Moister sensor

• US 20110011179A1
• Filed: 07/08/2010
• Published: 01/20/2011
• Est. Priority Date: 07/16/2009
• Status: Active Grant

• Current Assignee: Acreo AB
• Original Assignee: Acreo AB
• Inventors: Gustafsson, Göran, Crispin, Xavier, Wang, Xiaodong, Berggren, Magnus, Larsson, Oscar
• Granted Patent: US 8,236,164 B2
• Time in Patent Office: Days
• US Class Current: 73/335.03
• CPC Class Codes: G01N 27/223 for determining moisture content, e.g. humidity rain detectors on vehicle windows B60S1/0825
• CPC Class Codes: Y10T 29/49155 Manufacturing circuit on or in base

Abstract

A moister sensor, for measuring moister in a building without leaving visible scars to the building surface, is provided. The moister sensor includes a flexible carrier carrying an antenna for receiving EM-radiation between 9 kHz and 11 MHz and a resonant circuit including a moister reactive element. The moister reactive element includes a hygroscopic electrolyte arranged between a first and a second electrode, wherein the electrolyte in the presence of moister forms mobile ions and provides a complex impedance at least in response to the alternating voltage, which complex impedance varies with the moister content of the electrolyte.

Claims

1. A moister sensor for measuring moister in a building, comprising:

a flexible carrier for attaching said sensor to a floor or inner wall of a building;

a resonant circuit printed on said carrier;

a first antenna printed on said carrier, arranged to receive an electromagnetic signal within a first frequency range of 9 kHz to 11 MHz;

to convert said signal into an AC voltage, the AC voltage being arranged to alternate within said first frequency range; and

to feed said voltage to said resonant circuit,

said first antenna being further arranged to emit an electromagnetic signal indicative of an impedance of said resonant circuit; and

an encapsulation layer sealing said moister sensor, the encapsulation layer comprising a humidity permeable portion;

wherein said resonant circuit comprises a moister reactive element comprising;

a first and a second inert electrode comprising electrochemically substantially inert material, each electrode being arranged as a layer, and

a hygroscopic solid electrolyte arranged as a layer and spatially between said first and second inert electrodes, the hygroscopic solid electrolyte, at least in the presence of moister, forming mobile ions selected from a group consisting of cations and anions, and the hygroscopic solid electrolyte providing a complex impedance at least in response to said alternating voltage being applied across said first and second inert electrodes.

2. A sensor according to claim 1, wherein said hygroscopic solid electrolyte is sandwiched between said first and second inert electrodes.

3. A sensor according to claim 1, wherein the interface between said hygroscopic solid electrolyte and a respective one of said first and second inert electrodes is relatively smaller than the surface area of said hygroscopic solid electrolyte.

4. A sensor according to claim 1, wherein at least one of said first and second inert electrodes is provided with apertures.

5. A sensor according to claim 1, wherein said first and second inert electrodes are in direct electrical contact with said hygroscopic solid electrolyte.

6. A sensor according to claim 1, wherein said mobile ions are mobile at least in response to at least one frequency within said first frequency range.

7. A sensor according to claim 1, wherein said resonant circuit and said antenna are both arranged on the same side of said carrier.

8. A sensor according to claim 1, wherein said circuit is a passive resonant circuit.

9. A sensor according to claim 1, wherein said hygroscopic solid electrolyte, at least in the presence of moister, further forms immobile ions selected from a group consisting of polycations and polyanions.

10. A system comprising:

a moister sensor according to claim 1, and

a reader comprising;

a signal generator for generating and emitting an electromagnetic signal sweeping from a first to a second frequency within said first frequency range;

a circuit arranged to receive a electromagnetic signal from said moister sensor; and

a converter arranged to convert said received electromagnetic signal to a value indicative of the presence of moister in said moister sensor.

11. A system comprising:

a first sensor according to claim 1;

a second sensor arranged in accordance with claim 1, including an electrolyte moister level and being sealed with an moister impervious seal to maintain the said electrolyte moister level; and

a reader comprising;

a generator for generating and emitting an electromagnetic signal having a first frequency; and

an electric circuit comprising;

an antenna device arranged to receive a first reflected impedance from said first sensor and a second reflected impedance said second sensor, respectively; and

a comparison device arranged to compare said first impedance to second impedance and to determine the moister level of said first sensor based on the result of the comparison of said first and second moister levels.

12. A system according to claim 10, wherein the electromagnetic signal emitted by said reader is coupled into said first sensor by way of a magnetic coupling.

13. A building structure, the structure being selected from a group consisting of walls, floors and ceilings, comprising:

a moister sensor according to claim 1, wherein said moister sensor is arranged beneath a surface of said building structure to measure the humidity therein.

14. A method of producing a moister sensor according to claim 1, comprising:

providing a flexible substrate;

printing an antenna and a resonance circuitry on said flexible substrate further comprising;

providing a first electrode layer on said substrate;

printing a layer of hygroscopic electrolyte on said first electrode; and

providing a second electrode layer on said hygroscopic electrolyte.

15. A method according to claim 14, wherein said first and second electrode are provided by means of printing.

16. A method according to claim 14, further comprising providing a lacquer layer.

17. A method comprising:

using a moister sensor including a resonance circuit comprising a moister reactive element, the moister sensor being arranged according to claim 1.

18. A sensor according to claim 2, wherein the interface between said hygroscopic solid electrolyte and a respective one of said first and second inert electrodes is relatively smaller than the surface area of said hygroscopic solid electrolyte.

19. A system according to claim 11, wherein the electromagnetic signal emitted by said reader is coupled into said first sensor by way of a magnetic coupling.

20. A method according to claim 15, further comprising providing a lacquer layer.