Gas Flow Rate Measurement Device Using Digital Linearization
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Solution Overview
Problem
Conventional gas flow rate measurement devices face challenges with temperature-dependent errors, low resolution at high and low temperatures, and increased costs due to nonlinear gas temperature detection signals and the need for external diagnosis circuits.
Innovation Solution
A digital circuit is used to derive a linear output from nonlinear gas temperature detection signals, allowing for increased resolution and accuracy across a broader temperature range, while also enabling diagnostic checking of temperature detection elements without additional circuits, and optimizing arithmetic processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a thermistor is used as a temperature sensor to reduce cost, then the device becomes inexpensive, but the temperature detection signal becomes nonlinear resulting in low resolution at high and low temperatures
Solution Approach 1:
The patent transforms the nonlinear resistance-temperature relationship of the thermistor into a linear voltage-temperature relationship through circuit design. By using the thermistor in a voltage divider configuration with a fixed resistor and processing the output voltage signal, the system achieves linear temperature detection while maintaining the cost advantage of using a thermistor instead of expensive platinum resistors.
2Measurement precision
If a platinum resistor is used instead of a thermistor to achieve linear output characteristics, then temperature detection accuracy improves, but the device cost increases
Solution Approach 1:
The patent creates a functional copy of the platinum resistor's linear temperature detection capability using a thermistor-based circuit. Instead of directly using the expensive platinum resistor, the system replicates its linear output characteristic through voltage divider circuitry and signal processing, achieving the same measurement precision at lower cost.
3Measurement precision
If resistor-based analog circuits are used to improve gas temperature signal linearity, then temperature detection accuracy improves, but the output range becomes narrow and adjustment complexity increases
Solution Approach 1:
The patent extracts the temperature detection function from complex analog resistor networks and implements it through a simplified circuit configuration. By using a single thermistor in a voltage divider with a fixed resistor and processing the output signal, the system eliminates the need for multiple resistors and complex adjustments while maintaining signal linearity and expanding the output range.
4Reliability
If external fault diagnosis devices are installed to diagnose gas temperature sensor failures, then diagnostic capability improves, but the device cost and complexity increase
Solution Approach 1:
The patent enables the temperature detection system to perform self-diagnosis by monitoring its own output characteristics. The system can detect open circuits, short circuits, and other failures by analyzing the voltage output signal from the thermistor circuit, eliminating the need for external diagnosis devices and reducing overall system complexity while maintaining reliability.
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 provides a highly accurate and reliable gas flow rate measurement device with enhanced temperature range accuracy, reduced noise variations, and cost-effective diagnostic capabilities.
Implementation Method 1
the temperature detection signal of a thermistor or other independent temperature sensor disposed in an intake air flow path
Implementation Method 2
The intake air flow rate is measured, for instance, by a heat generation resistor type gas flow rate measurement device
Data Source
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AI summary
Provided is a highly accurate, highly reliable gas flow rate measurement device that provides an enlarged temperature range over which the resolution at a high temperature and at a low temperature can be increased to achieve high accuracy no matter whether the characteristics of a gas temperature detection element are nonlinear. The gas flow rate measurement device includes a plurality of resistors that are disposed in a gas flow path, a gas flow rate detection circuit that outputs a gas flow rate detection signal in accordance with the flow rate of a gas flowing in the gas flow path by detecting a current flowing in the resistors or by detecting a voltage generated in accordance with the current, and a gas temperature detection element 1 that detects the temperature of the gas in the gas flow path. The gas flow rate detection circuit includes signal conversion means for converting a signal output from the gas temperature detection element to a signal that has a predetermined maximum output and a predetermined minimum output and is linear within a predetermined temperature range.