US RE49,641 E1
Foreign object detection for ferromagnetic wire-like objects
Hans Peter Widmer, Wohlenschwil (CH); Andreas Daetwyler, Muhen (CH); and Lukas Sieber, Olten (CH)
Assigned to WiTricity Corporation, Watertown, MA (US)
Filed by WiTricity Corporation, Watertown, MA (US)
Filed on Nov. 24, 2021, as Appl. No. 17/534,926.
Application 17/534,926 is a reissue of application No. 15/498,094, filed on Apr. 26, 2017, granted, now 10,495,773, issued on Dec. 3, 2019.
Int. Cl. G01V 3/10 (2006.01)
CPC G01V 3/101 (2013.01) 34 Claims
OG exemplary drawing
 
1. An apparatus for detecting an object, comprising:
a sense coil; and
a detection circuit configured to:
determine an amount of change in a reactance of the sense coil from a reference reactance value for the sense coil;
determine an amount of change in a resistance of the sense coil from a reference resistance value for the sense coil; and
selectively increase a sensitivity of the detection circuit as [ by reducing a detection threshold by an amount that is a function of ] a ratio of the amount of change in the resistance [ reactance ] and the amount of change in the reactance [ resistance ] of the sense coil approaches a value of one, the sensitivity increased by reducing a detection threshold by an amount that is a function of the ratio [ as the ratio approaches a value by one] .