Humidity sensor

A packaged sensor device, comprising:

• a humidity sensor configured to form a corona discharge, comprising:
• at least one electrode configured to conduct a voltage greater than one kilovolt, the electrode having a base on a first surface of a substrate and having a shaft extending from the base to an end;
• a counter-electrode spaced from the end of the at least one electrode, having a first planar conductive surface facing the end;
• a package containing the at least one electrode, the substrate, and the counter-electrode in a cavity within the package, the cavity having at least one opening that allows an atmosphere to enter the cavity;
• an analog-to-digital converter (ADC) coupled to the humidity sensor and configured to receive a voltage of the at least one electrode while an ionization current flows between the at least one electrode and the counter-electrode;
• a data input/output circuit coupled to a digital output of the ADC and configured to output digital signals and to input digital signals at a data terminal;
• and
• a controller configured to couple the humidity sensor to a voltage supply sufficient to cause an ionization current to flow between the at least one electrode and the counter-electrode, the controller further configured to control the ADC to sample the voltage at the at least one electrode while the ionization current flows, and the controller configured to cause the data input/output circuit to output digital signals corresponding to the sampled voltage.

A method, comprising:

• applying a voltage sufficient to cause an ionization current to flow between at least one electrode spaced from a counter-electrode in a cavity of a packaged device that is filled with air;
• measuring the voltage at the at least one electrode while ionization current flows between the at least one electrode and the counter-electrode;
• and
• using the measured voltage, determining a relative humidity of the air in the cavity.

A method, comprising:

• forming at least one electrode on a first substrate, the at least one electrode having a base on the first substrate, and a shaft extending from the base to an end;
• forming a sacrificial layer over at least a portion of the first substrate and the at least one electrode to form an electrode assembly, the sacrificial layer having a first side, a second side opposing the first side, a third side that is perpendicular to the first side, and a fourth side opposing the third side and perpendicular to the first side;
• mounting the electrode assembly on a second substrate;
• encapsulating the electrode assembly with the sacrificial layer and a least a portion of the second substrate with a mold compound, the mold compound covering the first and second sides of the sacrificial layer and exposing the third and fourth sides of the sacrificial layer;
• mounting a counter-electrode over a top surface of the sacrificial layer;
• removing the sacrificial layer to expose the at least one electrode and a surface of the counter-electrode to air, forming a cavity in a package formed by the mold compound, the cavity being open to the air.