Moisture sensors

Patent metadata

Field	Value
Publication number	US-9780554-B2
Application number	US-201514814606-A
Country	US
Kind code	B2
Filing date	Jul 31, 2015
Priority date	Jul 31, 2015
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

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.

First claim

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.

Assignees

• Apple Inc

Inventors

• Kardassakis Peter J
• Panthaki Farhan
• Weiss Samuel B

Classifications

• H02H5/083 Primary

  responsive to the entry or leakage of a liquid into an electrical appliance (moisture alarm G08B21/20) · CPC title

• G01N27/121

  for determining moisture content, e.g. humidity, of the fluid (moisture content of the tested material G01N27/048) · CPC title

• G08B21/20

  responsive to moisture · CPC title