Two-Wire Field Device Maintenance Current Powers Radio Module
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Solution Overview
Problem
Existing two-wire field devices face challenges with energy supply limitations, requiring additional wiring or battery power for radio module operation, which increases installation and maintenance complexity, especially in environments where additional current supply lines are undesirable.
Innovation Solution
A two-wire field device design that uses a control unit, sensor, and radio module, where a maintenance current above the 4 mA to 20 mA range powers the radio module during active radio connections, allowing higher transmission power and data rates without additional energy sources, and signals the maintenance mode to the superordinate unit, enabling it to function as a pure energy source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If additional energy sources (batteries, energy harvesters, separate supply lines) are provided for the radio module, then the transmission power and data rate are improved, but the installation requirements and maintenance requirements increase
Solution Approach 1:
The two-wire line is designed to serve multiple functions: it provides both the standard 4-20 mA process control signal and supplies energy to the radio module. The superordinate unit can switch between measurement mode (4-20 mA signal transmission) and energy supply mode (providing maintenance current to the radio module), eliminating the need for separate energy supply infrastructure.
Solution Approach 2:
The field device is designed to autonomously switch between operational modes based on its needs. When radio transmission is required, the device automatically requests maintenance current from the superordinate unit, which then switches to energy supply mode. This self-service mechanism eliminates the need for manual configuration or additional control systems.
2Power
If the field device operates in maintenance mode to supply energy to the radio module, then the transmission power is improved, but the signal transmission capability is reduced
Solution Approach 1:
The field device operates in periodic cycles, alternating between measurement mode (signal transmission via 4-20 mA) and energy supply mode (radio transmission with higher power). The superordinate unit coordinates these mode switches, allowing the device to transmit process signals during measurement mode and perform radio communications during energy supply mode, thereby achieving both functions over time.
Data Source
AI summary
The invention relates to a measuring arrangement having a two-wire field device comprising a control unit, a sensor, and a radio module, a superordinate unit to which the field device is connected via a two-wire line, wherein signals from the field device are transmitted to the superordinate unit at least as a current injected by the field device in a predetermined range to the superordinate unit, wherein an error current below the predetermined range signals an error, and a maintenance current above the predetermined range signals a maintenance mode, and the field device is designed in such a manner that the maintenance current feeds the radio module in the radio operation.