Parallel Sub-Circuit Linearization for NTC Thermistors
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Solution Overview
Problem
Existing analog circuits for linearizing negative temperature coefficient (NTC) thermistor resistance-temperature characteristics are limited in their ability to provide accurate and stable measurements over wide temperature ranges, often introducing significant approximation errors and being unsuitable for multi-sensor networks.
Innovation Solution
A novel multiple sensor-based single operational amplifier circuit with a plurality of sub-circuits connected in parallel, each comprising a resistive sensor and a resistor, along with an inverting operational amplifier with a feedback path, which minimizes linearity deviations and reduces self-heating effects, allowing for precise temperature measurement across extended temperature ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single series or parallel resistor element is used for linearization, then the circuit complexity is reduced, but the measurement precision deteriorates due to significant approximation errors over wide temperature ranges
Solution Approach 1:
The linearization circuit is divided into multiple parallel sub-circuits, each containing a sensor and resistor. This segmentation allows each sub-circuit to handle specific portions of the temperature range, improving overall linearity accuracy while keeping individual sub-circuits relatively simple
Solution Approach 2:
Multiple sub-circuits are combined in parallel configuration, with their outputs summed at the operational amplifier. This merging of multiple linearization paths enables the system to achieve high measurement precision across wide temperature ranges by combining the strengths of different sub-circuit configurations
2Speed
If existing analog linearization circuits are used, then the response speed is fast, but the measurement precision deteriorates due to inability to maintain linearity over extended temperature ranges
Solution Approach 1:
The circuit dynamically adapts to different temperature ranges by utilizing multiple parallel sub-circuits with different resistor values. As temperature varies, the effective contribution of each sub-circuit changes, maintaining optimal linearity accuracy across the entire extended temperature range while preserving fast analog response speed
3Ease of manufacture
If previous art circuits are used, then the design is simple, but the reliability deteriorates due to significant approximation errors and unsuitability for multi-sensor networks
Solution Approach 1:
The linearization circuit is designed with a universal parallel sub-circuit structure that can be easily replicated and scaled for multi-sensor networks. Each sensor can be paired with an identical or customized sub-circuit, maintaining design simplicity while improving reliability through consistent, proven linearization architecture across multiple sensors
Solution Approach 2:
The operational amplifier provides feedback that sums the outputs from multiple parallel sub-circuits, automatically compensating for non-linearities. This feedback mechanism enhances measurement stability and reliability while maintaining relatively simple circuit implementation
4Device complexity
If exponential thermistor equation is used, then the mathematical model is simple, but the measurement precision deteriorates for wide temperature range implementation
Solution Approach 1:
Instead of relying on a single exponential thermistor equation valid only for narrow ranges, the circuit uses multiple sub-circuits with different resistor parameters (R1, R2, R3, etc.). This changes the effective parameters of the linearization across different temperature ranges, maintaining high measurement precision without requiring complex mathematical models
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
The solution achieves temperature measurement linearity of less than 0.004°C over a 100°C range, significantly improving upon previous art by reducing linearity errors and maintaining stability, while being cost-effective and simple to design and manufacture.
Implementation Method 1
an inverting operational amplifier with a feedback path, where a resistive sensor of the same type as in the sub-circuits is connected
Implementation Method 2
Negative Temperature Coefficient (NTC) thermistors have very high resistance - temperature sensitivity (its resistance decreases exponentially as the temperature of the thermistor increases)
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention relates to a linearization circuit (1) for linearizing of sensors (RT1, RT2, RT3, RTK) having nonlinear behavior, the circuit comprises; a sensor circuit (2) having a plurality of sub-circuits connected parallel to each other and each of which comprises a sensor (RT1, RT2, RT3, RTK) and a resistor (R1, R2, R3, Rk), and an inverting operational amplifier (3) having a feedback path (4) where a sensor (RTO) of the same type in the sub-circuits is connected, and whose inverting input (5) is connected to the sensor circuit (2).