Passive humidity sensors and methods for temperature adjusted humidity sensing
AssigneeHoneywell International Inc.
InventorWenwei Zhang
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Abstract
A humidity sensor having temperature sensing includes a substrate and a RLC (damped resonant) circuit formed in or on the substrate. The RLC circuit comprises a capacitor having a first and a second electrically conductive plate and a moisture sensitive dielectric interposed between the first and second plate. An RL network comprising an inductor and a resistor is coupled to the capacitor and comprises a high relative temperature coefficient of resistance (TCR) portion formed from a first material which is coupled to a low relative TCR portion formed from a second material different from the first material. The RLC circuit can be a series RLC circuit. In another embodiment, the RLC circuit can comprises a parallel RLC circuit.
Claims20
A humidity sensor having temperature sensing, comprising:
- a substrate;
- a resonant RLC circuit formed in or on said substrate, said resonant circuit comprising:
- a capacitor having a first and a second electrically conductive plate and a moisture sensitive dielectric interposed between said first and said second plate;
- an RL network comprising an inductor and a resistor coupled to said capacitor comprising a high relative temperature coefficient of resistance (TCR) portion formed from a first material coupled to a low relative TCR portion formed from a second material different from said first material.
A method of temperature compensated humidity sensing, comprising:
- exposing a resonant RLC circuit comprising an inductor, a capacitor, and a resistor to environmental conditions including a temperature and a relative humidity, wherein said capacitor comprises a first and second plate and a moisture sensitive dielectric interposed between said plates;
- measuring a resonant frequency value of said resonant circuit following said exposing;
- determining a relative humidity value from said resonant frequency value;
- measuring a quality factor (Q) value of said resonant circuit following said exposing;
- determining said temperature from said Q value, and
- adjusting said relative humidity value based on said temperature.
Dependencies are inferred from the claim text.