Automatic Test System Based On Virtual Instrument

The combination of computer technology and technology of test instruments results in the appearance of a new test instrument, virtual instruments (VI). The software strategy of VI is the developing direction of the third generation of automatic test system. Thanks to VI technology, the hardware and software resources can be shared, various automatic test systems can be built rapidly, and signal analysis, data processing and graphicalized display can be carried on conveniently. In the thesis, we study and analyze the system structure of VI, and classify it into four groups. And in according to practical requirements, we research deeply the automatic test system based on VI with PC-based DAQ (Data Acquisition). PC-based DAQ system consists of sensors, signal conditioning, data acquisition card, computer and software, etc. In order to meet the users?requirements, the hardware is modularized. In the signal conditioning circuit, variable-gain precision instrumentation amplifier; programmable lowpass filter and extended slots are designed. The multi-function data acquisition card, PLC-8 I 81-IG, is employed, with the sampling rate of 100KHz and resolution of 12-bit. And then the key technique needed by more higher sampling rate is studied and the solution is given. The software employs the hiberarchy and is divided into four layers, namely I/O interface driver, instruments driver, VI function layer and test manage layer. The automatic test system based on VI can accomplish the auto-test of temperature, pressure, flow rate and so on with one computer, which reduces the test cost, improves the test efficiency, enforces the system flexibility and facilitates the experiments.