和差压变送器。 Transmitters are roughly divided into pressure transmitters and differential pressure transmitters. Transmitters are commonly used to measure pressure, differential pressure, vacuum, level, flow, and density. Pressure transmitter, in addition to measuring pressure, it can also measure the liquid level in the device. In addition to measuring the differential pressure of two measured pressures, the differential pressure transmitter can also measure flow with various throttling elements. It can directly measure the liquid level of a pressure vessel and the pressure level of a normal pressure vessel, as well as the pressure and Negative pressure.
的选用上主要依据：以被测介质的性质指标为准，以节约资金、便于安装和维护为参考。 The main basis for the selection of pressure transmitters is based on the property index of the measured medium, with reference to saving money and facilitating installation and maintenance. When selecting the type, it is necessary to consider the corrosion of the capsule metal by its medium, and the material of the capsule must be selected, otherwise the outer diaphragm will be corroded in a short time after use, so the choice of material is very important. The material of the transmitter's capsule is ordinary stainless steel, 304 stainless steel, 316L stainless steel, tantalum capsule and so on. When selecting the type, the temperature of the measured medium should be considered. If the temperature is generally 200 ° C ~ 400 ° C, a high temperature type should be selected, otherwise the silicone oil will generate vapor expansion and make the measurement inaccurate. In the selection, the working pressure level of the equipment must be considered, and the pressure level of the transmitter must be consistent with the application. From an economic point of view, the material of the outer membrane box and the inserted part is more suitable. The isolation type pressure transmitter is best selected with a screw connection, which saves money and is convenient to install. For the selection of ordinary pressure and differential pressure transmitters, the corrosivity of the measured medium must also be considered, but the temperature of the medium used can be ignored, because ordinary pressure changes are induced into the table, and the long-term operating temperature is normal temperature. However, the maintenance amount of the ordinary type is larger than that of the isolated type. The first is the issue of thermal insulation. In sub-zero winters in the north, the pressure guiding tube will freeze, and the transmitter will not work or even be damaged. This requires additional heat tracing and insulation boxes.
时，只要不是易结晶介质都可以采用普通型变送器，而且对于低压易结晶介质也可以加吹扫介质来间接测量(只要工艺允许用吹扫液或气)，应用普通型变送器就是要求维护人员多进行定时检查，包括各种导压管是否泄漏、吹扫介质是否正常、保温是否良好等，只要维护好，大量使用普通型变送器一次性投资会节约很多。 From an economic point of view, when a pressure transmitter is selected, as long as it is not a crystalline medium, a common transmitter can be used, and for low-pressure crystalline medium, a purge medium can be added to measure indirectly (as long as the process allows a purge liquid Or gas), the application of ordinary transmitters requires maintenance personnel to perform more regular inspections, including whether various pressure pipes are leaking, whether the purge medium is normal, whether the insulation is good, etc. As long as the maintenance is good, a large number of ordinary transmitters are used A one-time investment will save a lot. From the perspective of selecting the measurement range of the transmitter, the general transmitter has a certain range of adjustable range. It is best to set the range of use to 1/4 to 3/4 of its range, so that the accuracy will be guaranteed. It is even more important for differential pressure transmitters. In practice, some applications (liquid level measurement) require the measurement range of the transmitter to be migrated. The measurement range and the amount of migration are calculated according to the installation location on the site. The migration has positive and negative migration.