AC Coupled Open Circuit Detection for Low Level DC Sensors
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Solution Overview
Problem
Low-level DC analog sensors in aircraft applications are susceptible to external disturbances and signal processing errors, particularly due to their low signal levels, leading to potential failures such as open circuits that can impact system reliability and require redundancy and overdesign to mitigate their impact.
Innovation Solution
A system and method for detecting open circuits in low-level DC sensors using AC coupling of signals with capacitors, allowing for precise detection and characterization of sensor failures without introducing offset errors, thereby enhancing system reliability and reducing electromagnetic interference susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If low-level DC analog sensors are used to detect aircraft parameters, then the sensors can provide accurate measurements, but they are susceptible to external disturbances and open circuit failures
Solution Approach 1:
An AC test signal is introduced as an intermediary to detect open circuit conditions. The AC signal is coupled through capacitors in series with the sensor, and its presence or absence at the controller indicates whether an open circuit exists. This intermediary test signal allows the system to distinguish between genuine sensor readings and open circuit failures without affecting the DC sensor operation.
Solution Approach 2:
The system employs periodic AC test signals to continuously monitor for open circuit conditions. By periodically injecting and detecting the AC signal, the system can dynamically identify failures as they occur, maintaining reliable operation throughout the sensor's service life while preserving measurement precision.
2Reliability
If redundancy and overdesign are implemented to mitigate sensor failures, then system reliability is improved, but device complexity increases
Solution Approach 1:
The sensor interface performs self-diagnosis by monitoring its own components. The controller detects open circuits in the wiring harness and sensor connections by analyzing the AC test signal response, eliminating the need for separate monitoring systems or redundant sensor configurations. This self-service approach maintains reliability while avoiding additional complexity.
3Measurement precision
If AC coupling is used to detect open circuits, then open circuit detection precision is improved, but offset errors may be introduced
Solution Approach 1:
The signal path is segmented into separate AC and DC components. Capacitors are used to couple the AC test signal separately from the DC sensor signal, allowing independent processing. The AC component is used for open circuit detection while the DC component maintains accurate sensor measurements, preventing offset errors from affecting either signal.
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
The AC coupling method effectively detects open circuits in low-level sensors, minimizing errors and electromagnetic interference, thus improving the reliability and precision of sensor monitoring in aircraft systems.
Implementation Method 1
AC coupling an AC signal with the sensor signal
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Embodiments herein relate to a system and method for detecting an open circuit in a sensor measurement system. The system including a sensor (22a - 22n) having a direct current (DC) output, operably connected to a wiring harness (27a - 27n) and configured to transmit a sensor signal, and a controller (100), the controller (100) operably connected to the wiring harness (27a - 27n). The controller (100) is configured execute a method including receiving a sensor signal from the sensor, AC coupling an AC signal with the sensor signal to form a coupled signal, measuring the coupled signal, determining if an open circuit is present based on the coupled signal and characterizing the sensor as failed if the open circuit is detected.