Method and apparatus for detecting a dry/wet state of a thermistor bead

Apparatus for detecting a dry/wet state of a thermistor bead comprising:

• a first circuit coupled to said thermistor bead for generating a current waveform that transitions between first and second current levels and for conducting said current waveform through said thermistor bead;
• a second circuit coupled to said thermistor bead for measuring a difference in voltage across said thermistor bead in response to said first and second current levels;
• and
• a third circuit coupled to said second circuit for detecting said dry/wet state of said thermistor bead based on said measured difference in voltage.

Method of detecting a transient dry/wet state of a thermistor bead comprising the steps of:

• conducting a current waveform through said thermistor bead;
• measuring a voltage waveform across said thermistor bead in response to said current waveform;
• differentiating the voltage waveform to produce a voltage pulse representative of a transition of the voltage waveform from one voltage potential to another;
• and
• detecting said transient dry/wet state of said thermistor bead based on said voltage pulse.

Apparatus for detecting a transient dry/wet state of a thermistor bead comprising:

• a first circuit coupled to said thermistor bead for conducting a current waveform therethrough;
• a second circuit coupled to said thermistor bead for measuring a voltage waveform across said thermistor bead in response to said current waveform and differentiating the voltage waveform to produce a voltage pulse representative of a transition of the voltage waveform from one voltage potential to another;
• and
• a third circuit coupled to said second circuit for detecting said transient dry/wet state of said thermistor bead based on said voltage pulse.

Method of detecting a dry/wet state of a thermistor bead comprising the steps of:

• generating a current waveform that transitions between first and second current levels;
• conducting said current waveform through said thermistor bead;
• measuring a voltage waveform across said thermistor bead in response to said current waveform;
• measuring a slope of said voltage waveform in response to said first and second current levels and generating a first signal indicative of said measured slope;
• differentiating said voltage waveform to produce a voltage pulse representative of a transition of said voltage waveform from one voltage potential to another and generating a second signal indicative of the polarity of said voltage pulse;
• and
• detecting said dry/wet state of said thermistor bead based on said first and second signals.

Apparatus for detecting a dry/wet state of a thermistor bead comprising:

• a circuit coupled to said thermistor bead for generating a current waveform that transitions between first and second current levels and conducting said current waveform through said thermistor bead;
• a circuit coupled to said thermistor bead for measuring a voltage across said thermistor bead in response to said current waveform and generating a voltage waveform signal representative thereof;
• a first detector circuit, coupled to said voltage measuring circuit, for determining a slope of said voltage waveform signal in response to said first and second current levels and generating a first signal indicative of said- determined slope;
• a second detector circuit, coupled to said voltage measuring circuit, for differentiating the voltage waveform signal to produce a voltage pulse representative of a transition of the voltage waveform signal from one voltage potential to another and generating a second signal indicative of the polarity of said voltage pulse;
• and
• a logic circuit coupled to said first and second detector circuits for detecting said dry/wet state of said thermistor bead based on said first and second signals generated thereby.