US H562 H · Accurate electronic thermometer

Abstract

A device is disclosed for accurately measuring temperature electronically, having a resistance-type sensor, such as a thermistor, used with a constant current to develop a voltage thereacross. Operational amplifier circuits provide a linear relationship between sensor voltage and resistance. The sensor's calculated resistance is used in a microprocessor to solve a log-polynomial equation relating resistance to temperature. Software corrections compensate for temperature-related variations in the circuitry, and a keyboard permits entry of the polynomial coefficients relating the sensor's output to the measured temperature, to allow interchangeability of sensors. The components are packaged in a compact, waterproofed container to provide a rugged, portable instrument usable in extremes of climatic conditions and capable of maintaining high accuracy over a wide temperature range.

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Claims15

Dependent claims

A temperature measuring apparatus of the type wherein the electrical resistance characteristic of a thermal sensor is measured and used to determine temperature, comprising:

a resistance-type thermal sensor having a temperature-resistance relationship given by ##EQU2## where:
T is temperature, in degrees Celsius;
R is the sensor's electrical resistance, in Ohms;
and A, B and C are calibration constants for the sensor:
means for providing a substantially constant electrical current to said sensor;
means for measuring the voltage produced across said sensor at said constant current, said voltage varying according to changes in the temperature of said sensor;
means for determining the resistance of said sensor from said voltage in accordance with Ohm's law, and for determining the sensor's temperature from said temperature-resistance relationship;
means for displaying said determined temperature;
and
means for providing said sensor calibration constants A, B ,C to said determining means for the determination of said temperature.

7 more elements

Dependencies are inferred from the claim text.

Description4,196 words

Summary934 words

#1. Field of the Invention

#The invention relates generally to temperature measuring devices and, more particularly, to an electronic device for accurately measuring temperature using a resistance-type sensor and developing a linear relationship between resistance and temperature.

#2. Description of the Prior Art

Brief description of the drawings2 figures

#FIG. 1 is a schematic diagram showing the components comprisrng the invention.

#FIG. 2 is a schematic diagram of an analog printed circuit board used in the invention.

Detailed description3,234 words

#The relationship between the resistance of a thermistor and the sensed temperature may be expressed by the following third-order log-polynomial equation: ##EQU1## where: T is the temperature, in degrees Celsius

#R is the sensor's resistance, in Ohms

#A, B, C are calibration constants for the sensor.

Accurate electronic thermometer

Life of this patent

Accurate electronic thermometer

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims15

Description4,196 words

Drawings

Classification0 codes

Life of this patent

Description4,196 words