Temperature Measurement Circuit Calibration Without Thermal Chambers
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Solution Overview
Problem
Conventional temperature measurement circuits face increased manufacturing costs due to two-point calibration, which requires creating low- and high-temperature environments for accurate calibration, and there is a need for a cost-effective method to achieve high accuracy.
Innovation Solution
An environment emulating calibration circuit element is added to the temperature measurement circuit to generate a calibration current emulating environmental temperature, allowing calibration at a constant temperature, reducing the need for external temperature environments during factory calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If two-point calibration is performed to achieve high measurement accuracy, then temperature measurement precision is improved, but manufacturing cost increases due to the need for low- and high-temperature environments
Solution Approach 1:
The patent creates a virtual copy of temperature environmental effects through the environment emulating calibration circuit element. Instead of physically creating low- and high-temperature environments, the circuit element generates calibration currents that mathematically emulate the electrical characteristics the temperature sensing circuit would exhibit at different temperatures. This copying approach achieves two-point calibration accuracy without the costly physical temperature environments.
Solution Approach 2:
The patent changes the operational parameters of the calibration process by using an environment emulating calibration circuit element that can be switched between different set states (first set state and second set state). Each set state generates a calibration current corresponding to a different temperature condition. This parameter change allows the system to simulate multiple temperature points while maintaining a constant physical temperature, eliminating the need for expensive temperature-controlled environments.
2Measurement precision
If two-point calibration is performed to calibrate both offset and slope, then temperature measurement accuracy is improved, but calibration time increases due to creating temperature environments
Solution Approach 1:
The patent performs preliminary action by pre-configuring the environment emulating calibration circuit element with different set states that correspond to different temperature conditions. During calibration, the system simply switches between these pre-configured states rather than waiting for physical temperature environments to stabilize. This preliminary preparation of calibration states significantly reduces calibration time while maintaining accuracy.
3Ease of manufacture
If one-point calibration is used to reduce manufacturing cost, then manufacturing cost decreases, but temperature measurement accuracy deteriorates as only offset is calibrated
Solution Approach 1:
The environment emulating calibration circuit element serves multiple functions: it generates calibration currents for both offset calibration (first set state) and slope calibration (second set state). This multi-functional component enables the system to perform complete two-point calibration within a single constant temperature environment, achieving both cost reduction and accuracy improvement simultaneously.
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 achieves high accuracy equivalent to two-point calibration without the need for external temperature environments, thereby reducing manufacturing costs and shortening calibration time.
Implementation Method 1
a threshold voltage in a forward current of a bipolar junction transistor (BJT) element is VT = kT/q, where k is the Boltzmann constant and q is the electron charge, and changes with temperature
Implementation Method 2
An environment emulating calibration circuit element operates to change an output current of a temperature sensing circuit by an amount of change according to an environmental temperature
Data Source
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AI summary
Disclosed is sensing calibration technology for permanently recording a calibration value of a measurement value when a temperature measurement circuit is manufactured. An environment emulating calibration circuit element configured to generate a calibration current emulating an environmental temperature is added to the temperature measurement circuit. The environment emulating calibration circuit element operates to change an output current of a temperature sensing circuit by the amount of change according to the environmental temperature according to a set state value input from an external calibration device during factory calibration. During factory calibration, the external calibration device calculates a calibration value from output values measured while changing a set state of the environment emulating calibration circuit element and sets the calibration value in the temperature measurement circuit.