Wetness sensor using RF circuit with frangible link
US9782302B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Feb 4, 2015 |
| Grant date | Oct 10, 2017 |
| Priority date | — |
| Expiry date | Jan 3, 2036 |
Classification
- Technology area (CPC A)Human Necessities
- CPC primaryA61F2013/424
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A wetness sensor includes a substrate that carries a tuned RF circuit. The circuit includes a conductive pattern applied to the substrate, a capacitor, and a jumper all disposed on a same side of the substrate. The conductive pattern includes an inductive coil, and an inner and outer terminus. The jumper electrically couples the inner terminus to the outer terminus. The jumper also includes a frangible link which, when contacted by a target fluid, produces a drastic change in the operation of the RF circuit. The drastic change can be interpreted by a remote reader as a “wet” condition. Contact of the frangible link by the target fluid may change the impedance or resistance of the RF circuit by at least a factor of 5, 10, 100, or more, and/or may cause the frangible link to disintegrate to produce an open circuit, and/or may substantially render the RF circuit inoperative.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.