Reciprocal Transceiver Circuit for Ultrasonic Flow Meters
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Solution Overview
Problem
Ultrasonic flow meters face measurement errors due to small delay differences in signal paths, which vary with temperature and transducer impedance, requiring costly calibration at low flow rates, and existing circuit topologies either fail to ensure reciprocity or require expensive amplifiers.
Innovation Solution
A transceiver circuit with a common signal path using a transimpedance amplifier and separate impedances for transmitting and receiving, allowing for reciprocal operation of transducers and avoiding delay differences, implemented with a simple circuit topology and discrete components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a two-input operational amplifier circuit topology is used as suggested in DE 10 048 959, then delay differences in signal paths can be addressed, but the amplifier inputs are driven in different ways during transmitting and receiving which influences the overall reciprocity of the circuit
Solution Approach 1:
The patent segments the impedance path by providing separate transmitting impedance ZTx and receiving impedance ZRx between the combined input/output terminal and the amplifier inputs. This segmentation allows independent optimization of transmit and receive paths while maintaining a common signal path, resolving the reciprocity issue caused by different driving conditions during transmit and receive modes.
Solution Approach 2:
Instead of using different circuit configurations for transmit and receive modes (as in the prior art), the patent inverts the approach by using a single common signal path configuration for both modes, with impedance matching achieved through separate impedance elements rather than different circuit topologies.
2Measurement precision
If calibration at low flow rates is performed to remove measurement errors, then measurement precision improves, but calibration time increases which reduces productivity
Solution Approach 1:
The patent implements preliminary design actions during the circuit design phase by establishing a common signal path topology with separate impedances that inherently minimizes delay differences and improves reciprocity. This preliminary optimization reduces measurement errors at the design level, thereby reducing or eliminating the need for time-consuming calibration procedures.
3Measurement precision
If expensive amplifiers are used to solve delay issues, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent changes the impedance parameters by providing separate transmitting impedance ZTx and receiving impedance ZRx values optimized for their respective functions. This parameter optimization allows the use of simpler, less expensive amplifier circuits while achieving the required delay compensation and measurement precision through careful impedance matching.
Data Source
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AI summary
The present invention relates to a transceiver circuit for a flow meter comprising a common signal path for signals to be transmitted and received, the transceiver circuit comprising a generator circuit, a signal processing circuit and a transimpedance amplifier, wherein the transimpedance amplifier comprises a combined input/output terminal being operatively connectable to one or more associated transducers, and wherein the transimpedance amplifier provides a separate transmitting impedance ZTx between an input terminal and the combined input/output terminal, and a separate receiving impedance ZRx between the combined input/output terminal and an output terminal.