Electronic moisture sensor

Patent metadata

Field	Value
Publication number	US-10161895-B2
Application number	US-201514976506-A
Country	US
Kind code	B2
Filing date	Dec 21, 2015
Priority date	Dec 23, 2014
Publication date	Dec 25, 2018
Grant date	Dec 25, 2018

Abstract

Moisture sensors that include a resonant circuit having a capacitive element and an inductive element, wherein the inductive element acts as an antenna; a conditionally conductive polymeric layer, wherein the conditionally conductive polymeric layer has a first level of conductivity when exposed to a first set of moisture conditions and has a second level of conductivity when exposed to a second set of moisture conditions; and an insulative layer disposed between the resonant circuit and the conditionally conductive polymeric layer.

First claim

The invention claimed is:

1. A moisture sensor comprising:
a resonant circuit having a resonant frequency and comprising a capacitive element and an inductive element, wherein the inductive element acts as an antenna;
a conditionally conductive polymeric layer, wherein the conditionally conductive polymeric layer has a first level of conductivity when exposed to a first set of moisture conditions and has a second level of conductivity when exposed to a second set of moisture conditions, wherein the conditionally conductive polymeric layer has a threshold conductivity at which the conditionally conductive polymeric layer acts as a magnetic shield for the resonant circuit when exposed to a threshold set of moisture conditions; and
an insulative layer disposed between the resonant circuit and the conditionally conductive polymeric layer,
wherein the moisture sensor can be used more than once.

2. The moisture sensor of claim 1 , wherein the moisture sensor is reversible.

3. The moisture sensor of claim 1 , wherein the conditionally conductive polymeric layer is a hydrogel.

4. The moisture sensor of claim 3 , wherein the hydrogel is premoistened.

5. The moisture sensor of claim 1 , wherein the conditionally conductive polymeric layer comprises more than one layer.

6. The moisture sensor of claim 1 , wherein the polymeric layer comprises a pressure-sensitive adhesive having a polymeric matrix comprised of copolymers of hydrogen bond donating monomers and hydrogen bond accepting monomers.

7. The moisture sensor of claim 1 , wherein the polymeric layer comprises a pressure-sensitive adhesive having a polymeric matrix comprised of copolymers of acrylic acid and N-vinylpyrrolidone.

8. The moisture sensor of claim 1 , wherein the conditionally conductive polymeric layer quantitatively changes from a first level of conductivity to a second level of conductivity when exposed to a relative humidity ranging from about 55% to about 95% relative humidity at 23° C.

9. The moisture sensor of claim 1 , wherein the sensor further comprises one or more layers selected from the group consisting of adhesives, films, paper, ink and combinations thereof.

10. The moisture sensor of claim 1 , wherein the conditionally conductive polymeric layer further comprises a salt.

11. A system comprising:
the moisture sensor of claim 1 ; and
a reader configured to transmit a reader radio frequency signal to the resonant circuit of the moisture sensor at least at the resonant frequency of the resonant circuit, and wherein the reader is further configured to receive a moisture sensor signal transmitted by the resonant circuit.

12. The system of claim 11 , wherein the moisture sensor signal is selected from a radio frequency signal and a non-signal.

13. The system of claim 11 , wherein the reader is further configured to generate an indication signal based on the moisture sensor signal received from the resonant circuit.

14. The system of claim 11 , wherein the reader is configured to receive a first moisture sensor signal from the resonant circuit of the moisture sensor when the moisture sensor is at a first set of moisture conditions and a second moisture sensor signal from the resonant circuit of the moisture sensor when the moisture sensor is at a second set of moisture conditions.

15. The system of claim 13 , wherein at least one of the first moisture sensor signal and second moisture sensor signal is a non-signal.

16. A method of detecting moisture comprising sequential steps:
(a) exposing a moisture sensor to a moist atmosphere, wherein the moisture sensor comprises a resonant circuit having a resonant frequency and comprising a capacitive element and an inductive element that acts as an antenna; a conditionally conductive polymeric layer, wherein the conditionally conductive polymeric layer has a first level of conductivity when exposed to a first set of moisture conditions and has a second level of conductivity when exposed to a second set of moisture conditions, wherein the conditionally conductive polymeric layer has a threshold conductivity at which the conditionally conductive polymeric layer acts as a magnetic shield for the resonant circuit when exposed to a threshold set of moisture conditions; and an insulative layer disposed between the resonant circuit and the conditionally conductive polymeric layer;
(b) transmitting a reader radio frequency signal from a reader to the resonant circuit of the moisture sensor at the resonant frequency of the resonant circuit to produce a moisture sensor signal, wherein the reader is configured to transmit a reader radio frequency signal to the resonant circuit of the moisture sensor at least at the resonant frequency of the resonant circuit;
(c) receiving, with the reader, a moisture sensor signal from the moisture sensor and generating, with the reader, an indication signal based on the moisture sensing signal received from the resonant circuit, wherein the reader is further configured to receive a moisture sensor signal transmitted by the resonant circuit and generate an indication signal based on the moisture sensor signal received; and
(d) determining a level of moisture within the moist atmosphere based on the signal generated by the reader.

17. The method of claim 16 , further comprising the step:
(a1) exposing the moisture sensor to drying conditions to at least partially dry the moisture sensor; wherein step (a1) occurs after step (a) and before step (b).

18. The method of claim 16 , wherein determining the level of moisture within the moist atmosphere is further based on the known humidity sensitivity of the conditionally conductive polymeric layer of the moisture sensor.

19. The method of claim 16 , wherein the indication signal is a non-signal.

20. A method comprising:
receiving, by a receiving device, a moisture sensor signal produced by a moisture sensor, the moisture sensor comprising
a resonant circuit having a resonant frequency and comprising a capacitive element and an inductive element that acts as an antenna;
a conditionally conductive polymeric layer, wherein the conditionally conductive polymeric layer has a first level of conductivity when exposed to a first set of moisture conditions and has a second level of conductivity when exposed to a second set of moisture conditions, wherein the conditionally conductive polymeric layer has a threshold conductivity at which the conditionally conductive polymeric layer acts as a magnetic shield for the resonant circuit when exposed to a threshold set of moisture conditions; and
an insulative layer disposed between the resonant circuit and the conditionally conductive polymeric layer; and
determining the moisture conditions to which the polymeric layer is exposed based on the moisture sensor signal received by the receiving device.

Assignees

• 3M Innovative Properties Co

Inventors

• Bommarito G Marco
• Johnson Justin M
• Landgrebe Kevin D

Classifications

• G01N27/225 Primary

  by using hygroscopic materials · CPC title

• G01N27/223

  for determining moisture content, e.g. humidity (rain detectors on vehicle windows B60S1/0825) · CPC title