Ultrasonic Flow Meter Temperature Compensation Using Piezoelectric Capacitance
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Solution Overview
Problem
High precision ultrasonic flow meters require complex and expensive temperature sensors to correct flow rate measurements, which degrade reliability and increase costs, as the relation between flow rate and transit time is not perfectly linear due to laminar to turbulent flow mode changes.
Innovation Solution
A flow meter using two piezoelectric ultrasound transducers to generate and receive ultrasound signals, where the processor calculates the flow rate correction based on the electric signal from one transducer, deriving temperature from the transducer's electric capacitance, eliminating the need for a separate temperature sensor and reducing complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate temperature sensor is added to the flow meter to improve temperature measurement precision, then the temperature correction precision is improved, but the device complexity and cost increase
Solution Approach 1:
The piezoelectric transducer is made to serve dual functions: (1) generating and receiving ultrasound signals for flow rate measurement, and (2) sensing temperature through its capacitance characteristics. By utilizing the inherent temperature dependence of the transducer's electrical properties, the system eliminates the need for a separate temperature sensor while maintaining temperature correction capability
Solution Approach 2:
The temperature sensing function is merged with the existing ultrasound transducer by measuring its electrical capacitance, which varies with temperature. This combines the flow measurement component and temperature sensing component into a single integrated element, reducing device complexity and component count
2Measurement precision
If a separate temperature sensor is added to the flow meter to improve temperature correction precision, then the temperature correction precision is improved, but the reliability degrades
Solution Approach 1:
The piezoelectric transducer is made to serve dual functions: (1) generating and receiving ultrasound signals for flow rate measurement, and (2) sensing temperature through its capacitance characteristics. By utilizing the inherent temperature dependence of the transducer's electrical properties, the system eliminates the need for a separate temperature sensor while maintaining temperature correction capability
Solution Approach 2:
The temperature sensing function is extracted from the separate temperature sensor and integrated into the existing transducer system by measuring the transducer's electrical capacitance, which inherently varies with temperature. This removes the separate temperature sensor component that was causing reliability issues
3Measurement precision
If a separate temperature sensor is added to the flow meter to improve temperature correction precision, then the temperature correction precision is improved, but the manufacturing cost increases
Solution Approach 1:
The piezoelectric transducer is made to serve dual functions: (1) generating and receiving ultrasound signals for flow rate measurement, and (2) sensing temperature through its capacitance characteristics. By utilizing the inherent temperature dependence of the transducer's electrical properties, the system eliminates the need for a separate temperature sensor while maintaining temperature correction capability
Solution Approach 2:
The temperature sensing function is merged with the existing ultrasound transducer by measuring its electrical capacitance, which varies with temperature. This combines the flow measurement component and temperature sensing component into a single integrated element, reducing device complexity and component count
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
Enables high precision flow rate measurements over a wide range of flow rates and temperatures without additional sensors or wiring, enhancing reliability and reducing costs by integrating temperature correction into the processor, thus providing accurate and reliable data for heat quantity determination.
Implementation Method 1
an ultrasound measurement arrangement including two piezoelectric ultrasound transducers arranged to generate and receive an ultrasound signal
Implementation Method 2
the processor, based on digital signal processing of the received electrical signal, is arranged to determine a measure related to temperature of the liquid based on a measure related to electric capacitance of the one piezoelectric ultrasound transducer
Data Source
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Figure 3~4
AI summary
The Invention provides a flow meter for measuring a liquid flow rate (V'). The flow meter Includes a well-known ultrasound measurement arrangement (UMA) including two piezoelectric ultrasound transducers (PT1, PT2), and a processor (P) eledrically connected thereto. The processor (P) is in a traditional manner arranged to measure a flow rate (V') based on ultrasonic measurement(s) of transit time difference(s) using the piezoelectric ultrasound transducers (PT1, PT2). In preferred embodiments, the processor (P) is further arranged to correct the measured flow rate (V') for an influence of a temperature (T) of the liquid in the measurement pipe. A measure of the temperature (T) of the liquid is based on a measurement of electrical capacitance, or at least measurement data related to the electrical capacitance of at least one of the two piezoelectric ultrasound transducers (PT1), thus utilizing the temperature dependence of electrical capacitance of the piezoelectric transducer element (PT1). The electrical measurement signal applied to the at least one transducer (PT1) may be a separate dedicated signal, or the temperature (T) may be derived from an electrical response to the electrical signal applied to the at least one transducer (PT1) for determining the ultrasonic transit time difference. The flow meter is capable of providing a high precision flow rate measurement over a wide range of flow rates and temperatures, and still the flow meter is simple and economical to manufacture since the temperature correction is performed without the need for a separate temperature sensor. The flow meter is suited for use in connection with a heat meter, e.g. in embodiments where the flow meter is arranged to transmit data related to the liquid temperature (T) to a heat calculation unit of the heat meter.