PATENT DOCUMENT

Publication Number: US-9780554-B2
Application Number: US-201514814606-A
Country: US
Kind Code: B2

Title: Moisture sensors

Abstract:
A moisture sensor includes one or more electrodes and sensor circuitry configured to detect the presence of moisture by detecting a change in an electrical measurement of the one or more electrodes. In response, the sensor may signal a component to perform an action. In some examples, capacitance and/or resistance between a pair of electrodes may be monitored, such as a pair of electrode sheets or meshes positioned in passage of a device that are separated by a gap. In various examples, a first electrode may be mounted cantilever to a second electrode and the presence of moisture between the electrodes may pull a free end closer to the second electrode. In some examples, the presence of moisture may cause bridging of a gap between two or more electrodes to complete or corrosion of a portion of an electrode to result in a change of resistance that can be detected.

Claims:
What is claimed is: 
     
       1. An electronic device comprising:
 a housing that defines an internal cavity of the electronic device, the housing having an opening; 
 a moisture sensor comprising:
 a first electrode in the opening; and 
 a second electrode in the opening interposed between the first electrode and the internal cavity, wherein the second electrode completely covers the internal cavity; and 
 
 sensor circuitry in the housing that monitors an electrical measurement between the first and second electrodes, wherein the sensor circuitry is configured to detect moisture in the opening based on a change in the electrical measurement between the first and second electrodes. 
 
     
     
       2. The electronic device of  claim 1 , further comprising a moisture-absorbent substrate positioned between the first and second electrodes that draws moisture away from the first and second electrodes. 
     
     
       3. The electronic device of  claim 1 , wherein the first electrode is formed from a first mesh, and the second electrode is formed from a second mesh. 
     
     
       4. The electronic device of  claim 1 , wherein the first electrode and the second electrode are coated with hydrophobic coatings. 
     
     
       5. The electronic device of  claim 1 , further comprising:
 an acoustic device mounted in the internal cavity, wherein the acoustic device is configured to output acoustic signals through the internal cavity and opening. 
 
     
     
       6. The electronic device of  claim 1 , wherein the opening forms at least part of a barometric pressure vent that is coupled to the internal cavity, and the barometric pressure vent is configured to equalize internal pressure within the internal cavity by allowing air to flow into and out of the internal cavity. 
     
     
       7. The electronic device of  claim 1 , wherein the sensor circuitry is configured to provide current to the first electrode in response to detecting moisture in the opening, and wherein the current causes the first electrode to expand and reduce a permeability of the first electrode. 
     
     
       8. The electronic device of  claim 1 , wherein the sensor circuitry is configured to take a capacitive measurement and a resistive measurement between the first and second electrodes, the electronic device further comprising:
 processing circuitry configured to determine the amount of moisture in the opening using the capacitive measurement and the resistive measurement. 
 
     
     
       9. The electronic device of  claim 1 , further comprising a vent configured to equalize pressure in the internal cavity in response to the detection of the moisture by the sensor circuitry. 
     
     
       10. The electronic device of  claim 1 , further comprising an air inlet valve, wherein the air inlet valve is configured to close to reduce an ingress of moisture through the opening in response to the detection of the moisture by the sensor circuitry. 
     
     
       11. The electronic device of  claim 1 , wherein the moisture sensor is a microelectromechanical systems moisture sensor. 
     
     
       12. A moisture sensor comprising:
 a moisture-absorbent layer having first and second opposing surfaces; 
 a first electrode mounted to the first surface of the moisture-absorbent layer; 
 a second electrode mounted to the second surface of the moisture-absorbent layer; and 
 sensor circuitry electrically connected to the first and second electrodes, wherein the sensor circuitry takes an electrical measurement between the first and second electrodes, wherein the sensor circuitry is configured to detect moisture on the first and second electrodes based on the electrical measurement, wherein the sensor circuitry is configured to provide current to the first and second electrodes, and wherein the moisture between the first and second electrodes shorts the first electrode to the second electrode and causes the current to pass through the first and second electrodes to thermally drive the moisture off of the first and second electrodes. 
 
     
     
       13. The moisture sensor of  claim 12 , wherein the current thermally drives the moisture off of the first and second electrodes by evaporating the moisture. 
     
     
       14. The moisture sensor of  claim 12 , wherein the electrical measurement is a resistive measurement. 
     
     
       15. The moisture sensor of  claim 12 , wherein the electrical measurement is a capacitive measurement. 
     
     
       16. The moisture sensor of  claim 12 , wherein the first and second electrodes are formed from copper. 
     
     
       17. An electronic device comprising:
 a housing that defines an internal cavity of the electronic device, wherein the housing includes an opening; 
 a first electrode mounted in the opening; 
 a second electrode mounted in the opening between the first electrode and the internal cavity; 
 sensor circuitry electrically connected to the first and second electrodes, wherein the sensor circuitry detects moisture based on an electrical measurement between the first and second electrodes; and 
 an acoustic device in the internal cavity, wherein the acoustic device is configured to produce tones that drive the moisture out of the opening in response to the sensor circuitry detecting the moisture, wherein the second electrode is separated from the acoustic device by a gap. 
 
     
     
       18. The electronic device of  claim 17 , wherein the opening forms at least a portion of an acoustic passage for the acoustic device. 
     
     
       19. The electronic device of  claim 17 , further comprising a water resistant membrane between the second electrode and the acoustic device. 
     
     
       20. The electronic device of  claim 17 , wherein the first and second electrodes are coated with a hydrophobic coating. 
     
     
       21. The electronic device of  claim 17 , wherein a layer of moisture absorbent foam is interposed between the first and second electrodes.

Description:
FIELD 
     The described embodiments relate generally to moisture detection. More particularly, the present embodiments relate to various moisture detection sensors positioned within an electronic device. 
     BACKGROUND 
     Many devices, such as smart phones, may be vulnerable to moisture, whether vapor or liquid form. Components such as housings, seals, and so on may be used to keep moisture away from moisture sensitive elements of the devices. However, such components may not keep out all moisture. This may particularly be the case where ports to an external environment are provided for device elements (such as ports for acoustic devices such as microphones or speakers), housing portions and/or other elements are joined at seams, and/or other such situations. 
     It may be useful to determine when a device and/or internal portions thereof is exposed to moisture. In some cases, a warrantee for a device may be voided if the device and/or internal portions thereof are exposed to moisture. In other cases, effectiveness of components such as housings or seals may be tested by determining whether or not moisture is present in internal portions of a device. 
     SUMMARY 
     The present disclosure describes systems, methods for, and apparatuses related to electrical moisture detection. A moisture sensor disposed in an interior of a device may include one or more electrodes and sensor circuitry configured to detect the presence of moisture by detecting a change in an electrical measurement of the one or more electrodes. In response to detection of moisture, the moisture sensor may signal a component of the device to perform one or more actions. 
     In some examples, capacitance and/or resistance between a pair of electrodes may be monitored to detect the presence of moisture. In one such example, a pair of hydrophobic coated electrode meshes may be positioned in an acoustic path of a device separated by a water absorbent material. In various examples, a first electrode may be mounted cantilever to a second electrode and the presence of moisture between the electrodes may pull a free end of the cantilever closer to the second electrode. In some examples, the presence of moisture may cause bridging of a gap between two or more electrodes to complete a circuit or corrosion of a portion of an electrode to open a circuit. 
     In various embodiments, an electronic device including a moisture sensor may include a housing, a first electrode sheet (such as a first mesh) positioned in a passage through the housing, a second electrode sheet (such as a second mesh) positioned in the passage and offset from the first electrode sheet by a gap, and sensor circuitry operatively coupled to the first and second electrode sheets. The sensor circuitry may be configured to detect a presence of moisture by detecting a change in an electrical measurement between the first and second electrode sheets. 
     In some examples, a moisture-absorbent substrate may be positioned in the gap that draws moisture away from the first or second electrode sheets. In various examples, the first electrode sheet and the second electrode sheet may be coated with hydrophobic coatings. 
     In one or more examples, the passage may be an acoustic path of the device, the acoustic path operatively coupled to an acoustic device and configured to pass acoustic signals. In other examples, the passage may be a barometric pressure vent for the device, the barometric pressure vent operatively coupled to an internal volume and configured to equalize internal pressure by allowing a flow of air into or out of the internal volume. 
     In various examples, the sensor circuitry may be configured to provide current to at least one of the first or second electrode sheets when the presence of moisture is detected to cause the at least one first and second electrode sheets to expand to reduce the liquid permeability of the first or second electrode sheets. 
     In some examples, the electrical measurement between the first and second electrode sheets may include a capacitance measurement and a resistance measurement and the device may be configured to characterize a type of the moisture or estimate a quantity of the moisture using the capacitance measurement and the resistance measurement. 
     In various examples, the sensor circuitry may be configured to signal the device based on the detection of the presence of moisture. In response to the signal, the device may perform an action. The action may include at least one of opening a vent to equalize internal pressure in an internal volume by allowing a flow of air or closing an air inlet valve to reduce ingress of moisture. In some examples, the device may perform the action in response to the signal upon computing an estimated quantity of the moisture based on the electrical measurement; and determining the estimated quantity is above a threshold value. 
     In some embodiments, a moisture sensor disposed in an interior of an electronic device may include a first electrode, a second electrode offset from the first electrode by a gap that is configured such that surface tension of moisture present in the gap causes at least a portion of the second electrode to deflect into the gap, and sensor circuitry operatively coupled to the first and second electrodes and configured to detect a presence of moisture by detecting a change in an electrical measurement between the first and second electrodes. 
     In various examples the second electrode may be mounted cantilever to the first electrode such that the second electrode has a fixed end and an unfixed end positioned over the first electrode. In some examples, the surface tension of the moisture present in the gap may bring the unfixed end closer to the first electrode. In one or more examples, the surface tension of the moisture present in the gap may cause the unfixed end to contact the first electrode. 
     In one or more embodiments, a moisture sensor disposed in an interior of an electronic device may include a substrate; a first electrode mounted on a surface of the substrate, a second electrode mounted on the surface of the substrate offset from the first electrode by a gap, and sensor circuitry operatively coupled to the first and second electrodes and configured to detect a presence of moisture by detecting a change in an electrical measurement between the first and second electrodes caused by conductive material bridging the gap. 
     In various examples, the conductive material may form in the gap as a result of the moisture. The conductive material may form in the gap as a result of corrosion of the first or second electrode caused by the moisture. 
     In some examples, the moisture sensor may further include a hydrophilic coating disposed in the gap that concentrates moisture for detection. 
     In various embodiments, a moisture sensor disposed in an interior of an electronic device may include a printed circuit board, a trace mounted on a surface of the printed circuit board that has a first portion and a second portion, and sensor circuitry operatively coupled to the trace and configured to detect a presence of moisture by detecting a change in resistance between the first portion and the second portion caused by corrosion. 
     In some examples, the change in resistance between the first portion and the second portion may result from corrosion of a third portion of the trace positioned between the first portion and the second portion caused by the presence of moisture. In various examples, the moisture sensor may further include a coating on the first portion and second portion that promotes corrosion of the third portion. In some examples, the third portion may a smaller height from the surface of the printed circuit board or a smaller width across the surface of the printed circuit board than the first portion and the second portion. In one or more examples, the moisture sensor may further include a hydrophilic coating disposed on the trace that concentrates moisture for detection. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements. 
         FIG. 1  shows a device that may include a moisture sensor. 
         FIG. 2  shows a cross-sectional view of the device of  FIG. 1  illustrating example moisture sensors, taken along line A-A of  FIG. 1 . 
         FIG. 3A  is a detail view of an example implementation of the indicated portion of  FIG. 2 . 
         FIG. 3B  shows the moisture sensor of  FIG. 3A  in the presence of moisture. 
         FIGS. 4A-8  shows additional examples of moisture sensors in accordance with further embodiments of the present disclosure. 
         FIG. 9  is a schematic diagram of example circuitry that may be utilized to implement the sensor circuitry of  FIG. 3A   
         FIG. 10  shows a block diagram illustrating an example of relationships between example components of the device of  FIG. 1 . 
         FIG. 11  shows a flow chart illustrating a method for detecting and responding to the presence of moisture. This method may be performed by and/or utilizing the devices and/or moisture sensors illustrated in  FIGS. 1-10 . 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to representative embodiments illustrated in the accompanying drawings. It should be understood that the following descriptions are not intended to limit the embodiments to one preferred embodiment. To the contrary, it is intended to cover alternatives, modifications, and equivalents as can be included within the spirit and scope of the described embodiments as defined by the appended claims. 
     The present disclosure describes systems, methods for, and apparatuses related to electrical moisture detection. A moisture sensor may include one or more electrodes and sensor circuitry configured to detect the presence of moisture by detecting a change in an electrical measurement (such as capacitance, resistance, and so on) of the one or more electrodes. The moisture sensor may be disposed in an interior of a device (such as a moisture vulnerable area like an acoustic path, a seam of a housing, proximate to moisture vulnerable components, and so on). In response to detection of moisture, the moisture sensor may signal a component of the device to perform one or more actions (such as opening a vent or other air outlet valve to equalize internal pressure in an internal volume by allowing the flow of air, closing an air inlet valve to reduce ingress of moisture, changing an operational state of the device, attempting to drive out the moisture such as by heating or producing tones, and so on). 
     In some examples, capacitance and/or resistance between a pair of electrodes may be monitored to detect the presence of moisture. In one implementation of such an example, a pair of electrode sheets (such as meshes) may be positioned in a passage (such as an acoustic path operatively coupled to an acoustic device and configured to pass acoustic signals) of a device separated by a gap. A water absorbent material may be positioned in the gap. The electrode sheets may be coated with hydrophobic coatings. Moisture on and/or between the electrode sheets may change a capacitance and/or resistance between the electrode sheets and may thus be detectable. In some cases, moisture between the electrode sheets may complete a circuit that passes current through the electrode sheets, causing the electrode sheets to expand and become less liquid permeable and/or become heated and thus evaporate moisture. 
     In various examples, a first electrode may be mounted cantilever to a second electrode. The presence of moisture between the electrodes may pull a free end of the cantilever (such as by surface tension) closer to the second electrode. The presence of moisture may be determined by detecting increase in proximity and/or contract between the two electrodes. 
     In some examples, the presence of moisture may cause bridging of a gap between two or more electrodes to complete a circuit or corrosion of a portion of an electrode to change a resistance that can be measured. 
     These and other embodiments are discussed below with reference to  FIGS. 1-11 . However, those skilled in the art will readily appreciate that the detailed description given herein with respect to these Figures is for explanatory purposes only and should not be construed as limiting. 
       FIG. 1  shows a device  100  that may include a moisture sensor. The device  100  may include one or more housings  101  and one or more entry points where moisture (such as water, water vapor, and so on) may enter the housing  101 , such as a passage  102  through an aperture in the housing  101 . One or more moisture sensors may be disposed in an interior of the housing  101 . Such moisture sensors may include one or more electrodes and sensor circuitry configured to detect the presence of moisture by detecting a change in an electrical measurement of the one or more electrodes. In response to detection of moisture, the moisture sensor may, or cause the device  100  to, signal a component or subsystem to perform one or more actions. 
       FIG. 2  shows a cross-sectional view of the device  100  of  FIG. 1  illustrating example moisture sensors  206  and  208 , taken along line A-A of  FIG. 1 . One or more such moisture sensors  206  or  208  may be disposed in a passage  102  (illustrated as an acoustic path for an acoustic device  203  that is operatively coupled to the acoustic device  203  and configured to pass acoustic signals), in an internal volume  205  of the housing  101  the device  100 , on a printed circuit board  207  positioned on an internal surface  204  of the housing  101 , and so on. The moisture sensors  206  or  208  may be disposed in moisture vulnerable areas (such as the passage  102 , a seam of a housing  101 , proximate to moisture vulnerable components such as components of the printed circuit board  207 , and so on). In the illustration of  FIG. 2 , the size of the passage  102  is exaggerated in order to better illustrate various components and/or features. 
       FIG. 3A  is a detail view of an example implementation of the indicated portion of  FIG. 2 . The moisture sensor  206  may be positioned in the passage  102 . As shown, the passage  102  is coupled to the acoustic device  203 . In some implementations, a water resistant membrane  316  (such as expanded polytetrafluoroethylene) may be positioned between the moisture sensor  206  and the acoustic device  203 . 
     Although the passage  102  is illustrated as an acoustic path for the acoustic device  203  that is operatively coupled to the acoustic device  203  and configured to pass acoustic signals, it is understood that this is an example. In some implementations, the passage  102  may be coupled to components other than an acoustic device  203 , such as a barometric pressure vent, another kind of vent, any other component, or open directly into the internal volume  205  without connection to a component. 
     The moisture sensor  206  include a first electrode  313  and a second electrode  314  positioned in the passage  102 . Positioning the first electrode  313  and the second electrode  314  in the passage  102  may include fully or partially disposing the first electrode  313  and the second electrode  314  within the passage  102 , coupling the first electrode  313  and the second electrode  314  to an opening of the passage  102 , and so on. The first electrode  313  and the second electrode  314  are illustrated as sheets of meshes, but may be any kind of electrodes such as copper, other conductive metals or other material, traces, and so on. The first electrode  313  and the second electrode  314  may be separated by a gap fully or partially filled by a moisture-absorbent material  312  (such as a foam, a wicking material, a desiccant such as silica gel, and/or any other moisture-absorbent substrate). The moisture-absorbent material  312  or other moisture-absorbent substrate may function to draw moisture away from the first electrode  313  and/or the second electrode  314 . Sensor circuitry  309  may be configured to monitor one or more electrical measurements of the first and second electrodes  313  and  314  via conductive pathways  310  and  311 . 
     For example, the sensor circuitry  309  may monitor a capacitance and/or a resistance between the first and second electrodes  313  and  314 . The sensor circuitry  309  may determine that moisture is present if the monitored capacitance and/or resistance between the first and second electrodes  313  and  314  changes. 
     By way of example, the sensor circuitry  309  may measure a capacitance and/or a resistance between the first and second electrodes  313  and  314  in the absence of moisture as illustrated in  FIG. 3A .  FIG. 3B  shows the moisture sensor  206  of  FIG. 3B  in the presence of moisture  317 . As shown, the moisture  317  may be disposed on and/or between the first and/or second electrodes  313  and  314 . This may change the capacitance and/or resistance between the first and second electrodes  313  and  314  monitored by the sensor circuitry  309 . Based on this detected change, the sensor circuitry  309  may detect the presence of moisture. 
     For example, moisture  317  that contacts and/or is positioned between the first and/or second electrodes  313  and  314  may alter capacitance between the first and second electrodes  313  and  314 . The higher the quantity of moisture  317  that is positioned between the first and second electrodes  313  and  314 , the more that capacitance between the first and second electrodes  313  and  314  may change. By monitoring and measuring changes in the capacitance between the first and second electrodes  313  and  314 , the sensor circuitry  309  may be able to detect the presence of moisture. 
     By way of another example, moisture  317  positioned on or between the first and/or second electrodes  313  and  314  may electrically connect the first and second electrodes  313  and  314 , decreasing resistance between the first and second electrodes  313  and  314 . The resistance change may vary by the quantity of moisture present. By monitoring and measuring changes in the resistance between the first and second electrodes  313  and  314 , the sensor circuitry  309  may be able to detect the presence of moisture, characterize a type of the moisture, estimate a quantity of the moisture, and so on. 
     In some implementations, the first and/or second electrodes  313  and  314  may be coated with one or more hydrophobic coatings  315 . Thus, in implementations where the moisture sensor  206  of  FIG. 3A  blocks the entirety or a majority of the passage  102 , the moisture sensor  206  may function as a moisture barrier for the device  100 . In such implementations, the hydrophobic coating  315  on the first electrode  313  may resist the passage of moisture in the direction of the moisture-absorbent material  312 , the moisture-absorbent material  312  may resist the flow of moisture in the direction of the second electrode  314 , and the hydrophobic coating  315  on the second electrode  314  may resist the flow of moisture in the direction of the water resistant membrane  316  and/or the acoustic device  203 . 
     As shown, the moisture sensor  206  of  FIG. 3A  is shown as positioned to entirely block the passage  102 . However, it is understood that this is an example. In various implementations, the moisture sensor  206  of  FIG. 3A  may be positioned such that it does not entirely block or block a majority of the passage  102  without departing from the scope of the present disclosure. 
     In various implementations, the sensor circuitry  309  may transmit one or more signals to a component of the device  100  upon the detection of moisture (such as the processing unit  1081  of  FIG. 10 ). Such signals may include indications that moisture is detected, data regarding the detection (such as the electrical measurements or changes), and so on). 
     In some cases, the sensor circuitry  309  and/or another component of the moisture sensor  206  may be directed in response to perform one or more actions related to the moisture. For example, the first and/or second electrodes  313  and  314  may be formed of materials configured to function as a heating element. The sensor circuitry  309  and/or another component may provide current that may be run through the first and/or second electrodes  313  and  314 . This may cause the first and/or second electrodes  313  and  314  to heat to thermally drive off moisture. By way of another example, the first and/or second electrodes  313  and  314  may be formed of a material (such as nickel titanium, or nitinol) that is configured to expand. Current may be run through the first and/or second electrodes  313  and  314 , which may cause the first and/or second electrodes  313  and  314  to expand, making it more difficult for moisture or liquid to pass through the moisture sensor  206  toward the acoustic device  203  and/or otherwise making the first and/or second electrodes  313  and  314  less permeable to liquid or moisture. 
     Although the above describes the moisture sensor  206  as being directed to perform the actions, in various implementations such actions may be performed passively. The presence of moisture on and/or between first and/or second electrodes  313  and  314  may complete a circuit and may thus cause current to run through the first and second electrodes  313  and  314 , causing heating, expansion, and/or various other effects. 
       FIGS. 4A-8  show additional examples of moisture sensors  206  or  208  in accordance with further embodiments of the present disclosure. 
       FIG. 4A  shows an example moisture sensor  420  mounted to a substrate  421  (such as a silicon substrate, a printed circuit board, and so on) that includes a first electrode  422  and a second electrode  423  coupled to a mount  424 . The first electrode  422  is mounted cantilever to the second electrode  423  such that the first electrode  422  has a fixed end coupled to the mount  424  and a free end positioned over the second electrode defining a gap  425  between the first electrode  422  and the second electrode  423 . As shown in  FIG. 4B , moisture  426  (e.g., a liquid droplet) may exert force (such as by surface tension of the moisture  426 ) to bring and/or otherwise pull the unfixed end of the cantilever closer to and/or in contact with the second electrode  423 . In other words, with reference to  FIGS. 4A and 4B , surface tension of moisture  426  present in the gap  425  causes at least a portion of the second electrode (the unfixed end) to deflect into the gap  425 . By monitoring a change in an electrical measurement between the first and second electrodes  422  and  423  (such as resistance, capacitance, and so on), an increased proximity between the cantilever and the second electrode  423  and thus the presence of moisture  426  may be detected. 
       FIG. 5A  shows another example moisture sensor  530  mounted to a substrate  531  that includes a first electrode  532  offset from a second electrode  533  by a gap  534 . A resistance between the first and second electrodes  532  and  533  may be monitored for changes. As illustrated in  FIG. 5B , the presence of moisture proximate to the moisture sensor  530  of  FIG. 5B  may cause the first and/or second electrodes  532  and  533  to corrode. With reference to  FIGS. 5A and 5B , this corroded material may form dendrites  535  and/or other structures in the gap  534  that bridge the gap  534 . Because this corroded conductive material forms in the gap  534  (bridging the gap  534  as a result of corrosion of the first and second electrodes  532  and  533  caused by the moisture), the resistance between the first and second electrodes  532  and  533  may change. Change in this resistance beyond a threshold (such as completion of the circuit between the first and second electrodes  522  and  523 ) may be detected as indicating the presence of moisture. 
     Formation of the corroded conductive material that bridges the gap  534  between the first and second electrodes  532  and  533  may not be reversible. As such, the moisture sensor  530  illustrated in  FIGS. 5A and 5B  may be “sacrificial” in that it may be used to detect whether or not the moisture sensor  530  has ever detected moisture but may not be able to detect whether or not moisture is currently present. 
       FIG. 6A  shows still another example moisture sensor  640  mounted to a substrate  641  that includes a first array  642  of conductive materials  644  and a second array  634  of conductive materials  645 , such as electrical traces formed on the substrate  641 . The first and second arrays  642  and  643  are positioned such that the conductive materials  644  and  645  are offset from each other by gaps and are at least partially interposed with one another, forming a set of interlocking fingers. As shown in  FIG. 6B , moisture  646  between and/or on one or more of the conductive materials  644  and/or  645  may change the dielectric constant of the gaps between the conductive materials  644  and/or  645 . By monitoring the dielectric constant of the gaps and detecting a change in the monitored dielectric constant, the presence of moisture may be detected. 
       FIG. 7A  shows yet another example moisture sensor  750  mounted to a substrate  751  that includes a trace or other electrode having a first portion  752  connected to a second portion  753  by a third portion  754 . A resistance between the first portion  752  and the second portion  753  may be monitored. Moisture  756  that is present may corrode the third portion  754 , as shown in  FIG. 7B , and corrode a break  757  in the third portion  754 , resulting in a change in the resistance between the first portion  752  and the second portion  753 . Change in the resistance beyond a threshold (such as opening of the circuit between the first portion  752  and the second portion  753 ) may be detected as indicating the presence of moisture  756 . 
     Like the moisture sensor  640  illustrated in  FIGS. 6A and 6B , the moisture sensor  750  illustrated in  FIGS. 7A and 7B  may be sacrificial. As such, it may be used to detect whether or not the moisture sensor  750  has ever detected moisture but may not be able to detect whether or not moisture is currently present. 
     The first, second, and third portions  752 ,  753 , and  754  are illustrated and described as separate components that may be differently dimensioned and may be made of different materials. For example, as illustrated the third portion  754  may have a smaller height from the surface of the substrate  751  or smaller width on the surface of the substrate  751  than either the first or second portions  752  and  753  such that it is configured to corrode more quickly than the first or second portions  752  and  753  in the presence of moisture. However, it is understood that this is an example. In various implementations, the first, second, and third portions  752 ,  753 , and  754  may be identical regions of a single electrode through which current is passed from the first portion  752  to the second portion  753 . In such an implementation, the third portion  754  may be any part of the electrode that corrodes to define the break  757 . 
     Further, in some implementations the moisture sensor  750  illustrated in  FIG. 7A  may include one or more coatings  755  positioned on the first, second, and/or third portions  752 ,  753 , and  754 . Such a coating may be a hydrophobic coating or water barrier coating on the first and second portions  752  and  753  that encourages moisture  756  to collect and concentrate on the third portion  754 , causing the third portion  754  to corrode faster than the first or second portions  752  and  753  to concentrate the moisture  756  for detection. Such a coating  755  may be a hydrophilic coating (such as positioned on the third portion  754  and/or the first, second, and third portions  752 ,  753 , and  754 ) that attracts and concentrates the moisture  756  on the moisture sensor  750  such that smaller amounts of moisture will corrode the break  757  and are thus detectable than would in the absence of such concentration. 
     As illustrated, the coatings  755  are disposed on the first and second portions  752  and  753 . However, it is understood that this is an example. In various other implementations, the coating  755  may be disposed on the third portion  754  and/or one or more coatings (hydrophobic coatings, hydrophilic coating, water barrier coatings, and so on) may be disposed on the first and/or second portions  752  and  753  to concentrate the moisture  756  on the third portion  754 . 
       FIG. 8  shows still another example moisture sensor  860  mounted to a substrate  861  that includes a single electrode  862 . The electrode  862  may be used as a capacitive self-reference such that measurement of a capacitive loading of the electrode  862  is monitored. The presence of moisture  863  on and/or near the electrode  862  may change the capacitive loading of the electrode  862 . As such, a change in the measured capacitive loading of the electrode  862  may be detected as indicating the presence of the moisture  863 . 
     Although  FIGS. 4A-8  illustrate the various example moisture sensors  420 - 860  mounted to substrates  421 - 861  in particular fashions, it is understood that these are examples. In various implementations, the various example moisture sensors  420 - 860  may be otherwise coupled to the respective substrates  421 - 861  (and/or one or more other substrates) in various orientations without departing from the scope of the present disclosure. 
     In various implementations, one or more of the moisture sensors  206 ,  208 , and/or  420 - 860  illustrated and described above may be a microelectromechanical systems (MEMS) moisture sensor. Such a MEMS sensor may be incorporated into another component and/or MEMS component of the device  100 , such as a MEMS acoustic device  203  (such as a MEMS microphone or speaker), a force sensor, and/or any other component. 
       FIG. 5  is a schematic diagram of example circuitry  970  that may be utilized to implement the sensor circuitry  407  of  FIG. 4A . As shown, the sensor circuitry  970  may include an analog to digital converter  973  connected to the conductive pathways  971  and  972  (such as the conductive pathways  408  and  409 ), digital logic  974  connected to the analog to digital converter  973 , and a sensor output line  975 . The sensor circuitry  970  may be configured to detect a presence of moisture by detecting a change in an electrical measurement between the first and second electrodes (such as the first and second electrodes  401  and  402 ) connected to the conductive pathways  971  and  972 . The sensor circuitry  970  may be so configured by the analog to digital converter  973  being configured to receive analog electrical signals regarding resistances and/or capacitances of the first and second electrodes via the conductive pathways  971  and  972 , convert the electrical signals to digital values that the analog to digital converter  973  provides to the digital logic  974 . The sensor circuitry  970  may be further so configured by the digital logic  974  being configured to evaluate the digital values provided by the analog to digital converter  973  to estimate a change in capacitance or resistance and/or determine whether or not a change has occurred and providing a sensor output accordingly via the sensor output line  975 . 
     Similarly, circuitry  970  may be utilized with any of the example moisture sensors  420 - 860  of  FIGS. 4A-8 . In such implementations, the circuitry  970  may be connected to the various electrodes  422 - 423 ,  532 - 533 ,  642 - 643 ,  752 , 753 , and  862  via the conductive pathways  971  and  972  such that the circuitry  970  may be operable to monitor the electrical properties of the electrodes  422 - 423 ,  532 - 533 ,  642 - 643 ,  752 , 753 , and  862 . 
     Referring again to  FIGS. 1-2 , although the device  100  is illustrated as a wearable device, it is understood that this is an example. In various implementations, the device  100  may be any device that may include a sensor positioned within or thereupon, such as a laptop computing device, a desktop computing device, a tablet computing device, a mobile computing device, a wearable device, a display, a speaker, an accessory, a digital media player, an input device, an output device, and so on. 
     Referring again to  FIGS. 1-2 , the device  100  may utilize the moisture sensor(s)  206  or  208  in a variety of ways.  FIG. 10  shows a block diagram illustrating an example of relationships between example components of the device  100  of  FIG. 1 . For example, the may include one or more processing units  1081 , non-transitory storage media  1082  (which may take the form of, but is not limited to, a magnetic storage medium; optical storage medium; magneto-optical storage medium; read only memory; random access memory; erasable programmable memory; flash memory; and so on), communication components  1083 , input/output components  1084 , power sources  1085 , inlet/outlet valves  1086  (which may be a pressure vent operatively coupled to an internal volume  205  and configured to equalize internal pressure by allowing a flow of air into/out of the internal volume  205 ), acoustic devices  203 , and moisture sensors  206  or  208  (or other moisture sensors). The processing unit  1081  may receive one or more signals from the moisture sensor(s)  206  or  208  (and/or sensor circuitry included therein) indicating the presence of moisture and may perform one or more actions based thereon. For example, the processing unit  1081  may open and/or close the inlet/outlet valve  1086  to block or reduce moisture ingress and/or let out pressure, cease providing power and/or reduce power provided from the power source  1085  to various components, transmit messages or provide notifications regarding the detected moisture via the communication component  1083  and/or the input/output component  1084 , activate a heating element such as an element of the moisture sensor  206  or  208  or acoustic device  203  to drive off moisture, produce tones using the acoustic device  203  to drive out moisture, and so on. 
     The processing unit  1081  may be configured to compute and/or determine characteristics of present moisture based on data included in the signals from the moisture sensor(s)  206  or  208 . For example, the data may include a capacitance measurement and a resistance measurement of one or more electrodes of the moisture sensor(s)  206  or  208  and the processing unit  1081  may use the capacitance measurement and the resistance measurement to compute or determine an estimated quantity of moisture present, a type of moisture present, and so on. The action(s) performed by the processing unit  1081  may be dependent upon the determined characteristics of the present moisture. 
     By way of example, any resistance change may indicate the presence of moisture but the magnitude of the capacitance change may indicate an amount of moisture present. Lower capacitance changes may indicate a smaller quantity of moisture present (such as a few drops of liquid from the moisture sensor  206  or  208  being splashed with a small quantity of liquid) whereas higher capacitance changes may indicate a larger quantity of moisture present (such as where the moisture sensor(s)  206  or  208  is submerged). In some cases, the processing unit  1081  may compute the estimated quantity and perform the action(s) only if the estimated quantity of moisture is above a threshold value, such as medium or high as opposed to low. This may allow the device  100  to perform actions in response to being submerged in liquid that should not be taken if the device  100  is merely splashed with liquid or is exposed to high humidity. 
     By way of another example, a higher resistance change may indicate the presence of moisture that is more conductive (such as salt water or sweat) whereas a lower resistance change may indicate the presence of moisture that is less conductive (such as fresh water or rain). In some cases, the processing unit  1081  may perform the action(s) only if the present moisture may be salt water as opposed to fresh water as salt water may be more corrosive to vulnerable components than fresh water. This may allow the device  100  to perform actions in response to being exposed to salt water that should not be taken if the device  100  is merely exposed to fresh water. 
       FIG. 11  shows a flow chart illustrating a method for detecting and responding to the presence of moisture. This method may be performed by and/or utilizing the devices and/or moisture sensors illustrated in  FIGS. 1-10 . 
     At  1110 , an electrical measurement of one or more conductors may be measured. The measurement may include monitoring a circuit, capacitance or resistance between two electrodes, capacitive loading of an electrode, a dielectric constant in a gap between electrodes, and so on. The measurement may be an electrical measurement that changes in the presence of moisture. 
     At  1120 , moisture may be detected based on a change in the monitored electrical measurement. For example, moisture may be detected based on opening or closing of a monitored circuit, a change in capacitance or resistance between two electrodes, a change in a capacitive loading of an electrode, a change in a dielectric constant in a gap between electrodes, and so on. In some implementations, moisture may be detected by comparing monitored multiple electrical measurements. 
     At  1130 , an action may be performed based on the detected moisture. Such actions may include opening a vent or other air outlet valve to release pressure and/or equalize internal pressure in an internal volume by allowing a flow of air, closing an air inlet valve to block or reduce ingress of moisture, changing an operational state of the device (such as putting one or more components into a sleep and/or other low power state to reduce damage that could be caused by moisture), attempting to drive out the moisture such as by heating or producing tones, providing a notification that moisture has been detected, and so on. 
     Although the example method  1100  is illustrated and described as including particular operations performed in a particular order, it should be understood that this is an example. In various implementations, various orders of the same, similar, and/or different operations may be performed without departing from the scope of the present disclosure. 
     For example, the method  1100  is illustrated and described as performing an action based on the detected moisture. However, in some implementations moisture may be detected without performing any actions in response. 
     As described above and illustrated in the accompanying figures, the present disclosure describes systems, methods for, and apparatuses related to electrical moisture detection. A moisture sensor may include one or more electrodes and sensor circuitry configured to detect the presence of moisture by detecting a change in an electrical measurement (such as capacitance, resistance, and so on) of the one or more electrodes. The moisture sensor may be disposed in an interior of a device (such as a moisture vulnerable area like an acoustic path, a seam of a housing, proximate to moisture vulnerable components, and so on). In response to detection of moisture, the moisture sensor may signal a component of the device to perform one or more actions (such as opening a vent or other air outlet valve to equalize internal pressure in an internal volume by allowing a flow of air, closing an air inlet valve to reduce ingress of moisture, changing an operational state of the device, attempting to drive out the moisture such as by heating or producing tones, and so on). 
     The foregoing description, for purposes of explanation, used specific nomenclature to provide a thorough understanding of the described embodiments. However, it will be apparent to one skilled in the art that the specific details are not required in order to practice the described embodiments. Thus, the foregoing descriptions of the specific embodiments described herein are presented for purposes of illustration and description. They are not target to be exhaustive or to limit the embodiments to the precise forms disclosed. It will be apparent to one of ordinary skill in the art that many modifications and variations are possible in view of the above teachings.

Metadata:
Filing Date: 20150731
Publication Date: 20171003
Grant Date: 20171003
Priority Date: 20150731
Inventors: KARDASSAKIS PETER J.
Panthaki Farhan
WEISS SAMUEL B.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02H5/083", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01N27/121", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02H5/083", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02H5/083", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01N27/121", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01N27/121", "inventive": false, "first": false, "tree": "[]"}, {"code": "G08B21/20", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 57882320