Patent Application
20240418577
The present disclosure relates to aircraft sensors, and more particularly, to aircraft liquid level and temperature probes.
Aircrafts utilize separate sensors to measure both liquid level and temperature. For example, the aircraft's water system may utilize one sensor to measure the temperature of water in a tank and one or more other sensors to measure the level of the water in the tank. The need to employ multiple sensors to measure the level and temperature of liquid in the tank increases the overall complexity, weight, and costs of the aircraft's hot water system.
According to a non-limiting embodiment, a dual-use level and temperature probe includes a stem configured to contact liquid, at least one sensor coupled to the stem, and a controller in signal communication with the sensor. The sensor includes an input terminal configured to receive electrical current and an output terminal configured to provide a return path for the electrical current. The controller is configured to deliver the input current to the input terminal and configured to monitor a voltage across the input and output terminals. The controller is configured to perform both a liquid level measurement and a temperature measurement based on the voltage.
In addition to one or more non-limiting embodiments, or in the alternative, the sensor is a resistive temperature device.
In addition to one or more non-limiting embodiments, or in the alternative, the resistive temperature device is a thermistor.
In addition to one or more non-limiting embodiments, or in the alternative, the controller is configured to vary a current level of the input current and to determine a temperature associated with the resistive temperature device based on the measurement signal.
In addition to one or more non-limiting embodiments, or in the alternative, the controller is configured to perform the liquid level measurement liquid level measurement during a first time duration and is configured to perform the temperature measurement during a second time duration different from the first time duration.
In addition to one or more non-limiting embodiments, or in the alternative, the controller performs the liquid level measurement in response to performing the operations of delivering a first amount of the electrical current to the input terminal to induce resistive heating of the resistive temperature device; in response to producing resistive heat, halting delivery of the electrical current to the resistive temperature device; measuring the voltage across the resistive temperature device indicative of a resistance and monitoring a decay rate of the resistance; and determining a temperature decay rate associated with the resistive temperature device based on the decay rate of the resistance.
In addition to one or more non-limiting embodiments, or in the alternative, the liquid level measurement further comprises: determining, by the controller, the stem is disposed in a presence the liquid in response to the temperature decay rate being equal to or exceeding to a decay threshold; and determining that the stem is not in the presence of the liquid in response to the temperature decay rate being less than the decay threshold.
In addition to one or more non-limiting embodiments, or in the alternative, the controller performs the temperature measurement after determining the presence of liquid, and generates an alert in response to determining the stem is not in the presence of the liquid.
In addition to one or more non-limiting embodiments, or in the alternative, the controller performs the temperature measurement in response to performing the operations of delivering a second amount of the electrical current to the first input terminal that is less than the first amount of the electrical current; measuring the voltage across the input and output terminals of the resistive temperature device; determining a resistance of the resistive temperature device based on the voltage; determining a temperature of the resistive temperature device based on the resistance; and determining a temperature of the liquid based on the temperature of the resistive temperature device.
According to another non-limiting embodiment, a dual-use level and temperature probe comprises a first sensor coupled to the stem, a second sensor coupled to the stem, and a controller in signal communication with the first sensor and the second sensor. The first sensor includes a first input terminal configured to receive a first electrical current and a first output terminal configured to output the first electrical current. The second sensor includes a second input terminal configured to receive a second electrical current and a second output terminal configured to output the second electrical current. The controller is configured to deliver the first electrical current to the first input terminal and the second electrical current to the second input terminal, and is configured to monitor a first voltage across the first input and output terminals and to monitor a second voltage across the second input and output terminals. The controller is configured to perform a liquid level measurement based on the first voltage and to perform a temperature measurement based on the second voltage.
In addition to one or more non-limiting embodiments, or in the alternative, the first sensor and the second sensor are each a resistive temperature device.
In addition to one or more non-limiting embodiments, or in the alternative, the first sensor is a first type of resistive temperature device and the second sensor is a second type of resistive temperature device.
In addition to one or more non-limiting embodiments, or in the alternative, at least one of the first resistive temperature device and the second resistive temperature device is a thermistor.
In addition to one or more non-limiting embodiments, or in the alternative, the controller is configured to perform both the liquid level measurement and the temperature measurement simultaneously.
In addition to one or more non-limiting embodiments, or in the alternative, the controller performs the liquid level measurement in response to performing the operations of delivering the first electrical current having a first current level to the first input terminal to induce resistive heating of the first resistive temperature device; in response to producing resistive heat from the first resistive temperature device, halting delivery of the first electrical current to the first resistive temperature device; receiving the first voltage signal from the first resistive temperature device indicative of a resistance; monitoring the decay rate of the resistance; and determining a temperature decay rate associated with the first resistive temperature device based on the decay rate of the resistance.
In addition to one or more non-limiting embodiments, or in the alternative, the liquid level measurement further comprises determining, by the controller, the stem is disposed in a presence of the liquid in response to the temperature decay rate being equal to or exceeding to a decay threshold; and determining that the stem is not in the presence of the liquid in response to the temperature decay rate being less than the decay threshold.
In addition to one or more non-limiting embodiments, or in the alternative, the controller performs the temperature measurement in response to performing the operations of delivering the second electrical current having a second current level to the second input terminal, the second electrical current having a current level that is less than the first current level; receiving the second voltage from the resistive temperature device indicative of a resistance of the resistive temperature device; determining a temperature of the resistive temperature device based on the second voltage; and determining a temperature of the liquid based on the temperature of the resistive temperature device.
In addition to one or more non-limiting embodiments, or in the alternative, the second electrical current is a current pulse.
In addition to one or more non-limiting embodiments, or in the alternative, the second current level of the current pulse is less than a current threshold that induces resistive heating of the second resistive temperature device.
According to another non-limiting embodiment, a method of performing a liquid level measurement and a liquid temperature measurement using a single resistive temperature device comprises coupling a single sensor to a stem configured to contact liquid and delivering an electrical current from a controller to an input terminal of the sensor, and outputting the electrical current flowing through the sensor to the controller via an output terminal of the sensor. The method further comprises monitor a voltage across the input and output terminals using the controller; and performing both the liquid level measurement and the temperature measurement based on the voltage.
Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed technical concept. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings.
For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts:
Currently, aircraft water heating systems typically employ two sensors to detect liquid presence and liquid temperature, rather than a single probe that can perform both level measurement and temperature measurement of liquid contained in a tank. Thermistors are Resistive Temperature Devices (RTDs) which operate using a resistance-to-temperature correlation principle. More specifically, as the temperature of a metal increases, so does the resistance to the flow of electricity. A current can be passed through the RTD and the voltage across the resistance element of the RTD can be used to measure the resistance of the device, which directory correlates to its temperature. For example, as the temperature of the resistance element increases the electrical resistance also increases, thereby allowing electrical resistance to be measured in Ohms. The resistance value can then be converted into temperature based on the characteristics of the element.
RTDs also have an inherent current threshold when measuring temperature (as they can self-heat if too much current is used) and this characteristic can be utilized to detect liquid level. When the current flowing through the thermistor exceeds a minimum level, the thermistor begins to produce a resistive heating effect which while detrimental for temperature measuring, can be beneficial for liquid presence measuring.
When using a thermistor to measure liquid level (i.e., when used as a point-level sensor), current having a level that exceeds the current threshold is used to induce resistive heating. The temperature decay rate of the thermistor is then monitored (e.g., by a controller), which varies depending upon if it is in air or water (or any heat-conductive medium). When using the thermistor as a temperature sensor, however, it is important to limit the thermistor current because the resistive heating effect reduces the accuracy of the temperature reading. Therefore, a single conventional thermistor cannot typically be utilized to accurately perform both liquid level measurement and liquid temperature measurement in an aircraft hot water heating system.
Various embodiments of the present disclosure solve the shortcomings of conventional thermistors by providing a dual-use liquid and temperature probe that can be employed in an aircraft hot water heating system to perform both liquid level measurement and liquid temperature measurement. According to a non-limiting embodiment, the dual-use liquid and temperature probe utilizes a single thermistor that operates according to an algorithm which selectively invokes the level measurement function and the temperature measurement function. In another non-limiting embodiment, the dual-use liquid and temperature probe implements a first thermistor configured to perform liquid level measurement and a second thermistor configured to perform liquid temperature measurement. The outputs of the first and second thermistors are delivered to a controller, which can simultaneously process the first and second thermistor outputs to perform both liquid level measurement and liquid temperature measurement.
With reference now to
The stem 110 includes a proximate end 112 that is coupled to the threaded portion 106 and extends continuously to a closed distal end 114. The stem 110 further includes a resistive temperature device (RTD) 116 disposed in distal end 114 of the stem 110. According to a non-limiting embodiment, the RTD 116 is a thermistor, but it should be appreciated that other types of RTDs 116 can be utilized without departing from the scope of the invention.
The RTD 116 includes an input terminal 118 and an output terminal 120. The input terminal 118 and the output terminal 120 are configured to establish signal communication with a controller 150. The input terminal 118 receives an input current 119 generated by the controller 150, while the output terminal 120 returns this measurement signal 121 to the controller 150.
The controller 150 is configured to vary the current level of the input current 119 and is configured to determine a temperature associated with the RTD 116. For example, the controller 150 can deliver the input current to the input terminal and configured to monitor a voltage across the input and output terminals, and perform both a liquid level measurement and a temperature measurement based on the voltage appearing across terminals 118 and 120.
To perform liquid level measurements, the controller 150 can deliver an amount of current (e.g., a first current level) to the RTD 116 that will induce resistive heating. In one or more non-limiting embodiments, the controller 150 outputs current 119 having a current level that is greater than the current threshold of the RTD 116 known to induce resistive heating. Once the RTD 116 is heated, the current 119 is reduced and the controller 150 monitors the decay rate of the resistance of sensor 116. According a non-limiting embodiment, the decay rate of the resistance can be determined by inducing electrical current flow through the sensor 116 and then monitoring the voltage across leads 118 and 120. According to another non-limiting embodiment, the decay rate of the resistance can be determined by applying electrical voltage across the leads 118 and 120 and then monitoring the current flow through the sensor 116. When the decaying strength of the measurement voltage across 118 and 120 is equal to or exceeds a decay threshold, the controller 150 determines that the stem 110 is disposed in the presence of surrounding liquid, (or other heat-conductive medium, including ice). When, however, the decaying strength of the measurement voltage across terminals 118 and 120 is below the decay threshold, the controller 150 determines that no liquid is present or surrounding the stem 110. Such an event could indicate, for example, that the liquid has fallen below a target liquid level or the liquid has drained completely from the tank.
For temperature measurements, the controller 150 delivers a second amount of current to the RTD 116 that is less than the amount generated when performing the liquid level measurement (e.g., less than the current threshold of the RTD 116). In one or more non-limiting embodiments, the current is delivered using one or more short pulses of current. In this manner, the controller 150 can measure the resistance of the RTD based on the voltage measurement across terminals 118 and 120, for example, and determine a present temperature of the RTD 116 indicative of the present temperature of the surrounding liquid based on the resistance indicated by the measured voltage across terminals 118 and 120. Because the controller 150 ensures that the level of the input current is below the heating current threshold, and because the current is only pulsed on for a short duration, the resulting temperature measurements remain accurate and are not susceptible to inaccuracies caused by resistive heating.
According to a non-limiting embodiment, the controller 150 utilizes an algorithm (e.g., stored in the memory of the controller 150) to selectively perform the liquid level measurements and temperature measurements described above. For example, the controller 150 executing the algorithm may not initialize heater activation and invoke the temperature measurement mode to perform liquid temperature measurements until the dual-use liquid and temperature probe 100 first detects liquid. Once liquid is detected, the controller 150 invokes liquid heating along with the temperature measurement mode to monitor that liquid's temperature. The controller 150 then runs an optimized algorithm to alternate between monitoring liquid presence and liquid temperature. While the temperature is less than or equal to a temperature threshold, the controller 150 can continue monitoring the temperature of the liquid. When, however, the monitored temperature exceeds a temperature threshold, the controller 150 can determine the liquid has possibly fallen below a level threshold, and then invoke the level measurement mode. In this manner, the dual-use liquid and temperature probe 100 can be employed in an aircraft hot water heating system to perform both liquid level measurement and liquid temperature measurement.
In another example, the algorithm can command the controller 150 to intermittently switch between the level measuring mode and the temperature measuring mode according to a set time period, e.g., every 30 seconds. In this manner, a greater number of liquid level measurements can be obtained rather than waiting until the temperature measurement exceeds the temperature threshold before invoking the level measurement mode.
Referring to
When, however, the temperature decay exceeds the decay threshold, the method proceeds to operation 316 and determines liquid level is equal to or above the level threshold. At operation 318, a second amount of current less than the first amount of current is delivered to the RTD to support reading the RTD temperature. At operation 320, the present temperature of the RTD is determined (e.g., by the controller 150). At operation 324, a determination is made (e.g., by the controller 150) as to whether the temperature is less than or equal to a temperature threshold. When true, the controller then applies heat to the liquid at operation 326 and returns to operation 320 to continue determining the temperature of the liquid. When, however, the temperature exceeds the temperature threshold, the method stops delivering heat to the liquid at operation 328, and returns to operation 302 and delivers the first amount of current to the RTD to invoke the liquid level measuring operation described in detail above to confirm whether the liquid has fallen below the liquid level threshold.
Turning now to
The dual-use liquid and temperature probe 200 includes a stem 110 that contains two individual RTDs 116a and 116b. A first RTD 116a can be located at the stem distal end 114 and a second RTD 116b can be located the proximate end 112. In this example, the first RTD 116a is utilized as a liquid level measurement sensor while the second RTD 116b is utilized as a temperature measurement sensor. It should be appreciated, however, that the first RTD 116a can be utilized as a temperature sensor while the second RTD 116b can be utilized as a liquid level measurement sensor. In any case, the first and second RTDs 116a and 116b can be implemented as a thermistor or other type of RTD. In one or more non-limiting embodiments, the first and second RTDs 116a and 116b can be the same type of RTD. In other non-limiting embodiments, the first RTD 116a can be a first type of RTD, while the second RTD 116b can a different second type of RTD. In other non-limiting embodiments, both sensors can function as redundant temperature or level sensors.
The first RTD 116a includes a first input terminal 118a and a first output terminal 120a. The first input terminal 118a and the first output terminal 120a are configured to establish signal communication between the first RTD 116a and a controller 150. The first input terminal 118a receives a first input current 119a generated by the controller 150, while the first output terminal 120a delivers a first measurement signal 121 (e.g., output current) to the controller 150.
Likewise, the second RTD 116b includes a second input terminal 118b and a second output terminal 120b. The second input terminal 118b and the second output terminal 120b are configured to establish signal communication between the second RTD 116b and the controller 150. The second input terminal 118b receives a second input current 119b generated by the controller 150, while the second output terminal 120b delivers a second measurement signal 121b (e.g., output current) to the controller 150.
To perform liquid level measurements, the controller 150 delivers an amount of current 119a (e.g., a first current level) to the first RTD 116 via the first input terminal 118a that will induce resistive heating. In one or more non-limiting embodiments, the controller 150 outputs current 119a having a current level that is greater than the current threshold of the first RTD 116a known to induce resistive heating. Once the first RTD 116a is heated, the heavier current is cut off while a lower current sufficient to measure RTD temperature continues, and the controller 150 monitors the decay of the signal strength (e.g., voltage) across terminals 118a and 120a which is indicative of the temperature decay of the first RTD 116a. When the decaying strength of the first measurement voltage across signals terminals 118a and 120a (within a preset window of time) is equal to or above a decay threshold, the controller 150 determines that the stem 110 is disposed in the presence of surrounding liquid (or other heat-conductive medium). When, however, the decaying strength of the first measurement voltage across terminals 118a and 120a (within the same preset window of time) falls below the decay threshold, the controller 150 determines that no liquid is present or surrounding the stem 110.
For temperature measurement, the controller 150 delivers an amount of current 119b (e.g., a second current level) to the second RTD 116b via the second input terminal 118b that is less than the amount of current 119a delivered to the first RTD 116a when performing the liquid level measurement (e.g., less than the current threshold of the first RTD 116a). In this manner, the controller 150 measures the resistance of the second RTD 116b based on the second voltage measurement across terminals 118b and 120b, and determines a present temperature of the second RTD 116b so as to determine the present temperature of the surrounding liquid. In one or more non-limiting embodiments, the controller 150 can simultaneously deliver the first and second currents 119a and 119b to the first and second RTDs 116a and 116b via terminals 118a and 118b, respectively. Likewise, the controller 150 can simultaneously process the first and second voltages appearing across terminals 118a and 120b and 118b and 120b to simultaneously perform level measurements and temperature measurements of the liquid. In this manner, the dual-use liquid and temperature probe 200 can be employed in an aircraft hot water heating system to perform both liquid level measurement and liquid temperature measurement with a single probe, rather than having multiple probes mounted in system to individually measure both water temperature and level.
Turning to
At operation 408, a determination is made as to whether the temperature decay exceeds a decay threshold. When the temperature decay is below the decay threshold, an alert is generated (e.g., by the controller 150) that the liquid level is below a liquid level threshold at operation 410, and the method restarts at operation 400. When, however, the temperature decay is greater than the decay threshold, it is determined (e.g., by the controller 150) at operation 412 that the liquid is equal to or greater than the liquid level threshold at operation 416 and the method restarts at operation 400.
Turning to operation 403, a second amount of current less than the first among of current is delivered to a second RTD included in the single dual-use liquid level and temperature probe. It should be appreciated that the first current (i.e., operation 402) and the second current (i.e., operation 403) can be output (e.g., by the controller 150) simultaneously or can be output at different times. At operation 405, the temperature of the second RTD is determined (e.g., by the controller 150). At operation 407, a determination is made (e.g., by the controller 150) as to whether the temperature is less than or equal to a temperature threshold. If true, the controller enables heating of the liquid at operation 409 and then returns to operation 405 and continues determining the temperature of the second RTD. When, however, the temperature exceeds the temperature threshold, the heating can be disabled/stopped at operation 411, and the method restarts to operation 400.
As described herein, various embodiments of the present disclosure provide a dual-use liquid and temperature probe that can be employed in an aircraft hot water heating system to perform both liquid level measurement and liquid temperature measurement. Accordingly, the dual-use liquid and temperature probe described herein provides technical effects and benefits including reducing cost and weight of an aircraft water system, also simplifying the assembly and design of a water tank (e.g., the aircraft hot water tank).
The corresponding structures, materials, acts and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the technical concepts in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
While the preferred embodiments to the disclosure have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure first described.
