US 12,332,204 B2
Sensing frost and ice accumulation using capacitance
Bjoern Oliver Eversmann, Zolling (DE); Andreas Felix Martin Kraemer, Eichenau (DE); and Michael Seidl, Freising (DE)
Assigned to Texas Instruments Incorporated, Dallas, TX (US)
Filed by TEXAS INSTRUMENTS INCORPORATED, Dallas, TX (US)
Filed on May 23, 2022, as Appl. No. 17/750,615.
Application 17/750,615 is a division of application No. 15/936,059, filed on Mar. 26, 2018, granted, now 11,371,954.
Claims priority of provisional application 62/552,911, filed on Aug. 31, 2017.
Prior Publication US 2022/0283109 A1, Sep. 8, 2022
Int. Cl. G01N 27/22 (2006.01); F25D 21/00 (2006.01); F25D 21/02 (2006.01); F25D 21/08 (2006.01)
CPC G01N 27/228 (2013.01) [F25D 21/006 (2013.01); F25D 21/02 (2013.01); F25D 21/08 (2013.01)] 7 Claims
OG exemplary drawing
 
1. A capacitance sensing system comprising:
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 coupled in parallel with the first capacitor; and
a circuit coupled to the tank oscillator and configured to:
determine a resonant frequency of the tank oscillator;
determine a capacitance value of the first capacitor based on the resonant frequency of the tank oscillator;
determine that the capacitance value is greater than a threshold; and
transmit a heater activation command in response to determining the capacitance value is greater than the threshold.