Safety Controller Cross-Circuit Detection via Magnetic Field Sensing
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Solution Overview
Problem
Conventional methods for testing supply circuits in safety controllers for cross-circuits, such as using blanking intervals, are unsuitable as they lead to undesired electromagnetic emissions and can cause undesirable behavior in certain actuators, particularly over long line lengths.
Innovation Solution
A safety controller with an evaluation system that uses current measuring devices at each output to detect cross-circuits by measuring currents and recognizing differences, maintaining power supply integrity during switching off, and employing parallel current paths to avoid pulses, allowing for dynamic testing without blanking intervals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If blanking intervals are used to test supply circuits for cross-circuits, then cross-circuit detection capability is improved, but electromagnetic emissions and undesirable actuator behavior occur
Solution Approach 1:
The patent replaces the conventional electrical testing method (blanking intervals that generate electromagnetic pulses) with a magnetic field-based detection method. A magnetic field sensor detects the magnetic field generated by current flow in the supply circuit, allowing cross-circuit detection without generating electromagnetic emissions that cause harmful effects.
Solution Approach 2:
The patent introduces a magnetic field as an intermediary to transfer information about current flow. Instead of directly measuring electrical parameters that generate emissions, the magnetic field serves as a mediator that carries information about the circuit state without causing the harmful electromagnetic effects.
2Reliability
If test pulses are sent to detect cross-circuits, then safety monitoring is improved, but actuator performance deteriorates due to undesirable reactions
Solution Approach 1:
The patent replaces electrical test pulses that cause actuator reactions with magnetic field-based detection. The magnetic field sensor passively detects current flow without injecting test signals, thereby maintaining actuator performance while achieving safety monitoring.
Solution Approach 2:
The patent utilizes the existing current flow in the supply circuit to generate the magnetic field for detection. The circuit's own operating current serves the dual purpose of powering the load and providing the detection signal, eliminating the need for separate test pulses that disrupt actuator operation.
3Reliability
If conventional current testing methods are used, then cross-circuit detection is achieved, but pulse generation at outputs occurs causing interference
Solution Approach 1:
The patent replaces electrical current measurement methods that generate output pulses with magnetic field sensing. The magnetic field sensor detects current flow through the supply circuit without generating electrical pulses at the outputs, thereby achieving cross-circuit detection without electromagnetic interference.
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
Enables reliable detection of cross-circuits and switch functionality without generating pulses at outputs, reducing electromagnetic interference and ensuring safety without the need for blanking intervals, thus enhancing safety and operational efficiency.
Implementation Method 1
the status of the supply circuit is determined magnetically by means of a magnetic field sensor depending on a magnetic field generated by current flow
Data Source
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AI summary
Safety control (1), designed for safely switching on and off an electrical load in accordance with a safety regulation, comprising a safe switching element (18, 20) and a first and a second output (4A, 4B) to which the electrical load can be connected by forming a supply circuit for the electrical load that can be safely switched by means of the switching element (18, 20), further comprising an evaluation system for testing the supply circuit for cross-circuits, is intended to enable reliable testing of the output circuits without the need for conventional blanking intervals.The evaluation system includes a first current measuring device (40) assigned to the first output (4A) and a second current measuring device (36, 38) assigned to the second output (4B), wherein a condition linking the current intensities (11, 12, 13) measured in the current measuring devices (36, 38, 40) for the detection of a cross-circuit is stored in the evaluation system.