초록 ▼

A humidity sensing apparatus which includes a humidity sensor which detects humidity as a function of impedance is provided. A reference resistor has a predetermined resistance value. A charge switching circuit selectively couples one of the reference resistor or the humidity sensor in series with a

A humidity sensing apparatus which includes a humidity sensor which detects humidity as a function of impedance is provided. A reference resistor has a predetermined resistance value. A charge switching circuit selectively couples one of the reference resistor or the humidity sensor in series with a reference capacitor which has a predetermined capacitance. A voltage judging circuit determines whether the terminal voltage of the reference capacitor is high or low. A charge/discharge switch selectively charges and discharges the reference capacitor in accordance with the output of the voltage judging circuit. A sensor direction switching circuit inverts the direction of current flowing through the humidity sensor during charging of the reference capacitor. An oscillation frequency counter counts the number of charge/discharge cycles which are repeated during a predetermined time period. A humidity sensor resistance value calculating circuit calculates the resistance value of the humidity sensor in accordance with the number of repeated charge/discharge cycles when the reference capacitor is coupled to the reference resistor for charging and the number of repeated charge/discharge cycles when the reference capacitor is coupled to the humidity sensor during charging. A humidity determining circuit determines the humidity from the resistance value of the humidity sensor calculated by the humidity sensor resistance value calculating circuit.

대표청구항 ▼

A humidity measuring apparatus comprising: humidity sensor means for sensing humidity as a function of resistance; a reference resistor having a predetermined resistance value; a reference capacitor having a predetermined capacitance; charge switching means for selectively coupling one of said refer

A humidity measuring apparatus comprising: humidity sensor means for sensing humidity as a function of resistance; a reference resistor having a predetermined resistance value; a reference capacitor having a predetermined capacitance; charge switching means for selectively coupling one of said reference resistor or said humidity sensor means in series to said reference capacitor to charge said reference capacitor; voltage judging means for determining whether the terminal voltage of the reference capacitor is at about a predetermined high voltage (H) or at about a predetermined low voltage (L); charge/discharge switching means for selectively charging and discharging said reference capacitor in accordance with the output of said voltage judging means producing an oscillating charge/discharge cycle in response to the output of the voltage judging means; sensor direction switching means coupled to said charge/discharge switching means for inverting the direction of current flowing through said humidity sensor means during at least a portion of the period said reference capacitor is charged through said humidity sensor means in response to the output of the charge/discharge switching means; determining means coupled to said voltage judging means for determining the resistive value of said humidity sensor means and said humidity as a function of the charge/discharge cycle.