In Situ Sensor Testing via Signal Injection
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Solution Overview
Problem
Existing methods for testing and characterizing sensor and transducer systems are incomplete, require additional hardware and cabling, and do not effectively test the preamplifier in situ, limiting their reliability and accuracy.
Innovation Solution
A method and apparatus that inject a test signal into the sensor-conditioning preamplifier to analyze the electrical characteristics of the sensor and amplifier, using current modulation on the output terminal from an external control source, allowing for remote testing of transducer arrays without extra accessories or cabling, and enabling detailed characterization of capacitive, magneto-restrictive, and piezo-electric sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a piezo-electric transducer is exited from a generator and the resulting ringing is analyzed, then the transducer can be tested, but the characterisation of the transducer system is not complete and control systems need to be installed separately
Solution Approach 1:
The patent combines the transducer, preamplifier, and test functions into a single integrated system. The secondary transducer is built together with the primary transducer, and the preamplifier is integrated into the same housing, eliminating the need for separate control systems and reducing overall device complexity while maintaining testing reliability
Solution Approach 2:
The integrated system performs multiple functions: the secondary transducer serves as both a sensor and a test signal generator, the preamplifier amplifies both operational signals and test responses, and the system can characterize both primary and secondary transducers using the same hardware infrastructure
2Reliability
If a primary and secondary transducer are built together with the secondary energized to generate mechanical excitation, then the transducer can be tested, but considerably more special hardware and twice the cabling of a conventional circuit is required
Solution Approach 1:
The patent merges the test signal generation and transduction functions into a single secondary transducer element. The secondary transducer is piezoelectrically coupled to the primary transducer, allowing mechanical excitation to be generated and sensed through the same physical coupling mechanism used in normal operation, thereby eliminating the need for separate test hardware and reducing cabling requirements
Solution Approach 2:
The secondary transducer serves itself by generating the test excitation signal through its own piezoelectric properties when energized electrically, and simultaneously serves as the sensing element that detects the mechanical response. This self-service capability eliminates the need for external test equipment and complex cabling arrangements
3Reliability
If the preamplifier is disconnected for analysis of the transducer, then the transducer can be tested, but the preamplifier in situ is not under test and implementation and control remains an issue
Solution Approach 1:
The patent merges the transducer and preamplifier into a single integrated assembly where the preamplifier is built into the same housing as the transducer elements. This integration allows the complete system to be tested in situ without disconnection, enabling simultaneous characterization of both the transducer and preamplifier while maintaining their operational connection
Solution Approach 2:
The integrated system allows the preamplifier to serve dual functions: amplifying operational sensor signals during normal use and amplifying test response signals during characterization. The same preamplifier circuitry handles both operational and test modes, enabling complete system testing without requiring separate test amplifiers or disconnection
4Measurement precision
If a test signal is injected through a capacitor into the preamplifier junction point, then capacitive voltage sensors can be tested, but a separate connection point with very high quality cabling in addition to normal signal cabling is required
Solution Approach 1:
The patent combines the test signal injection path with the existing signal cabling by coupling the secondary transducer directly to the primary transducer through their mechanical mounting. The test signal travels through the same physical pathway as operational signals, eliminating the need for separate high-quality test cabling and additional connection points
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 a more integrated, universal, and reliable testing of complete sensor and amplifier systems with improved accuracy and reduced complexity, allowing for the measurement of impedance, resonance, and cable characteristics without additional wiring, enhancing signal-to-noise ratio and phase information.
Implementation Method 1
The injection takes place by modulation of the current on the output terminal of a transducer by a current originating from an external control source and from an external test generator
Implementation Method 2
a piezo-electric transducer is exited from a generator and the resulting ringing of the transducer is analyzed
Implementation Method 3
the resulting ringing of the transducer is analyzed
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The present invention provides a method and an apparatus for in situ test of transducers comprising sensing elements and associated conditioning preamplifiers. The invention makes it possible to evaluate the characteristics of the complete transducer by means of higher integration of the transducer circuitry. Tests can be performed from a remote central location without additional wiring and while the transducer is in operating environment., Testing is performed by superposing test signals and test sequence control signals on the wiring for the transducer output signal, hereby offering flexibility without sacrificing simplicity. Test signalling is by additional circuitry in the transducer interpreted and routed to the input of the conditioning preamplifier based on signalling from the remote test generator, and the signals engendered from the test signals can be analyzed from a remote analyzing system for complete qualifications of the transducer under test.