Photodiode Flame Scanner Signal Conditioning for UV Tube Replacement
Solution Overview
Problem
Existing flame scanners using ultraviolet (UV) tubes have a short lifespan and unsafe failure modes, such as 'runaway' triggering, where a flame is falsely indicated when none is present.
Innovation Solution
A flame scanner comprising a photodiode and a signal conditioner that generates an output signal emulating a UV tube scanner, using a pulse generator, amplifier, and voltage-to-frequency converter to produce a waveform with adjustable components, operating at high voltage and drawing low current to prevent false triggers, ensuring safe and long-lasting operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UV tube is used for flame detection, then flame presence can be detected, but the device has a short lifespan and unsafe failure modes
Solution Approach 1:
The patent replaces the UV tube (electronic component with short lifespan) with a photodiode-based solid-state detection system. The photodiode has no moving parts and significantly longer operational life, eliminating the lifespan limitation of the UV tube while maintaining flame detection functionality.
Solution Approach 2:
The patent changes the detection mechanism from UV light absorption (UV tube) to photodiode current generation. By transforming the detection principle and using solid-state electronics, the system achieves longer lifespan and safer operation while maintaining the same flame detection function.
2Reliability
If a UV tube is used for flame detection, then flame presence can be detected, but runaway triggering occurs indicating false flame presence
Solution Approach 1:
The patent implements a feedback mechanism through the signal conditioner that processes the photodiode output signal. The circuit includes amplification and frequency conversion stages that provide controlled feedback to the controller, enabling the system to distinguish between actual flame presence and false signals, thereby eliminating runaway triggering.
Solution Approach 2:
The signal conditioner acts as an intermediary between the photodiode and the controller. It processes the raw photodiode signal through controlled amplification and frequency conversion, filtering out false signals and providing clean, reliable output to the controller, thus preventing false triggers.
3Reliability
If the signal conditioner draws high current, then flame detection is reliable, but false triggers may occur
Solution Approach 1:
The patent optimizes the current draw parameter of the signal conditioner to operate at low current levels while maintaining detection reliability. The photodiode-based system naturally operates at lower currents compared to UV tubes, and the signal conditioner is designed to process these low-level signals effectively, eliminating false triggers caused by high current draw.
4Adaptability or versatility
If UV tube flame scanner output is emulated, then compatibility with existing controllers is maintained, but component complexity increases
Solution Approach 1:
The patent creates a signal conditioner that copies the output characteristics of the traditional UV tube scanner. By emulating the same pulse frequency and voltage characteristics, the solid-state photodiode system becomes compatible with existing controllers designed for UV tubes, avoiding the need for controller modifications while maintaining backward compatibility.
Solution Approach 2:
The signal conditioner is designed to perform multiple functions: amplifying the photodiode signal, converting it to the appropriate frequency range, and emulating the UV tube output characteristics. This multi-functional design maintains compatibility with existing controllers while using a modern solid-state detection system.
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 solution provides a reliable, long-lasting flame detection system with a safe failure mode, as the photodiode fails to indicate flame presence when malfunctioning, and the signal conditioner's low current draw prevents false triggers, allowing seamless replacement of UV tube scanners without controller modifications.
Implementation Method 1
a photodiode to generate a detection signal
Data Source
Figure 1
Figure 2
AI summary
A flame scanner (10) includes terminals (32) for connection to a controller (50) The flame scanner includes a photodiode (14) to generate a detection signal; and a signal conditioner (20) coupled to the photodiode, the signal conditioner to generate an output signal across the terminals, the output signal emulating an output of an ultraviolet tube flame scanner.