Magnetic-Inductive Flowmeter Measuring Circuit Interference Compensation
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Solution Overview
Problem
Magnetic-inductive flowmeters face challenges in accurately measuring volume flow rates of low-conductivity liquids due to interference components that overwhelm the small, time-varying useful components, requiring high-resolution digitization and complex compensation circuits that can disrupt electrochemical processes.
Innovation Solution
The implementation of a compensation circuit with adjustable DC voltages and operating modes within the measuring electronics to reduce interference components and enhance the digitization of useful components, allowing for higher digital resolution and maintaining measurement accuracy without affecting electrochemical processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex compensation circuits are used to reduce interference components, then measurement precision improves, but device complexity increases and electrochemical processes are disrupted
Solution Approach 1:
The patent extracts the interference component from the measured signal by introducing a reference electrode that senses only the interference potential. This separated reference signal is then used in the evaluation circuit to subtract the interference component mathematically, achieving high measurement precision without complex analog compensation circuits that would disrupt electrochemical processes.
Solution Approach 2:
The reference electrode acts as an intermediary element that mediates between the interfering electrochemical potentials and the measurement system. By measuring the interference potential separately through this intermediary, the system can eliminate interference without directly manipulating the measurement electrodes or disrupting the electrochemical processes occurring in the liquid.
2Measurement precision
If high-resolution digitization is used to resolve small useful components, then measurement precision improves, but device complexity and cost increase
Solution Approach 1:
The patent converts the harmful effect of large interference components into a beneficial measurement approach. By intentionally measuring the interference component separately through the reference electrode and then subtracting it digitally, the system enables the use of moderate-resolution ADCs to achieve effective high-resolution measurement of the useful signal, avoiding the need for expensive ultra-high-resolution converters.
3Measurement precision
If compensation voltages are applied to reduce interference, then measurement precision improves, but electrochemical processes are disrupted
Solution Approach 1:
The patent implements a feedback mechanism where the reference electrode continuously monitors the interference potential, and the evaluation circuit uses this feedback information to dynamically subtract the interference component from the measurement signal. This closed-loop approach maintains measurement precision without requiring compensating voltages that would disrupt the electrochemical processes in the liquid.
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 approach enables high-resolution digitization of useful components with less than 10 nV/bit, improving measurement accuracy and dynamics while minimizing interference, thus enhancing the measurement of volume flow rates in low-conductivity liquids.
Implementation Method 1
a first measuring electrode (111, 121) connected to a first circuit input (112, 122) of the input circuit and with a second measuring electrode (113, 123) connected to a second circuit input (114, 124) of the input circuit, wherein the respective electrical potential of the measuring electrodes is dependent on an electrical voltage occurring in a liquid guided in the measuring tube and caused, for example, by charge carrier displacement within the liquid
Implementation Method 2
a magnetic field generator (130, 140) set up to generate a magnetic field (B) which at least partially penetrates a lumen of the measuring tube (2)
Data Source
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AI summary
The invention relates to an electronic measuring device for determining a potential difference (Ʌφ12) between a first measuring electrode having an electrical potential (φ12) and a second measuring electrode having an electrical potential (φ2). The electronic measuring device thereby comprises a reference electrode (GRN) having a reference potential (φRef), an input circuit having two circuit inputs that can be connected to the first and/or the second measuring electrode, two signal voltage outlets, a compensation circuit having a first compensation voltage outlet and a second compensation voltage outlet. Said electronic measuring device further comprises a control signal inlet and, for generating a digital voltage measurement signal (UD), a measurement and control circuit having two signal voltage inlets respectively connected to one of the signal voltage outlets of the input circuit, two signal voltage inlets, each electrically connected to one of the compensation voltage outlets of the compensation circuit, and a compensation control outlet connected to the control signal inlet of the compensation circuit. The compensation circuit is configured to provide a compensation voltage (UC1), that is, an adjustable direct-current voltage relative to the reference potential, at the first compensation voltage outlet, and to provide a compensation voltage (UC2), that is, a direct-current voltage relative to the reference potential, at the second compensation voltage outlet. The compensation circuit is further provided with at least two operating modes that can be selected by way of a compensation control signal, which can be placed at the control signal inlet. In a first operating mode, the compensation voltage (UC1) is set to a specified voltage value, UC11, and in a second operating mode, the compensation voltage (UC1) is set to a specified voltage value, UC12. The measurement and control circuit, on the other hand, is configured to provide a compensation control signal at the compensation control outlet for selecting one of the selectable operating modes of the compensation circuit.