Experimental Study On Range Ability Extension Of Differential Pressure Flow Meters

This paper analysis the reasons of the error of measurement under the condition of small flow, reveal differential pressure type flow measuring devices is the essence of the range of small differential pressure transmitter of the margin of error in small flow caused by the formation of the relative error is too large. One of reasonable assumption to solve the problem is:In the small flow to make the primary device output of the differential pressure corresponding transmitter output for larger values, the actual situation is, however, whether a device output differential pressure for any value, transmitter output current is proportional to the differential pressure into 0-20 mADC current, unless the output differential pressure into more measured, which convert primary devices output of differential pressure by multiple differential pressure transmitter according to section loaded with 4-20mA current respectively. This followed by outflow coefficient C must be calculated separately, industrial personal computer signal processing system according to select different outflow coefficient between differential pressure. Follow the idea, this paper proposed the solution:In terms of the second proposition of differential pressure flow measurement device as an example, first of all, according to the GB/T 2624.1-4-2006 " Circular cross section is measured with a differential pressure device with pipe fluid flow in pipes" " International standard ISO 5167-2 2nd edition. Measurement of fluid flow by means of pressure differential devices inserted in circular cross-section conduits running full", which gives the calculation method of design on the flow measurement device, design results include the largest flow qmax corresponding output maximum differential pressure of primary devices △pmax and minimum flow qmmin corresponding minimum differential pressure △pmin and outflow coefficient C, among them △pmin～△pmax is proportional to the converted into 0 to 20mA DC current signal by differential pressure transmitter DPI, differertial pressure between 0～△pmiin is proportional to the converted into 0 to 20mA DC current signal by differential pressure transmitter DP2. The outflow coefficient C小 corresponding The differential pressure between 0～△pmin output by the primary devices is obtained by the first kind of proposition solving method. Then, the solution on the premise of fully follow GB/T 2624.1-4-2006, the scope of the device degree is improved from 3:1 to 4:1 to 9:1 to 16:1. This paper also designs the experimental scheme, built the experimental apparatus and by way of experiments prove the validity and feasibility of the theory.