Patent Description:
In today's modern aircraft, there are many locations that require a positive position indication to ensure that safety conditions are met. One such example is the cabin door of an aircraft, wherein if the cabin door is not fully secured the safety of the passengers and crew is at risk. In fact, if the cabin door is not fully secured the survivability of the entire aircraft may be threatened. For example, an incorrect indication that the cabin door is secured may cause the aircraft to takeoff when the passenger cabin is not properly sealed. This can prevent the cabin Environmental Control System (ECS) from operating properly and thus, pressurization of the cabin may not occur as discussed below.

Another such example is the aircraft's Weight-On-Wheels (WOW) system. The WOW system typically utilizes safety critical proximity sensors (WOW sensors) that are configured to detect when a landing gear strut is fully-compressed. These WOW sensors may also be tied to a variety of additional complex systems such as brakes, aircraft pressurization, and spoilers. In fact, without the WOW sensors, the pilot may not know when the aircraft is in the air or on the ground. Failure of this type of switch could translate to the pilot being unable to retract the gear on takeoff because the system 'thinks' that the aircraft is still on the ground. Additionally, in turbine aircraft, the WOW sensors keep the pilot from pressuring the cabin while on the ground, and thus failure of this sensor may keep the pilot from pressuring the cabin in the air.

In some cases, aircraft systems use a hall effect sensor/switch that detects the position (proximity) of a metal target (object), wherein the metal target is constructed from a ferromagnetic material. <FIG> illustrates a general hall-effect sensor configuration. Unfortunately, however, hall effect sensors as proximity indicators typically only operate well over a narrow temperature range such as -<NUM> to +<NUM>. This is undesirable because the typical operating temperature range of aviation electronics can be between -<NUM> to +<NUM>. One way to address this narrow operating range and 'force' proper operation over a wide temperature range is to employ special temperature compensation techniques, such as using an Application Specific Integrated Circuit (ASIC) with memory components, or a microcontroller with software. Unfortunately, employing these 'special temperature compensation techniques' make the hall effect sensors overly complicated and require a large investment to comply with aviation standard requirements, such as DO-<NUM> and/or DO- <NUM>.

<CIT> discloses a proximity sensor having an oscillation circuit containing an inductance (<NUM>) and a capacitance (<NUM>), with a resonance resistance dependent on the distance between the inductance and the detected object (<NUM>). An oscillator (<NUM>) coupled to the oscillation circuit has a first setting element (<NUM>) for providing a digitally variable feedback current, a second setting element (<NUM>) for temperature-dependent adjustment of a comparison threshold and a third setting element (<NUM>) for providing an analogue variable feedback current, the second and third setting elements coupled to the oscillation circuit. An Independent claim for a compensation and/or calibration method for a proximity sensor is also included.

A proximity sensor system is provided, wherein the proximity sensor system includes a sensor article having a sensor sensing surface, wherein the sensor article is configured to sense the magnetic field of a magnetic target article located proximate the sensor sensing surface and generate a sensor signal. The proximity sensor system includes a Temperature Compensation Article (TCA), wherein the Temperature Compensation Article includes, a first Digital-to- Analog Converter (DAC), a first thermistor and a first biasing resistor, wherein the first thermistor and the first biasing resistor are connected in a parallel configuration and the first DAC is connect to the first thermistor and the first biasing resistor in a series configuration, a second DAC and a second thermistor <NUM>, wherein the second DAC and second thermistor are connected in a series configuration, a third DAC and a Resistive Temperature Detector (RTD), wherein the third DAC and RTD are connected in a series configuration, a fourth DAC and a second biasing resistor, wherein the fourth DAC and the second biasing resistor are connected in a series configuration, wherein the outputs of the first thermistor and first biasing resistor combination, second thermistor, RTD and the second biasing resistor are connected together to generate a TCA output signal. The proximity sensor system also includes processing circuitry, wherein the processing circuitry is configured to process the sensor signal and the TCA output signal to generate a sensor system output signal.

A method for implementing a proximity sensor system is provided, wherein the proximity sensor system includes a sensor article, a Temperature Compensation Article having a plurality of Digital to Analog Converters (DACs) and processing circuitry. The method includes generating first sensor output data for a magnetic target article located at a first distance away from the sensor article, generating second sensor output data for the magnetic target article located at a second distance away from the sensor article, processing the first sensor output data and the second sensor output data to generate threshold data, configuring the Temperature Compensation Article responsive to the threshold data, calculating the digital data responsive to the threshold data, introducing the digital data into the DACs to generate a TCA output signal, generating sensor operating data, wherein the sensor operating data is generated by operating the sensor article across an operational temperature range and processing the TCA output signal and the sensor operating data to generate a sensor system output signal.

A method for generating a proximity system output signal for a proximity sensor system is provided, wherein the proximity sensor system includes a sensor article, a temperature compensation article and a processor. The method includes operating the sensor article to generate first sensor output data, wherein the first sensor output data is responsive to the sensor article sensing the magnetic field of a magnetic target article across a predefined temperature range and located at a first distance away from the sensor article, operating the sensor article to generate second sensor output data, wherein the second sensor output data is responsive to the sensor article sensing the magnetic field of a magnetic target article across the predefined temperature range and located at a second distance away from the sensor article and processing the first sensor output data and the second sensor output data to generate threshold data. The method further includes configuring the temperature compensation article to generate an output signal responsive to the threshold data, generating sensor operating data, wherein the sensor operating data is generated by operating the sensor article across an operational temperature range, wherein the operational temperature range is within the predefined temperature range and comparing the threshold data and the sensor operating data to generate at least one of a high signal and a low signal.

The foregoing and other features and advantages of the present invention should be more fully understood from the accompanying detailed description of illustrative embodiments taken in conjunction with the following Figures in which like elements are numbered alike in the several Figures:.

As discussed hereinafter and in accordance with the present invention, a hall-effect based proximity sensor and a method for implementing a hall-effect based proximity sensor is provided, wherein the hall-effect based proximity sensor uses analog techniques to achieve proper operation over a wider temperature range than is currently achievable and which will not require a large investment to comply with applicable aviation standards, such as DO-<NUM> and/or DO-<NUM>. Hall effect sensors operate on the presence or absence of a magnetic field, wherein the magnetic field is supplied by a discrete magnet and a ferromagnetic target is used as the sensing target. Referring to <FIG>, the present invention achieves hall-effect sensing by packaging a discrete magnet inside the body of the sensor, which imparts a constant magnetic bias on a chip. Then, when a ferromagnetic target comes in close proximity to the chip, the magnetic field is altered, which allows for the creation of signals that indicate the location of the target relative to the sensor (i.e. 'near' and 'far' signals).

In accordance with one embodiment of the present invention, referring to <FIG> and <FIG>, a schematic block diagram of a hall-effect based proximity sensor system <NUM> is shown and includes a sensor article <NUM> having a sensor sensing surface (datum) <NUM> and a sensor output <NUM>, a ferromagnetic (metal) target article <NUM>, a Temperature Compensation Article (TCA) <NUM> and a processing module <NUM> having a processing module output signal <NUM>. It should be appreciated that the hall-effect based proximity sensor system <NUM> is configured such that the sensor article <NUM> senses the proximity of the target article <NUM> relative to a distance away from the sensor sensing surface (datum) <NUM>. Referring to <FIG>, when the target article <NUM> is at a distance D<NUM> which is relatively close to the datum <NUM>, the sensor article <NUM> will sense the higher magnetic field generated by the closeness of the target article <NUM> to the datum <NUM> and generate a first signal which will indicate that the target article <NUM> is close to the datum <NUM> (i.e. "TARGET NEAR" signal). Referring to <FIG>, when the target article <NUM> is at a distance D<NUM> which is relatively far from the datum <NUM> (i.e. farther then distance D<NUM>), the sensor article <NUM> will sense the lower magnetic field generated by the larger distance of the target article <NUM> from the datum <NUM> and generate a second signal which will indicate that the target article <NUM> is far from the datum <NUM> (i.e. "TARGET NEAR" signal).

It should be appreciated that although the invention is disclosed herein as having the convention that a higher (or stronger) magnetic field is associated with a closer target and a lower (or weaker) magnetic field is associated with a farther target, other embodiments may employ any convention suitable to the desired end purpose. For example, in another embodiment, the invention may be configured such that a higher (or stronger) magnetic field may be associated with a farther target and a lower (or weaker) magnetic field may be associated with a closer target. It should be appreciated that, in one embodiment, the sensor article <NUM> generates an analog signal proportional to the magnetic field which is directly related to the distance between the sensor sensing surface (datum) <NUM> and the target article <NUM>. It should be further appreciated that the output of the sensor article <NUM> may be analog (i.e. continuous) indicating distance and/or the output of the sensor article <NUM> may be discrete to function as a proximity switch. Accordingly, it is contemplated that the sensor article may be configured to simultaneously or non-simultaneously sense distance and proximity if desired. Moreover, although the hall-effect based proximity sensor system <NUM> is disclosed herein as the sensor article <NUM> being separate from the Temperature Compensation Article (TCA) <NUM> and the processing module <NUM>, it is contemplated that the sensor article <NUM> the Temperature Compensation Article (TCA) <NUM> and the processing module <NUM> may all be packaged within the same enclosure.

Referring to <FIG>, a graph <NUM> showing the output signal of one embodiment of the sensor article <NUM> for seven (<NUM>) different temperatures between about - <NUM> and +<NUM> at two (<NUM>) different distances (target near, target far) is provided. It should be appreciated that, in general, in this embodiment the closer the target article <NUM> is to the datum <NUM>, the higher the magnetic field sensed by the datum <NUM>. Likewise, in general, in this embodiment the farther the target article <NUM> is from the datum <NUM>, the lower the magnetic field sensed by the datum <NUM>. As can be seen in <FIG>, the sensor article <NUM> is configured to generate a higher voltage with a higher magnetic field (the target article <NUM> is closer than the threshold distance <NUM>) and a lower voltage with a lower magnetic field (the target article <NUM> is farther than the threshold distance <NUM>). It should be appreciated that in another embodiment, the sensor article <NUM> may be configured to have an opposite signal polarity. As such the sensor article <NUM> may be configured to generate a lower voltage with a higher magnetic field (the target article <NUM> is closer than the threshold distance <NUM>) and a higher voltage with a lower magnetic field (the target article <NUM> is farther than the threshold distance <NUM>).

Referring to <FIG>, one embodiment of the hall-effect based proximity switch system <NUM> is shown and uniquely provides for accuracy in generating the desired non-linear switching threshold point between the "TARGET NEAR" and "TARGET FAR" signals. The TCA <NUM> of the hall-effect based proximity switch system <NUM> includes a plurality of Digital-to-Analog Converters (DACs) <NUM> and includes a first DAC <NUM>, a first thermistor <NUM> and a first biasing resistor <NUM>, wherein the first thermistor <NUM> and the first biasing resistor <NUM> are connected in a parallel configuration and the first DAC <NUM> is connect to the first thermistor <NUM> and the first biasing resistor <NUM> in a series configuration. The hall-effect based proximity switch system <NUM> further includes a second DAC <NUM> and a second thermistor <NUM>, wherein the second DAC <NUM> and second thermistor <NUM> are connected in a series configuration.

Additionally, the TCA <NUM> further includes a third DAC <NUM> and a Resistive Temperature Detector (RTD) <NUM>, wherein the third DAC <NUM> and RTD <NUM> are connected in a series configuration. The TCA <NUM> also includes a fourth DAC <NUM> and a second biasing resistor <NUM>, wherein the fourth DAC <NUM> and the second biasing resistor <NUM> are connected in a series configuration. The outputs of the first thermistor <NUM> and first biasing resistor <NUM> combination, second thermistor <NUM>, RTD <NUM> and the second biasing resistor <NUM> are connected together as output VOut <NUM>. It should be appreciated that any number of DACs and biasing resistors may be used as desired. For example, in <FIG> a fifth DAC <NUM> and a third biasing resistor <NUM> is shown as 'DACn' and 'Rn' respectively to indicate that 'n' number of DAC's and 'n' number of biasing resistors may be used if desired. The output VOut <NUM> and the sensor output <NUM> is then introduced into processing circuitry, such as comparator <NUM> having a feedback resistor Rf, wherein the comparator <NUM> is configured to generate a digital output signal <NUM> which is at least one of high and low. This digital output signal <NUM> may then be introduced into the aircraft system as the proximity signal. Referring to <FIG>, a graph illustrating the output threshold signal <NUM> of the TCA article <NUM> of <FIG> at signal output <NUM> is shown. It should be appreciated that this threshold signal <NUM> is responsive to the selection of the components of the TCA article <NUM> and thus can be predetermined based on the selection of the components of the TCA article <NUM>.

In this embodiment, the five (<NUM>) DACs <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are used to generate five (<NUM>) bias points which are summed together to form output VOut. A mathematical analysis is performed to select appropriate output values from each of the DACs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, which in turn is dependent upon the values selected for the first thermistor <NUM>, the second thermistor <NUM>, the first biasing resistor <NUM>, the second biasing resistor <NUM>, the third biasing resistor <NUM> and the RTD <NUM>. It should be further appreciated that this embodiment includes three (<NUM>) additional biasing points than TCA article <NUM>, wherein the three (<NUM>) additional control points that are used to generate the desired non-linear threshold point and advantageously allows the ability to create the desired function in a manner which eliminates the manual resistor selection as well as results in a close to near-perfect function fit.

It should be appreciated that in one embodiment, the TCA article <NUM> may be configured by operating the sensor article <NUM> across a predefined temperature range with a magnetic target article at a first distance away from sensor (such as Target Near) to generate first sensor output data (analog). The sensor article <NUM> may then be operated across the predefined temperature range with the magnetic target article at a second distance away from the sensor (such as Target Far) to generate second sensor output data (analog). Threshold data may then be generated by averaging the first sensor output data and the second sensor output data. The components (i.e. resistor values, temperature dependent resistor values, etc.) of the TCA article <NUM> may then be selected responsive to the threshold data, wherein the values of these components may have already been optimized, i.e. the exact NTC thermistors (with correct betas), RTDs and resistor used. The digital values that are to be introduced into the EEPROM registers of the DAC's <NUM> to achieve the desired TCA output <NUM> may be calculated and the TCA output <NUM> may be compared with the real time sensor data <NUM> to generate a high or low signal output <NUM>. Basically, once the threshold voltage has been calculated from the far and near locations, equations are solved to yield the DAC <NUM> settings. These DAC <NUM> settings are then loaded and stored in the EEPROM of each device (here using I2C). These DACs <NUM> may have some type of memory to hold these values for the life of the part.

It should be appreciated that the TCA article <NUM> may be configured via any method and/or using any components suitable to the desired end purpose. In one embodiment, the component values may be optimized to reproduce any nonlinear function. And depending on how the non-linear behavior is, some DAC and resistive components may be eliminated altogether, if desired. The mathematical solution will tell which DACs are needed or not needed. For example, equations to calculate DAC output voltages for <NUM> different temperatures are shown immediately hereinafter:
<MAT>
<MAT>
<MAT>
<MAT>
<MAT>
<MAT>
<MAT>
<MAT>.

Wherein, Vthr_x are the calculated threshold voltages, Vrv is the voltage out of DAC <NUM> with the fixed resistor <NUM>, Vrtd is the voltage out of DAC <NUM> with RTD <NUM>, Vntca is the voltage with the NTCa thermistor <NUM> and Vntcb is the voltage with the NTCb thermistor <NUM>.

Once these voltages are known, the DAC <NUM> settings can be calculated (here shown as <NUM>-bit DACs and a DAC reference voltage of <NUM> VDC) as shown immediately hereinafter:
<MAT>
<MAT>
<MAT>
<MAT>
Wherein DACrv = DAC <NUM>, DACrtd = DAC <NUM>, DACntca = DAC <NUM> and DACntcb = DAC <NUM>.

It should be appreciated that in one embodiment, the electronic architecture of the TCA article <NUM> may employ <NUM>-bit digital-to-analog (DAC) converters <NUM>, along with a pt500 RTD <NUM>, a <NUM> resistor for fixed resistor Ra <NUM>, an NTC thermistor <NUM> with a β <NUM>/<NUM> coefficient of <NUM>, and an NTC thermistor <NUM> with a β <NUM>/<NUM> coefficient <NUM> in parallel with a <NUM> resistor <NUM>. Any suitable combination of positive and negative coefficient resistive devices, some with parallel or series fixed resistors, can be used to achieve any desired non-linear voltage output <NUM>.

Referring again to <FIG>, <FIG>, <FIG> and <FIG>, the graph <NUM> includes a first signal trace <NUM> that represents the output of the sensor article <NUM> for multiple temperatures between about -<NUM> and about +<NUM> at first distance D<NUM>, when the target article <NUM> is relatively close to the datum <NUM>. The graph <NUM> further includes a second signal trace <NUM> that represents the output of the sensor article <NUM> for multiple temperatures between about -<NUM> and about +<NUM> when the target article <NUM> is at second distance D<NUM>, wherein the second distance D<NUM> is farther away from the datum <NUM> than the first distance D<NUM>. It will be noticed that the same temperature data points were used to create the first signal trace <NUM> and the second signal trace <NUM>.

Once the first signal trace <NUM> and second signal trace <NUM> are generated, a threshold or third signal trace <NUM> is calculated, wherein the threshold or third signal trace <NUM> represents an 'average' of the first signal trace <NUM> and second signal trace <NUM>. Referring to <FIG>, a graph <NUM> is provided and includes first signal trace <NUM>, second signal trace <NUM> and third signal trace <NUM> which represents the threshold signal that is calculated using the data from the first signal trace <NUM> and the data from the second signal trace <NUM>. It should be appreciated that although in one embodiment the third signal trace <NUM> is calculated by averaging the first signal trace <NUM> and the second signal trace <NUM>, any method for generating third signal trace <NUM> may be used.

It should also be appreciated that the third signal trace <NUM> is representative of the target article <NUM> being located at a threshold distance DT away from the datum <NUM>, wherein the threshold distance DT is located between the first distance D<NUM> and the second distance D<NUM>. It should be appreciated that although only seven (<NUM>) temperatures were used to generate the first signal trace <NUM> and second signal trace <NUM> above, any number of temperatures as desired may be used. It should be appreciated that in accordance with one embodiment of the invention, the TCA <NUM> is then configured to generate a signal output <NUM> that resembles the threshold or third signal trace <NUM>, wherein this threshold signal trace <NUM> represents and is very similar to the third signal trace <NUM> across a range of temperatures between about -<NUM> and about +<NUM>.

In accordance with one embodiment of the invention, the TCA <NUM> may be configured to generate the threshold signal trace by selecting an appropriate combination of components used in the TCA <NUM> that are necessary to produce the threshold signal trace <NUM>. It should be appreciated that the selection of the combination of components may be determined using common circuit equations. Referring to <FIG>, another embodiment of TCA <NUM> is shown and includes a first biasing resistor <NUM>, a second biasing resistor <NUM>, a third biasing resistor <NUM>, a Resistive Temperature Detector (RTD) <NUM> and a thermistor article <NUM>, wherein one or more of the biasing resistors <NUM>, <NUM>, <NUM> may be fixed and/or variable resistors. Additionally, it will be noted that in this embodiment the first biasing resistor <NUM>, third biasing resistor <NUM>, Resistive Temperature Detector (RTD) <NUM> and thermistor article <NUM> are connected in series configuration and the second biasing resistor <NUM> is connected in parallel with the thermistor article <NUM>. Although in one embodiment the RTD <NUM> may be a component that has a linear dependence on temperature and increases its resistance with an increase in environmental temperature, it should be appreciated that any positive temperature coefficient device may be used as desired, such as, for example a PTC in conjunction with a parallel resistor. Moreover, the thermistor article <NUM> is preferably a component that has a non-linear dependence on temperature and decreases its resistance with an increase in environmental temperature.

It should be appreciated that appropriate selection of the values for biasing resistors <NUM>, <NUM> and <NUM> may provide the capability to create virtually any non-linear and non-monotonic function of temperature desired regardless of whether the RTD <NUM> and the thermistor article <NUM> are connected together in parallel and/or series. Additionally, it should be appreciated that the TCA article <NUM> may further include a first signal input <NUM>, a second signal input <NUM> and a signal output <NUM>, <NUM>, wherein for the TCA article <NUM> shown in <FIG>, the first signal input <NUM> is shown as Vcc and the second signal input <NUM> is shown as ground.

Referring to <FIG>, the TCA article <NUM> is shown in accordance with another embodiment, wherein the first signal input <NUM> is shown as VHigh and the second signal input <NUM> is shown as VLow. It is contemplated that VHigh and VLow may be set to any voltage level desired via any method suitable to the desired end purpose, such as a standard potentiometer (such as trim-pot) or by a programmable potentiometer. It should be appreciated that this method advantageously reduces the need to implement non-standard resistor values my combining multiple resistors together by programming the potentiometer(s) to the desired value(s).

It should be appreciated that in accordance with the present invention, the desired threshold signal <NUM> can be determined by taking measurements <NUM>) from a sensor <NUM> across a temperature range of about -<NUM> (±<NUM>%) and about +<NUM> (±<NUM>%) while the target article was located at a distance near (i.e. D<NUM>) to the datum <NUM>) from a sensor across a temperature range of about -<NUM> (±<NUM>%) and about +<NUM> (±<NUM>%) while the target article was located at a distance far (i.e. D<NUM>, where D2>D1) from the datum <NUM>, and <NUM>) averaging the data collect at D<NUM> and at D<NUM> for each of the temperature points. It should also be noted that the threshold signal <NUM> of the TCA article <NUM> closely resembles the third signal trace <NUM> (i.e. at the threshold distance <NUM>) in <FIG> and therefore represents a temperature dependent, non-linear, non-monotonic function response which matches the hall-effect Sensor output at the threshold distance <NUM> (i.e. third signal trace <NUM>). Accordingly, since the threshold signal <NUM> of the TCA article <NUM> matches the third signal trace <NUM>, this indicates that the hall-effect based proximity switch system <NUM> will properly operate as a proximity sensor over a wide range of temperatures ranging from about -<NUM> (±<NUM>%) to about +<NUM> (±<NUM>%). It should be appreciated that the present invention is operable over across a temperature range that exceeds about -<NUM> to about +<NUM>. In fact, the temperature operating range of the present invention is determined by the operating ranges of the components used to implement the TCA article <NUM> (i.e. signal conditioning electronics, power input electronics, etc.) and thus, is theoretically unlimited. For example, an operating range of about -<NUM> to about +<NUM> is possible if the components used to implement the invention are able to operate in such an environment. Furthermore, it is contemplated that in one embodiment, a high temperature magnet may be used.

It should be appreciated that in this embodiment, the five (<NUM>) DACs <NUM>, <NUM>, <NUM>, <NUM>, <NUM> are used to generate five (<NUM>) bias points which are summed together to form output VOut. A mathematical analysis is performed to select appropriate output values from each of the DACs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, which in turn is dependent upon the values selected for the first thermistor <NUM>, the second thermistor <NUM>, the first biasing resistor <NUM>, the second biasing resistor <NUM>, the third biasing resistor <NUM> and the RTD <NUM>. It should be further appreciated that this embodiment includes three (<NUM>) additional biasing points than TCA article <NUM>, wherein the three (<NUM>) additional control points that are used to generate the desired non-linear threshold point and advantageously allows the ability to create the desired function in a manner which eliminates the manual resistor selection as well as results in a close to near-perfect function fit.

Furthermore, referring to <FIG>, it is contemplated that in other embodiments, the hall-effect based proximity sensor system <NUM>, <NUM> may also be configured to operate as a speed sensor, wherein the sensor article <NUM> can be configured to measure the rotating speed of a shaft. In this embodiment, a ferromagnetic gear may be rigidly attached to the shaft, wherein the revolution speed of the gear may (or may not) be the same as that of the shaft (i.e. geared up or down). Referring to <FIG> and <FIG>, the ferromagnetic gear may have a predefined number of teeth, wherein the outer diameter or width surface of each tooth may act to generate a "TARGET NEAR" signal. Additionally, each of the cavities (i.e. tooth spacing) between the gear teeth may act to generate a "TARGET FAR" signal. Thus, as the gear rotates, the hall-effect based proximity sensor system <NUM>, <NUM> 'detects' the "TARGET NEAR" and "TARGET FAR" conditions and generates an alternating signal which can be used to measure the rotation speed (frequency of the sensor output may be proportional to the gear revolution speed).

In accordance with an additional embodiment of the invention, referring to <FIG>, an operational block diagram illustrating a method <NUM> for implementing a hall-effect based proximity switch system <NUM>, <NUM>, having a sensor article <NUM> with a datum <NUM>, a sensor output <NUM>, a ferromagnetic target <NUM>, a TCA <NUM> and a processor <NUM> is provided and includes generating first sensor output data for a predefined temperature range with a target article at a first distance away from the sensor article <NUM>, as shown in operational block <NUM>. This may be accomplished by positioning the target article at a first distance away from the sensor article <NUM> and operating the sensor article <NUM> at varying temperatures across the predefined temperature range and recording the first sensor output data for one or more temperatures.

The method <NUM> further includes generating second sensor output data for the predefined temperature range with a target article at a second distance away from the sensor article <NUM>, as shown in operational block <NUM>, wherein the first distance is not equal to the second distance. This may be accomplished by positioning the target article at a second distance away from the sensor article <NUM> and operating the sensor article <NUM> at varying temperatures across the predefined temperature range and recording the second sensor output data for one or more temperatures. It should be appreciated that although it is contemplated that the same or similar temperature points are used to generate first sensor output data and second sensor output data, other embodiments may use different temperature points.

The method <NUM> includes processing the first sensor output data and the second sensor output data to generate threshold data, as shown in operational block <NUM>. This may be accomplished by averaging the output data for each of the temperature points of the first and second sensor output data. The method <NUM> further includes configuring the TCA <NUM> to generate an output signal that is very similar to the threshold data across a predefined temperature range, as shown in operational block <NUM>. This may be accomplished by designing the TCA <NUM> with the appropriate components necessary to produce TCA output data that is similar or exact to the threshold data across the predefined temperature range.

Furthermore, the method <NUM> includes configuring the processor <NUM> to process the threshold data and sensor data (as the sensor is operating in its installed environment) to generate a system output signal <NUM>, as shown in operational block <NUM>, wherein the system output signal <NUM> may be at least one of a high signal and a low signal. In one embodiment, this may be accomplished via comparing the sensor data with the threshold data and if the sensor data is greater than or equal to the threshold data for a particular temperature, the system output signal <NUM> may be high (or low), else the system output signal <NUM> may be low (or high). In another embodiment, this may be accomplished via comparing the sensor data with the threshold data and if the sensor data is less than or equal to the threshold data for a particular temperature, the system output signal may be high (or low), else the system output signal <NUM> may be low (or high). The method <NUM> further includes introducing the system output signal <NUM> to an aircraft system as the proximity signal, as shown in operational block <NUM>.

It should be appreciated that in one embodiment, the system output signal <NUM> may be generated via a comparator that compares the sensor signal <NUM> to the threshold signal <NUM>. Referring to <FIG>, an operational block diagram illustrating a method <NUM> for generating a proximity system output signal <NUM> is shown and includes identifying a plurality of threshold points on a threshold signal <NUM>, as shown in operational block <NUM>, wherein each of the plurality of threshold points corresponds to a specific temperature across a temperature range of about -<NUM> to about +<NUM>. It should be appreciated that the threshold signal <NUM> may be generated in response to a TCA article <NUM> that was designed with components that were specifically selected to cause the TCA article <NUM> to generate a voltage output signal across a wide temperature range having desired characteristics. For example, in one embodiment, it is desired to have a TCA output signal with defined voltage versus temperature characteristics across a temperature range of about -<NUM> to about +<NUM>. One such signal is shown in <FIG>, wherein the signal was calculated as discussed herein above.

The method <NUM> further includes identifying a plurality of sensor points on a sensor signal, as shown in operational block <NUM>, as the sensor is operating in its installed environment and wherein each of the plurality of sensor points corresponds to a specific temperature within a temperature range which is between about -<NUM> to about +<NUM>, wherein the plurality of threshold points and the plurality of sensor points correspond to the same (or similar) temperature values. The method <NUM> further includes comparing the voltage of the threshold points with the voltage of the sensor points at the same or similar temperature values, as shown in operational block <NUM>. The method <NUM> further includes, for each of the temperature values, generating at least one of a high and a low signal, as shown in operational block <NUM>, and as discussed herein above.

Claim 1:
A proximity sensor system (<NUM>), comprising:
a sensor article (<NUM>) having a sensor sensing surface (<NUM>), wherein the sensor article (<NUM>) is configured to sense the magnetic field of a magnetic target article (<NUM>) located proximate the sensor sensing surface (<NUM>) and generate a sensor signal (<NUM>);
a Temperature Compensation Article, TCA, (<NUM>), wherein the Temperature Compensation Article (<NUM>)includes,
a first Digital-to-Analog Converter, DAC, (<NUM>), a first thermistor (<NUM>) and a first biasing resistor (<NUM>), wherein the first thermistor (<NUM>) and the first biasing resistor (<NUM>) are connected in a parallel configuration and the first DAC (<NUM>) is connect to the first thermistor (<NUM>) and the first biasing resistor (<NUM>) in a series configuration,
a second DAC (<NUM>) and a second thermistor (<NUM>), wherein the second DAC (<NUM>) and second thermistor (<NUM>) are connected in a series configuration,
a third DAC (<NUM>) and a Resistive Temperature Detector ,RTD, (<NUM>), wherein the third DAC (<NUM>) and RTD (<NUM>) are connected in a series configuration,
a fourth DAC (<NUM>) and a second biasing resistor (<NUM>), wherein the fourth DAC (<NUM>) and the second biasing resistor (<NUM>) are connected in a series configuration,
wherein the outputs of the first thermistor (<NUM>) and first biasing resistor(<NUM>) combination, second thermistor (<NUM>), RTD (<NUM>) and the second biasing resistor (<NUM>) are connected together to generate a TCA output signal (<NUM>); and
processing circuitry, wherein the processing circuitry is configured to process the sensor signal (<NUM>) and the TCA output signal (<NUM>) to generate a sensor system output signal (<NUM>).