How To Quickly Select A Model Of Rosemount Pressure Transmitter

Pressure transmitter is a kind of equipment that converts pressure into pneumatic signals or electric signals for control and remote transmission, it is the most commonly used sensor in industrial practice, and it is widely used in various industrial automatic control environments. Pressure is a very important parameter, and pressure, temperature, and flow are called the three major elements of industrial automation control. Therefore, the selection of the pressure transmitter is particularly important.

The most important parameters of the pressure transmitter: measuring range, measuring medium, wetted material, accuracy level, procurement cost, etc. will be considered as parameters for customer selection.

Before selecting the type, determine the type of pressure transmitter that the customer wants, whether it is threaded or flanged.

Now analyze the following selection parameters:

The range of the transmitter generally has a certain range of adjustable, and it is best to set the range of the transmitter to 1/4~3/4 of its range, so that the accuracy will be guaranteed. Generally, the pressure transmitter has a range ratio of 100:1, and when selecting the model, keep in mind that the maximum capacity should be higher than the limited minimum range (as shown in the figure below). In practice, there are applications where the measuring range of the transmitter needs to be migrated, in which case the measurement range and amount of migration need to be calculated according to the installation location in the field, and then the positive or negative migration is carried out. If the customer has a small measuring range, it is recommended to use the flange connection type.

 

In some cases, the measuring medium is corrosive, and it is necessary to use materials compatible with the measuring medium or to carry out special processes to ensure that the transmitter is not damaged. If the measurement is a relatively clean fluid, such as water, the standard 316L stainless steel diaphragm is directly used; if the measured medium is high viscosity and easy to crystallize and strong corrosion, the diaphragm must be carefully selected, such as caustic soda, then it is best to use Hastelloy alloy diaphragm, and the medium is seawater, it is best to use tantalum diaphragm.

Referring to the measuring medium, the corrosiveness of the medium of the transmitter to the metal of the diaphragm box should be considered when selecting the model, and some special media should select the appropriate diaphragm according to the working conditions, which can effectively prevent the contact between the medium and the pressure transmitter in the wetted part, so as to protect the pressure transmitter and prolong the service life; otherwise, the diaphragm will be corroded in a short time after use.

Accuracy level refers to meet certain measurement requirements, so that the error is kept within the specified limit of the measuring instrument, the level, the smaller the reference error, the higher the accuracy of the instrument, and the reference error is related to the range of the instrument, so when using the same precision of the instrument, often take the compression range to reduce the measurement error. The reference accuracy is as follows:

Due to the needs of various acquisitions, there are 4-20MA and HART protocols on the market, which is also the most commonly used protocol, and there are also F OUNDATION ™ fieldbus protocols, PROFIBUS ® PA protocols, etc., the quotations of each protocol are different, and they can be selected according to the requirements of the site.

The temperature of the measuring medium should be within the operating temperature range of the transmitter, which is determined by the process filling liquid of the pressure transmitter, generally silicone oil silicone oil fills the sensor -40~121°C, and the inert liquid fills the sensor temperature is: -30 to 121°C (-22 to 250°F). In the production process of pressure transmitters, the temperature effects will be measured and compensated to ensure that the measurement errors caused by the influence of temperature are within the range required by the accuracy level. In the case of high temperature, you can consider choosing a high-temperature pressure transmitter or installing condenser pipes, radiators and other auxiliary cooling measures. The ambient temperature difference of every 28°C (50°F) will affect the long-term stability of the transmitter. Continued exposure to extreme ambient temperatures of -40°C or 85°C (-40°F or 185°F) may reduce transmitter life by nearly 20%. If the storage temperature is higher than 85°C, the sensor should be adjusted prior to installation.

After determining the above parameters, it is necessary to confirm the process connection interface of the pressure transmitter, the pressure transmitter is generally based on 1/2-14NPT female thread as the standard, if you want other sizes of interfaces, such as M20*1.5 process connection, you can configure a process adapter. If it is used in special occasions, such as natural gas or oil, it is flammable and explosive, etc., and explosion-proof and protection level should also be considered. Other options can be selected according to the requirements of the site, such as whether to bracket B4, whether to display the meter head M5, or whether to protect the lightning/surge T1 code.

PRESSURE TRANSMITTER, MEDIUM: WATER, ROOM TEMPERATURE, RANGE 0-1.6MPA, CALIBRATION CERTIFICATE REQUIRED, SIL2 CERTIFICATION.

The selection is: 

3051TG3A2B21AB4M5Q4QTHR5