The Development Of A Testing System For The Inner Communication Box Based On Virtual Instrument

The research of virtual instrumental test system for Inner Communication Box is introduced in this paper. The system is designed using Single-Chip Microcomputer and virtual instrumental technology with the idea of modularization, integration and virtualization. It has been used in the periodic examination and malfunction diagnostication of helicopter's Inner Communication Box. The system is composed of hardware plat and software. The hardware plat includes digital low-frequency sine-wave signal generator, data collection and storage module, and load automatic switch module, which not only achieves the generation of standard input signal for Inner Communication Box, but also conduct the sampling, analog-to-digital conversion, data storage of output signal and the automatic load switch. The software accomplishes function of the test system by processing the sample data and calculating the eigenvalue of measured signal in real-time. The digital signal generator is constitutive of Single-Chip Microcomputer and accurate digital-to-analog converter and is based on the DDS technology. It has the characteristic of high frequency discriminability, good frequency stability and low distortion. It also has power amplification circuit and amplitude transform circuit, which enable it of giving several different amplitude and good power capacity signal. With proper software, the signal generator can be used as random wave signal generator. The data collection and storage module is finished with data collection board with PCI data bus, which can communicate with computer in high speed and improve system's real-time trait. Harmonic analysis via FFT algorithm is used in data processing. Soft-frequency measurement and interpolating secondary sampling algorithm for approximately synchronous sampling is proposed in order to reduce the frequency spectrum leakage effect owing to asynchronous sampling, which ensure high testing precision as well as simplify the hardware structure. The testing system have achieved anticipative function and run stably.