The Research Of Digital Pressure Measuring Instrument Based On SCM

Pressure is one of the important thermal parameters in the field of production and life,industrial sites, and scientific experiments that various gases, liquid pressure measurement ina wide range of applications. Therefore, the research and development digital pressuremeasuring instrument of high-performance for the promotion of the development ofinformation technology and automation technology， improve the performance of theequipment and the level of automation has significance that should not be underestimated.Pressure sensor of piezoresistive is widely used because of its high sensitivity, dynamicresponse, easy to miniaturization. The piezoresistive coefficient of silicon is a function oftemperature and so the thermal zero drift occur in pressure sensor of piezoresistive that is themain reason of causing measurement accuracy reducing. In this paper, temperaturecompensation of pressure sensor is achieved by using software algorithms, and themeasurement accuracy of the entire system is improved. Digital pressure measuringinstrument is designed with high precision，digital communications between the host and thepressure instrument, and anti-interference ability are concerned.First of all, the thesis analyzes the principle of the pressure sensor of piezoresistive, andthe main factors which affect the sensor temperature drifting. Neural network softwarecompensation model is established in the thesis, which is based on the pressure sensor in thework pressure corresponds to the voltage being measured, and volume resistance withtemperature change and the resulting voltage value. K-means and the method of least squaresare used to adjust the parameter of RBF neural network so that the network can betterapproximate to the system input-output model, thus reach the purpose of measurement datacompensation. Software compensation has the advantage of high precision, speed, goodstability, high reliability, which can improve pressure measurement accuracy. In this paper, the pressure measurement is instrument with data acquisition, digitalstorage, temperature compensation processing, digital communications, which can measurethe pressure accurately. The hardware includes five parts. The first one is input part, thephysical quantity is mainly converted into electrical signal, which mainly uses workingprinciple of Wheatstone bridge to collecting pressure signals. The second one is the A/Dconversion section that mainly uses the AD719for data conversion0. The third one isMSP430F5310microprocessor circuit, including the timing control and arithmetic. The fourthone is communication part,which can achieve the upper computer and PC digitalcommunications. The last one is power section where the±5V analog supply voltage and the±3.3V digital supply voltage output supplied. The software consists of two parts. One uses themodular design of the C language to complete the task activation, query, execution, triggeredinterrupts and data communications. The other is based on VB language achieves uppercomputer data display and reservation.