Skin detection using voltage representations of frequencies

A method for a wearable device, comprising:

• driving, with an oscillating waveform, a first electrode positioned on an exterior of the wearable device, the first electrode forming a first side of a reporting capacitor, wherein a second side of the reporting capacitor is formed by skin of a user when the wearable device is being worn by the user;
• monitoring a capacitance at the reporting capacitor based on changes in a frequency of the oscillating waveform;
• converting the frequency of the oscillating waveform to a voltage representation;
• and
• identifying a presence of skin of the user, based on recognizing a threshold change in the voltage representation at an envelope detector.

A circuit for determining a frequency of an oscillating waveform using envelope detection, comprising:

• an oscillator, configured to output the oscillating waveform with a frequency based at least on a capacitance of a reporting capacitor;
• a voltage follower, comprising at least a unipolar amplifier, the unipolar amplifier configured to output an oscillating signal based on the frequency of the oscillating waveform;
• a differentiator, configured to:
• receive the oscillating signal from the voltage follower;
• take a differential of the oscillating signal to generate a pulsed signal;
• and
• output the pulsed signal;
• and
• an envelope detector, configured to:
• receive the pulsed signal from the differentiator;
• pass the pulsed signal through a diode configured in a forward bias;
• charge a detection capacitor so that a peak voltage of the pulsed signal is in a steady state with an output voltage;
• and
• indicate a frequency of the oscillating signal based at least on the output voltage.