Sensor Signal Path Verification for Field Device Accuracy
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Solution Overview
Problem
Field devices in industrial plants are exposed to extreme conditions that negatively affect the signal path of their electronic sensor circuits, leading to measurement inaccuracies and functional degradation.
Innovation Solution
A method is introduced to check the signal path by replacing raw analog measurement values with an analog verification signal, traversing the path, and comparing the resulting measurement value with a predetermined reference value to detect any deviations, thereby identifying changes in the signal path state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If field devices are used to measure process variables in industrial plants, then measurement functionality is provided, but extreme conditions (temperature fluctuations, vibrations, humidity, EMC) negatively affect the signal path and measurement accuracy over time
Solution Approach 1:
The patent applies preliminary action by performing self-tests of the signal path during idle periods before actual measurement operations. The microcontroller executes test routines that send test signals through the signal path and compare received signals against reference values, detecting deviations before they affect normal measurements. This proactive approach ensures reliability by identifying and addressing signal path degradation early.
2Measurement precision
If the measurement operation is interrupted for verification, then signal path integrity can be checked, but measurement productivity is reduced
Solution Approach 1:
The patent implements periodic action by scheduling self-tests to occur at predetermined intervals during idle periods when the field device is not actively measuring. The microcontroller is configured to automatically initiate verification routines at these intervals, performing signal path checks without requiring continuous interruption of measurement operations. This periodic verification maintains measurement precision while minimizing impact on productivity.
Solution Approach 2:
The patent applies dynamics by making the verification frequency and timing adaptable to the operational state of the field device. The system dynamically adjusts when self-tests occur based on available idle periods and operational requirements, allowing more frequent checks during low-activity periods while reducing verification frequency during high-demand measurement operations. This dynamic approach optimizes the balance between measurement precision and productivity.
3Reliability
If an analog verification signal is used to test the signal path, then the complete signal path including analog-to-digital converter can be verified, but the testing complexity increases compared to simple digital signal testing
Solution Approach 1:
The patent applies universality by designing the microcontroller to serve multiple functions: it acts as both the normal measurement controller and the verification signal generator. The same microcontroller that controls the field device's measurement operations also generates analog verification signals, processes test responses, and performs self-diagnostics. This multi-functionality reduces overall system complexity while enabling comprehensive signal path verification including the analog-to-digital converter.
Solution Approach 2:
The patent implements self-service by enabling the field device to perform its own self-testing and verification without requiring external test equipment or additional dedicated testing components. The microcontroller autonomously generates verification signals, routes them through the signal path, captures responses via the analog-to-digital converter, and compares results against stored reference values. This self-diagnostic capability reduces system complexity while ensuring reliable verification of the complete signal path.
Data Source
Figure 1
AI summary
The invention relates to a method for checking a signal path of a sensor circuit (1) for a field device in automation technology, the sensor circuit (1) comprising a signal path (3) having a transducer element (2) for outputting analog raw measured values, an analog-digital converter (6) connected downstream to convert the raw measured values into digital raw measured values, and a digital processor (5) which is designed to further process the supplied digitised raw measured values to provide measured values. The method comprises the following steps: - interrupting the measurement operation; - replacing the analog raw measured values at an output of the transducer element (2) by an analog check signal; - passing the analog check signal through the signal path (3), so that the digital processor (5) determines a corresponding value for the analog check signal; - checking the determined measured value with a comparison value determined for the signal path (3), and, if the measured value determined for the analog check signal is outside a defined tolerance range for the comparison value, identifying a change in the state of the signal path (3).