Making determination of inductance-change immune to changes in environmental conditions

A method implemented in a device, said method comprising:

• receiving first sustained non-decaying oscillations at a first resonant frequency generated by a first combination of a first LC (inductor-capacitor) tank circuit and a first amplifier, said first combination representing a first oscillator, wherein said first resonant frequency is determined by said first LC tank circuit, wherein a first inductor of said first LC tank circuit has a first default inductance;
• receiving second sustained non-decaying oscillations at a second resonant frequency generated by a second combination of a second LC (inductor-capacitor) tank circuit and a second amplifier, said second combination representing a second oscillator, wherein said second resonant frequency is determined by said second LC tank circuit, wherein a second inductor of said second LC tank circuit has a second default inductance;
• and
• comparing, using a frequency comparison block provided external to each of said first oscillator and said second oscillator, the frequencies of the first sustained oscillations and the second sustained oscillations to determine a change in a corresponding one of said first default inductance and said second default inductance,
• wherein each of said first oscillator, said second oscillator and said frequency comparison block is comprised in said device.

A device comprising:

• a first oscillator comprising a first inductor-capacitor (LC) tank circuit, said first oscillator to generate first sustained oscillations at a first resonant frequency determined by said first LC tank circuit, wherein a first inductor of said first LC tank circuit has a first default inductance;
• and
• a second oscillator comprising a second LC tank circuit, said second oscillator to generate second sustained oscillations at a second resonant frequency determined by said second LC tank circuit, wherein a second inductor of said second LC tank circuit has a second default inductance;
• and
• a frequency comparison block, provided external to each of said first oscillator and said second oscillator, and coupled to receive each of said first sustained oscillations and said second sustained oscillations,
• wherein, when a metal is in proximity to one of said first inductor and said second inductor, the corresponding one of said first default inductance and said second default inductance changes, thereby changing the frequency of the corresponding one of said first sustained oscillations and said second sustained oscillations from said first resonant frequency and second resonant frequency respectively,
• wherein said frequency comparison block is designed to perform a comparison of the frequencies of said second sustained oscillations and said first sustained oscillations to determine a change in a corresponding one of said first default inductance and said second default inductance as a basis to conclude that said metal is in proximity to one of said first inductor and said second inductor,
• wherein said first default inductance is equal to said second default inductance, wherein said first resonant frequency is equal to said second resonant frequency,
• wherein said comparison enables said frequency comparison block to determine a change in inductance of any of said first inductor and said second inductor caused by factors other than environmental conditions in which said device operates.