Thermistor Self-Heating Compensation for Wide-Range Temperature Sensing

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Thermistors, particularly NTC thermistors, exhibit non-linear resistance-temperature behavior and self-heating effects, leading to significant measurement errors when used in environments with wide temperature ranges, such as in vehicles operating from −40° C. to +150° C.

Innovation Solution

A control system using a microprocessor to determine thermistor self-heating and compensate for these effects by measuring voltage, determining resistance and temperature, and subtracting thermal rise from the sensed temperature, employing a thermistor linearization network with switchable pull-up resistors and a control model to improve accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a thermistor is used to measure temperature in wide temperature ranges, then the measurement coverage is improved, but self-heating effects cause measurement errors to increase

Engineering Contradiction:

Improvetemperature range coverageVSAvoidtemperature measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent implements a feedback mechanism where the control system continuously monitors the voltage across the thermistor, calculates the current flowing through it, determines the power dissipation, and uses this information to calculate and apply a compensation value. This closed-loop feedback approach dynamically corrects the self-heating error based on real-time operating conditions, thereby maintaining measurement accuracy across the wide temperature range of -40°C to +150°C.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces physical mechanical solutions (such as reducing current through hardware design or using complex cooling mechanisms) with an electronic/software-based compensation approach. By substituting the mechanical/physical correction method with an algorithmic calculation that computes thermal rise based on electrical parameters (voltage, current, power dissipation) and subtracts it from the raw temperature reading, the system achieves accurate measurements without additional mechanical complexity.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If current is increased to improve signal strength, then measurement sensitivity is improved, but self-heating effects increase causing measurement errors

Engineering Contradiction:

Improvemeasurement sensitivityVSAvoidself-heating effects

Core Design Contradiction:

Measurement precisionVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful self-heating effect into a useful piece of information for compensation. By measuring the voltage across the thermistor and calculating the current and power dissipation, the system determines the thermal rise caused by self-heating. This previously harmful effect becomes the basis for calculating a compensation value that is subtracted from the raw temperature reading, thereby transforming the source of error into a means for achieving accurate measurements.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent dynamically adjusts the interpretation of temperature readings by changing the compensation parameter based on operating conditions. The control system calculates different compensation values depending on the current flowing through the thermistor and the resulting power dissipation. By varying the compensation applied based on these electrical parameters, the system optimizes measurement accuracy across different current levels and temperature conditions.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Enhances thermistor accuracy by estimating and correcting self-heating errors, providing precise temperature measurements across broad temperature ranges.

Implementation Method 1

Thermistors, particularly those known as NTC thermistors (having a negative temperature coefficient, exhibiting decreasing resistance with increasing temperature)

Methodology Applied

Scientific EffectNegative temperature coefficient: Thermistor

Implementation Method 2

conducting a relatively large amount of current due to inherently low thermistor resistance at higher temperatures

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentUS12523548B2Thermistor self-heating compensation

Publication Date: 2026.01.13 BORGWARNER INC

AI summary

A temperature monitoring circuit and control system for compensating for self-heating effects of a thermistor used for measuring a temperature within a system includes a thermistor, a pull-up resistor, a node configured to receive a reference voltage, and a node configured to supply a sensed voltage; the control system measures a voltage across the thermistor; determines a thermistor resistance based on a known supply voltage and a known biasing impedance supplying current to the thermistor; determines thermistor temperature based on the thermistor resistance; determines a thermal rise value due to thermistor self-heating based on the known supply voltage, the thermistor's heat dissipation constant, and the calculated thermistor resistance; and creates a compensated thermistor temperature value by subtracting the thermal rise value from the determined thermistor temperature thus providing a more accurate measurement of the device being monitored by the thermistor.