Relative humidity and condensation measurement with a capacitive humidity sensor

摘要

A method and apparatus for measuring relative humidity including condensing environmental conditions using a circuit with a capacitive humidity sensor and a reference resistor each connected to an input of a switch device and thence a quadrature sampling circuit. A sinusoidal source is first connected to the reference resistor and secondly to the capacitive humidity while a signal ground is first connected to the capacitive humidity sensor and secondly to the reference resistor. This produces a first voltage and a second voltage that are each sampled in quadrature. A complex ratio of the sampled voltages is calculated and converted into a representation of relative humidity.

主权项

1. An electronic circuit arrangement for measuring relative humidity comprising:
a. a quadrature sampling circuit having an input and an output; b. a capacitive humidity sensor having an input and an output wherein the output of the capacitive humidity sensor is connected to the input of the quadrature sampling circuit; c. a reference resistor, having an input and an output wherein the output of the reference resistor is connected to the input of the quadrature sampling circuit; d. a sinusoidal source having an output; e. a plurality of switches having a first state and a second state, wherein
i. the first state comprises connecting the input of the capacitive humidity sensor to a signal ground and the input of the reference resistor to the output of the sinusoidal source, producing a first voltage at the input of the quadrature sampling circuit andii. the second state comprises connecting the input of the capacitive humidity sensor to the output of the sinusoidal source and the input of the reference resistor to the signal ground, producing a second voltage at the input of the quadrature sampling circuit; f. a computer having in input wherein the output of the quadrature sampling circuit is connected to the input of the computer; g. wherein said quadrature sampling circuit digitizes a plurality of quadrature-samples of the first voltage producing a first set of data samples, and digitizes a plurality of quadrature-samples of the second voltage producing a second set of data samples; h. wherein said computer
i. computes a first peak-to-peak complex voltage from the first set of data samples, andii. computes a second peak-to-peak complex voltage from the second set of data samples, andiii. computes the complex ratio of the first peak-to-peak complex voltage and second peak-to-peak complex voltage, andiv. from said complex ratio, computes a value representative of relative humidity.