Pressure Data Acquisition System Based On USB Data Acquisition Card

Pressure value is an important parameter index in the field of industrial production and scientific research, modern management of industrial production need to provide real-time data collection and monitoring of pressure data. Data acquisition devices based on traditional bus restrict the development of inconvenient installation, which has low transferring rate and less mountable equipments and other issues. Because of the characteristics of USB bus in supporting plug-and-play, fast data transferring and high cost performance, a pressure data acquisition system based on USB data acquisition card which can solve the problems faced by the traditional bus, is presented in this paper.The features of USB bus are introduced the situation of the development of USB data acquisition devices at home and abroad are described. After a detailed description of relevant provisions of the USB protocol, in accordance with system performance, the overall program of pressure data acquisition system based on USB acquisition card are designed. The pressure signals of pressure transmitters are collected and the pressure datas are transferred by USB bus in this system which can achieve real-time dynamic pressure data acquisition.The minimum system of PIC16F886 microcontroller, USB interface circuit and serial debugging circuit are included in the hardware design of the system. The USB interface chip used in the USB interface circuit is PDIUSBD12. The pressure signals of pressure transmitters are collected by 10 bit internal A/D module of PIC16F886. The pressure datas are transferred to PC via the USB interface. The information of the USB enumeration process is printed out by the debugging assistant through the serial debugging circuit. MCU firmware programs for USB, USB device driver programs and acquisition applications programs are included in the software design of the system. The MCU firmware programs are the bottom part of the software design of the system, including the initialization procedures, USB enumeration process procedures and pressure data acquisition programs. The USB enumeration procedures are used to complete the identification of PC on USB acquisition card. The USB device driver program provide an interface that the acquisition application can access the USB data acquisition card. And the acquisition application programs provide an interface of pressure data acquisition system, dynamically displaying the pressure datas collected. The input voltage range of the system is 0 to 5V, the range of the pressure datas collected is 0 to 1Mpa and the allowable error range of the pressure values is ±0.5%. The test results of the system show that the system can achieve functions of pressure data acquisition and the error range of the pressure values is ±0.5%.The pressure datas are collected and transferred to PC to display through the USB bus in the system, which has the advantages of supporting hot-plugging and are easy to use.