An online non-contact fault detection technique of LED chips is presented based on the photovoltaic effect in diodes. By
observing the current in the bonding lead frame of a LED chip, which is induced by illuminating the chip, the LED chip
and its electric connection with the lead frame during packaging are checked. The fault detection principle is described
in detail in this paper. Red, yellow and green LED chips are tested in the experiment. The experimental results show that
the method can be easily realized, and thus can be used for online fault detection of LED chips in packaging.
For a novel method of characterize stress of concrete structure by measuring embedded ceramic disc, we establish a model of a piezoelectric ceramic disc under the situation mentioned above, and then the relationships between the complex coefficients and the equivalent circuit parameters are obtained. Derived from the piezoelectric equations with complex coefficients, the dissipation factors are related to the equivalent circuit parameters. Experimental results show that there are linear relationships between most of the equivalent parameters and the loadings applied on the concrete structure. The mechanisms of the results are discussed by use of the theory of moving domain walls and point defects. The results also support the method of estimating the stress by measuring the value of equivalent circuit parameters of piezoelectric ceramic.
This paper introduces a novel coding resonant SAW passive wireless sensing system. A composite sensor structure with a resonator, a delay line and matching circuit is designed and the sensor system is constructed. It analyses sensor impulse response and response to sinusoidal burst signal input. The frequency of the response signal is related to sensing parameter. The delay time of the response signal is used to encode sensor elements. The duration of input signal has a significant effect to waveform and amplitude of response. An optimal duration of exciting burst signal can be selected. Because the composite structure can combine both sensitivity of high Q SAW resonator and massive coding ability of delay line, this coding resonant sensor can be used in long distance and large-scale distributed measurement as well.
The paper discusses the instrumentation of leak detection and location on underground water supply pipelines based on adaptive algorithms. The equipment is designed to be self-contained and portably mobile with sensors, signal conditioning and data acquisition units and a laptop PC operating signal processing, information analysis and instrument control. The vibrational acoustic signals collected on tubular pipelines are used for pinpointing a leak or leaks in buried pipelines. Because of the complexity and the heavy corruption with ambient noises, it is essential to use an appropriate signal model and the scheme of analysis and synthesis in order to extract leak signatures and specify leak locations. In addition, the features of vibrational acoustic signals vary with the materials, the sizes and the inbuilt conditions of tubular pipes. It is difficult to pre-determine the knowledge of signals, such as the spectral knowledge. Here, an adaptive detection and estimation strategy is proposed based on LMS adaptive filtering and modified Wavelet denoising. The availability for leak detection and pinpointing estimation is automatically analyzed by the signal processing procedure without any prerequisite on signals and the procedure may adaptively find the way to get better estimate.
In this paper, principle and system fabrication for concrete health monitoring based on embedded distributed piezoelectric sensing network are presented. Piezoelectric circular plates are embedded in concrete and the electrodes of the piezoelectric plates are wired together according to some order to form a passive stress-sensory network. For a passive piezoelectric sensory device only senses dynamic physical observables, to test the structural state in concrete, which is usually determined by static parameters, the structure is mechanically or acoustically excited to cause impact wave or acoustic wave propagation within concrete. The state parameters will modulate the caused wave and the modulated wave propagation is sensed by the piezoelectric distributed sensing network embedded in concrete. As the piezoelectric distributed sensing network can work without a power supply and outputs of all sensory elements in the network are passed through limited signal channels by addressing them, it is feasible to build up a sensing network distributed over a range of the concrete structure in large dimensions. Compared with the ultrasonic testing technique of concrete, the concrete structural health monitoring technique based on the passive piezoelectric distributed sensing network will exactly determine the structural state by capturing parameters at multiple points and avoid the uncertainty in ultrasonic testing caused by uncertain coupling condition of transmitters and receivers. The varied phase and frequency in sensing output, compared with the exciting signal, reflect the state in concrete. It is required to address one element in the sensing network in a sustained duration to get continuous output for analysis. Here, readout method of continuous output for each element in the sensing network is described in detail.
This paper introduces a new principle of no-scanning tactile resonant sensor array. All sensory elements in this sensor array form independent oscillators which ave different resonant frequency because of the fabrication of different thickness on electrodes and the special resonant circuits connected with them. Once a pressure or force is applied on the surface of piezoelectric plane, the resonant frequencies in the application area will change along with diversity of the applied pressure or force quickly. The resonant frequencies in the application area will change along with diversity of the applied pressure or force quickly. The resonant frequencies in the application area will change along with diversity of the applied pressure or force quickly. The resonant signals in all sensor elements are taken out from parallel output lines continuously. Since only the data which have designated meaning are processed, thus the data are compressed and a real-time sensing system may be obtained. The output of the array is quasidigital signal and can be processed in a digital way easily, its antijam is well. The sensor array contains two functional units: the sensory unit, the signal generating and processing unit, which can be integrated or be wired together easily. So the sensor array may be feasible for both large dimensions sensing and perception of fine object.
This paper presents a technology to design and fabricate sensor array using separate sensors or individual sensory devices for distributed sensing in smart structural systems. It reports in detail on a non-integrated piezoelectric passive sensor array, which is constructed of separate piezoelectric devices along the spatial distribution of the measurand. As piezoelectric sensory devices can be used as self-generating sensors, the piezoelectric sensory array will sense passively without power supply. The sensor array consists of an X-Y matrix of m X n piezoelectric elements accompanied by diodes. The space of sensory elements ranges from 0.1 meter to several meters and the external connections of the sensor array are m + n. The array is addressed as a memory and the sampling signals of analog sensing outputs of the elements can be taken out as a serial wave form to a single output port of the array. It is also possible to read the analogy output of one element by sustaining addressing of it. A description of the arrangement and control of the array is presented, in addition, the electric response to mechanical input of piezoelectric sensory element is also analyzed to determinate the design of feasible preconditioning circuits for the sensor array.
This paper presents the principle to enhance the spatial 2D resolution of spatial 2D resolution and the possibility of available limitation of maximum resolution. The paper also reports on image signal processing for 2D high definition pictures and the hanging-up piezoelectric bimorph construction designed to improve both horizontal and vertical resolution respectively by one time. The regenerated signal can be compatible with current TV mode.
This Paper introduces a self—adaptive and training concepts to improve the speed of slow visual inspection system to near one order of magnitude. In this scheme, the system is designed to work in three modes : Mode I (fast inspecti on) ,Mode I I (slow inspecti on) and Mode I I I . The first two modes automatical ly shi ft to each other depending on the condi tion of rol 1 er surface . Mode I I I is for automatic optimal binary threshold selection of defect image, in which a bifurcated searching algorithm is employed. At last, an algorithm for dot group pattern recognition of roller defects is discussed.