20 is described below with reference to fig3 because q is adversely affected by losses resonant sensor 20 should be manufactured with low loss electric and magnetic materials and loaded as lightly as practical to maintain a q ranging from about 30 to about 100 at the operating frequency major sources of loading include high impedance 14 buffer amplifier 24 and coupling to object 22 high impedance 14 is preferably a high value resistor that lightly couples oscillator 12 to resonant sensor 20 the light coupling also reduces 34 pulling 34 of the predetermined frequency of oscillator 12 and reduces to an acceptable level radio frequency energy radiating from resonant sensor 20 an alternative embodiment of high impedance 14 is a voltage to current converter 40 formed by a pair of transistors 42 and 44 connected in a differential current steering configuration in which the emitters of transistors 42 and 44 are electrically connected together and to one end of a bias current determining resistor 46 the other end of resistor 46 is connected to a fixed voltage source oscillator 12 is electrically connected to the base of transistor 42 the base of transistor 44 is preferably grounded the collector of transistor 44 provides to resonant sensor 20 a high impedance alternating current version of the voltage.