# US 5,343,746 A · Humidity sensing apparatus

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- Number: US 5,343,746 A
- Document ID: US5343746A
- Status: Granted
- Kind: A
- Application number: 08/020,714
- Filed: 1993-02-22
- Granted: 1994-09-06
- Earliest claimed: 1992-02-20
- Assignees: Samsung Electronics Co., Ltd.
- Inventors: Jin K. Choi
- Web page: https://patentgrep.com/patent/US5343746A

## CPC

- G01N 27/122: {Circuits particularly adapted therefor, e.g. linearising circuits}
- G01N 27/121: {for determining moisture content, e.g. humidity, of the fluid (moisture content of the tested material G01N27/048)}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A humidity sensing apparatus is operated by an AC power supply. The humidity sensing apparatus comprises a humidity sensing section including a humidity sensor and a divider resistor connected in parallel to the humidity sensor; a humidity sensor operating section for supplying the humidity sensor with an AC voltage within predetermined voltage levels; and, a humidity signal converting section including diodes, condensers and resistors. The humidity signal converting section converts the AC humidity signal output from the humidity sensing section into a corresponding DC humidity signal by selecting the time constants of the pair of condenser-resistor circuits and then supplies the peripheral digital circuits with the converted signals.

## Claims

### Claim 1

A humidity sensing apparatus, comprising:
means for supplying a predetermined AC voltage, said means including a first AC output terminal and a second AC output terminal;
a humidity sensor connected between a first humidity sensor terminal and a second humidity sensor terminal, said first humidity sensor terminal being connected to said first AC output terminal;
a first diode, a cathode of said first diode being connected to said second humidity sensor terminal;
a first charging/discharging means connected between an anode of said first diode and said second AC output terminal;
a second diode, an anode of said second diode being connected to said second humidity sensor terminal;
a second charging/discharging means connected between a cathode of said second diode and said second AC output terminal; and
means connected to said cathode of said second diode for calculating a humidity level based on a current signal passing through said second diode.

### Claim 2 (depends on 1)

The humidity sensing apparatus of claim 1 wherein said supplying means includes,
a low-voltage transformer for stepping down an input AC power supply,
a divider resistor wherein a first terminal thereof is connected in series to a first terminal of a secondary winding of said transformer, and
a pair of zener diodes, each zener diode having an anode connected between a second terminal of said divider resistor and a second terminal of said secondary winding, a cathode of each zener diode being connected to a cathode of the other, each of said first AC output terminal and said second AC output terminal being respectively connected to an anode of a respective one of said pair of zener diodes.

### Claim 3 (depends on 1)

Apparatus as claimed in claim 1, wherein said first charging/discharging means comprises:
a resistor connected between said anode of said first diode and ground; and
a capacitor connected between said anode of said first diode and said second AC output terminal.

### Claim 4 (depends on 1)

Apparatus as claimed in claim 1, wherein said second charging/discharging means comprises:
a resistor connected between said cathode of said second diode and said second AC output terminal; and
a capacitor connected between said cathode of said second diode and said second AC output terminal.

### Claim 5 (depends on 1)

Apparatus as claimed in claim 1, wherein said means connected to said cathode of said second diode for calculating a humidity level based on a current signal passing through said second diode comprises:
a current limiting resistor connected to said cathode of said second diode; and
a microprocessor connected to said cathode of said second diode through said current limiting resistor.