PATENT DOCUMENT

Publication Number: US-9752999-B2
Application Number: US-201414290866-A
Country: US
Kind Code: B2

Title: Moisture ingress sensors

Abstract:
This application relates to a moisture ingress sensor. In particular, this application relates to a moisture ingress sensor that can detect liquid ingress into an electronic device. The moisture ingress sensor can include a resistor, an N-channel MOSFET, an operation amplifier, comparators, and an AND logic gate. The moisture ingress sensor is configured to provide a lower power means for accurately detecting moisture in an electronic device. Multiple areas of the electronic device can include the moisture ingress sensor in order to optimize the detection of moisture for at a variety of regions of the electronic device. Additionally, the electronic device can record signals from the moisture ingress sensor and shut down components of the electronic device that could be affected by the detected moisture. Furthermore, the moisture ingress sensor can be tuned to detect one or more types of liquids.

Claims:
What is claimed is: 
     
       1. A moisture sensor capable of detecting multiple moisture events, comprising:
 a moisture interface element capable of providing an electrical parameter value associated with a moisture detection event, wherein a first moisture event comprises: the moisture interface element providing a first electrical parameter value having a first peak value that is less than a threshold value such that the moisture interface element is prevented from issuing an activation signal, and wherein, a second moisture event subsequent to the first moisture event comprises: the moisture interface element remaining operable to provide a second electrical parameter value having a second peak value that includes at least the first peak value such that when the second peak value is greater than the threshold value, the moisture interface element provides the activation signal; 
 a logic circuitry connected to the moisture interface element; and 
 a signal processing portion connected to the logic circuitry and the moisture interface element, wherein the signal processing portion is arranged to (i) receive the activation signal, and (ii) send a corresponding reference signal to the logic circuitry such that the logic circuitry uses the corresponding reference signal to provide a moisture indication signal that corresponds to the first or the second moisture event. 
 
     
     
       2. The moisture sensor of  claim 1 , wherein the moisture interface element is a passive component comprising a first node and a second node coupled to a bias voltage. 
     
     
       3. The moisture sensor of  claim 1 , further comprising:
 a bias switch connected to the moisture interface element, wherein the bias switch is configured to allow the activation signal to pass through. 
 
     
     
       4. The moisture sensor of  claim 3 , wherein the bias switch opens in response to receiving the activation signal. 
     
     
       5. The moisture sensor of  claim 1 , wherein an electrical resistance of the moisture interface element is increased upon the detection of any of the first or second moisture events. 
     
     
       6. The moisture sensor of  claim 1 , wherein the logic circuitry comprises:
 at least two comparators connected to the moisture interface element, and an AND gate connected to the at least two comparators, wherein the at least two comparators define a tolerance that determines when the AND gate will cause the logic circuitry to output the moisture indication signal. 
 
     
     
       7. The moisture sensor of  claim 1 , wherein the signal processing portion includes an insulated gate device. 
     
     
       8. The moisture sensor of  claim 7 , wherein the signal processing portion includes an operational amplifier, and the insulated gate device is biased to a reference voltage of the operational amplifier. 
     
     
       9. The moisture sensor of  claim 1 , wherein the threshold value is a peak resistance. 
     
     
       10. A moisture ingress sensor for minimizing damage to an electronic component of a device, comprising:
 a moisture interface element having an electrical resistance that is adjusted upon exposure of the moisture interface element to a first moisture event such that: (i) when a result of a detection of the first moisture event exceeds a threshold, then issuing a first activation signal, otherwise (ii) when the result of the detection of the first moisture event is less than the threshold: adjusting the electrical resistance upon the exposure of the moisture interface element to a second moisture event, and issuing a second activation signal upon determining that the second moisture event exceeds the threshold; 
 a bias switch that is configured to open in response to receiving any of the first or second activation signals from the moisture interface element; 
 a logical component coupled to the moisture interface element; and 
 a signal processing portion connected to the moisture interface element, wherein the signal processing portion is capable of (i) receiving any of the first or second activation signals, and (ii) sending a corresponding reference signal to the logical component, thereby causing the logical component to utilize the corresponding reference signal to provide a moisture indication signal. 
 
     
     
       11. The moisture ingress sensor of  claim 10 , wherein the moisture interface element is a passive element that decreases in electrical resistance when the first or second moisture events exceed the threshold. 
     
     
       12. The moisture ingress sensor of  claim 10 , further comprising:
 at least two comparators, wherein the at least two comparators define a high tolerance and a low tolerance. 
 
     
     
       13. The moisture ingress sensor of  claim 12 , wherein the signal processing portion includes an insulated gate device. 
     
     
       14. The moisture ingress sensor of  claim 13 , wherein the signal processing portion includes an operational amplifier, and the insulated gate device is biased to a reference voltage of the operational amplifier. 
     
     
       15. A method for detecting multiple moisture events by a moisture ingress sensor of a computing device, the moisture ingress sensor including a moisture interface element capable of providing an electrical parameter value associated with a detection of a moisture event, the method comprising:
 when the moisture interface element detects a first moisture event:
 providing a first electrical parameter value having a first peak value that is less than a threshold value such that the moisture interface element is prevented from issuing an activation signal to a logic component of the moisture ingress sensor; 
 
 when the moisture interface element detects a second moisture event subsequent to the first moisture event, the second moisture event causes the moisture interface element to provide a second electrical parameter value having a second peak value that includes at least the first peak value:
 providing the activation signal to the logic component when the second peak value satisfies the threshold value, 
 causing the logic component to send a moisture indication signal, and 
 sending a switch signal to a bias switch that opens the bias switch of the moisture ingress sensor. 
 
 
     
     
       16. The method of  claim 15 , further comprising:
 preventing further operation of an electronic component of the computing device when the second peak value of the second moisture event satisfies the threshold value. 
 
     
     
       17. The method of  claim 15 , wherein the activation signal is transmitted to a metal oxide semiconductor field effect transistor (MOSFET) and a reference voltage is transmitted to the logic component when the second peak value of the second moisture event satisfies the threshold value. 
     
     
       18. The method of  claim 17 , further comprising:
 causing comparators to allow a reference voltage to proceed to the logic component when the reference voltage is within a predetermined tolerance of the comparators. 
 
     
     
       19. The method of  claim 15 , wherein the threshold value corresponds to a predetermined peak resistance value. 
     
     
       20. The method of  claim 15 , wherein an electrical resistance of the moisture interface element is increased upon the detection of any of the first or second moisture events.

Description:
FIELD 
     The described embodiments relate generally to moisture sensors. More particularly, the present embodiments relate to moisture ingress sensors for detecting the ingress of liquid in an electronic device. 
     BACKGROUND 
     Moisture ingress is a common problem for electronic devices because of the ability of liquids to cause shorts and corrosion within an electronic device. Often times, an electronic device may contact a liquid but only manifest symptoms of moisture ingress after an extended period of time. In the case of a mobile phone, where certain features of a mobile phone may only be used occasionally, a substantial amount of time may pass before a user notices the degeneration of certain features of the mobile phone caused by moisture ingress. For example, a headphone jack of a mobile phone may be rarely utilized by users who do not play music through their phone or conduct phone calls through a wearable headset. However, should the headphone jack contact a liquid, the headphone jack could be shorted by the liquid and degrade other portions of the mobile phone as the liquid progresses through the mobile phone. If a user is not aware of the liquid ingress, they may not be able to shut off the mobile phone in time to prevent shorting. Moreover, even if the user was made aware of the liquid ingress, they may not be provided with any way of mitigating damage caused by shorting and corrosion within the mobile device. 
     SUMMARY 
     This paper describes various embodiments that relate to moisture ingress sensors. In some embodiments, an apparatus is set forth as having a moisture interface element and a logic circuit connected to the moisture interface element. The apparatus can further include an amplifier circuit connected to the logic circuit and the moisture interface element. Additionally, when the moisture interface element contacts moisture, the apparatus can transmit an activating signal through the amplifier circuit and the logic circuit can output a moisture indication signal. If the apparatus is configured within a computing device, the moisture indication can be received by a processor in the computing device and respond according to a protocol stored within the computing device. 
     In some embodiments, a moisture ingress sensor is set forth herein as having a moisture interface element and a bias switch connected to the moisture interface element. The moisture ingress sensor can further include an operational amplifier and N-channel (metal oxide semiconductor field effect transistor) MOSFET connected between the moisture interface element and a grounded bias resistor. Additionally, the moisture ingress sensor can include a logical component and a comparator coupled to the N-channel MOSFET and the moisture interface element. The moisture ingress sensor can be configured to provide a moisture indication signal as a result of the moisture interface element contacting a liquid and an activation signal being transmitted through the N-channel MOSFET. Moreover, the moisture indication signal can be sent when a reference voltage received at the comparator is within a predetermined tolerance defined by the comparator. Thereafter, the moisture indication signal can be used by a computing device in which the moisture ingress sensor can be installed to shut down portions of the computing device to mitigate damage caused by the liquid. 
     Furthermore, in some embodiments, a system and a machine-readable non-transitory storage medium are set forth to carry out steps that include providing a periodic voltage signal to the moisture ingress sensor. The steps can also include causing a logic component of the moisture ingress sensor to send a moisture indication when the moisture ingress sensor contacts a liquid. Additionally, the steps can include receiving a moisture indication from the moisture ingress sensor and sending a switch signal to open a bias switch of the moisture ingress sensor. 
     Other aspects and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the described embodiments. 
    
    
     
       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, and in which: 
         FIG. 1A-1B  illustrate perspective views of points of potential moisture ingress of various computing devices; 
         FIG. 2A-2B  illustrate diagrams of an ingress sensor circuit according to some of the embodiments described herein; 
         FIG. 3  illustrates an ingress sensor circuit diagram having multiple moisture interfaces; 
         FIG. 4A-4B  illustrate circuit diagrams of a portion of the ingress sensor according to some embodiments described herein; 
         FIG. 5A-5B  illustrate circuit diagrams of a portion of the ingress sensor according to some embodiments described herein; 
         FIG. 6A-6B  illustrate a graph of the signals transmitted during operation readings of the ingress sensor; 
         FIGS. 7A-7B  illustrates a graph of the signals transmitted during operation of the ingress sensor according to some embodiments described herein; 
         FIG. 8  illustrates a method for constructing the ingress sensor according to some of the embodiments described herein; 
         FIG. 9  illustrates a method for indicating a presence of moisture at the ingress sensor according to some embodiments; 
         FIG. 10  illustrates a method of tuning the ingress sensor according to some embodiments described herein; and 
         FIG. 11  illustrates a method of operating the ingress sensor of a computing device according to some embodiments described herein. 
     
    
    
     DETAILED DESCRIPTION 
     Representative applications of methods and apparatus according to the present application are described in this section. These examples are being provided solely to add context and aid in the understanding of the described embodiments. It will thus be apparent to one skilled in the art that the described embodiments may be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the described embodiments. Other applications are possible, such that the following examples should not be taken as limiting. 
     In the following detailed description, references are made to the accompanying drawings, which form a part of the description and in which are shown, by way of illustration, specific embodiments in accordance with the described embodiments. Although these embodiments are described in sufficient detail to enable one skilled in the art to practice the described embodiments, it is understood that these examples are not limiting; such that other embodiments may be used, and changes may be made without departing from the spirit and scope of the described embodiments. 
     Common issues still prevalent in many electronic devices are corrosion and damage caused by moisture ingress. Moisture can invade various portions of a computing device causing shorts that create conductive pathways to areas of the computing device not intended to receive certain amounts of current. Although many computing device housings are intended to be sealed, moisture can still find a way to enter computing device housings. In order to deal with this ingress, embodiments of a moisture ingress sensor (also referred to as an ingress sensor) are provided herein. The moisture ingress sensor uses a passive component for detecting moisture ingress. The passive component is electrically coupled to an active current source having a resistor, N-channel metal oxide semiconductor field effect transistor (MOSFET), an operational amplifier, two comparators, and an AND logic gate. This configuration for the moisture ingress sensor provides a low powered means for detecting moisture ingress while also producing accurate moisture ingress indication. Moreover, the moisture ingress sensor operates on a low frequency and low voltage duty cycle thereby utilizing less power from a battery of the computing device. The moisture ingress sensor can send one or more moisture indication signals to a computing device in which the moisture ingress sensor is incorporated. In this way, the computing device can react appropriately to the detection of moisture by shutting down a portion of the computing device and/or isolating a portion of the computing device. Moreover, the ingress sensor can be incorporated into printed circuit boards, flexible circuits, and integrated circuits allowing the ingress sensors to be placed near potential ingress locations, while taking up very little space. Multiple ingress sensors can be incorporated into a single computing device for detecting moisture ingress at numerous areas of the computing device. The ingress sensor can also be used for tracking data associated with moisture ingress events, and/or sending notifications to a user of the computing device. The computing device can also stop function of the ingress sensor by switching open a bias switch in order to mitigate corrosion and dendrite growth. 
     These and other embodiments are discussed below with reference to  FIGS. 1A-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. 1A-1B  illustrate perspective views of potential points of moisture ingress for various computing devices. Specifically,  FIG. 1A-1B  show certain points susceptible to water ingress that can potentially damage or destroy the functionality of a computing device. In  FIG. 1A , a laptop computing device  100  is illustrated as having multiple cavities that can provide entry for moisture. These entry ways can include keys of a keyboard  102  and external device ports  104 .  FIG. 1B  illustrates a portable computing device  106 , such as a cell phone, which can also have multiple entry ways for moisture to enter the device. For example, the portable computing device  106  can include a speaker aperture  110 , various buttons  108 , and a charging port  112 . These cavities and entry ways of  FIGS. 1A-1B , although useful for many functions of the devices, can be the reason for the degeneration of the device. Because of the nature of many liquids, a variety of internal components such as a main logic board can come into contact with moisture despite not being proximate to an entry of cavity of the device. The embodiments discussed herein are directed toward handling the entry of moisture into a computing device. In particular, the embodiments herein describe circuits for detecting and handling moisture that a computing device may come into contact with, and mitigating any damage that might be caused by the moisture. 
       FIG. 2A-2B  illustrate diagrams of an ingress sensor circuit according to some of the embodiments described herein. In particular,  FIG. 2A-2B  illustrate the arrangement of the circuit components for the ingress sensor described herein. It should be noted that the term “sensor” can include one or more components when referring to the various embodiments described herein. For example, the ingress sensor  200  of  FIGS. 2A-2B  includes multiple components in order to indicate a presence of moisture in or near a computing device. In particular, ingress sensor  200  includes a moisture interface  202  that is configured to interface with any moisture that enters the computing device. The computing device can be one of the computing devices illustrated in  FIGS. 1A-1B  or any other computing device that can incorporate protection from moisture such as a media player, server, desktop computer, etc. The computing device can receive data related to liquid ingress from the ingress sensor through a logic component  218  of the ingress sensor. In some embodiments, the logic component  218  is an AND gate that can indicate a “1” or a “0” depending on the detection or lack of detection of moisture, respectively. Moreover, in some embodiments the logic component  218  can be an “OR” gate or any other suitable logic gate, alone or in combination with other logic gates in order to provide an indicator for the detection of moisture. 
     In order to accurately distinguish moisture detection signals originating from the moisture interface  202 , the ingress sensor  200  can further include a first comparator  216  and a second comparator  220  for providing a tolerance threshold for the moisture detection signals. In some embodiments, the first comparator  216  can be configured to compare a variety of moisture detection signals to a high tolerance voltage  216   a . The high tolerance voltage  216   a  can be set at any suitable voltage for a particular design or comparator. In some embodiments, the high tolerance voltage  216   a  is set at approximately 0.505 volts. Similarly, the second comparator  220  can be configured to compare a variety of moisture sensor detection signals to a low tolerance voltage  220   a . The low tolerance voltage  220   a  can be set to any suitable voltage for a particular design or comparator. In some embodiments, the low tolerance voltage  220   a  is set at approximately 0.495 volts. Additionally, in some embodiments the difference between the high tolerance voltage  216   a  and the low tolerance voltage  220   a  can be set at 0.010 volts, or any suitable voltage that is appropriate for a particular circuit. For example, some ingress sensors  200  may require a smaller or larger tolerance depending on the tuning of the circuit and the purpose of the sensor. 
     The sensing portion of the ingress sensor  200  is provided in part by the moisture interface  202 . The moisture interface  202  can be comprised of a variety of materials such as metal, plastic, glass, liquids, gases, etc., or air gap, in order to provide measurable signal when the moisture interface  202  contacts a liquid, gas, or any other molecule that could be harmful to the computing device in which the ingress sensor  200  is incorporated. In some embodiments, the moisture interface is configured such that when moisture  224  contacts the moisture interface  202 , the moisture interface  202  converts from a high or low resistance (as shown in  FIG. 2A ) into a low or high resistance circuit having a moisture resistance  226  (as shown in  FIG. 2B ), respectively. The value of moisture resistance  226  depends on the configuration of the ingress sensor  200  and the type of moisture that the moisture interface  202  has come into contact with. Additionally, the value of measurable resistance can determine the variance of the moisture detection signal that is sent to the logic component  218 , and other components  222  of the computing device. 
     In order to provide an accurate moisture detection signal to the logic component  218 , the ingress sensor  200  includes a combination of electrical components for comparing electrical signals. Specifically, the ingress sensor  200  can include an N-channel metal oxide semiconductor field effect transistor (MOSFET)  210  that can be connected to an operational amplifier  206 , bias resistor  212 , and the moisture interface  202 . The N-channel MOSFET  210  can be biased to a particular voltage determined by the reference voltage  206   a  of the operational amplifier  206 . In this way, the logic component  218  can receive the reference voltage  206   a  and a reference signal  230  when the N-channel MOSFET  210  is activated by an activating current  228 . For example, when the moisture interface  202  is not contacting moisture, the moisture interface  202  remains as a highly resistive circuit or open circuit thereby preventing any current from moving through the N-channel MOSFET  210 , as shown in  FIG. 2B . Alternatively, when moisture interface  202  comes into contact with moisture, the moisture interface  202  allows the activating current  228  to travel between a bias voltage  208  and bias switch  204 , and through the moisture interface  202 , and the N-channel MOSFET  210 . Depending on the tuning of the ingress sensor  200 , the activating current  228  will cause a conductive pathway to be created at the N-channel MOSFET  210  allowing the reference voltage  206   a  to be applied across the logic component  218  and ground  214 , and a reference signal  230  to be sent through the first comparator  216  and second comparator  220 . The reference signal  230  can then be characterized by the logic component  218 . 
     The ingress sensor  200  can be tuned in a variety of ways in order to be activated by certain liquids or molecules. For example, the moisture interface  202  can be configured for specific liquids, including, but not limited to, water. Water has a resistivity of approximately 18 mega-ohm centimeters (MΩ cm). If the contacts of the moisture interface  202  are spaced apart by 0.5 millimeters (mm) and the moisture interface has a total surface area of 1 cm 2 , then the measured resistance at the contacts of the moisture interface  202  will be 0.9 MΩ based on the following formula: 
     
       
         
           
             
               
                 
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     In some embodiments, based on this calculated resistance value, the remaining portions of the ingress sensor  202  can be configured to not only send a signal indicating that moisture is present, but also design an ingress sensor  202  that consumes very little power. For example, by using a reference voltage  206   a  of 0.5 volts, the bias resistor  212  can be modified in order to establish an activating current  228  that is as low as possible while still being high enough to induce a conductive pathway in the N-channel MOSFET  210 . In some embodiments, the bias resistor  212  has a value of approximately 500 kΩ. Additionally, in some embodiments, the total sensor power can be approximately between 18-20 microwatts. 
     The bias switch  204  is configured to open and close after the logic component  218  has indicated that moisture  224  is present at the moisture interface  202 . In this way, the bias switch  204  acts as a safety mechanism to prevent further damage caused by the moisture  224 . Such damage can include corrosion or dendrite growth, which can be exacerbated by the presence of charge such as the bias voltage  208 . Other portions of the computing device, in which the ingress sensor  200  can be incorporated, can also be shut off or isolated as a result of a detection of moisture  224 . For example, if the moisture interface  202  is near a camera flash of a computing device and the moisture interface  202  detects moisture  224 , the logic component can send an indication to the computing device that moisture  224  is present near the camera flash. As a result, the computing device can execute an application or set of instructions that shuts down the camera flash and prevents further use of the camera flash. The computing device can also shut down components and/or devices neighboring the camera flash, in order to isolate the camera flash. The computing device can record the received indicators from the ingress sensor  200  and keep a record of where, when, and what time the presence of moisture  224  occurs. 
       FIG. 3  illustrates an ingress sensor  300  circuit diagram having multiple moisture interfaces. In particular, the ingress sensor  300  is configured to have the moisture interface  202  and an additional moisture interface  302  located at different portions (e.g., on and around a main logic board) of a computing device. In this way, multiple parts of the computing device can be monitored and protected from moisture. It should be noted that  FIG. 3  includes all of the elements of  FIGS. 2A and 2B , and an additional set of elements to accommodate the additional moisture sensor  302 . For example, as compared to  FIGS. 2A-2B , ingress sensor  300  also includes a bias voltage  308  and bias switch  304  that can supply a same or a different voltage, and be triggered in a same or a different way than the ingress sensor  200 . Additionally, the tuning of the ingress sensor  300  can be modified such that the MOSFET  310 , operational amplifier  306 , reference voltage  306   a , and/or bias resistor  312  detect a type of moisture that is different than the moisture detected by the moisture interface  202 . Moreover, the voltage tolerance for detecting moisture can be modified such that a high tolerance voltage  316   a  and a low tolerance voltage  320   a  are different than the tolerances of ingress sensor  200 . In this way, a first comparator  316  and second comparator  320  can be set to be more or less strict when detecting a voltage resulting from the detecting of moisture. This modification to tolerances and thresholds can cause the logic component  318  to indicate moisture more or less often, or at the same time, as the logic component  218 . 
     The ingress sensor  300  of  FIG. 3  can be configured to provide the computing device with indicators for types of liquids detected at the moisture interface  202  and  302 . In some embodiments, the components connected to moisture interface  202  can be tuned differently than the components connected to moisture interface  302  such that moisture interface  202  indicates the presence of moisture differently than moisture interface  302  detects moisture. For example, moisture interface  202  can be configured to detect oils while moisture interface  302  can be configured to detect water. Upon the detection of either oil or water, logic component  218  or logic component  318 , respectively, will provide an indicator to the other components  222  of the computing device. The types of moisture detected can be classified, ranked, and stored within the computing device for later use, or acted on immediately by the computing device. Additionally, in some embodiments, if the moisture interfaces  202  and  302  detect moisture at the same time, a more invasive operation could be performed by the computing device to protect the computing device. For example, in some embodiments, the battery of the computing device can be completely isolated from the computing device by a switching mechanism when the ingress sensor  200  and/or the ingress sensor  300  detect a certain type of liquid, detect a liquid a certain number of times, and/or detect a liquid for a certain period of time. Additionally, in some embodiments, the safety procedures of the computing device can be based on an integral or derivate operation of the incoming data from the ingress sensor  200  or  300 . 
       FIG. 4A-4B  illustrate circuit diagrams of a portion of the ingress sensor according to some embodiments described herein. Specifically,  FIG. 4A  illustrates the moisture interface  202  incorporated into a representative version of the ingress sensor for purposes of explaining the tuning process of the ingress sensor according to some embodiments. The moisture interface  202  can be configured as an open circuit as provided in  FIG. 4A  such that an almost infinite resistance would be measured at an ohm meter  402 , basically preventing any current from passing through moisture interface  202 . In some embodiments, the moisture interface  202  can allow for some leakage of current over the moisture interface  202  and a base resistance  404  to be measured. When tuning the ingress sensor with respect to some embodiment described herein, the base resistance  404  should be taken into account in order to provide a more accurate indicator of moisture ingress to a computing device. For example, as illustrated in  FIG. 4A , when moisture  224  is received by the moisture interface  202 , a new resistance value will be measured at the ohm meter  402 . The new resistance value will be a total of the base resistance value  404  and the moisture resistance  226 . By taking into account the new resistance value, a designer can modify the base resistance and input voltage of the circuit in order to lower the total power for the ingress sensor while also providing an accurate indicator of moisture ingress. 
       FIG. 5A-5B  illustrate circuit diagrams of a portion of the ingress sensor according to some embodiments described herein. Specifically,  FIG. 5A  illustrates an embodiment of the ingress sensor having multiple moisture interfaces. A first moisture interface  406  is configured in parallel to a second moisture interface  408  in order to provide multiple areas of a computing device with moisture ingress detection. The circuit of  FIG. 5A  can be tuned in a similar manner as discussed with  FIGS. 4A-4B . For example, the base resistance  404  would be measurable from an ohm meter  402  as either an almost infinite value in the case of both the first moisture interface  406  and the second moisture interface  408  being open circuits. In other embodiments, the first moisture interface  406  and the second moisture interface can allow for some current leakage in order to provide the ohm meter  402  with a finite base resistance  404 . The first moisture interface  406  and the second moisture interface  408  can be made from the same materials, or different materials listed herein. As shown in  FIG. 5B , when moisture  224  contacts the moisture interface  406 , the moisture resistance  226  can be measured and compared to the resistance measured at the ohm meter  402 . The computing device incorporating the ingress sensor can be configured to respond in a variety of ways depending on whether one or more of moisture interfaces detect moisture ingress. For example, as shown in  FIG. 5B , the measured resistance at ohm meter  402  will be the total of the moisture resistance  226  and the base resistance  404 ; however, if moisture was present at the second moisture interface  408 , the total resistance measured at ohm meter  402  (e.g., a parallel combination of two moisture resistance values plus the base resistance  404 ) would be adjusted accordingly. In this way, the resistance, voltage input, and indicators provided at the ingress sensor can be modified to have a low operating power, accurate moisture indication for both the first moisture interface  406  and second moisture interface  408 , and detect a variety of moisture ingress scenarios at multiple areas of a computing device. 
       FIG. 6A-6B  illustrate a graph of the signals transmitted during operation of the ingress sensor  200 . Specifically, graph  600  illustrates a variety of signals transmitted during a non-moisture event of the ingress sensor  200  and graph  612  illustrates a variety of signals transmitted during a moisture event of the ingress sensor  200 . In  FIG. 6A , the duty cycle  604  is a pulse of voltage provided to the ingress sensor  200 . The duty cycle  604  starts at zero volts  608  and pulses to a desired voltage value that can be adjusted, along with the period and frequency of the duty cycle  604 . In some embodiments, the duty cycle includes a pulse having a length of one microsecond every second. In some embodiments, the pulse width can be between a 0.1-0.001 seconds. Additionally, the period between for a pulse can be about a second. These values can be increased or decreased for any suitable application. However, by keeping a low frequency and low pulse voltage, there is less opportunities for corrosion and dendrite growth near the ingress sensor  200 . 
       FIG. 6A  further illustrates the peak resistance  602  that can trigger the ingress sensor  200  to send a moisture indication to the computing device. As time  610  passes, the duty cycle  604  will pulse a voltage at the ingress sensor  200  in order to detect whether the resistance  606  at the moisture interface  202  has changed. In  FIG. 6A , the resistance  606  stays below the peak resistance  602  during a non-moisture event. However, as shown in  FIG. 6B , the duty cycle  604  will change at pulse  620  as a result of the ingress sensor  200  receiving moisture. At region  618 , moisture ingress is beginning to occur as indicated by the resistance  606  increasing toward the peak resistance  602  over time. At region  614 , the duty cycle  604  does not indicate moisture because the resistance  606  has not reached the peak resistance  602 . However, at region  616 , the resistance  606  is above the peak resistance  602  when the pulse  620  is initiated, and as a result the ingress sensor  200  will provide a moisture indication. 
       FIGS. 7A-7B  illustrates a graph of the voltmeter readings of the ingress sensor  200  according to some embodiments described herein. In particular,  FIGS. 7A-7B  show an embodiment having a modified duty cycle  704 . Although  FIGS. 7A-7B  incorporate many of the same elements of  FIGS. 6A-6B , the modified duty cycle  704  is illustrated to provide an example of how the voltage, period, and frequency, of the duty cycle  604  can be modified in order to provide a lower voltage operation for the ingress sensor  200 . In this way, the pulse  706  of  FIG. 7B  would be triggered at a modified peak resistance  708  because of the change in voltage of the duty cycle  704 . Other changes can also be made to the duty cycle including modifying the shape of the wave form from a square to another shape such as a triangle, sine, cosine, sawtooth, etc. Additionally, the wave form can oscillate from a negative voltage to a positive voltage, wherein the negative and positive voltages can be the same or different. Moreover, in some embodiments, the duty cycle can be adjusted dynamically depending on operation of the computing device. For example, the duty cycle can be modified to account for a low battery indicator from the computing device in order to save energy. 
       FIG. 8  illustrates a method  800  for constructing an ingress sensor according to some of the embodiments described herein. The method  800  can include a step  802  of connecting a logic component to multiple comparators. At step  804 , the method  800  can include connecting the comparators to a high tolerance voltage supply and a low tolerance voltage supply. At step  806 , the method  800  can include connecting each voltage comparator to an N-channel MOSFET and a moisture interface. Additionally, at step  808 , the method  800  can include connecting the moisture interface contact to a bias switch and bias voltage supply. Furthermore, the method  800  can include a step  810  of connecting the n-channel MOSFET to an operational amplifier and a grounded bias resistor. The method  800  can be arranged in any suitable order or manner, and can be modified according to any of the embodiments described herein. 
       FIG. 9  illustrates a method  900  for indicating a presence of moisture at the ingress sensor according to some embodiments. Specifically,  FIG. 9  discloses a method  900  having a step  902  of transmitting a periodic voltage signal across an ingress sensor circuit. The voltage signal can be a duty cycle or any repetitive signal for energizing a portion of the ingress sensor. The method  900  further includes a step  904  of measuring a resistance of a moisture interface of the ingress sensor circuit. Upon measuring the resistance, a decision step  906  is provided for determining if the resistance of the moisture interface is above a predetermined peak resistance value. If the resistance of the moisture interface is below a predetermined peak resistance value, the method  900  returns to step  902  where the periodic voltage signal is sent across the ingress sensor. If the resistance of the moisture interface is above (or equal to, in some embodiments) a predetermined peak resistance value, the method  900  proceeds to step  908  wherein a moisture indication is sent to the computing device. The moisture indication can be a digital or analog signal based in part on the output of the ingress sensor. The method  900  further includes an optional step  910  of shutting down a portion of the computing device to mitigate damage from moisture. The method  900  can be arranged in any suitable order or manner, and can be modified according to any of the embodiments described herein. 
       FIG. 10  illustrates a method  1000  of tuning the ingress sensor according to some embodiments described herein. The ingress sensor can be tuned in a variety of ways and for a multitude of applications. At step  1002  of method  1000 , a resistance of a liquid to be detected by the moisture ingress sensor is calculated. This resistance value will be used in further steps to design the ingress sensor for the liquid to be detected. At step  1004 , a resistance of a portion of the moisture ingress sensor is measured. The portion of the ingress sensor to be measured can be one or more components connecting a moisture interface to the ingress sensor, a component connecting the ingress sensor to ground, or any other suitable portion of the ingress sensor that provides a non-negligible resistance. At step  1006 , the method  1000  includes modifying a resistance of a portion of the moisture ingress sensor to be approximately the resistance of the liquid, or a predetermined resistance value that indicates a presence of moisture, when the liquid contacts a moisture interface of the moisture ingress sensor. Step  1006  can be performed by increasing or decreasing the resistivity of a portion of the ingress sensor by adding and/or removing certain components of the ingress sensor. Furthermore, the method  1000  can include a step  1008  of modifying a voltage that is received by the moisture ingress sensor to mitigate power usage while providing an accurate indication of a presence of moisture. Step  1008  is an optional step a designer can take to reduce power consumption of the ingress sensor by considering the dependency of resistance on voltage and current. For example, should a designer prefer a very low current design, the resistance and voltage of the circuit can be modified accordingly, while also maintaining the accuracy of the ingress sensor when detecting moisture. The method  1000  can be arranged in any suitable order or manner, and can be modified according to any of the embodiments described herein. 
       FIG. 11  illustrates a method  1100  of operating an ingress sensor of a computing device according to some embodiments described herein. The method  1100  includes a step  1102  of providing a periodic voltage signal to the moisture ingress sensor. At step  1104 , the method  1100  includes receiving a signal from the moisture ingress sensor indicating the presence of moisture at a portion of the computing device. Moreover, the method  1100  can include a step of sending a signal to open a bias switch of the moisture ingress sensor. As discussed herein, opening the bias switch can be a preventative measure to reduce corrosion and dendrite growth at the point of moisture ingress. The method  1100  can further include sending a signal to isolate or shut down the portion of the computing device affected by the moisture. The method  1100  can be arranged in any suitable order or manner, and can be modified according to any of the embodiments described herein. For example, the computing device can send a signal to shutdown multiple portions of the computing device and keep a record in memory of the dates, times, types, severity, etc., of moisture ingress events. 
     The various aspects, embodiments, implementations or features of the described embodiments can be used separately or in any combination. Various aspects of the described embodiments can be implemented by software, hardware or a combination of hardware and software. The described embodiments can also be embodied as computer readable code on a computer readable medium for controlling manufacturing operations or as computer readable code on a computer readable medium for controlling a manufacturing line. The computer readable medium is any data storage device that can store data which can thereafter be read by a computer system. Examples of the computer readable medium include read-only memory, random-access memory, CD-ROMs, HDDs, DVDs, magnetic tape, and optical data storage devices. The computer readable medium can also be distributed over network-coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. 
     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 specific embodiments are presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the described 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: 20140529
Publication Date: 20170905
Grant Date: 20170905
Priority Date: 20140529
Inventors: KALINICHEV KIRILL
KEELER KEVIN M.
MENZEL BRIAN C.
Assignee: APPLE INC
CPC Classifications: [{"code": "G01N27/048", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02H5/083", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01N27/121", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01N27/048", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01N27/121", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02H5/083", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02H5/083", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01N27/121", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 54701412