Embedded wireless and passive sensor

1. A wear monitoring system for measuring incursion depth into an abradable coating comprising:

a layer of abradable coating including a depth;

a measurement circuit including a plurality of conductive leads disposed within the abradable coating, the conductive leads spaced radially apart within a common radial plane corresponding to the depth of the abradable coating;

a radio frequency identification tag (RFID) disposed within the abradable coating and connected to the measurement circuit;

a plurality of resistor elements corresponding with the plurality of conductive leads, each of the plurality of resistor elements in electrical communication with one of the plurality of conductive leads disposed within the common radial plane of the corresponding one of the plurality of conductive leads; wherein an electrical characteristic of the measurement circuit varies responsive to cutting of one or more of the plurality of conductive leads by a passing airfoil.

2. The wear monitoring system as recited in claim 1 , wherein each of the plurality of resistor elements are arranged in parallel.

3. The wear monitoring system as recited in claim 2 , wherein at least two of the plurality of resistor elements provide a different resistance.

4. The wear monitoring system as recited in claim 1 , including an antenna disposed within the abradable coating and connected to the RFID.

5. The wear monitoring system as recited in claim 4 , wherein the RFID includes a microcontroller.

6. The wear monitoring system as recited in claim 5 , wherein the RFID includes an analog to digital converter and can read both analog and digital signals.

7. The wear monitoring system as recited in claim 1 , wherein each of the resistor elements comprises a resistor element material dispersed between end leads corresponding with the corresponding one of the plurality of conductive leads.

8. The wear monitoring system as recited in claim 1 , wherein the measurement circuit is formed on an insulating layer and an encapsulating layer is applied over the measurement circuit, wherein each of the insulating layer, measurement circuit and encapsulating layers are disposed within separate and parallel radially extending planes.

9. The wear monitoring system as recited in claim 1 , including a controller communicating over a wireless communication link with the RFID, the controller receiving information over the wireless communication link indicative of a resistance of the measurement circuit.

10. A gas turbine engine comprising:

an airfoil having a tip;

an abradable coating that wears away responsive to incursion of the tip to define a desired clearance;

a wear sensor system comprising a measurement circuit including a plurality of conductive leads disposed within the abradable coating, the conductive leads spaced radially apart within a common radial plane corresponding to the depth of the abradable coating, a plurality of resistor elements corresponding with the plurality of conductive leads and a radio frequency identification tag disposed within the abradable coating and in communication with the conductive leads, wherein an electrical characteristic of the measurement circuit varies responsive to cutting of one or more of the plurality of conductive leads by the tip; and

a controller coupled through a wireless communication link with the RFID for communicating the electrical characteristic of the measurement circuit.

11. The gas turbine engine as recited in claim 10 , wherein each of the plurality of resistor elements are arranged in parallel.

12. The gas turbine engine as recited in claim 10 , including an antenna disposed within the abradable coating, the antenna connected to the RFID for communicating over the wireless communication link with the controller.

13. The gas turbine engine as recited in claim 12 , wherein the RFID is part of a structure including a microcontroller and an analog to digital converter.

14. The gas turbine engine as recited in claim 10 , wherein each of the resistor elements comprises a resistor element material dispersed between end leads corresponding with the corresponding one of the plurality of conductive leads.

15. The gas turbine engine as recited in claim 10 , wherein the controller in communication with the measurement circuit receives information indicative of an incursion of the airfoil into the radial depth of the abradable material.

16. A method of forming a wear sensor system for monitoring wear of an abradable coating comprising:

applying a layer of abradable coating to a desired radial depth proximate an airfoil;

forming a plurality of conductive leads disposed within the abradable coating, the conductive leads spaced radially apart;

assembling a plurality of resistor elements corresponding with the plurality of conductive leads, each of the plurality of resistor elements in electrical communication with one of the plurality of conductive leads; and

assembling a radio frequency identification (RFID) tag within the abradable coating to the conductive leads for receiving information indicative of a changing electrical characteristic upon interruption of one of the plurality of conductive leads.

17. The method as recited in claim 16 , wherein assembling the plurality of conductive leads and the plurality of resistor elements includes applying an electrically conductive material within the abradable coating with an additive manufacturing process.

18. The method as recited in claim 17 , including forming an antenna within the abradable coating with an additive manufacturing process and connecting the RFID tag to the antenna.

19. The method as recited in claim 18 , wherein the RFID tag is part of a structure including a microcontroller and an analog to digital converter and is capable of communicating over a wireless communication link with a controller separate from the abradable coating.