Abstract: A system for automatically preventing the discharge of spilled oil from electrical distribution substation equipment into streams or ground water. The system utilizes a containment basin, sump, electric operated water drain valve and a thermal dispersion type oil/water interface detector. The oil/water interface probe is placed at a specified height in the sump. It is capable of determining if the probe is in oil, water or air. The interface detector along with other relays will allow water to be draped from the containment basin but prevent oil from being discharged. The system will also initiate an alarm which may locally or remotely warn that a spill has occurred.

Abstract: A sensor for detecting whether liquid is present at a location in a tank, comprises a probe placed at the location, containing a negative temperature coefficient resistor (NTC) and a positive temperature coefficient resistor (PTC) mutually connected in series relation. The positive temperature coefficient resistor exhibits a progressive resistance variation responsive to temperature change. An electrical power source delivers a constant electric current to the probe. The detector further comprises a comparator for comparing the total resistance of the serially mounted resistors with a threshold.

Abstract: A book binding process and apparatus are shown wherein polyurethane adhesive (PUR) attaches a crepe portion of a book binding to a book block and hot glue attaches the crepe portion to the book cover. The PUR delivery system includes an inclined trough positioned adjacent a polyurethane adhesive delivery roll. A polyurethane adhesive source delivers polyurethane adhesive upon the inclined surface of the trough and the polyurethane adhesive is metered onto the roller as a function of the separation of the leading edge of the trough and the roller.

Abstract: A method and apparatus are disclosed for detecting the presence of steam in a volume of air at a predetermined temperature. The apparatus includes a temperature sensor having two respective temperature build-up times representing an under steam temperature build-up time and an under air temperature build-up time. The method for detecting the presence of steam comprises the steps of placing the temperature sensor in the presence of the volume air, such that the sensor can reach a predetermined set point temperature that is lower than the predetermined temperature, taking a temperature measurement with the sensor, and determining if the measured temperature reaches the set point temperature in order to indicate whether the sensor is in the presence of steam.

Abstract: An apparatus is provided for use in monitoring the level and temperature of a liquid flowing through a horizontally extending line that is to remain full of liquid, wherein the temperature of the liquid is to be maintained below an established acceptable value. The apparatus includes a chamber interposed in the line and formed with an enlarged transverse cross-sectional area, and is disposed at least partially above the line. The chamber is closed except for an inlet and outlet in fluid communication with the line. A sensing assembly is provided within the chamber for sensing the level and temperature of the liquid flowing through the chamber. A control assembly measures the liquid level and temperature sensed by the sensing assembly and activates an alarm when either the level of the liquid in the chamber drops below a predetermined level or the temperature exceeds a predetermined value above the established acceptable value.

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: Precise information is obtainable concerning the position of a fluid-fluid interface (28, 33), such as between a gas and a liquid or between liquids. Such information is important for the control and automation of molten metal refining processes. Specifically, in an electrolytic process for removing magnesium from molten aluminum, knowledge of the vertical position of an interface (33) between the electrolyte and the magnesium and an interface (28) between the electrolyte and the aluminum facilitates the automatic removal of the purified metals when drained or drawn from the furnace. Heat energy is conducted through a thermocouple-heater assembly 34 to a thermocouple (38) located at its tip (36). The equilibrium temperature at the thermocouple junction is dependent upon the heat loss through tip (36).

Abstract: A cryogenic fluid level sensor utilizing a high temperature ceramic superconductor material driven above its level of critical current density, an exterior housing for holding the length of ceramic superconductor material, a support material disposed between the ceramic superconductor material and the exterior housing, and a resilient retention material disposed opposite the ceramic superconductor material for holding the superconductor material while allowing expansion and contraction thereof during thermal cycling. A method of producing a superconductor material having a low level of critical current density and favorable structural properties is also disclosed.

Abstract: Disclosed is an indicator (15, 35) for determining the level of contents in an opaque, plastic container (10). The container (11) is filled with a solid chemical (11), such as a detergent. A spray of warm or hot water (19) impinges upon the eroding surface (16) of the solid chemical (11) to produce a chemical solution. The container (10) is provided with a thermo-chromatic strip (15, 35) for detecting the level of solid chemical (11) within the plastic capsule (10). A method of dispensing a solid chemical (11) and a dispensing container (10) are also disclosed.

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 level sensing apparatus for detecting variations in heat transfer for measuring the level of a fluid in a container. The apparatus has a plurality of spaced Darlington pair transistor configurations within an elongate housing. The Darlington pair transistor configurations are so positioned in the housing and biased such that their conductivity is dependent upon the cooling effects of the fluid. A predetermined potential difference is provided across each one of the respective Darlington pair transistor configurations due to the cooling effects of the fluid when in a liquid form. A potential difference lower than the pre-determined potential difference is provided due to the cooling effects of the fluid when in a gaseous form.

Abstract: A thermochromic level indicator for determining the level of a material inside a container includes a temperature responsive strip including at least two thermochromic materials of different opacities and transition temperatures, the thermochromic materials with greater opacity having relatively lower transition temperatures than the thermochromic materials with lesser opacities. Other accurate thermochromic level indicators are also disclosed.

Abstract: To eliminate an ambient temperature correcting sensor and further to improve the sensor response speed in a heat radiating type liquid level sensing system, a constant current pulse is periodically passed through a level sensor to heat it; level sensor voltages sampled at predetermined time intervals when the level sensor is being heated are divided by each initial sensor voltage to obtain sensor voltage ratios with respect to time; an approximate voltage is calculated on the basis of the the obtained ratios in accordance with an approximation equation; a liquid level is calculated and displayed on the basis of the calculated approximate sensor voltage. Further, it is preferable that the system is provided with an additional inclination correcting sensor or an acceleration sensor, in order to correct the inclined liquid level.

Abstract: A method and apparatus for determining whether a fluid, such as a refrigerant, is a liquid or a gas. To determine whether the fluid at a predetermined level (14) of a storage container (20) is a liquid or a gas, fluid is withdrawn from the container at the predetermined level, depressurized under conditions that would cause it to become a gas if it is a liquid before such depressurization, then the temperature of the fluid after depressurization is measured and compared to a reference temperature that is or is related to the temperature of the fluid in the container. If the temperature of the fluid after depressurization and the reference temperature are approximately equal, one can conclude that the fluid withdrawn from the predetermined level is a gas. If the temperature of the fluid after depressurization is considerably lower than the reference temperature, one can conclude that the fluid withdrawn from the predetermined level is a liquid.

Abstract: An apparatus is provided for use in monitoring the level and temperature of a refrigerant, wherein the temperature of the liquid phase of the refrigerant is to be maintained below an established acceptable value. The apparatus includes a chamber interposed in a liquid line of a cooling system, wherein the chamber has a transverse cross-sectional area greater than the area of the liquid line, and is disposed at least partially above the line. A temperature sensor and a heater are provided within the chamber above the height of the liquid line and the sensor is connected to an alarm through a control which measures the temperature of the sensor and activates the alarm when the sensor temperature exceeds a predetermined value above the established acceptable value of the refrigerant liquid.

Abstract: A semiconductor sensor detects the existence of liquified gases by immersion or approaching the liquid. A high signal amplitude of the sensor permits a simple signal evaluation of high reliability. The sensor permits the realization of filling level measuring devices or level control devices for liquified gases.

Abstract: A method for measuring the level of filling, such as the level of oil in an automotive engine, employs a hot-wire measuring device in which a hot-wire transmitter (5) is charged with a predetermined constant current, and an increase in voltage over the hot-wire transmitter is detected within a predetermined period of time. Errors due to digitizing and inaccurate calibration are avoided by the simplest possible means. For this purpose, a current source (1), which is controlled by an input voltage, is used as a source of the constant current. Furthermore, in a preparatory stage, after an assembly of the hot-wire measuring device, an input voltage (PWM) is changed until, at an input-voltage value wherein the current source (1) produces the predetermined constant current (IK). The input-voltage value is used in subsequent measuring stages to control the source of current.

Abstract: A liquid level detecting device used in a vacuum processing apparatus, the device comprising a liquid container section, an inlet pipe for liquid supply connected to the liquid container section, and outlet pipe for discharging the liquid when the liquid in the liquid container section overflows a predetermined liquid level, a temperature measurement terminal provided in the liquid container section, for detecting the temperature of the liquid in the container section, means for heating or cooling the temperature measurement terminal, and a liquid level detecting section for detecting the surface level of the liquid on the basis of the difference between two temperatures of the liquid measured when the heating or cooling means is in contact with the liquid and when not in contact.

Abstract: A heat radiating type level sensor measurement of liquid level capable of preventing the errors in a case of sudden environmental temperature change, and accounting for the agitated motion of the liquid surface. The measured liquid level can be obtained as the steady state output voltage plus a difference between the initial output voltage for a present measurement and the initial output voltage for an immediately preceding measurement, with the difference multiplied by a predetermined constant.

Abstract: Apparatus and method are described for providing a discrete readout of the collapsed water level within a boiling water reactor. An elongate gauge housing is mounted within the reactor vessel extending through the collapsed level from a steam environment into a boiling water environment. A serially coupled sequence of junction defining thermocouple element pairs are positioned within the gauge housing and are arranged with a heating assembly to generate an output signal which corresponds with the water level. Also located under the influence of the heating assembly are reference thermocouples, one providing a reference output corresponding with the instantaneous temperature of the boiling water environment and the other providing a reference output corresponding with the steam environment above the collapsed water level. The signals from the reference thermocouples and the serial coupled level determining thermocouple structures are then treated to define instantaneous water level.

Abstract: A liquid detector for thin-walled tanks Operating in a zero gravity environment (e.g., outer space). The liquid detector includes a small heater, such as a 1-watt patch heater, and two thermistors positioned on either side of the heater and diametrically opposed to each other. The heater and two thermistors are located on the outside of a propellant tank of, for example, a satellite. One of the thermistors is positioned directly over a region where a propellant management device retains liquid. The other thermistor is spaced apart from the region, while the heater is proximate to the region. In operation, the heater is activated for a short period of time and the change in temperature at each of the two thermistors is observed. The temperature of a thermistor located over a spot having liquid propellant in contact with the tank wall will increase less than the temperature of the thermistor located at a spot where no liquid propellant is present.

Abstract: A liquid level measuring and indicating system using a positive temperature coefficient wire as a sensor, a microprocessor based operating circuit, and an electronically controlled display device. With energy to operate the system being supplied by a battery, circuit includes energy conservation provisions.

Abstract: The interface gauge includes at least one transducer for sensing the interface between two media within a reservoir. An elongated flat member has at least one transverse bore. A transducer is loosely contained within the bore. Conductors connect the transducer to a signal comparator and logic network for monitoring an impedance change in the transducer in response to a change in the interface within the reservoir. The gauge can replace conventional mechanical dipsticks in factory made dipstick tubes for crankcases and automatic transmissions in order to monitor oil and transmission fluid levels.

Abstract: An extended resistance temperature sensor formed of a plurality of lengths of pre-insulated resistance temperature detector (RTD) wire. The RTD wire is either unheated, self heated or is heated by means of strands of heater wire integrated with or placed closely adjacent to the RTD wire. The RTD wire itself, or together with the heater wire, is bonded together in one embodiment. Alternatively the RTD wire, or with the heater wire, may be encased in insulated shrink tubing, thin wall metal tubing or both. Connectors are provided to supply electrical current for heating purposes or to connect the RTD wire to detection circuitry, or both. Protective sheaths are provided over the connectors.

Abstract: A PTC resistive strip is mounted on a wall of a washer tub. Water in the tub carries away heat from the energized strip thereby reducing its resistance. The water level in the tub is measured by measuring the voltage drop across the strip. The resistance of the strip can be compared to the resistance across a variable resistance or resistor to indicate that the water has reached a desired level. A comparator output can be used to control the water level and washer motor operation via a control circuit which operates the water supply valves and motor switch. A second PTC resistive element is also provided for sensing overfill.

Abstract: A temperature controller with an integral liquid level control is contained within one unit. The unit consists of an electrical and heat conductive housing, which serves as a first electrode of the liquid level sensor. A metal clamp and a means to attach the housing to the liquid vessel is insulated from the housing and serves as a second electrode. The electrodes are connected in an electrical circuit such that when the electrodes are immersed within a conductive liquid, the resistance between the electrodes is reduced and a current is allowed to flow. A temperature sensor, such as a thermistor, RTD, or thermocouple, is contained within the housing. The housing conducts heat from the housing environment for radiation within the housing.

Abstract: The detecting device according to the present invention is provided with a case, a first and second detecting pads which juts from the case and which can be closely attached to the outer wall of the receptacle, supports which are connected to the first and second detecting pads in a thermal-conducting manner, a first thermistor and heater embedded in the support of the first detecting pad, a second thermistor embedded in the support of the second detecting pad, and a detector circuit which measures the quantity of heat transmitted from the first detecting pad into the receptacle in accordance with a change in the output of the first thermistor when the first detecting pad and the support thereof are heated by the heater to a preset temperature which is above the reference temperature of the second detecting pad and the support thereof, thus detecting the level of a liquid in the receptacle from the measured quantity of heat transmitted.

Abstract: The present invention provides a level detector to sense whether the level of a liquid having a nonambient temperature such as a cryogenic liquid has reached a predetermined point. A stainless steel type T thermocouple probe is provided for generating a temperature signal referrable to absolute temperature. A high thermal conductivity the type T thermocouple probe is adapted to be mounted so that it submerges in the liquid when the level of the liquid has reached the predetermined point tube is, at one end, in good thermal contact with a thermocouple contained within distal end of the thermocouple probe and, at the other end, is exposed to ambient conditions. The high thermal conductivity tube acts to conduct heat between the ambient and the thermocouple.

Abstract: An RTD (resistance temperature sensor or detector) sensing device which is a long, thin, unitary device adapted to be distributed across an extended field for the continuous, uninterrupted sensing or interrogation of such field, avoiding the inaccuracy, unreliability, and excessive expense of conventional "point" RTD and thermocouple sensors currently employed for this purpose. According to the invention, a very long, thin, ductile protective metal outer sheath houses a coextensive body of insulation material, which in turn supports and electrically insulates one or more coextensive RTD filaments and in most forms of the invention one or more heater filaments. Distributed RTDs of the invention may, along their lengths, have continuous linear function sensitivity, continuous variable function sensitivity, or step function sensitivity.

Abstract: A liquid level detector comprises a thermistor and circuitry for determining electrically if the thermistor is wet or dry and additionally, and continuously, if the thermistor is open or shorted. The voltage across the thermistor is filtered to remove low frequency electrical noise, then compared with a reference low voltage to determine if shorted and to a transition voltage chosen to be between the thermistor's normal wet and dry voltages to determine if the thermistor is wet or dry. The voltage is also compared to the supply voltage using a CMOS gate circuit element to determine if the thermistor is open. The gate passes both faults on to an LED to signal that a fault condition exists or indicates by another LED the wet or dry condition of the thermistor. A pump may be activated through a relay if the thermistor tests wet or dry, as desired.

Abstract: A fault-tolerant system for interfacing a single sensor unit to multiple display/control modules. The system includes a fixed resistor connected in series with the sensor unit and multiple data centralization units each including a source for providing a separate excitation signal to the sensor unit. The data centralization units also include detection circuits for measuring the voltage drop across the fixed resistor. The output from the sensor unit is adjusted according to the level of excitation provided to the sensor unit so that accurate measurements can be taken despite one or more data centralization units being non-operational.

Abstract: A thermoresistive sensor system compensates for ambient temperature of a medium. First and second side-by-side sensors are mounted in the medium, each having a resistance that varies with temperature change in the medium. A thermal compensation control circuit supplies current to the first sensor such that the cube of its current times its resistance (I.sub.1.sup.3 .times.R.sub.1) is constant. The control circuit supplies current to the second sensor at a multiple of the current through the first sensor. A signal based upon the voltages across each sensor is produced as a temperature compensated output. In this manner, the system automatically compensates for temperature changes in the medium which would otherwise degrade the accuracy of the output.

Abstract: A carriage type ink printer having a replenishable ink cartridge and ink jet printhead mounted on the carriage for translation across a printing region of an ink jet printer. The replenishable ink cartridge having means to keep the necessary negative pressure at the printhead by way of a foam-like material contains an ink supply monitoring means which uses a thermistor and constant current circuitry to indicate when it should be resupplied with ink. The printer controller moves the replenishable cartridge to a predetermined side of the printer beyond the printing region and into position to receive ink from a fixed ink supply container. The ink supply monitoring means indicating when the replenishable cartridge is filled in order to prevent over filling the cartridge.

Abstract: A cryogenic level sensor assembly. A sensor assembly includes a continuous length of high temperature ceramic superconductor material, an exterior housing for holding the length of ceramic superconductor material, a support material disposed between the ceramic superconductor material and the exterior housing, and a resilient retention material disposed opposite the ceramic superconductor material for holding the superconductor material while allowing expansion and contraction thereof during thermal cycling.

Abstract: A temperature compensated, self-heating, resistance thermal detector in a sensor circuit for determining fluid level or fluid flow. A resistor in shunt with the detector provides the temperature compensation. The resistor and the thermal detector are connected between electrical input and output lines. Alternative embodiments include a speed enhancing lead network and a fully automated circuit under microprocessor control.

Abstract: The present invention relates to a method for determining the level of concrete in a concrete mixer comprising the steps of contacting the exterior of concrete mixing drum with a strip of thermal color sensitive material and observing the interface on the color sensitive material produced by the temperature differential between the concrete and the air above. This level can then be lined up horizontally with a graduated volume indicator, to yield the concrete volume in the truck to aid in determining an effective amount of additive to be added to the concrete.

Abstract: The mass of fluid remaining in a container 10 is determined by switching on a series of heating elements 14 and sensing the temperature of the container and contents over a period of time using sensor 16, thereby to deduce the thermal time constant. The thermal time constant is used to determine the mass of the remaining fluid contents from a look-up table or other means. In an alternative arrangement, the thermal response on cooling may be used in a similar manner.

Abstract: A level sensor with an amplifier circuit includes one of the level detection resistor and the temperature compensation resistor as an input resistor or a grounding resistor to the negative input terminal of the operational amplifier, and includes the other resistor as a negative feedback resistor.

Abstract: A surveying rod leveling device and method for checking the accuracy of the level attached to the surveying rod comprising an elongated vertical bracket mounted to a vertical surface, having a movable joint at the top of the bracket and an adjustable horizontal plate with a center point at the bottom of the bracket. A plumb line and bob hangs from the movable joint. The center point of the adjustable bottom plate is aligned with the point of the plumb bob and the bottom plate is secured in place. The center point is removed from an aperture is the adjustable horizontal plate and the surveying rod is inserted into the same aperture. The upper end of the rod is secured to the joint at the top plate. The rod is thus held plumb and the level attached to the rod may be adjusted to produce an accurate reading.

Abstract: A temperature controller with an integral liquid level control contained within one unit. The unit consists of an electrical and heat conductive housing, which serves as a first electrode of the liquid level sensor. A metal clamp and a means to attach the housing to the liquid vessel is insulated from the housing and serves as a second electrode. The electrodes are connected in an electrical circuit such that when the electrodes are immersed within a conductive liquid the resistance between the electrodes is reduced and a current is allowed to flow. A temperature sensor, such as, a thermistor, RTD, or thermocouple, is contained within the housing. The housing conducts heat from the housing environment for radiation within the housing.

Abstract: A sensor comprising a heating element and a temperature detecting element used to measure a temperature of the heating element are both held out of contact with each other within a sensor protecting tube. For fluid exhibiting slow changes in its state as time elapses, a fluid state is measured on the basis of a differential temperature between temperatures prior to and during heating of the heating element. For the fluid exhibiting rapid changes in its state as time elapses, the sensor is caused to generate heat while the temperature of this sensor is measured, and a separate temperature measuring sensor measures the temperature of the fluid. The fluid state is determined on the basis of the differential temperature between the temperatures of the sensor and the temperatures of the fluid.

Abstract: A constant power thermal property sensor compensates for changes in the temperature of the medium into which the sensor is disposed. The sensor has two side-by-side probes mounted in the medium with resistances that vary with temperature. A constant power source produces a current through the first probe and a current source applies a current to the second probe at a fixed ratio of the current in the first probe. The voltages across the probes are monitored and compared, and a signal is produced which is divided by current through the first probe. The resulting signal is representative of the heat transfer between the probes and the medium. The signal does not appreciably vary with changes in the temperature of the medium, and the medium may be a liquid, a gas, a liquid flow, a gas flow, or a combination of media. In this construction, two principal applications for the sensor are liquid level detectors and flow monitors.

Abstract: Provided is a fuel level detector for use in a fuel tank of an automobile or the like which can accurately detect a fuel level with a reduced power consumption exhibiting an improved reliability regardless of the ambient temperatures and the temperatures of liquid fuel in order to overcome the problems involved in a thermistor method and a metal wire method. A spontaneously heated sensing resistor having a high temperature resistance coefficient is formed on a substrate so as to detect a change in the resistance value due to cooling by heat of vaporization at a portion of the sensing resistor which is dipped in fuel as a differential output voltage. In order to prevent errors in the differential output voltage due to the correction of the ambient temperature in the fuel tank, a temperature compensating resistor is provided on the substrate.

Abstract: An apparatus for measuring a level of a cryogenic fluid in a cryostat includes a semiconductor pressure sensor mounted at the end of an elongated vertically disposed tube. The semiconductor pressure sensor is located at the bottom of the tube and is sealed in the bottom of the tube by a polymeric insulating material. The upper end of the tube is provided with a vent hole which communicates vapor pressure within the cryostat to the interior of the tube. The pressure sensor outputs an electrical signal in accordance with the differential pressure exerted on a semiconductor element of the pressure sensor from opposite sides by the vapor pressure within the tube and the fluid pressure outside the tube.

Abstract: The temperature of one or several sensors which are electrically heated or cooled to a temperature substantially different from a stagnant or running fluid surrounding the said sensor or sensors by applying an electric current to the said sensor or sensors, and the temperature of the said fluid are measured simultaneously to calculate the temperature difference between the said sensor or sensors and the said fluid at an equilibrium state of heat transfer at the surface of the said sensor or sensors, thereby measuring a change in state of the said fluid collectively on an in-line processing basis without disturbing the said fluid; a change in this state results in a change in heat transfer coefficient at the surface of the said sensor or sensors, the coefficient being collectively correlated with the viscosity, density, specific heat, thermal conductivity, thermal diffusivity, coefficient of volumetric expansion, flow speed or flow direction of the said fluid at a given temperature.

Abstract: A heat radiating type liquid level sensor comprises a liquid level measuring resistor having a first temperature coefficient and an inverting amplifier gain of which is dependent on the change in resistance of an input resistor thereof. The input resistor has a second temperature coefficient. The liquid level measuring resistor and the input resistor are placed side by side so that the input resistor can experience the same ambient temperature as the liquid level measuring resistor.

Abstract: Apparatus for measurement of average temperature change in the liquid in a storage tank. A series connected plurality of discrete, temperature sensitive elements, at predetermined spacings in the liquid provide a direct output reading representing average temperature change of the entire volume of liquid in the tank. The invention also includes the method for measuring the average temperature change of the liquid in the storage tank.

Abstract: A method for determining the level of heavier particulate waste material in a storage tank of liquid. The method comprises mounting a heated sensor below an unheated or reference sensor so that the reference sensor is influenced under some circumstances by the heater, but is insulated therefrom when the heated sensor is embedded in the particulate material. The invention includes the apparatus for accomplishing the method.

Abstract: A level gauge and measurement method are provided using a sensing element comprising a superconductive alloy represented by the formula:Mo.sub.a Ru.sub.b Z.sub.cwherein Z is phosphorous, boron, or a mixture of phosphorous and boron,b has a value of about 20 to about 40,c has a value of about 10 to about 30, anda+b+c=100.The sensing element has a superconductivity critical temperature of at least 4.2K and is useful for measuring the level of liquid helium independently of pressure fluctuations in the reservoir vessel.

Abstract: A device for electrically measuring the oil level of a machine, particularly of an internal combustion engine, is connected with a device for temporarily blocking re-measurement. The device for the measurement of the oil level comprises a measurement probe (2) which is heated by a constant current during a connect time which is commenced in an automotive vehicle by a switch on a battery terminal (15). Furthermore, means are provided for comparing an initial voltage U.sub.O of the measurement probe at the start of the connect time with a measured voltage at the end of the connect time of a measurement period in order to form a result of the comparison which corresponds to the oil level. A signalling logic (7) which signals ranges of the oil level can be controlled by said result. The blocking-time transmitter, in combination with a control logic (10) for the total program control, blocks repeated measurement during at least one predetermined period of time after the machine is turned off or again turned on.