Flame Scanner Non-Linear Amplifier With Temperature-Stable Gain Switching
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Solution Overview
Problem
Flame scanners face challenges in maintaining consistent signal amplification across varying input voltages due to the need for high gain at low voltages and low gain at high voltages, which can lead to amplifier saturation and temperature-induced variance in gain settings.
Innovation Solution
A non-linear amplifier assembly with a switch and thermally variable element that adjusts gain based on output voltage levels and temperature, using feedback paths with resistances and a MOSFET transistor, and a diode for temperature compensation to maintain a consistent breakpoint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high gain is used to amplify low voltage signals, then signal amplification is improved, but amplifier saturation occurs at high voltage levels
Solution Approach 1:
The amplifier gain is made dynamic through a switch that changes the feedback path based on output voltage level. When output voltage is low, the amplifier operates with high gain for better signal amplification. When output voltage exceeds a threshold, the switch changes state to reduce gain, preventing saturation. This dynamic adaptation resolves the contradiction between needing high gain for low signals and avoiding saturation at high signals.
Solution Approach 2:
The feedback resistance parameter is changed based on operating conditions. The system switches between different feedback resistance values (R1 for high gain, R2 for low gain) depending on the output voltage level. This parameter change allows the amplifier to maintain optimal performance across different signal ranges, preventing both poor amplification and saturation.
2Device complexity
If fixed gain settings are used in the amplifier, then circuit simplicity is maintained, but temperature-induced variance in gain settings occurs
Solution Approach 1:
A temperature sensing element provides feedback about the amplifier's thermal state. This feedback is used to dynamically adjust the breakpoint voltage that controls the gain-switching mechanism. As temperature changes, the feedback ensures the breakpoint remains stable, maintaining consistent gain transition points despite thermal drift. This feedback loop adds temperature compensation without requiring complex external control circuits.
Solution Approach 2:
The amplifier circuit uses its own temperature characteristics to compensate for thermal drift. The temperature sensing element, which is part of the amplifier circuit itself, generates a voltage that automatically adjusts the breakpoint. This self-service approach allows the circuit to compensate for its own temperature-induced variations without external intervention, maintaining gain stability while keeping the circuit relatively simple.
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 stable and adaptive gain settings that prevent amplifier saturation and maintain consistent performance across varying temperatures, ensuring accurate flame detection.
Implementation Method 1
a thermally variable element connected to the switch, the thermally variable element configured to generate a compensation voltage to maintain the breakpoint in response to varying temperature of the switch
Data Source
AI summary
An amplifier assembly (100) includes an amplifier (102) having an input terminal, an output terminal and a feedback terminal; a first feedback path connecting the output terminal to the feedback terminal; a second feedback path connecting the output terminal to the feedback terminal; a switch (124) positioned in the second feedback path, the switch (124) opening or closing in response to a voltage at the output terminal relative to a breakpoint, when the switch (124) is open, the amplifier assembly (100) has a first gain and when the switch (124) is closed, the amplifier assembly (100) has a second gain; and a thermally variable element (152) connected to the switch (124), the thermally variable element (152) configured to generate a compensation voltage to maintain the breakpoint in response to varying temperature of the switch (152).