Differential pressure flow transmitter is one of the combination instruments with pneumatic instrument and electrical unit and usually used with standard orifice plate. It is an important instrument widely used by the industrial enterprises for energy measurement and trading settlement. Generally, the flow transmitter is calibrated by maintenance and verification personnel on site. During calibration, the flow value will be converted into differential pressure value. To calibrate a differential pressure flow transmitter, complicated calculation is required before the standard signal input values at each point are determined. This may lead to more workloads on the maintenance and verification personnel on site and likely occurrence of errors. Besides, this makes it difficult to increase the efficiency of calibrating centralized control measurement instruments. In practice, the author finds a simple method to calculate the standard input calibration value of flow transmitter based on the design value of the instrument scale and the calculated value of maximum differential pressure. This method is applicable to the calculation of the input calibration value of the differential flow transmitters equipped with the standard orifice plate flowmeter for all other countries. It is hereby recommended.

The secant method for solving nonlinear equation is used to calculate the unknown parameters of pressure differential devices. It is shown that the important advantages are needing only unique iterative equation without considering different unknows, easily to obtain convergent solutions without to calculate the derivatives which can not be finished for complex nonlinear equation, and yielding high precision solutions. The formulae of initial values and the example for showing the results are presented, the results are excellent.

Based on the operating principles of elbow flow meters, this paper states that the core of standardization of elbow flow meters is the standardization of hardware's structural dimension. On condition that the elbow flow meters' feature structural dimension parameters R/D are strictly kept the same, the flow coefficients of elbow flow meters with the same conduit diameter determined by experiments have good consistency. Comparison of the experimental results of several elbow flow meters with different conduit diameters shows that the flow coefficient increases as the conduit diameter decreases. The experiments and comparisons prove that the determination of hardware's structural dimension is essential in the standardization of elbow flow meters.

Flow meter is calibrated by flow standard facilities by master meter method, is becoming trend of flow meter calibration method. The research of the calibration method and evaluation of uncertainty are focused in science field. This paper analyzes the influence facts of the process of calibration of flow meter by standard meter method around the calibration of turbine flow meter by standard turbine flow meter, establishes the mathematical model and give out the evaluation method and program of calibration uncertainty.The method was verified by test.

This paper introduced a piston-type dynamic flow standard device and the method for applying step flow rate to the turbine flowmeter. Setting up math model of the turbine flowmeter and analyzing the dynamic parameter (step response time constant) and things that affect dynamic performance of the flowmeter in theory. Acquiring the step flow response data of the flowmeter by experiment and calculating the time constant. The reality result is consistent with theory.