Temperature Measurement Circuit in Coriolis Flowmeter
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Solution Overview
Problem
Conventional temperature measurement circuits in Coriolis flowmeters face issues with accuracy due to poor temperature characteristics of components, large individual differences among components, and the need for additional components for multiple temperature measurement positions, leading to measurement errors and complexity.
Innovation Solution
A temperature measuring circuit with first and second resistor-type temperature sensors in a serial connection, line-to-line resistors, a voltage reference, a switching device, a multiplexer, and an A/D converter, which reduces the number of components and minimizes the effect of individual differences and temperature changes by using a hyperbolic approximate expression to correct the line-to-line resistor value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a V/F converter is used to convert voltage output to frequency for temperature measurement, then the temperature can be determined through frequency conversion, but the measurement accuracy deteriorates because the capacitor in the V/F converter has poor temperature characteristics and is affected by ambient temperature changes
Solution Approach 1:
The patent removes the V/F converter from the temperature measurement circuit. Instead of converting voltage to frequency, the system directly measures voltage output from the bridge circuit and converts it to resistance values through arithmetic operations in the CPU, thereby eliminating the temperature sensitivity issues associated with the V/F converter's capacitor.
Solution Approach 2:
The patent replaces the frequency-based measurement mechanism (V/F converter) with a direct voltage measurement and arithmetic conversion approach. The CPU performs resistance calculation using voltage division ratios, substituting the hardware-based frequency conversion with software-based computational methods that are less sensitive to temperature variations.
2Measurement precision
If multiple resistors are used in the resistor bridge unit to determine output voltage, then the voltage can be measured, but the measurement accuracy deteriorates because temperature characteristics of all six resistors simultaneously affect the output voltage
Solution Approach 1:
The patent simplifies the bridge circuit configuration by reducing the number of resistors from six to four. This reduction decreases the cumulative effect of temperature characteristics on the output voltage while still enabling accurate temperature measurement through the modified bridge configuration and corresponding arithmetic calculations.
Solution Approach 2:
The patent changes the bridge circuit parameters by reducing the resistor count and adjusting the measurement approach. Instead of measuring voltage across a complex six-resistor bridge, the system uses a simplified four-resistor configuration with modified voltage division ratios, thereby reducing the overall temperature sensitivity of the circuit.
3Adaptability or versatility
If additional components are added to provide multiple temperature measuring positions, then more temperature points can be monitored, but the device complexity increases and individual differences among components become more significant
Solution Approach 1:
The patent implements a universal temperature measurement circuit that can measure temperature at multiple positions by configuring the bridge circuit with available resistors rather than adding separate measurement circuits for each position. The system uses the inherent resistor values and their temperature characteristics to determine temperatures at different locations, making the circuit multi-functional without increasing component count.
Solution Approach 2:
The patent combines multiple temperature measurement functions into a single integrated bridge circuit. Instead of having separate measurement circuits for each temperature position, the system merges the measurement capability into one unified circuit that can determine temperatures at multiple points through arithmetic operations on the bridge output voltage, thereby reducing overall device complexity.
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
This configuration significantly reduces measurement errors across a wide temperature range, maintaining high accuracy while minimizing the number of components and their characteristic changes, thus improving the overall performance of the temperature measurement.
Implementation Method 1
first and second resistor-type temperature sensors which are provided at first and second measuring positions in the flowmeter
Implementation Method 2
a switching device that is connected to both of the second electric wire and the third electric wire and turns those electric wires to a conductive state or a non-conductive state wherein the switching device has an ON-resistance
Data Source
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AI summary
A value of a line-to-line resistor (24) is determined by subtracting a resistance value determined as a product of a voltage ratio based on divided voltages and a value of a reference resistor in a non-conductive state between a second electric wire (26) and a third electric wire (27) from a resistance value determined as a product of a voltage ratio based on the divided voltages and the value of the reference resistor in a conductive state therebetween. Once the value of the line-to-line resistor (24) is determined, it becomes possible to determine a compensated resistance value related to temperature.