# US 5,350,237 A · Temperature measuring circuit for heating and cooking appliances

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- Number: US 5,350,237 A
- Document ID: US5350237A
- Status: Granted
- Kind: A
- Application number: 07/962,405
- Filed: 1992-10-16
- Granted: 1994-09-27
- Earliest claimed: 1992-10-16
- Assignees: Funai Electric Co., Ltd.
- Inventors: Kiyonori Hida
- Web page: https://patentgrep.com/patent/US5350237A

## CPC

- G01K 15/00: Testing or calibrating of thermometers
- G01K: MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR (radiation pyrometry G01J5/00)

## Abstract

In a temperature measuring circuit connecting a temperature sensor such as a thermistor to a standard voltage source through tap resistances, detecting a sensed value of the temperature sensor by comparing the voltage of the sensor connecting point with the specified voltage by a comparator, a simplified construction of the circuit makes it possible to detect failures of the temperature sensor such as breakage or burn-out.

## Claims

### Claim 1

A temperature measuring circuit for heating and cooking appliances operative at predetermined temperatures, comprising a resistance network comprising a plurality of resistors having different resistance values; temperature detecting means exhibiting changes in resistance responsive to temperature variations; said temperature detecting means selectively cooperating with one of resistors at each predetermined temperature for generating first control voltage representative of an associated predetermined temperature; comparator means for comparing each control voltage with a reference voltage; and switching means for switching one of said resistors to cooperate with said temperature detecting means when a preselected relationship is established between said control and reference voltages.

### Claim 2 (depends on 1)

A measuring circuit as defined in claim 1, wherein one of said resistors in said resistance network has a value substantially greater than the resistances of the other resistors in the network, said one of said resistors when cooperating with said temperature detecting means generating a second control voltage representative of a failure of said temperature detecting means.

### Claim 3 (depends on 1)

A measuring circuit as defined in claim 1, wherein said temperature detecting means comprises a thermistor.

### Claim 4 (depends on 1)

A measuring circuit as defined in claim 1, wherein a source of voltage is provided for applying a predetermined voltage to said resistance network, and means for providing said reference voltage equal to substantially one-half of said predetermined voltage.

### Claim 5 (depends on 1)

A measuring circuit as defined in claim 1, wherein said plurality of resistors each has one terminal connected to said temperature detecting means and another terminal connected to said switching means.

### Claim 6 (depends on 5)

A measuring circuit as defined in claim 5, wherein said switching means comprises a transistor connected in series with each resistor; and a CPU means for selectively actuating one of said transistors, whereby only the resistor in series with an actuated transistor effectively cooperates with said temperature detecting means.

### Claim 7 (depends on 6)

A measuring circuit as defined in claim 6, further comprising display means controlled by said CPU means for providing a visual display representative of said predetermined temperatures.