The Application Of Virtual Instrument In Engine

Today, with the development of science and technology, the requirement on measurement technology is getting more and more important. The application of electronic measurement technology has extended to more fields than before. Due to limited functions and big size, traditional electronic measuring equipments are no longer suitable to common purposes.With the development of computer science, more and more measure functions that used to be acquired by hardware can be realized through software. So the intimate combination between computer science and measurement technology brings a new type of instrument, which is virtual instrument. The software strategy of VI is the developing trend of the third generation of automatic test system. The emergence of virtual instrument makes the measurement system become more flexible and more integrated which will help users to construct complicated measurement system. The testing system can be extended, amended and upgraded without changing the hardwares or only changing a little. The whole system is flexible, low wasting and high efficient.In this paper the concept of virtual instruments, the composition of LabView and how they have been applied in cars and engines in our country and in foreign countries were summaried, and introduces the basic theory of data acquisition, including signal classification, signal sampling principle, the data acquisition process and two sample patteras(real time sampling and equivalent time sampling). Then the paper discusses the data acquisition system. It includes the data acquisition system's form, structure and hardware design. This paper expounds in details the structure, principles, signal's characteristic of the sensors using on the EFI engine. According to this, it introduces the method of the signal acquired of sensor, including input protection circuit, low pass filter circuit, high pass filter circuit, output protection circuit, power circuit, system antijamming electric circuit. According to the item actual situation and economical suitable principle, the selection data acquisition card is AC6621. AC6621 is a 12 bit data acquisition card. It has 16 group analog inputs and support namely inserts, namely uses and real-time gathering. At last we complete the design of managed-circuits ahead of the sensor's signal acquired. By using of the data acquired card and the LabView of the National Instruments Co, it achieves acquired and display of wave-forms of EFI engine's sensors. The test system is developed under 2000 environments Windows, and has compiled data acquisition, processing and memory module in terms of the subject content, and compiled program has realized non- NI's drive hardware by means of the program of hardware control, the data sampling program is compiled according to the actual use condition.The data acquisition system designed by Labview has stable performance, high accuracy and a friendly interface. And the users operate conveniently. It fully embodies the advantages of virtual instrument.