Temperature sensor failure detection arrangement using a heater energy counter

• US 4,788,398 A
• Filed: 09/30/1987
• Issued: 11/29/1988
• Est. Priority Date: 09/30/1987
• Status: Expired due to Term

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hornung, Richard E.
• Primary Examiner(s): PASCHALL, MARK H
• Application Number:
  US07/103,051
• Time in Patent Office: 426 Days
• Field of Search: 219/483, 219/486, 219/448, 219/492, 219/494, 219/506, 219/501, 219/497, 219/507, 219/508-509, 219/440-442, 307/38-41, 323/235, 323/319, 340/588, 340/589, 340/584
• US Class Current: 219/483
• CPC Class Codes: F24C 15/106 electric circuits
• CPC Class Codes: G01K 15/007 Testing
• CPC Class Codes: G05D 23/24 the sensing element having a resistance varying with temperature, e.g. a thermistor

Abstract

An improved temperature sensor failure detection arrangement for a temperature controlled heating device of the type having a heater, an electronic controller for controlling the power level applied to the heater, and a temperature sensor. The controller includes an internal heater energy counter, which is incremented and decremented at rates determined as a function of the power level applied to the heater such that the count of the heater energy counter approximately tracks the temperature of the heater. The controller periodically compares temperature information from the temperature sensor with the count of the heater energy counter to check for abnormal operating condition of the temperature sensor. An abnormal condition is detected when the count of the heater energy counter is within a predetermined reference range and the sensed temperature is outside a correlative predetermined reference temperature range, which ranges are selected such that under normal operating conditions, whenever the count is within the predetermined range, the temperature will be within the reference temperature range.

Claims

1. In a temperature controlled heating device of the type having heater means, control means for controlling the power level applied to the heater means and temperature sensing means for sensing the temperature of a load heated by the heater means, an improved temperature sensor failure detection arrangement wherein:

said control means includes heater energy counter means, means for incrementing and decrementing said heater energy counter means at rates determined as a function of the power level applied to the heater means such that the count of said heater energy counter approximately tracks the temperature of the heater means, and means responsive to the temperature sensing means and said heater energy counter means, operative to detect a first abnormal operating condition of the temperature sensing means when the count of said heater energy counter is within a predetermined reference range and the sensed temperature is outside a correlative predetermined reference temperature range.

2. The improved sensor failure detection arrangement of claim 1 further comprising means for generating a user discernible signal upon detection of said abnormal condition.

3. The improved sensor failure detection arrangement of claim 2 wherein said reference count range is bounded by predetermined maximum and minimum diagnostic reference counts and said reference temperature range is bounded by correlative predetermined maximum and minimum diagnostic reference temperatures and said means for detecting an abnormal condition is operative to detect a first abnormal condition when the count of the heater energy count is less than said maximum diagnostic reference count and the sensed temperature is greater than said predetermined maximum diagnostic reference temperature and to detect a second fault condition when the count of the heater energy counter is greater than said predetermined minimum diagnostic reference count and the sensed utensil temperature is less than said predetermined minimum reference diagnostic temperature.

4. In a temperature controlled heating device of the type having heater means, control means for controlling the power level applied to the heater means and temperature sensing means for sensing the temperature of a load heated by the heater means, an improved temperature sensor failure detection arrangement wherein:

said control means includes heater energy counter means, means for incrementing and decrementing said heater energy counter means at rates determined as a function of the power level applied to the heater means such that the count of said heater energy counter approximately tracks the temperature of the heater means, and means responsive to the temperature sensing means and said heater energy counter means, operative to detect a first abnormal operating condition of the temperature sensing means when the count of said heater energy counter is less than a predetermined diagnostic reference count and the sensed temperature is greater than a correlative predetermined diagnostic reference temperature.

5. The improved sensor failure detection arrangement of claim 4 further comprising means for generating a user discernible signal upon detection of said abnormal condition.

6. In a cooking appliance of the type having heater means for heating a cooking utensil, user input selection means for enabling the user to select the desired heating level for the heater means, temperature sensing means operative to sense the temperature of the utensil being heated by the heater means, heater energy counter means for approximately tracking the heater means temperature and counter control means for selectively incrementing and decrementing the energy counter at rates such that the count of the heater energy counter is approximately proportional to the temperature of the heater means, and control means responsive to the user input selection means and the temperature sensing means, operative to apply a power level to the heater means as a function of the sensed temperature and the user selected heating level, an improved fault detection arrangement for detecting a failure of the temperature sensing means wherein:

said control means further comprises means responsive to the heater energy counter for detecting an abnormal operating condition for the temperature sensing means when the count of the heater energy counter is within a predetermined reference range and the sensed utensil temperature is outside a correlative predetermined reference temperature range; and

said arrangement further comprising means operative to generate a user discernible signal upon detection of said abnormal condition.

7. The improvement of claim 6 wherein said reference count range is bounded by predetermined maximum and minimum diagnostic reference counts and said reference temperature range is bounded by correlative predetermined maximum and minimum diagnostic reference temperatures and said means for detecting an abnormal condition is operative to detect a first abnormal condition when the count of the heater energy count is less than said maximum diagnostic reference count and the sensed temperature is greater than said predetermined maximum diagnostic reference temperature and to detect a second fault condition when the count of the heater energy counter is greater than said predetermined minimum diagnostic reference count and the sensed utensil temperature is less than said predetermined minimum reference diagnostic temperature.

8. The improvement of claim 7 wherein said temperature sensing means comprises a negative temperature coefficient thermistor and wherein said first abnormal operating condition comprises a short circuit fault condition for said thermistor, and said second abnormal operating condition comprises an open circuit fault condition for said thermistor.

9. In a cooking appliance of the type having heater means for heating a cooking utensil, user input selection means for enabling the user to select the desired heating level for the heater means, temperature sensing means operative to sense the temperature of the utensil being heated by the heater means, heater energy counter means for approximately tracking the heating element temperature and counter control means for selectively incrementing and decrementing the energy counter at rates such that the count of the heater energy counter is approximately proportional to the temperature of the heating element, and control means responsive to the user input selection means and the temperature sensing means, operative under normal conditions to apply a power level to the heater means determined as a function of the user selected heating level and the sensed temperature, an improved fault detection arrangement for detecting a failure of the temperature sensing means wherein:

said control means further comprises means responsive to the heater energy counter means and the temperature sensing means operative to detect an abnormal operating condition of the temperature sensing means when the count of the heater energy counter is less than a predetermined diagnostic reference count and the sensed temperature is greater than a correlative predetermined diagnostic reference temperature.,

said arrangement further comprising user discernible signal means responsive to said control means and operative to generate a user discernible signal in response to detection by said control means of said abnormal operating condition of said sensor means.

10. In a cooking appliance of the type having heater means for heating a cooking utensil, user input selection means for enabling the user to select the desired heating level for the heater means, temperature sensing means operative to sense the temperature of the utensil being heated by the heater means, heater energy counter means for approximately tracking thettemperature of the heating means and counter control means for selectively incrementing and decrementing the energy counter at rates such that the count of the heater energy counter is approximately proportional to the temperature of the heating means and control means responsive to the user input selection means and the temperature sensing means operative to apply a power level to the heating means as a function of the sensed temperature and the user selected heating level, a method of detecting a failure of the temperature sensing means comprising the steps of:

periodically comparing the count of the heater energy counter to a predetermined maximum reference count indicative of heater means operation at a relatively high temperature;

upon detection of a heater energy count less than said maximum reference count, comparing the sensed utensil temperature to a maximum reference diagnostic temperature;

if the sensed temperature is less than the maximum reference temperature, comparing the heater energy count to a minimum reference count representative of operation of a heater means at a relatively low temperature;

if the count is greater than said minimum reference count, comparing the sensed utensil temperature to a minimum diagnostic reference temperature representative of a utensil temperature less than a normal steady state operating temperature for a utensil operating at the lowest available power level for the heating means;

detecting an abnormal operating condition for the sensor means if the sensed temperature is greater than the maximum reference temperature or less than the minimum diagnostic reference temperature;

upon detection of the abnormal operating condition, generating a user discernible signal indicative thereof.