Galvanic Isolation in Process Automation Field Devices
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Solution Overview
Problem
Existing field devices for process automation face challenges in maintaining interference immunity, particularly at high data transmission rates, due to inefficiencies in galvanic isolation and filtering methods, which limit communication and measuring accuracy.
Innovation Solution
The implementation of galvanic isolation components in data lines and current-compensated or non-current-compensated chokes in supply lines, along with capacitors, to minimize interference and meet EMC standards, while allowing higher data transmission rates and improved measuring dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation components are inserted into data lines to prevent interference signal transmission, then interference immunity is improved, but device complexity and cost increase
Solution Approach 1:
The patent applies partial galvanic isolation by inserting isolation components into only the data lines rather than isolating the entire power supply system. This selective approach provides sufficient interference immunity for the critical data transmission path while avoiding the complexity and cost of complete system isolation.
Solution Approach 2:
The patent implements different isolation strategies for different parts of the system: galvanic isolation components are placed in data lines where interference immunity is critical, while the power supply lines use filtering components (chokes and capacitors) instead of galvanic isolation. This localized quality approach optimizes the balance between reliability and complexity.
2Reliability
If strong filtering is applied to supply lines to meet EMC standards, then interference immunity is improved, but signal loss and power loss increase
Solution Approach 1:
The patent uses current-compensated chokes with specifically optimized inductance values and low DC resistance to achieve effective interference filtering while minimizing power loss. The filtering parameters are carefully selected to provide sufficient EMC protection without excessive energy dissipation.
Solution Approach 2:
The patent employs composite filtering structures combining current-compensated chokes with capacitors arranged in specific configurations. This composite approach provides superior interference rejection compared to single-component filters while maintaining lower power losses through the complementary characteristics of the combined components.
3Reliability
If low-pass filters are used to suppress interference couplings, then interference immunity is improved, but high-frequency communication is impaired
Solution Approach 1:
The patent uses galvanic isolation components as intermediary elements in the data lines. These isolators effectively block interference signals from coupling between different electrical grounds while maintaining bidirectional data transmission capability at high frequencies, thus mediating between interference suppression and communication performance requirements.
4Reliability
If galvanic isolation is implemented for voltage transmission, then interference immunity is improved, but transmission efficiency decreases and power loss increases
Solution Approach 1:
The patent applies galvanic isolation selectively only to data lines where interference immunity is critical for reliable communication, rather than implementing it for power supply lines where it would cause excessive power loss. This partial application optimizes the trade-off between reliability and energy efficiency.
Solution Approach 2:
The patent implements different isolation strategies for different parts of the system: galvanic isolation components are placed in data lines where interference immunity is critical, while the power supply lines use filtering components (chokes and capacitors) instead of galvanic isolation. This localized quality approach optimizes the balance between reliability and 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 solution enhances interference immunity, increases measuring accuracy, reduces material costs, and minimizes the size of galvanic isolating components, enabling higher data transmission rates and improved performance of field devices.
Implementation Method 1
at least one galvanic isolation component, which is inserted into the at least one data line and which prevents the transmission of interference signals via the data line
Implementation Method 2
a filter is provided in the supply lines, which is designed in such a way that EMC standards specifiable respective requirements for the immunity to interference of the supply lines are met, with the filter means being current-compensated or non-current-compensated chokes
Data Source
Figure 1
Figure 2a
Figure 2b
AI summary
The invention relates to an apparatus for reducing or minimizing interference signals in a process automation field device (1), wherein the field device (1) has a control/evaluation unit (5) and a sensor (7) with at least one main electronic unit (HE) and with at least one sensor electronic unit (SE), wherein at least one data line (11, 12) is provided, via which data line the main electronic unit (HE) and the sensor electronic unit (SE) communicate, wherein at least one DC-isolating component (8a, 8b) is provided, which DC-isolating component is inserted into the at least one data line (11, 12) and prevents interference signals from being transmitted via the data line(s) (11, 12), wherein supply lines (13) are provided and are used to provide the sensor (7) with a supply voltage (VCC) which suffices to operate the sensor (7), and wherein filter means (6; C1, C2) are provided in the supply lines (VCC, GND) and are designed in such a manner that predefined requirements for the interference immunity of the supply lines (VCC, GND) are met.