorter than the middle resistor element. A power source is connectable to the resistor arrangement. Voltage drops across or currents flowing through the resistor elements are measured. A microprocessor is arranged to calculate the immersed length of the resistor arrangement or the temperature of the liquid from predetermined lengths of the resistor elements and from the measured voltages or currents.

Abstract: A liquid level sensor comprising a thermistor probe and a power source connected to the thermistor probe to heat the thermistor probe. A cover encases the thermistor probe and includes openings allowing liquid to enter and exit an interior of the cover and contact the thermistor probe. A detector detects a liquid level in response to a voltage at the thermistor probe.

Abstract: Representative embodiments provide for a media level measurement apparatus, including a sensor to provide an ambient temperature signal, a controller, and a source configured to provide an electrical current. Also included are a thermistor device configured to provide a level signal corresponding to a level of a media in contact with a lengthwise portion of the thermistor device during an application of the pulse of electrical current, and a signal processor configured to provide a media level signal in accordance with the level signal and the ambient temperature signal. A method includes the steps of supporting a lengthwise portion of a thermistor device in contact with a media, applying an electrical pulse to the thermistor device, sensing a level signal from the thermistor device after a predetermined period of time, and providing a media level signal in corresponding to the level signal.

Abstract: A method and device for detecting an accumulation of a solid material in a vessel that contains at least one fluid phase. The device includes an electric conductor element that is positioned in a region inside the vessel where the accumulation is likely to occur, the electric resistance of the conductor element being a function of the temperature thereof, elements for providing electrical power to the conductor element and elements for repeatedly measuring the electrical resistance of the conductor element.

Abstract: The present invention provides a probe having a resistance that varies with temperature and is operable to determine the quantity of a fluid, such as hydrogen, in a storage tank, such as a cryogenic storage tank. The probe relies upon differing heat transfer rates for the gaseous and liquid phases of the fluid and a change in resistance due to a change in temperature of the probe to ascertain the quantity of fluid within the storage tank. The probe can be configured to account for the geometry of the storage tank thereby providing a linearized signal indicative of the quantity of fluid in the storage tank.

Abstract: The present invention is a compact apparatus and method that provides an efficient manner for monitoring the condition and level of a functional fluid directly in operating equipment. A sensor device is provided that includes a plurality of liquid sensors and a plurality of vapor sensors that when used in conjunction with one another at different temperatures, can provide a thorough evaluation of the oxidative degradation, liquid contamination and solid contamination of the fluid to detect the end of the useful life of the fluid. By providing liquid sensors and vapor sensors on the same device, the present invention allows for a compact, efficient, and economically feasible manner to monitor the condition of fluid as well as detecting abnormal operating conditions prior to further component damage and eventual equipment failure.

Abstract: A parts washer including a receptacle positioned on a reservoir for cleaning liquid having a drain opening and a module which engages a portion of the reservoir in the cleaning liquid for adjusting the temperature of the cleaning liquid and circulating the cleaning liquid into the receptacle. The module includes a heating element, a sensor and pump. An enclosure houses a temperature controller which displays the temperature of the cleaning liquid and a low liquid level condition. A bridge thermally links the heating element to the sensor so that the sensor normally generates a signal representative of the temperature of the cleaning fluid unless the level of the cleaning fluid is disposed below the sensor.

Abstract: An electrical current is passed through a thermistor to raise its temperature above the temperature of oil flowing in pulses past the thermistor. A change is measured in the temperature of the thermistor occurring with respect to one or more of the pulses. A level of oil flow is determined corresponding to the measured change in temperature. A signal is issued based on the determined flow level.

Abstract: A vertical series of electrical heat sensors adhered to the outer surface of a water heater tank. The sensors are electrically connected to a corresponding vertical series of display lights in reverse order. Heated water fills the tank from the top down. The sensors are activated from the top down based on the amount of hot water in the tank. The lights are correspondingly activated from the bottom up, showing the tank “filling-up” with hot water. The lights can be labeled such as “Full”, “Half Full”, etc. The sensors can be provided in sequence on a rod with magnets. Thus, the rod can be quickly attached to the tank, holding the sensors in a vertical line in the correct order. Displays can be remote from the tank via wiring or radio signaling, allowing them to be mounted in each bathroom or elsewhere.

Abstract: An improved liquid level sensor is disclosed which provides a reliable and simple device for accurately determining the level of a liquid within a vessel. The sensor utilizes a plurality of thermocouple junctions grouped in pairs with the pairs being spaced along a line extending generally in the direction in which the liquid level may vary. A first thermocouple junction of each pair is located in relatively close thermal proximity to an electrically powered heater and the second of each pair of thermocouple junctions is spaced away from the heater. The thermocouple junctions are connected in series and produce a signal indicative of the level of liquid along the sensor. Alternatively, a single threshold liquid level sensor is provided for use with a hermetic interface to provide a signal to indicate a level of liquid within a container. Additionally, a pressure sensing circuit may also be incorporated with either liquid level sensor.

Abstract: Representative embodiments provide for a media level measurement apparatus, including a sensor to provide an ambient temperature signal, a controller, and a source configured to provide an electrical current. Also included are a thermistor device configured to provide a level signal corresponding to a level of a media in contact with a lengthwise portion of the thermistor device during an application of the pulse of electrical current, and a signal processor configured to provide a media level signal in accordance with the level signal and the ambient temperature signal. A method includes the steps of supporting a lengthwise portion of a thermistor device in contact with a media, applying an electrical pulse to the thermistor device, sensing a level signal from the thermistor device after a predetermined period of time, and providing a media level signal in corresponding to the level signal.

Abstract: A level detector for storage tanks for fluids comprises a microprocessor, a network of resistive elements connected in series or parallel, and a plurality of conductive elements between them, connected across a power source. The resistive elements have a high temperature coefficient, and are heated by passing a high electric current through them, after which a low electric current is passed through them and the voltage between them is sampled by the microprocessor. The resistive elements lose heat through conduction, so that a pair of resistive elements can be detected having differential cooling between them as a consequence of being adjacent to the void within the tank or the fluid within the tank. Thus, an approximation of the fluid level within the storage tank can be determined and signalled remotely.

Abstract: The liquid level detector system of the present invention comprises a heater thermally coupled to the interior of the vessel. A linear sensor, having a vertical longitudinal axis, is located in proximity to the heater such that discrete elevations of the interior of the vessel are thermally coupled to corresponding longitudinal portions of the sensor. The correspondence is incrementally continuous such that the elevations corresponding to the portions of the sensor increase from one to the other end of the sensor. The sensor may be actuated resulting in a resistance measurement indicative of the temperature detected by it. The vertical dimension of the sensor is sufficiently large such that the resistance measurement will vary in proportion to the longitudinal portion of the sensor thermally coupled to the liquid. The sensor generates an electrical signal defining a temperature signal indicative of the resistance measurement and thereby the temperature detected by the sensor.

Abstract: The present invention deals with determining the level of fluid in a container. Typically, a beverage container containing a liquid will absorb heat energy from the surrounding environment at a greater rate than a gaseous component in the headspace of the beverage container. Thus, as the liquid is drawn from a beverage container a greater headspace results. If a thermometric measuring device is employed along the height of the beverage container the volume may be determined by observing the difference in the temperature along the height of the beverage container. In practice, a beer keg may exhibit a difference of as much as 9 degrees Fahrenheit on the exterior surface of the beer keg when measured at the headspace as opposed to the area where the liquid is present in the beverage container.

Abstract: A method and apparatus for aspirating a liquid (e.g., blood) from a container uses an electrically biased thermistor element, mounted proximate the tip of a liquid-aspirating probe, to determine that the probe is safely submerged within a body of liquid to be aspirated at all times during the aspiration process. Also disclosed are different aspiration probe assemblies that are useful in the method and apparatus of the invention.

Abstract: A level indicator and method is provided which is intimately affixed to the outside surface of the outside wall of a container, for use in the determination of the level of the interface between a liquid and the void volume above it within a container. The level indicator includes a thermochromic leucodye ink layer which has at least one, and usually at least two, leucodye inks. Each of the leucodye inks responds chromatically within a different operating temperature range. In one embodiment, the level indicator vertically extends substantially the height of the container. In an alternative embodiment, the level indicator vertically extends along the height of the container, in the region of the top portion of the container, and at least above the legal safe-fill level of the liquid within the container such that overfilling of the liquid in the container is detectable.

Abstract: An improved liquid level sensor is disclosed which provides a reliable and simple device for accurately determining the level of a liquid within a vessel. The sensor utilizes a plurality of thermocouple junctions grouped in pairs with the pairs being spaced along a line extending generally in the direction in which the liquid level may vary. A first thermocouple junction of each pair is located in relatively close thermal proximity to an electrically powered heater and the second of each pair of thermocouple junctions is spaced away from the heater. The thermocouple junctions are connected in series and produce a signal indicative of the level of liquid along the sensor. Alternatively, a single threshold liquid level sensor is provided for use with a hermetic interface to provide a signal to indicate a level of liquid within a container. Additionally, a pressure sensing circuit may also be incorporated with either liquid level sensor.

Abstract: A level indicator and method is provided which is intimately affixed to the outside surface of the outside wall of a container, for use in the determination of the level of the interface between a liquid and the void volume above it within a container. The level indicator includes a thermochromic leucodye ink layer which has at least one, and usually at least two, leucodye inks. Each of the leucodye inks responds chromatically within a different operating temperature range. In one embodiment, the level indicator vertically extends substantially the height of the container. In an alternative embodiment, the level indicator vertically extends along the height of the container, in the region of the top portion of the container, and at least above the legal safe-fill level of the liquid within the container such that overfilling of the liquid in the container is detectable.

Abstract: A level detector for storage tanks for fluids comprises a microprocessor, a network of resistive elements connected in series or parallel, and a plurality of conductive elements between them, connected across a power source. The resistive elements have a high temperature coefficient, and are heated by passing a high electric current through them, after which a low electric current is passed through them and the voltage between them is sampled by the microprocessor. The resistive elements lose heat through conduction, so that a pair of resistive elements can be detected having differential cooling between them as a consequence of being adjacent to the void within the tank or the fluid within the tank. Thus, an approximation of the fluid level within the storage tank can be determined and signalled remotely.

Abstract: An electrical current is passed through a thermistor to raise its temperature above the temperature of oil flowing in pulses past the thermistor. A change is measured in the temperature of the thermistor occurring with respect to one or more of the pulses. A level of oil flow is determined corresponding to the measured change in temperature. A signal is issued based on the determined flow level.

Abstract: A method of gas tank ullage indication is designed to be made up of a coating or film attached to the surface of a tank for holding compressed gas. This is used normally when the tank is warm as is the case right after the tank is pressured with gas. The coating includes materials which change in appearance when various specific temperatures are reached. The changed appearance allows indications to be seen that tell the observer how the pressure will change after the tank has equilibrated to some specific temperature.

Abstract: Apparatus and a method of operating any structural configuration of a heater and array of temperature sensors to measure with high accuracy, the level of stratified liquids like water and oil or water and gasoline and non-stratified liquids, liquid temperature, and other liquid properties and detect ice formation on aircraft surfaces. Thin and narrow strips of dissimilar material will be used for the heater, array of temperature sensors, mount, and coating. The connecting wires to and from the apparatus will be from the same material. Simultaneous measurements from all the temperature sensors, before and after heat is applied, will be used to generate accurate temperature profiles for the entire configuration and not just from two adjacent temperature sensors. Different features of the temperature profiles will determine accurately the liquid level, liquid temperature and other liquid properties. Apparatus of the invention may also be used to detect ice formation.

Abstract: A level indicator and method is provided which is intimately affixed to the outside surface of the outside wall of a container, for use in the determination of the level of the interface between a mass of flowable material and the void volume above it within a container. The level indicator includes a thermochromataic layer which has at least two thermochromatic materials. Each of the thermochromatic materials responds chromatically within a different operating temperature range. In one embodiment, the level indicator vertically extends substantially the height of the container. In an alternative embodiment, the level indicator vertically extends along the height of the container, in the region of the top portion of the container, and at least above the legal safe-fill level of the flowable material within the container such that overfilling of the flowable material in the container is detectable.

Abstract: A sensor capable of operating in ambient temperatures that are either above or below operating systems specification. comprises a transducer adapted to be coupled to a power supply for generating signals corresponding to and representative of the status of the targeted system. Signal conditioning means are coupled to the transducer and are responsive to generated signals. The signal conditioning means produces status signals in a format that is compatible with an information utilization device. A thermo electric module is attached to the signal conditioning means for changing the temperature of the signal conditioning means. In an alternative embodiment, the thermo electric module is connected to control the environment in which the signal conditioning means operate. The signal conditioning means are then able to operate in ambient temperatures that are outside of the normal operating parameters to which the to which the signal conditioning means were originally designed.

Abstract: A method of detecting a dry/wet state of a thermistor bead comprises the steps of: conducting current through the thermistor bead selectively between first and second current levels; measuring a difference in voltage across the thermistor bead in response to the first and second current levels; and detecting the dry/wet state of the thermistor bead based on the measured difference in voltage. In one embodiment, the first and second current levels conducted through the thermistor bead are both less than thirty milliamps. Apparatus for embodying this detection method is also disclosed.

Abstract: A sprayer including a sprayer container adapted to be filled with a fluid. The sprayer container has at least a portion thereof including thermochromic color-changing properties. The sprayer container includes an interior surface and an exterior surface. A spraying gun is connected to the sprayer container, with the spraying gun including a trigger for selectively spraying pressurized fluid in the sprayer container onto a predetermined object. The sprayer container indicates the amount of fluid in the sprayer container by a color change line located at a transition line between the fluid and gas within the sprayer container when fluid is located within the sprayer container, thereby causing a top area of the sprayer container having the interior surface adjacent the gas to be a first color and a bottom area of the sprayer container having the interior surface adjacent the fluid to be a second color.

Abstract: A vertical series of electrical heat sensors adhered to the outer surface of a water heater tank. The sensors are electrically connected to a corresponding vertical series of display lights in reverse order. Heated water fills the tank from the top down. The sensors are activated from the top down based on the amount of hot water in the tank. The lights are correspondingly activated from the bottom up, showing the tank “filling-up” with hot water. The lights can be labeled such as “Full”, “Half Full”, etc. The sensors can be provided in sequence on a rod with magnets. Thus, the rod can be quickly attached to the tank, holding the sensors in a vertical line in the correct order. Displays can be remote from the tank via wiring or radio signaling, allowing them to be mounted in each bathroom or elsewhere.

Abstract: A probe assembly for monitoring the water level in boilers with an electric immersion resistor heater, of the type that comprises at least one sensor element to be arranged inside a hollow body which is in turn associated and partially inserted in the boiler. The hollow body has, on the portion arranged outside the boiler, a plug which axially supports the sensor element; the end of the sensor element arranged at the plug is connected, when the plug is installed, by way of at least one electrical contact, to an electrical power supply cable, whose contact end is arranged at the portion of hollow body that is arranged outside the boiler.

Abstract: In a device for measuring the filling level, thermoelements (20) are used which are disposed on a sheet-shaped support (25). The thermoelements (20) consist of two different materials and are disposed in two rows (71, 72) placed side by side. Two adjacent thermoelements (20) of said rows (71, 72) have a common junction point (23) that is heated. Both rows (71, 72) of thermoelements also have two additional junction points that are cold. A first group of thermoelements (20) is disposed with their supports (25) in the interior of the container and operate as measuring detectors. A second group of thermoelements (20) serves as reference sensors since they regulate the heat flow impinging upon the junctions points (23) relative to a defined reference voltage.

Abstract: A method of detecting a dry/wet state of a dual thermistor bead sensor over a wide operating temperature range comprises the steps of: conducting first and second predetermined currents through one and another of the thermistor beads of the sensor, respectively, the second predetermined current being substantially less than the first predetermined current; measuring a first voltage across the one thermistor bead in response to the first predetermined current and generating a first signal representative thereof; measuring a second voltage across the other thermistor bead in response to the second predetermined current and generating a second signal representative thereof; modifying the second signal by an offset and gain to generate a third signal; and detecting the dry/wet state of the sensor over the wide operating temperature range based on the first and third signals.

Abstract: A method for controlled proportioning of liguids with a postive-displacement device (2) for dislocating a gas cushion (17) includes measuring the pressure (pab) in the gas cushion (17) at the time of a complete discharge of a liquid volume, measuring the discharge time (tab) for a complete discharge of the liquid volume and determining the time demand (&Dgr;t) to compress the gas cushion (17) by the postive-displacement device by means of the pressure (pab), the dead volume (Vo) of the gas cushion (17), a gas condition equation, and the volumetric gas flow (Q) discharged by the postive-displacement device. A corrected discharge time (toab) is determined as a proportioning control magnitude by a deduction of the time demand (&Dgr;t) from the measured dischage time (tab) with outputting, and/or saving, and/or resorting to the deviation of the corrected discharge time (toab) from a desired discharge time (tsoll) for regulating the discharge of the liquid volume.

Abstract: An upright capillary tube is located at a position in a liquid container such that its lower end can be reached by the surface of the liquid level in the container as the liquid level rises and falls with changes in the amount of liquid in the container. A thermal sensor, e.g., a thermistor is provided on the capillary tube. As the liquid level rises and reaches the lower end of the capillary tube, the liquid rises in the tube due to surface tension. As the liquid in the capillary tube reaches the location of the thermal sensor, the sensor responds to a temperature change to detect the liquid level. The capillary sensing system can be miniaturized and is capable of superior sensitivity.

Abstract: An improved liquid level sensor is disclosed which provides a reliable and simple device for accurately determining the level of a liquid within a vessel. The sensor utilizes a plurality of thermocouple junctions grouped in pairs with the pairs being spaced along a line extending generally in the direction in which the liquid level may vary. A first thermocouple junction of each pair is located in relatively close thermal proximity to an electrically powered heater and the second of each pair of thermocouple junctions is spaced away from the heater. The thermocouple junctions are connected in series and produce a signal indicative of the level of liquid along the sensor. Alternatively, a single threshold liquid level sensor is provided for use with a hermetic interface to provide a signal to indicate a level of liquid within a container. Additionally, a pressure sensing circuit may also be incorporated with either liquid level sensor.

Abstract: A humidifier including a reservoir adapted for retaining liquid and an evaporative media supported in adsorbing contact with the liquid. A reservoir temperature sensor detects a temperature within the reservoir at a low liquid level and provides a reservoir temperature signal indicative thereof. An air inlet temperature sensor detects a temperature of air upstream from the evaporative media and provides an air inlet temperature signal indicative thereof. An air outlet temperature sensor detects a temperature of air downstream from the evaporative media and provides an air outlet temperature signal indicative thereof. A controller determines an operating condition of the humidifier based upon at least one of the reservoir temperature signal, the air inlet temperature signal, and the air outlet temperature signal.

Abstract: A system for detecting the level of a liquid in a vessel, comprises a detector assembly including a thermally conductive substrate supported within the vessel. One or more heaters are mounted on the substrate within the vessel. One or more temperature sensors, each associated with a respective heater, are mounted on the substrate. The sensor(s) may be actuated to generate an electrical signal defining a temperature signal indicative of the detected temperature. A processor is electrically connected to the sensor(s) for receiving the temperature signal(s) after actuation of the associated heater(s). The processor is programmed to calculate a “temperature index” proportional to the temperature signal(s). The temperature index(s) indicates the temperature increase detected by the sensor(s) resulting from actuation of the heater(s). This, in turn, indicates the presence of liquid or vapor adjacent to the sensor(s).

Abstract: A limit-level sensor for measuring level of a liquid has a resistance element which has an electric resistance which suddenly varies a transition temperature which lies above the maximum liquid temperature. The resistance element is first of all heated by electric current. Thereupon, the electric resistance of the resistance element is measured. When the resistance element is covered with liquid, the heat generated by the electric current is led away so that the temperature of the resistance element is less than its transition temperature. If the resistance element is not covered by liquid, this heat is scarcely led away, so that the temperature of the resistance element remains above the transition temperature.

Abstract: The low gravity liquid level sensor rake measures the liquid surface height of propellant in a propellant tank used in launch and spacecraft vehicles. The device reduces the tendency of the liquid propellant to adhere to the sensor elements after the bulk liquid level has dropped below a given sensor element thereby reducing the probability of a false liquid level measurement. The liquid level sensor rake has a mast attached internal to a propellant tank with an end attached adjacent the tank outlet. Multiple sensor elements that have an arm and a sensor attached at a free end thereof are attached to the mast at locations selected for sensing the presence or absence of the liquid. The sensor elements when attached to the mast have a generally horizontal arm and a generally vertical sensor.