Select the type of first. Each type has a fixed direction of use. For example, in the pressure measurement of boiler, the pressure instrument that can measure large pressure data is mainly selected. Because the pressure generated by the boiler is relatively large, if an accident occurs, it will have a great impact. Therefore, the main indicator selected is the measurement range. In addition, observing the data displayed by the pressure instrument is an important reference coefficient, which plays a guiding role for the users (boilers and enterprises). By observing the coefficient, we can judge which aspects can be improved and which aspects need to be paid more attention.