Abstract: A capacitance sensing system senses frost and ice accumulation in an energy efficient defrost system. The capacitance sensing system comprises a first capacitor including a portion of a metal heat exchanger and a sensor electrode electrically isolated from the metal heat exchanger; a tank oscillator including a second capacitor and an inductor coupled in parallel with each other and with the first capacitor; and a circuit coupled to the tank oscillator. The circuit determines a resonant frequency of the tank oscillator, determines a capacitance value of the first capacitor based on the resonant frequency of the tank oscillator, and transmits a heater activation command in response to determining the capacitance value is greater than a threshold.

Abstract: A capacitance sensing system senses frost and ice accumulation in an energy efficient defrost system. The capacitance sensing system comprises a first capacitor including a portion of a metal heat exchanger and a sensor electrode electrically isolated from the metal heat exchanger; a tank oscillator including a second capacitor and an inductor coupled in parallel with each other and with the first capacitor; and a circuit coupled to the tank oscillator. The circuit determines a resonant frequency of the tank oscillator, determines a capacitance value of the first capacitor based on the resonant frequency of the tank oscillator, and transmits a heater activation command in response to determining the capacitance value is greater than a threshold.

Abstract: A capacitance sensing system for sensing frost and ice accumulation. The capacitance sensing system comprises a first capacitor formed by a portion of a metal heat exchanger and a sensor electrode electrically isolated from the metal heat exchanger, a tank oscillator comprising a second capacitor and an inductor connected in parallel with each other and coupled in parallel with the first capacitor, and a circuit coupled to the tank oscillator. The circuit coupled to the tank oscillator is configured to determine a resonant frequency of the tank oscillator, determine a capacitance value based on the resonant frequency of the tank oscillator, determine that the capacitance value is greater than a predefined threshold, and transmit a heater activation command in response to determining the capacitance value is greater than the predefined threshold.

Abstract: A capacitance sensing system for sensing frost and ice accumulation. The capacitance sensing system comprises a first capacitor formed by a portion of a metal heat exchanger and a sensor electrode electrically isolated from the metal heat exchanger, a tank oscillator comprising a second capacitor and an inductor connected in parallel with each other and coupled in parallel with the first capacitor, and a circuit coupled to the tank oscillator. The circuit coupled to the tank oscillator is configured to determine a resonant frequency of the tank oscillator, determine a capacitance value based on the resonant frequency of the tank oscillator, determine that the capacitance value is greater than a predefined threshold, and transmit a heater activation command in response to determining the capacitance value is greater than the predefined threshold.

Abstract: A touch-sensitive glass barrier has a conductive coil affixed to the first side of a glass barrier, a capacitor connected to the conductive coil to form a resonator, and an inductance-to-digital converter (LDC) connected to drive an alternating current through the resonator. The LDC determines whether a conductive target has touched the second side of the glass barrier at a point opposite the conductive coil; and responsive to determining that the conductive target has touched the second side of the glass barrier at the point, provides a signal.

Abstract: A touch-sensitive glass barrier has a conductive coil affixed to the first side of a glass barrier, a capacitor connected to the conductive coil to form a resonator, and an inductance-to-digital converter (LDC) connected to drive an alternating current through the resonator. The LDC determines whether a conductive target has touched the second side of the glass barrier at a point opposite the conductive coil; and responsive to determining that the conductive target has touched the second side of the glass barrier at the point, provides a signal.