Carbon Monoxide Sensor Functional Testing Circuit
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Solution Overview
Problem
Existing methods for testing the functionality of carbon monoxide sensors in gas warning devices and fire detectors are not precise and require complex circuitry, especially when dealing with issues like loose connections, electrolyte drying, or short-circuiting, which can lead to incorrect readings and device malfunction.
Innovation Solution
A method and circuit that measure the output signal decay after switching off the test voltage, using a clamping diode to maintain a fixed potential for one electrode and switching the other electrode to a higher potential for testing, allowing for comparison with reference values to detect errors such as missing or short-circuited sensors and electrolyte drying, without requiring additional voltage or complex switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing testing methods are used, then sensor functionality can be tested, but the circuit complexity increases and measurement precision decreases
Solution Approach 1:
The patent extracts the essential testing function by removing unnecessary circuit components. Instead of using complex symmetrical voltage sources and multi-pole switching, the invention uses a single-pole switch and asymmetrical voltage source to achieve the same capacitive charge reversal test, thereby simplifying the circuit while maintaining testing precision
Solution Approach 2:
The patent changes the voltage parameters from symmetrical ±15V to asymmetrical single-polarity voltages. By applying a test voltage that creates a potential difference between the reference electrode and working electrode, the system achieves the required capacitive charge reversal without needing complex symmetrical power supplies, thus reducing circuit complexity while preserving measurement accuracy
2Reliability
If symmetrical voltage supply and two-pole switching are used, then sensor testing can be performed, but the circuit becomes more complex
Solution Approach 1:
The patent removes the two-pole switching mechanism and replaces it with a single-pole switch. The switch connects either the test voltage source or the amplifier output to the working electrode, eliminating the need for complex multi-position switching while maintaining the ability to perform both normal measurement and functional testing
Solution Approach 2:
Instead of using symmetrical voltage switching to achieve the test, the patent inverts the approach by using asymmetrical voltage application. The test voltage is applied in a single polarity direction, and the functional test is achieved through the resulting capacitive charge reversal rather than through symmetrical voltage cycling
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
Provides a more precise and simplified functional testing of carbon monoxide sensors, capable of detecting errors and ensuring proper sensor operation without additional voltage requirements, suitable for integration into fire detectors and gas warning devices.
Implementation Method 1
The applied voltage produces salt ions through electrolytic decomposition
Implementation Method 2
the current which the sensor supplies to an external circuit after the test voltage has been switched off, analogous to a fuel cell, decays approximately in accordance with an e-function
Data Source
Figure 1~2
AI summary
The method involves connecting electrodes with a differential amplifier (DV) and measuring an output signal at a pre-determined time after switching off a testing voltage. Measured value is compared with a given minimum value and generates an error signal, if the measured value is less than the minimum value. An independent claim is also for a circuit for functional testing of electro-chemical, electrolyte containing gas sensor, particularly carbon monoxide sensor.