Differential Thermistor Circuit With Offset and Calibration Compensation
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Solution Overview
Problem
Traditional temperature measurement circuits using thermistors suffer from larger measurement errors due to unstable power supply voltage and offset voltages, leading to inaccurate resistance calculations and temperature readings.
Innovation Solution
A temperature measurement circuit incorporating a differential amplifier circuit and a conversion circuit, where the non-inverting input terminal is connected to a thermistor or calibration resistor, allowing for the output of offset, calibration, and temperature measurement voltages, which are then used to accurately determine the temperature signal, reducing the impact of power supply instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermistor is used to measure temperature in a traditional circuit, then the measurement can be implemented, but the measurement error becomes larger due to unstable power supply voltage and offset voltage
Solution Approach 1:
The patent segments the temperature measurement process into three distinct phases: offset voltage measurement (with non-inverting input unloaded), calibration voltage measurement (with calibration resistor connected), and temperature measurement (with thermistor connected). Each phase independently measures and compensates for specific error sources, thereby improving overall measurement precision and reliability.
2Ease of operation
If offset voltage and power supply instability are present in the circuit, then the circuit can operate, but the resistance calculation of the thermistor becomes inaccurate
Solution Approach 1:
The patent performs preliminary measurements of offset voltage and calibration voltage before the actual temperature measurement. These preliminary measurements allow the system to pre-calculate compensation values that are then applied to correct the thermistor resistance calculation, ensuring accurate results even in the presence of power supply instability and offset voltages.
Solution Approach 2:
The patent implements a feedback mechanism where the measured offset voltage and calibration voltage are used to calculate compensation factors. These compensation factors are fed back into the resistance calculation formula to correct for circuit imperfections, thereby maintaining high measurement precision despite operating conditions that would normally cause errors.
3Duration of action of moving object
If the non-inverting input terminal is continuously connected to the thermistor, then temperature measurement can be continuous, but offset voltage and calibration errors cannot be compensated
Solution Approach 1:
The patent employs periodic switching of the non-inverting input terminal connection state, cycling through three modes: unloaded state for offset measurement, calibration resistor connection for calibration measurement, and thermistor connection for temperature measurement. This periodic action enables continuous temperature monitoring while systematically compensating for offset and calibration errors at regular intervals, maintaining both continuity and precision.
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 proposed solution significantly improves the accuracy of temperature measurements by isolating and compensating for offset and calibration voltages, thereby reducing the influence of power supply fluctuations and environmental changes.
Implementation Method 1
the thermistor is configured to convert a temperature signal of a measured object to a resistance signal
Implementation Method 2
The differential amplifier circuit is configured to output an offset voltage when the non-inverting input terminal of the differential amplifier circuit is unloaded, to output a calibration voltage when the non-inverting input terminal of the differential amplifier circuit is connected to the calibration resistor, and to output a temperature measurement voltage of the measured object when the non-inverting input terminal of the differential amplifier circuit is connected to the thermistor
Data Source
Figure 1~3A
Figure 3B~3E
Figure 3F~4
AI summary
The present disclosure relates to the field of biometric parameter measurement, and in particular, to a temperature measurement circuit, a temperature measurement method, a temperature and light intensity measurement circuit, a temperature and light intensity measurement method, a chip, a module, and an electronic device. A temperature signal is obtained based on an output voltage of a differential amplifier circuit when a non-inverting input terminal of the differential amplifier circuit is unload, an output voltage of the differential amplifier circuit when the non-inverting input terminal of the differential amplifier circuit is connected to a calibration resistor, and the output voltage of the differential amplifier circuit when the non-inverting input terminal of the differential amplifier circuit is connected to a thermistor, which improves the accuracy of the temperature measurement.