Flame Sensing Circuit Diagnostics via Residual AC Component
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Solution Overview
Problem
Conventional flame sensing systems in residential combustion systems lack effective diagnostic capabilities to ensure the integrity and reliability of the flame sensing circuit during operation, which is critical for safety.
Innovation Solution
A circuit design that utilizes the residual AC component at the flame sensing input to diagnose the system's condition by monitoring the amplitude and properties of the AC component, allowing for continuous monitoring and reporting of errors, and identifying potentially faulty components through synchronized data sampling and storage in non-volatile memory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional flame sensing systems are used, then the system can detect flames, but the system lacks diagnostic capabilities to ensure circuit integrity and reliability
Solution Approach 1:
The flame sensing circuit monitors its own operational status by detecting residual AC components from the high voltage AC signal. The system uses self-diagnostic capabilities where the flame sensor circuitry analyzes its own signal characteristics to detect faults in the sensing rod, wiring, or circuit components without requiring external diagnostic equipment.
Solution Approach 2:
The system implements feedback by continuously monitoring the AC component amplitude and comparing it against expected ranges. The controller receives feedback signals indicating the presence or absence of proper AC components, allowing it to identify when the flame sensing circuit is malfunctioning and report diagnostic information about circuit integrity.
2Measurement precision
If high voltage AC is used for flame sensing, then the sensing capability is improved, but the system cannot distinguish between actual flame presence and circuit faults
Solution Approach 1:
The system extracts the residual AC component from the flame sensing signal using filtering circuitry. By separating and analyzing only the AC portion of the signal, the system can specifically monitor the health of the high voltage AC generation circuitry without interference from the DC flame detection signal, enabling independent diagnostic capability.
Solution Approach 2:
The system monitors changes in the amplitude and characteristics of the residual AC component to detect circuit faults. When the AC component amplitude falls outside expected parameters, the system identifies a potential fault in the sensing rod, wiring, or circuit components, allowing differentiation between normal operation and abnormal conditions.
3Object-affected harmful factors
If extensive filtration is applied to the flame sensing signal, then noise is reduced, but the AC component needed for diagnostics is removed
Solution Approach 1:
The signal processing is segmented into separate functional paths: one path handles DC flame detection while another path extracts and analyzes the AC component for diagnostics. This segmentation allows the system to apply appropriate filtering to each path independently, reducing noise in the flame detection path while preserving the AC component in the diagnostic path.
Data Source
AI summary
A diagnostic flame sensing circuit having less filtration so that an AC component of a flame sensing input is available for circuit diagnostics. Synchronized data sampling may used to detect the peak to peak magnitude of the residual AC component. A comparison of the magnitude of the component relative to a magnitude of the component during normal operation of the circuit may be used to check the condition of nearly all of the elements in the circuit.