Flame Sensor Impedance-Based Capacitor Charging for Signal Evaluation
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Solution Overview
Problem
Existing flame monitoring technologies face challenges in simple signal evaluation and are not adaptable to diverse flame types and sensor impedances, often requiring active signal amplification and being prone to errors and foreign light interference.
Innovation Solution
A method where a capacitor is cyclically charged and discharged based on the flame sensor's impedance, allowing for single-channel evaluation and using uniform threshold values, which also functions as a signal filter, and can detect component faults and foreign light without active amplification, using various flame sensors like photoresistors, ionization current electrodes, and UV tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If active signal amplification is used to evaluate flame sensor signals, then signal evaluation capability is improved, but device complexity and component count increase
Solution Approach 1:
The capacitor serves multiple functions simultaneously: it acts as both the timing element for cyclic charge/discharge operation and as a signal filter with lowpass characteristics. This multi-functionality eliminates the need for separate active signal amplification circuits, reducing component count while maintaining signal evaluation capability
Solution Approach 2:
The flame sensor's own impedance characteristics are utilized directly in the RC circuit configuration. The sensor's impedance variations due to flame presence automatically modulate the capacitor's charge/discharge behavior, enabling signal evaluation without requiring external active amplification components
2Ease of operation
If uniform threshold values are used for different sensor impedances, then ease of operation is improved, but measurement precision may worsen
Solution Approach 1:
The system changes the evaluation parameter from direct impedance measurement to voltage signal evaluation at the capacitor. By evaluating the voltage signal obtained during the charging phase against a uniform threshold, the system achieves both operational simplicity and maintained precision across different sensor types and impedances
Solution Approach 2:
The capacitor acts as an intermediary that converts diverse sensor impedance variations into a unified voltage signal format. This standardization at the capacitor output level allows uniform threshold evaluation to work effectively across different sensor types (photoresistors, ionization electrodes, UV tubes) without sacrificing detection accuracy
3Reliability
If foreign light detection is added to the monitoring system, then reliability is improved, but device complexity increases
Solution Approach 1:
The system continuously monitors the capacitor voltage signal during the charging phase to detect both flame conditions and foreign light interference. By evaluating the voltage signal at the end of the charging phase, the system can identify static impedance changes caused by foreign light without requiring separate detection circuits, maintaining reliability while avoiding additional complexity
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 efficient monitoring of different flames with minimal components, detects faults and foreign light effectively, and allows for both permanent and intermittent burner operation, ensuring reliable flame detection across various scenarios.
Implementation Method 1
a capacitor connected to a voltage source is charged during a charging phase up to a voltage value and during a discharging phase the capacitor is discharged via a coupling element connected with the flame sensor
Implementation Method 2
the radiation created by the flame is recorded by a photoresistor and the sensor signal is evaluated
Implementation Method 3
an ionization stream flows as a result of flame generation the capacitor is discharged
Data Source
AI summary
A capacitor connected to a voltage source is charged during a charging phase up to a voltage value, and during a discharging phase the capacitor is discharged via a coupling element connected to the flame sensor. The period for the charging or discharging phase of the capacitor respectively is selected in this case as a function of the characteristics of the flame sensor, especially of its impedance. For flame monitoring the charging and discharging of the capacitor is repeated cyclically, with the voltage signal obtained in this way being evaluated in single-channel mode with the aid of a threshold value.