Signal Conditioning Circuit Calibration for Offset and Gain Error Detection
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Solution Overview
Problem
Circuit arrangements for converting analog electrical signals to digital values in safety devices, such as those requiring Safety Integrity Level 3 (SIL3), face challenges in reliably detecting defects like short-circuits and component manipulations without complex calibration processes.
Innovation Solution
Incorporating a first switching apparatus to selectively separate or supply the input signal to the conditioning circuit and a second switching apparatus to manage the reference signal, allowing the control device to determine offset and gain errors by comparing actual and expected digital values, thereby identifying defects and enabling calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex calibration processes are used to detect defects in safety devices, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent applies preliminary action by performing calibration measurements at defined points in time (e.g., during manufacturing, before operation, or periodically) rather than continuously. The control device determines offset and gain errors by comparing actual digital values with expected values from reference sources, enabling defect detection without requiring complex continuous calibration processes during normal operation.
Solution Approach 2:
The patent uses switching apparatus as an intermediary to selectively connect reference sources to the input circuit or separate them. This switching mechanism enables the control device to perform calibration measurements by comparing signals from known reference sources against the measurement path, simplifying the calibration process while maintaining high measurement precision for defect detection.
2Measurement precision
If calibration processes are performed frequently to maintain precision, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent implements periodic action by performing calibration measurements at specific intervals or defined points in time rather than continuously. The control device switches between normal signal measurement mode and calibration mode, where calibration is performed periodically to maintain precision without continuously interrupting productivity-critical signal measurements.
Solution Approach 2:
Calibration is performed preliminarily at defined moments (e.g., during manufacturing, before operation, or at scheduled intervals) to establish baseline offset and gain error values. These preliminary calibration results are then used to correct subsequent measurements, maintaining high precision without requiring frequent interruptions to normal operation.
3Measurement precision
If switching apparatus is added to enable calibration, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The switching apparatus serves multiple functions: it selectively connects reference sources to the input circuit for calibration measurements, separates reference signals during normal operation, and enables the control device to perform both defect detection and calibration using the same hardware path. This multi-functionality reduces the need for separate dedicated calibration circuits.
Solution Approach 2:
The patent merges the calibration function with the normal signal measurement path by using the same input circuit, conditioning circuit, and analog-to-digital converter for both calibration and operational measurements. The switching apparatus enables this merging by routing either reference signals or input signals through the shared measurement path, simplifying the overall device architecture.
Data Source
AI summary
The invention relates to a circuit arrangement comprising a control device, an input circuit for applying an input signal, a conditioning circuit electrically connected to the input circuit for converting the input signal into a measured signal, an analog-to-digital converter electrically connected to the conditioning circuit for converting the measured signal into a digital value, and a reference source that outputs a known reference signal. In this respect, a first switching apparatus is provided that selectively separate the input signal from the conditioning circuit or supplies it to the conditioning circuit and a second switching apparatus is provided that selectively supplies the reference signal to the input circuit or separates it from the input circuit, wherein the control device is configured to determine an offset error and to determine a gain error of the circuit arrangement.