Signal transmission system

Abstract

The invention relates to a signal transmission system, comprising at least one signal value generator having an electronic unit and a current source, the signal value generator feeding an applied current in a range between a predetermined first value and a predetermined second value into the line, a line, and a control and evaluation unit having a load and a microprocessor, the voltage dropped across the load or the current flowing through the load is detected and evaluated in a control and evaluation unit. The load is connected in series in the control and evaluation unit with at least one electrical component on which a DC voltage drop occurs when a current flows through the electrical component, and the at least one electrical component can be selectively bridged by means of a switch, and the microprocessor compares the voltage U1 dropped across the load when the electrical component is bridged or the current flowing through the load with the voltage U2 dropped across the load when the electrical component is connected in series with the load or the current flowing through the load, and identifies an error when a threshold value is exceeded or below.

Description

technical field [0001] The invention relates to a signal transmission system with at least one signal value generator, a circuit and a control and evaluation unit, wherein the signal value generator has an electronic unit and a current source and switches between a predetermined first value and a predetermined second An applied current between two values, in particular in the range between 4 mA and 20 mA, is fed into the line. The control and evaluation unit has a load and a microprocessor and detects the voltage drop across the load. Furthermore, the invention relates to a measured value generator and an evaluation unit for a corresponding signal transmission system. Background technique [0002] Signal transmission systems are used in particular in process control and plant technology to transmit process values ​​from various locations to mostly central monitoring and control locations. For this purpose, corresponding signal value generators are located on site, for exam...

AI Technical Summary

Problems solved by technology

[0006] Even though the transmission of measured values ​​by means of applied current has proven valuable over the years due to its reliability and its extremely low susceptibility to electromagnetic disturbances, it brings with it the following disadvantages: In addition to the actual measured values ​​and the above-mentioned Beyond the two error states, it is almost impossible to transmit other information

Although this solution can be implemented without problems when constructing new installations, in the case of existing installations all components need to be replaced, i.e. all measuring sensors, control and evaluation units and especially all wiring, which brings not only high costly and often require long interruptions to ongoing processes

Therefore, a complete replacement of the signal transmission system is usually not considered in the case of existing installations

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