1, according to the measurement range, the required accuracy and measurement function to choose.

2, measuring instruments in the face of the environment, such as petrochemical industrial environment, there are flammable (toxic) and the presence of explosive hazardous atmosphere, there is a higher ambient temperature, etc..

3, the physical and chemical properties of the measured medium and the state, such as strong acid, strong alkali, viscous, easy solidification crystallization and gasification conditions.

4, changes in operating conditions, such as medium temperature, pressure, concentration changes. Sometimes it is necessary to take into account the changes in the concentration and density of the gas and liquid phases from driving to the normal production.

5, the object of the container structure, shape, size, the equipment inside the container accessories and all kinds of import and export pipe mouth to consider, such as towers, solution tank, reactor, boiler drum, vertical tank, spherical tank, etc..

6, other requirements, such as environmental protection and health requirements.

7, the selection of engineering instruments must have a unified consideration, as far as possible to reduce the variety of specifications, reduce spare parts, in order to facilitate management.

8, according to the specific requirements of the process patent.

9, according to the actual process.

A. consider which type of device the device is. Such as tank, tank type, the smaller the volume of the tank, the measurement range will not be too large; tank volume is larger, the measurement range may be larger.

B. depends on the physical and chemical properties and cleanliness of the medium, the first choice of the conventional differential pressure transmitter and float level transmitter, but also on the part of the contact media material selection.

C. for some of the suspension, foam and other media can be used single flange differential pressure transmitter. A new type of double flange differential pressure transmitter, which is easy to precipitate and crystallize.

D. for the high viscosity of the liquid level of the medium and high pressure equipment level, because the equipment can not be opened, can choose to use the radiation level meter to measure.

E. in addition to the measurement methods and technical issues, as well as investment instruments. To sum up, the transmitter selection, technically feasible, economically reasonable, convenient management.