Study Of Quasi-static Absolute Calibration Method Based On Pressure Electric Measuring System

Piezoelectric pressure measuring systems which are widely used for dynamic pressure measurement have advantages of high inherent frequency and good dynamic performance.Due to its poor low frequency characteristics,the drift of response is caused and charge of sensor leak out inevitably if the static calibration is used to make calibration.As a result,the accuracy of sensor parameters we gained is not high.In addition,the long loading-time will bring loss to expensive sensors.Furthermore,the dynamic calibration such as using shock tube can not satisfy low frequency detection and high-pressure sensor calibration because of its short duration of step signal and low amplitude of pressure.Therefore,quasi-static calibration which uses drop hammer device is proposed to improve calibration accuracy.At present,there are two main quasi-static calibration methods,inter-comparison and absolute type,which are commonly used.For the former,the fact that the standard pressure monitoring system is made up of multichannel high precision pressure measurements means it is high cost even if its high calibration accuracy.For these reasons above,the quasi-static absolute calibration that force detects pressure is studied in the essay.Quasi-static absolute calibration and its superiority are introduced in the essay.The dynamic theory model in which force detects pressure is established and its feasibility is proved.The high accuracy force sensor applied to drop hammer device is designed according to accuracy requirement proposed.It can avoid pre-tightening force,decrease inertial force and eliminate influence of hammer quality on the nature frequency of sensors.And the fact that static and dynamic characteristics satisfy the requirement of quasi-static calibration is proved by theoretical calculation,simulation analysis and experimental study.The computing method for effective area of pistons is studied and its error is analyzed.Through the experiments,it is known that the uncertainty is 0.25 percent.That is to say,the pressure in cylinder can be calculated according to the area of pistons and force measured by sensors.The effective bandwidth of ideal semi-sine signals and pressure signals obtained by standard pressure monitoring system are analyzed and the influence of sensitivity under the inspiration of different pulse width is studied.The signals with 4ms pulse width are chosen as excitation signals.Taking SYC-8000-1566 for example,the corresponding relation between force and pressure and quasi-static calibration models can be established according to carry out experiments with the state of different pressure range and pulse width.Furthermore,the computational method of effective area for precision piston component and its error are also studied.The calculation of working characteristic parameters,influencing factors and computational methods for uncertainty will be discussed based on differences between quasi-static and static calibration.The evaluation model of measurement uncertainty for pressure is established.The research provides theoretical basis and experimental support to study the quasi-static absolute calibration,and it is of great significance.