The selection of pressure gauge should be based on the use of production process requirements, according to specific circumstances to do specific analysis. On the premise of meeting the technological requirements, it should be considered comprehensively based on the principle of economy, and generally how to determine and select the measuring range and precision grade of pressure gauge used in pump should be considered.

In order to ensure that the elastic element can work reliably within the safe range of elastic deformation when the pressure gauge used in pump is selected, there must be enough leeway according to the magnitude of the pressure measured and the speed of the pressure change, the upper limit of the pressure used gauge in pump should be above the maximum possible pressure in the process. According to“The technical regulation of automatic control design of chemical industry”, the maximum working pressure should not exceed 2/3 of the upper limit value when measuring the stable pressure, the maximum working pressure shall not exceed 1/2 of the upper limit of the measurement, and when measuring high pressure, the maximum working pressure shall not exceed 3/5 of the upper limit of the measurement. In general, the minimum measured pressure should not be less than 1/3 of the upper limit of instrument measurement. The linear relationship between the output and the input of the instrument can not be directly used as the measuring range after the upper and lower limits of the instrument are calculated according to the maximum and minimum values of the measured parameters.

According to the maximum absolute error and the maximum range of the selected instrument, the maximum reference error of the instrument is calculated, and the accuracy of the instrument is determined by the accuracy grade specified by the state. In general, the more precise the instrument selected, the more accurate and reliable the measurement results. But it can not be considered that the higher the accuracy of the selected instruments, the better because the more accurate instruments are generally more expensive, the more difficult to operate and maintain.