Patent Description:
This background description is set forth below for the purpose of providing context only. Therefore, any aspects of this background description, to the extent that it does not otherwise qualify as prior art, is neither expressly nor impliedly admitted as prior art against the instant invention.

Numerous components in numerous different fields are dependent on the presence or absence of liquid, or a certain amount of liquid. Accordingly, sensors have been developed for detecting the presence of fluid. One sensor type is an electro-optic sensor including a light source, a prism, and a light detector.

In electro-optic liquid sensors, light emitted from the light source may be returned to the light detector by the prism only if no liquid is present. If liquid is present, no light or limited light may be returned to the light detector.

<CIT> relates to a method for operating an electro-optic liquid sensor, involving determining whether liquid is present in a liquid chamber, based on a first and a second amount of light, in which a first sensitivity level is different from a second sensitivity level.

There is a desire for solutions/options that minimize or eliminate one or more challenges or shortcomings of electro-optic sensors. The foregoing discussion is intended only to illustrate examples of the present field and should not be taken as a disavowal of scope.

The present invention is a method of operating an electro-optic sensor which comprises disposing at least a portion of the electro-optic sensor in a liquid chamber; testing, via a timer, for a timeout occurrence associated with the timer, the timer including a timing circuit; if there is a timeout occurrence, then indicating that the electro-optic sensor (<NUM>) is not functioning; if there is no timeout occurrence associated with the timer, then providing light from a light source of the electro-optic sensor at a first intensity; driving a light detector of the electro-optic sensor at a first sensitivity level; receiving, via the light detector, a first amount of light from the light source; determining whether liquid is present in the liquid chamber according to the first amount of light, providing light from the light source at a second intensity; driving the light detector at a second sensitivity level; receiving, via the light detector, a second amount of light from the light source; and confirming whether liquid is present in the liquid chamber according to the second amount of light. The first sensitivity level is different from the second sensitivity level. The electro-optic sensor includes a prism and a reflective optical member. The reflective optical member is arranged to reflect light emitted by the light source to the light detector when a liquid is disposed between the light source and the reflective optical member. In accordance with the present invention the electro-optic sensor includes a photo diode-based sensor, the light source includes an LED, and the timing circuit is configured to cap an amount of energy through a circuit of the electro-optic sensor. Determining whether liquid is present in the liquid chamber according to the first amount of light may include comparing the first amount of light to a threshold value, and determining that liquid is not present if the first amount of light is greater than the threshold value.

In embodiments, if the first amount of light is less than the threshold value, the second intensity may be greater than the first intensity and the second sensitivity level may be more sensitive than the first sensitivity level. Confirming whether liquid is present in the liquid chamber may include confirming that liquid is present if the second amount of light is greater than a second threshold value and determining an error has occurred if the second amount of light is not greater than the second threshold value.

If the first amount of light is not greater than the threshold value, the second intensity may be less than the first intensity and the second sensitivity level may be less sensitive than the first sensitivity level (e.g., effectively a third intensity and a third sensitivity). Confirming whether liquid is present in the liquid chamber may include confirming that liquid is not present if the second amount of light is less than a third threshold value and determining an error has occurred if the second amount of light is not less than the third threshold value.

The light detector may include an optical head assembly disposed in the liquid chamber and an electronic module assembly disposed outside of the liquid chamber. The optical head assembly may be connected to the electronic module assembly via one or more fiber optic cables. At least one fiber optic cable of the one or more fiber optic cables may be connected to a wall of the liquid chamber via a hermetically sealed fitting. The one or more fiber optic cables may include a single fiber. The method may include disposing all active components of the electro-optic sensor outside of the liquid chamber.

With examples not according to the claimed invention, a method of operating an electro-optic sensor may include providing a liquid chamber; providing the electro-optic sensor including a light source and a light detector that may include a photodiode-based transimpedance amplifier; conducting a first test of the electro-optic sensor without liquid in the liquid chamber and with the light source off; conducting a second test of the electro-optic sensor without liquid in the liquid chamber and with the light source on; conducting a third test of the electro-optic sensor with liquid in the liquid chamber and with the light source off; conducting a fourth test of the electro-optic sensor with liquid in the liquid chamber and with the light source on; setting a threshold value for the electro-optic sensor according to results of the fourth test; and/or operating the electro-optic sensor in a normal operating mode, including determining that liquid is present in the liquid chamber if at least one of an intensity and an amount of light received by the light detector is less than the threshold value.

An electro-optic sensor that may be used in the claimed method may include an electronic module assembly; an optical head assembly configured to be disposed in a liquid chamber; and/or a fiber optic cable configured to connect the electronic module assembly with the optical head assembly. The fiber optic cable may include a first section, and/or a first section and a second section. In embodiments, a first section may include a first end configured for connection to the optical head assembly and a second end configured for connection or connecting through a wall of the liquid chamber. The fiber optic cable may include a second section with a first end configured for connection with the second end of the first section. The second end of the second section may be configured for connection with the electronic module assembly. An electro-optic sensor may include a first connector connected to the second end of the first section of the fiber optic cable, and a second connector connected to the first end of the second section of the fiber optic cable. The first connector and the second connector may be configured to be connected together. An electro-optic sensor may include a third connector connected to the second end of the second section of the fiber optic cable. The electronic module assembly may include a connector configured to be connected with the third connector. At least one of the first section and the second section may include a single fiber. An electro-optic sensor may include a light source configured to be driven at a plurality of intensities. The optical head assembly may be configured to receive light from the light source.

Liquid sensors that may be used in the claimed method may improve on other electro-optic liquid sensors by providing capability for assessing the operational state of the sensor in the presence of liquid. In contrast, some electro-optic sensors are generally only capable of being tested while not in liquid. Accordingly, electro-optic sensors that may be used in the claimed method may enable improved testing and functionality over other electro-optic liquid sensors.

The foregoing and other aspects, features, details, utilities, and/or advantages of embodiments of the present invention will be apparent from reading the following description, and from reviewing the accompanying drawings.

Embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:.

Reference will now be made in detail to embodiments of the present invention, examples of which are described herein and illustrated in the accompanying drawings. While the present invention will be described in conjunction with embodiments and/or examples, it will be understood that they are not intended to limit the present invention to these embodiments and/or examples. On the contrary, the present invention is intended to cover alternatives, modifications, and equivalents.

Referring to the figures, in which like reference numerals refer to the same or similar features in the various views, <FIG> is a block diagram view of a system <NUM> including a component <NUM> for which determining the presence of liquid may be desirable. The component <NUM> may include a liquid chamber <NUM>, and the system <NUM> may include a liquid sensor <NUM> and/or an electronic control unit (ECU) <NUM>.

The component <NUM> may be any component in any field that includes or may be exposed to liquid in its operation. For example, the component <NUM> may be or may be included in a mechanical, electrical, hydraulic, pneumatic, and/or other known actuator or actuation system. The component <NUM> may include a liquid chamber <NUM> configured to store and/or receive a liquid. The liquid may be, for example only, of a type necessary for the functionality of the component <NUM> (e.g., hydraulic fluid, liquid for lubrication, fuel, etc.), liquid incidental to the environment of the component <NUM>, and/or liquid that is detrimental to the function of the component <NUM>.

The liquid sensor <NUM> may be coupled with the component <NUM>. For example, the liquid sensor <NUM> may be disposed at least partially within the liquid chamber <NUM> of the component <NUM>. The liquid sensor <NUM> is an electro-optic sensor, such as that described in conjunction with <FIG> and/or <FIG> and <FIG>.

With continued reference to <FIG>, an ECU <NUM> may be electrically coupled to the sensor <NUM> and may be configured to drive the sensor <NUM>, receive feedback from the sensor <NUM>, assess whether liquid is present or absent in the liquid chamber <NUM>, and/or assess the operational state of the sensor <NUM>. An ECU <NUM> may comprise, one or more of a processor, a non-volatile computer-readable memory, an application-specific integrated circuit (ASIC), field-programmable gate array (FPGA), and/or other known processing or memory devices. The ECU <NUM> may be or may comprise a dedicated processing resource for the sensor <NUM>, or may be or may comprise processing resources for numerous sensors, components, and/or systems. The ECU <NUM> may be electrically coupled to the sensor <NUM> through known wired and/or wireless connections. The ECU <NUM> may be configured to perform various functions, including those described in greater detail herein, with appropriate programming instructions and/or code embodied in software, hardware, and/or other media. The ECU <NUM> may include a plurality of controllers. The ECU <NUM> may include and/or be connected to an input/output (I/O) interface and/or a display.

<FIG> is a diagrammatic view of an example of the electro-optic liquid sensor <NUM> that may be used in the claimed method. The sensor <NUM> includes a light source <NUM>, a light detector <NUM>, a prism <NUM>, and a reflective optical member <NUM> (which may also be referred to as an optical shield), which may be generally disposed within a housing <NUM>. The housing <NUM> may include one or more liquid ports <NUM> for permitting liquid to flow into and out of a chamber <NUM> of the housing <NUM>. The chamber <NUM> may define a gap between the prism <NUM> and the optical member <NUM> of a size d. For example, and without limitation, in an embodiment, d may be about <NUM>,<NUM> (an inch) or less. Of course, other dimensions may be employed as appropriate for particular applications.

The light source <NUM> may be configured to emit light of one or more chosen frequencies and powers/intensities appropriate for a given application (e.g., appropriate for the characteristics of the other elements of the sensor <NUM>, such as shape, orientation, materials, reflectivity, etc., and/or according to characteristics of the liquid to be detected, such as density, scattering properties, etc.). As used herein, a light frequency should be understood to include either or both of a specific frequency of light and a frequency band. The light source <NUM> may be configured to emit light in the infrared portion and/or the near-infrared portion of the electromagnetic spectrum. The light source <NUM> includes light-emitting diode (LED), or, according to examples not encompassed by the wording of the claims, a laser, or other known light source.

The light detector <NUM> may be configured to detect light of one or more frequencies of light, including at least the frequency of light emitted by the light source <NUM>. The light detector <NUM> includes a photo diode-based sensor, or, according to examples not encompassed by the wording of the claims, one or more of a phototransistor, photodiode, and/or other light detecting device.

The prism <NUM> may include a member, article, and/or device comprising one or more components that may be configured in size, shape, and/or materials to reflect light/a light signal from the light source <NUM> to the light detector <NUM> in certain conditions and to pass light from the light source <NUM> through the prism <NUM> in certain conditions. For example only, the prism <NUM> may be configured to reflect light from the light source <NUM> to the light detector <NUM> when liquid is not present around the prism <NUM>, and to pass light from the light source through the prism <NUM> when liquid is present around and/or near the prism <NUM> (e.g., in chamber <NUM>). For example only, the prism <NUM> may comprise borosilicate glass, fused silica (quartz), one or more polymers, etc., that is optically transmissive at least to light of the frequency or frequencies emitted by the light source <NUM>. Thus, the prism <NUM> may be optically-transmissive to light in the infrared and/or near-infrared portions of the electromagnetic spectrum, for example only.

The reflective optical member <NUM> is arranged and configured to reflect light emitted by the light source <NUM> to the light detector <NUM>, in certain conditions. The optical member <NUM> may have a degree of reflectivity for one or more frequencies of light that may be tailored for a particular application. In certain embodiments, the optical member <NUM> may have complete or near-complete reflectivity for the frequency or frequencies of light emitted by the light source <NUM>. In other embodiments, the optical member <NUM> may have less-than-complete reflectivity for the frequency or frequencies of light emitted by the light source <NUM>.

The reflective optical member <NUM> may be disposed on/at a side of the housing <NUM> opposite the light source <NUM> and the light detector <NUM>. The light source <NUM> may emit light in the direction of the optical member <NUM>. The prism <NUM> may be disposed at least partially between the light source <NUM> and the optical member <NUM> and at least partially between the light detector <NUM> and the optical member <NUM>. Accordingly, in the example generally illustrated in <FIG>, light may travel from the light source <NUM>, through the prism <NUM>, through the chamber <NUM>, to the optical member <NUM>, and may be reflected by the optical member <NUM> back through the chamber <NUM> and prism <NUM> to the light detector <NUM>, in certain conditions. The distance d between the optical member <NUM> and the prism <NUM> may be tailored to the geometric relationship between the optical member <NUM>, prism <NUM>, light detector <NUM>, and light source <NUM> for the optical member <NUM> to effectively reflect light emitted by the light source <NUM> to be returned to the light detector <NUM>.

The electro-optic liquid sensor <NUM> may be configured to detect the presence of liquid by returning a different amount of light from the light source <NUM> to the light detector <NUM> when liquid is present in the chamber <NUM> than when liquid is not present in the chamber <NUM>. For example, as shown in <FIG>, when no liquid is present in the chamber <NUM>, and the chamber <NUM> is filled with air, the prism <NUM> may return a first amount of light from the light source <NUM> to the light detector <NUM>. The prism <NUM> may return substantially all light emitted by the light source <NUM> to the light detector <NUM> when no liquid is present. In contrast, as shown in <FIG>, when the chamber <NUM> is filled with liquid, the prism <NUM> may return very little of or none of the light from the light source <NUM> to the light detector <NUM>. The prism <NUM> may pass some portion of the light emitted by the light source <NUM>, some of which light may disperse in the liquid, and some of which light may propagate to the optical member <NUM>, be reflected by the optical member <NUM> to the light detector <NUM>, and be received by the light detector <NUM>. Accordingly, a relatively higher amount of light received by the light detector <NUM> may be associated with the absence of liquid from the chamber <NUM>, and a relatively smaller amount of light received by the light detector <NUM> may be associated with the presence of liquid in the chamber <NUM>.

Examples that may be used in the claimed method of an electro-optic liquid sensor <NUM> may improve on other electro-optic sensors by enabling the sensor <NUM> to be tested in the presence of liquid. Other electro-optic sensors generally do not provide any means by which a light signal may be returned to the light detector in the presence of liquid. As a result, a faulty sensor may be indistinguishable from the presence of liquid in known sensors. In contrast, because the electro-optic sensor <NUM> that may be used in the claimed method may return a light signal to the light detector <NUM> in the presence of liquid, a faulty sensor (which may always indicate zero light received by the light detector <NUM>) may be distinguished from the presence of fluid (which may indicate a nonzero amount of light received by the light detector, but less light received by the light detector <NUM> than when liquid is absent).

Although examples that may be used in the claimed method of the electro-optic liquid sensor <NUM> are described herein with respect to particular materials, shapes, dimensions, light characteristics, etc., it should be understood that such details are exemplary only and are not limiting except as explicitly recited in the claims. Numerous modifications and alterations may be made within the scope of the present invention as it is defined in the appended claims.

Referring to <FIG>, an ECU <NUM> may be configured to operate the electro-optic sensor <NUM> to determine whether liquid is present in the chamber <NUM> and to determine whether the sensor <NUM> is or is not operating properly (e.g., assess the operational state of the sensor <NUM>). Accordingly, in an embodiment, the ECU <NUM> may be configured to operate the sensor <NUM> in a liquid detection mode and a test mode. The liquid detection mode and the test mode may be implemented separately by the ECU, or may be implemented together.

<FIG> is a flow chart generally illustrating a method <NUM> of operating an electro-optic sensor <NUM> not according to the claimed invention, but useful to understand it. One or more steps of the method <NUM> may be performed by the ECU <NUM> shown in <FIG> to operate the sensor <NUM> of <FIG>. The method <NUM> may include steps for implementing a liquid detection mode and a test mode of the electro-optic sensor <NUM> together.

Referring to <FIG> and <FIG>, the method <NUM> may begin with a first driving step <NUM> that includes driving (e.g., providing light from) the light source <NUM> at a first frequency and intensity. The frequency and intensity may be selected according to the characteristics of the components of the sensor <NUM> and/or according to the liquid to be detected. The method <NUM> may continue to a first receiving step <NUM> that may include receiving reflected light with the light detector <NUM>. The received light may be of the same frequency as that emitted by the light source <NUM> in the first driving step <NUM>. In a first comparison step <NUM>, the amount or intensity or light received, R1, may be compared to a first threshold, T1.

If the amount or intensity of light R1 detected in the first receiving step <NUM> is less than the first threshold T1, the method <NUM> may continue to a second driving step <NUM> that includes driving the light source <NUM> at a second frequency and intensity. The second frequency may be the same as the first frequency, in an embodiment. The second intensity may be the same as the first intensity. In another example, the second frequency and/or intensity may be different from the first frequency and/or intensity. For example only, the second intensity may be greater than the first intensity. A higher intensity may be used in the second driving step <NUM> than in the first driving step <NUM> to ensure that, if liquid is present, the light will have sufficient energy to propagate through the liquid from the light source <NUM> to the optical member <NUM> and back to the light detector <NUM>. Thus, as in the first driving step <NUM>, the frequency and intensity of light in the second driving step <NUM> may be selected according to the type of liquid to be detected and the characteristics of the elements of the sensor.

The method <NUM> may continue to a second receiving step <NUM> that includes receiving reflected light with the light detector <NUM>. The received light may be of the same frequency as that emitted by the light source <NUM> in the second driving step <NUM>. In a second comparison step <NUM>, the amount or intensity or light received, R2, may be compared to a second threshold, T2. If the amount or intensity of light received is greater than the second threshold (e.g., if R2 > T2 ), it may be concluded at a first conclusion step <NUM> that liquid is present and that the sensor <NUM> is functioning properly. If the amount or intensity of light received R2 is not greater than the second threshold T2, it may be concluded at a second conclusion step <NUM> that the sensor <NUM> is not functioning properly.

In the first comparison step <NUM>, if the amount or intensity of light received is greater than the first threshold (e.g., if R1 > T1 ), the method <NUM> may advance to a third driving step <NUM> that may include driving the light source <NUM> at a third frequency and intensity. The third frequency may be the same as either or both of the first frequency and the second frequency. The third intensity may be the same as either or both of the first intensity and the second intensity. In another embodiment, the third frequency and/or intensity may be different from either or both of the first and second frequency and/or intensity. The frequency and intensity of light in the third driving step <NUM> may be selected according to the type of liquid to be detected and the characteristics of the elements of the sensor.

The method <NUM> may continue to a third receiving step <NUM> that includes receiving reflected light with the light detector <NUM>. The received light may be of the same frequency as that emitted by the light source <NUM> in the third driving step <NUM>. In a third comparison step <NUM>, the amount or intensity or light received, R3, may be compared to a third threshold, T3. The third threshold T3 may be set to an amount or intensity of light that is higher than a properly-functioning sensor could detect given the amount or intensity of light emitted in the third driving step <NUM>. If the amount or intensity of light R3 received is less than the third threshold T3, it may be concluded at a third conclusion step <NUM> that no liquid is present and that the sensor <NUM> is functioning properly. If the amount or intensity of light received R3 is greater than the third threshold T3, it may be concluded again at the second conclusion step <NUM> that the sensor <NUM> is not functioning properly.

The thresholds T1, T2, T3 for determining whether liquid is present and whether the sensor <NUM> is functioning properly may be selected according to the characteristics of the liquid to be detected and the characteristics of the elements of the sensor <NUM>. Additionally or alternatively, the thresholds T1, T2, T3 may be experimentally determined.

The steps of the method <NUM> may be performed to assess whether liquid is present and whether the sensor <NUM> is functioning properly on an ongoing basis. That is, a continuous loop of driving the light source <NUM>, receiving light with the light detector <NUM>, and comparing the amount or intensity of light received to one or more thresholds may be executed. In an example in which the first, second, and third driving steps <NUM>, <NUM>, <NUM> utilize the same frequency and intensity of light, the light source <NUM> may be continuously driven at a single frequency and intensity.

In an alternate example, the third driving, receiving, and comparing steps <NUM>, <NUM>, <NUM> may be omitted and, if the first amount of received light R1 is greater than the first threshold T1, it may be concluded that no liquid is present.

The first driving, receiving, and comparing steps <NUM>, <NUM>, <NUM> may be considered steps in an example of a method of assessing the presence of liquid (e.g., a liquid detection mode). The second and third driving, receiving, and comparing steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be considered steps in an example of a method of assessing the operational state of the sensor (e.g., a testing mode). The liquid presence assessment method may be performed separately and independently from the operational state assessment method. For example, the operational state assessment method steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be performed on a less-frequent basis than the liquid presence assessment steps <NUM>, <NUM>, <NUM>. Furthermore, although methods (e.g., method <NUM>) may be illustrated and described such that operational state assessment steps (e.g., steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>) are only performed after performing liquid presence assessment steps (e.g., steps <NUM>, <NUM>, <NUM>), such description and illustration is exemplary only. In an example, the operational state assessment steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be performed regardless of performance of the liquid presence assessment steps <NUM>, <NUM>, <NUM>.

Increasing the intensity of the light source <NUM> may involve providing a relatively high electrical current to the light source <NUM> and/or creating a temporary current spike in sensor power consumption. In some examples, the degree to which the intensity of light from light source <NUM> can be increased (e.g., via increasing electrical current) may be limited. For example, and without limitation, there may be limits on available electrical current and/or electrical voltage, high electrical currents may strain components of sensor <NUM>, and/or other related components may not be fully compatible with higher currents. In addition to (or as an alternative to) modifying the intensity of the light from the light source <NUM>, the sensitivity level of the light detector <NUM> may be modified. The light detector <NUM> may include, for example, a photodiode-based transimpedance amplifier (TIA) receiver, and may be driven at various sensitivity levels that may correspond with the frequency and/or intensity of light of the light source <NUM>. A photodiode TIA receiver may be more easily adjusted than a photo-IC and a photo transistor. Sensor <NUM> and/or ECU <NUM> may, in at least some circumstances, be configured to operate the photodiode-based TIA receiver in a linear region.

Referring to <FIG>, a method <NUM> not according to the claimed invention, but useful to understand it, of operating an electro-optic sensor <NUM> that includes modifying light intensity and/or detector sensitivity may include initiating a built-in-test (step <NUM>). The method may continue with driving the light source <NUM> at a first frequency and intensity (step <NUM>). The frequency and intensity may be selected according to the characteristics of the components of the sensor <NUM> and according to the liquid to be detected. The method <NUM> may include driving the light detector <NUM> at a first sensitivity level (step <NUM>). The method <NUM> may continue to a first receiving step <NUM> that includes receiving reflected light R1 with the light detector <NUM> with the first sensitivity level. In a first comparison step <NUM>, the received light R1 may be compared to the first threshold T1.

If the amount or intensity of light R1 detected in the first receiving step <NUM> is less than the first threshold T1, the method <NUM> may continue to a second driving step <NUM> that includes driving the light source <NUM> at a second frequency and intensity. The second frequency may be the same as the first frequency. The second intensity may be the same as the first intensity. In another example, the second frequency and/or intensity may be different from the first frequency and/or intensity. For example only, the second intensity may be higher than the first intensity. A higher intensity may be used in the second driving step than in the first driving step to ensure that, if liquid is present, the light will have sufficient energy to propagate through the liquid from the light source <NUM> to the optical member <NUM> and back to the light detector <NUM>. The method <NUM> may include driving the light detector <NUM> at a second sensitivity level that may be the same or similar to the first sensitivity level (step <NUM>). Additionally or alternatively, the second sensitivity of the light detector <NUM> may be modified (e.g., increased), which may help ensure that light is detected. Thus, as in the first driving step <NUM>, the frequency and intensity of light and the detector sensitivity in the second driving steps <NUM>, <NUM> may be selected according to the type of liquid to be detected and the characteristics of the elements of the sensor <NUM>.

The method <NUM> may continue to a second receiving step <NUM> that may include receiving reflected light with the light detector <NUM> with the second sensitivity level. The received light may be of substantially the same frequency as that emitted by the light source <NUM> in the second driving step. In a second comparison step <NUM>, the amount or intensity of light received, R2, may be compared to the second threshold, T2. If the amount or intensity of light received is greater than the second threshold (e.g., if R2 > T2 ), it may be concluded at a first conclusion step <NUM> that liquid is present and that the sensor <NUM> is functioning properly. If the amount or intensity of light received R2 is not greater than the second threshold T2, it may be concluded at a second conclusion step that the sensor <NUM> is not functioning properly (step <NUM>). Increasing both the intensity of the light and the sensitivity of the detector (e.g., simultaneously) may achieve at least similar functionality/sensing ability and include a smaller increase in total current than configurations in which only the light intensity is increased.

In the first comparison step <NUM>, if the amount or intensity of light received is greater than the first threshold (e.g., if R1 > T1 ), the method <NUM> may advance to a third light driving step <NUM> that may include driving the light source <NUM> at a third frequency and intensity, and/or a third detector driving step <NUM> that may include driving the light detector <NUM> at a third sensitivity level. The third frequency may or may not be the same as either or both of the first frequency and the second frequency. The third intensity may or may not be the same as either or both of the first intensity and the second intensity. In another example, the third frequency, intensity, and sensitivity level may be different from (e.g., less than) either or both of the first and second frequency, intensity, and/or sensitivity. The frequency, intensity, and sensitivity level in the third driving steps <NUM>, <NUM> may be selected according to the type of liquid to be detected and the characteristics of the elements of the sensor <NUM>.

The method <NUM> may continue to a third receiving step <NUM> that includes receiving reflected light with the light detector <NUM> at the third sensitivity level. The received light may be of substantially the same frequency as that emitted by the light source <NUM> in the third driving step. In a third comparison step <NUM>, the amount or intensity of light received, R3, may be compared to a third threshold, T3. The third threshold T3 may be set to an amount or intensity of light that is higher than a properly-functioning sensor could detect given the amount or intensity of light emitted in the third driving step. If the amount or intensity of light received R3 is less than the third threshold T3, it may be concluded at a third conclusion step <NUM> that no liquid is present and that the sensor <NUM> is functioning properly. If the amount or intensity of light received R3 is greater than the third threshold T3, it may be concluded at the second conclusion step <NUM> that the sensor <NUM> is not functioning properly.

Referring to <FIG>, an example not according to the claimed invention, but useful to understand it, of a method <NUM> of operating an electro-optic sensor <NUM> is generally illustrated. One or more steps of the method <NUM> may be used for testing and/or calibration of the sensor <NUM> (e.g., a test mode) and one or more steps may be used for normal operation (e.g., a liquid detection mode). In a first step <NUM>, if the light detector <NUM> of the electro-optic sensor <NUM> includes a photo-IC receiver (or some other type of receiver), a photodiode TIA receiver may be added and/or used instead. In a second step <NUM>, in the absence of liquid (e.g., with effectively only air), and with the light source <NUM> off, the light detector <NUM> may detect a first amount of light (e.g., ambient light). If the first amount of light is above an expected amount of ambient light, which may be very little or no light, the ECU <NUM> may detect a malfunction, such as with the light detector <NUM>. In a third step <NUM>, the light source <NUM> may be turned on and the light detector <NUM> may detect a second amount of light (e.g., including reflected light from the light source <NUM>). If the second amount of light is below an expected amount of reflected light, the ECU <NUM> may detect a malfunction, such as, for example, with the light source <NUM> and/or with the prism <NUM>. In the third step <NUM>, the electrical current driving the light source <NUM> (e.g., a nominal current) may be adjusted so that the photodiode TIA of the light detector <NUM> is not saturated. The method may continue to a fourth step <NUM> in which the sensor <NUM> may be disposed at least partially in a fluid and/or liquid. In a fifth step <NUM>, the light detector <NUM> may detect a third amount of light with the light source <NUM> off. If the third amount of light is greater than an expected amount of light, the sensor <NUM> may detect a malfunction. In a sixth step <NUM>, the light source <NUM> may be turned on and the light detector <NUM> may detect a fourth amount of light, which ECU <NUM> may use as and/or use to calculate a threshold amount that may be used during normal operation. Such a threshold may be used, for example and without limitation, for threshold T1 in connection with method <NUM>.

In a seventh step <NUM>, the ECU <NUM> may transition the sensor <NUM> to normal operation (e.g., liquid detection mode). In the liquid detection mode, the light detector <NUM> may detect a current amount of light, which may be compared to the threshold amount. If the current amount of light detected is less than the threshold, the sensor <NUM> may determine that there is fluid present (step <NUM>). If the current amount of light detected is not less than the threshold, the sensor <NUM> may determine that fluid is not present (step <NUM>).

One or more of the steps of the method <NUM> and/or of the method <NUM> (e.g., the first through sixth steps) may be omitted, modified, and/or duplicated for certain applications. One or more steps of the method <NUM> and the method <NUM> may be carried out, at least in part, via the ECU <NUM>.

Referring to <FIG> and <FIG>, examples that may be used in the claimed method of a light detector <NUM> are generally illustrated. A light detector <NUM> may include an optical head assembly <NUM> with a prism <NUM> and/or an optical shield <NUM>, and an electronic module assembly <NUM>. The optical head assembly <NUM> may be connected to the electronic module assembly <NUM> via one or more fiber optic cables (or one or more connected fiber optic segments). A fiber optic cable may comprise at least a first section <NUM>, and/or a first section <NUM> and a second section <NUM>. The fiber optic cable may comprise a first section <NUM> that may be connected to the optical head assembly <NUM> at a first end <NUM> and connected to a first connector <NUM> at a second end <NUM>. The first section <NUM> may extend and/or be connected or connecting through a wall <NUM> of a liquid chamber <NUM> (e.g., a fuel tank wall), such as via a fitting <NUM> (e.g., a hermetically sealed bulkhead fitting). A first end <NUM> of a second section <NUM> may be connected with a second connector <NUM> and a second end <NUM> of the second section <NUM> may be connected with a third connector <NUM>. The second connector <NUM> may be configured for connection with the first connector <NUM>. The third connector <NUM> may be configured for connection with a connector <NUM> of the electronic module assembly <NUM>. In examples, such as generally illustrated in <FIG>, the first section <NUM> may be connected to the optical head assembly <NUM> via a pair of corresponding connectors <NUM>, <NUM>.

The optical head assembly <NUM> may be configured to be disposed in a liquid chamber <NUM> (e.g., a tank) that may include volatile and/or explosive materials, such as fuel or other flammable chemicals or gases. A hermetically sealed bulkhead fitting <NUM> may prevent materials from exiting the liquid chamber <NUM>. While the optical head assembly <NUM> may be disposed in a volatile environment, the electronic module assembly <NUM> may be disposed outside of the volatile environment (e.g., outside the liquid chamber <NUM>), and the fiber optic cable(s) (e.g., cable sections <NUM>, <NUM>) may allow for communication between the optical head assembly <NUM> and the electronic module assembly <NUM>. In such configurations, passive components (e.g., the optical head assembly <NUM>, the fitting <NUM>, and/or fiber optic cable <NUM>) may be the only components of the sensor <NUM> and/or light detector <NUM> disposed in the volatile environment. Active components, such as the electronic module assembly <NUM>, may be disposed outside of and/or at a safe distance from the volatile environment. Disposing only passive components in the volatile environment may significantly reduce or even eliminate the possibility of causing a spark or otherwise potentially igniting material in the volatile environment. Other designs intended to limit the possibility of a spark/ignition may not be as effective, may be more expensive, and/or may be more complicated/time consuming.

The one or more fiber optic cable(s) (e.g., cable sections <NUM>, <NUM>) of the light detector <NUM> may include a single fiber. The electronic module assembly <NUM> may be configured to separate incoming signals received via the single fiber. The received signals may correspond to light received, such as from the light source <NUM>, and may include an intensity and/or a frequency. The electronic module assembly <NUM> may be configured to provide an output corresponding to the amount, intensity, and/or frequency of light received at the optical head assembly <NUM>. The electronic module assembly <NUM> may be connected to and/or incorporated with the ECU <NUM>. Fiber optic cables, including single fiber cables, may be relatively lightweight (e.g., up to or about <NUM> times lighter) compared to copper wiring, which may allow for greater cable lengths to be used (and for the electronic module assembly <NUM> to be disposed at greater distances from the optical head assembly <NUM> and/or at more convenient locations). Lighter cables may be particularly advantageous in applications in which weight is a significant design factor (e.g., airplanes). Fiber optic cables may also be smaller (e.g., in diameter) and/or more flexible than copper wiring.

<FIG> and <FIG> are diagrammatic views of examples of electro-optic liquid sensors that may be used in the claimed method which are generally indicated as 16A and 16B, respectively. The sensor 16A,16B includes a light source <NUM>, a photo sensor (or light detector) <NUM>, a prism <NUM>, and a reflective optical member <NUM> (which may also be referred to as an optical shield), which may be generally disposed within a housing <NUM>. The housing <NUM> may include one or more liquid ports <NUM> for permitting liquid to flow into and out of a chamber <NUM> of the housing <NUM>. Additionally, the chamber <NUM> may define a gap between the prism <NUM> (or an extent thereof) and the optical member <NUM>, such as generally illustrated in connection with dimension d. For example, and without limitation, d may be about <NUM>,<NUM> (an inch) or less. Of course, other dimensions may be employed as appropriate for particular applications.

In examples such as generally illustrated in <FIG> and <FIG>, electro-optic liquid sensors may include an optically isolating chassis <NUM>. An optically isolating chassis <NUM> may, for example, be disposed between two separate photo sensors <NUM> and/or between a photo sensor <NUM> and a light source <NUM>. Moreover, an optically isolating chassis may additionally be disposed on a side of the same side of a prism <NUM> as a light source <NUM> and/or opposite a reflective optical member <NUM>. Additionally, as generally illustrated, one or more photo sensors and a light source may be provided between portions or segments of an optically isolating chassis.

In examples that may be used in the claimed method, an LED is used to change a light intensity (e.g., high/low) as necessary or desired to interrogate a sensor with respect to an in-fluid or an in-air state. The sensors use a photo-IC (e.g., a photo diode-based sensor) or, according to examples not encompassed by the wording of the claims, may use a transistor. With an LED, a high dynamic range (e.g., to allow for reliable fluid absence/presence detection) may be achieved by applying a relatively high current to an LED. However, with some embodiments, a BIT function may be modified or improved to include an optical power compensation circuit (such as a photo diode), which may provide for more consistent/continuous interrogation of a light source irrespective of a sensor's physical environment (e.g. in-air or in-fluid). The inclusion of a photo diode based circuit, which may operate in a linear region may address certain limitations. The inclusion of a timing circuit caps an amount of energy that is permitted through a circuit. Among other things, including a photo diode based circuit may provide for a better operational dynamic range, may reduce sensor power management requirements, may improve sensor reliability (for example by lowering thermal stresses on primary components), many improve sensor safety in fuel/gaseous environments, and/or may better control sensor threshold sensitivity.

Referring to <FIG>, an embodiment of a method <NUM> of operating an electro-optic sensor <NUM> according to the claimed invention is generally illustrated. The method may have a number of similarities to the method disclosed in connection with <FIG>. However, the illustrated embodiment of <FIG> includes, inter alia, a timer that is associated with and/or follow a built-in-test step (e.g., step <NUM>). If there is no timeout occurrence or event associated with the timer, the method proceeds with (i) driving receiver at 1st threshold (step <NUM>) and/or (ii) driving light source at 1st frequency and intensity (step <NUM>). However, if there is a timeout occurrence or event associated with the timer, the methods moves to a timeout related action (for example, step <NUM>) - which may, for example, indicate that a sensor is not functioning.

<FIG> is a diagrammatic view of an example of an in-liquid electro-optic testing configuration/arrangement, which is generally indicated as 16C. The configuration/arrangement 16C may include a sensor prism <NUM>', a light source <NUM>', and a photo sensor <NUM>'. With respect to <FIG>, a light path ( LP ) is shown in a fluid. As generally indicated, a sensor prism <NUM>' may be immersed in a fluid. Additionally, as generally shown, residual light reflection ( RL ) within the prism may be directed as indicated. Such residual light reflection ( RL ) may comprise an always present low level light signal.

Including those disclosed herein, a system can be provided that, inter alia, monitors sensor performance (e.g., health) continuously (e.g., in real time) regardless of whether a sensor head is in liquid or in air.

Various examples are described herein for various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments.

Reference throughout the specification to "various embodiments," "with embodiments," "in embodiments," or "an embodiment," or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases "in various embodiments," "with embodiments," "in embodiments," or "an embodiment," or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment/example may be combined, in whole or in part, with the features, structures, functions, and/or characteristics of one or more other embodiments/examples without limitation given that such combination is not illogical or non-functional. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the present invention without departing from the scope thereof.

It should be understood that references to a single element are not necessarily so limited and may include one or more of such element. Any directional references (e.g., plus, minus, upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of embodiments.

Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily imply that two elements are directly connected/coupled and in fixed relation to each other. The use of "e.g." in the specification is to be construed broadly and is used to provide non-limiting examples of embodiments of the invention, and the invention is not limited to such examples. Uses of "and" and "or" are to be construed broadly (e.g., to be treated as "and/or"). For example and without limitation, uses of "and" do not necessarily require all elements or features listed, and uses of "or" are intended to be inclusive unless such a construction would be illogical.

Claim 1:
A method (<NUM>) of operating an electro-optic sensor (<NUM>), the method comprising:
disposing at least a portion of the electro-optic sensor (<NUM>) in a liquid chamber (<NUM>);
testing, via a timer, for a timeout occurrence associated with the timer, the timer including a timing circuit;
if there is a timeout occurrence, then indicating that the electro-optic sensor (<NUM>) is not functioning;
if there is no timeout occurrence associated with the timer, then:
providing light from a light source (<NUM>) of the electro-optic sensor (<NUM>) at a first intensity;
driving a light detector (<NUM>) of the electro-optic sensor (<NUM>) at a first sensitivity level;
receiving, via the light detector (<NUM>), a first amount of light from the light source (<NUM>);
determining whether liquid is present in the liquid chamber (<NUM>) according to the first amount of light;
providing light from the light source (<NUM>) at a second intensity;
driving the light detector (<NUM>) at a second sensitivity level;
receiving, via the light detector (<NUM>), a second amount of light from the light source (<NUM>);
confirming whether liquid is present in the liquid chamber (<NUM>) according to the second amount of light;
wherein the first sensitivity level is different from the second sensitivity level; and
wherein the electro-optic sensor (<NUM>) includes a prism (<NUM>) and a reflective optical member (<NUM>), wherein the reflective optical member (<NUM>) is arranged to reflect light emitted by the light source (<NUM>) to the light detector (<NUM>) when a liquid is disposed between the light source (<NUM>) and the reflective optical member (<NUM>);
wherein the electro-optic sensor (<NUM>) includes a photo diode-based sensor,
the light source (<NUM>) includes an LED, and
the timing circuit is configured to cap an amount of energy through a circuit of the electro-optic sensor (<NUM>).