Pressure transmitter selection

The pressure transmitter is widely used in various industrial automation environments involving water conservancy and hydropower, with its simple structure, robustness, high durability, high precision and good linearity characteristics. Railway transportation, intelligent buildings, production automation, aerospace, military, petrochemical, oil wells, electric power, ships, machine tools, pipelines and many other industries, the following briefly introduces some common transmitter selection and troubleshooting methods.

one. Transmitter selection

The selection of the transmitter should mainly consider its pressure range, pressure medium, precision grade, temperature range, signal output, excitation voltage, interchangeability, explosion protection and protection class.

1, pressure range:

To confirm the maximum value of the measurement pressure in the system, it is usually necessary to select a transmitter with a pressure range that is about 1.5 times larger than the maximum value. Therefore, when selecting the transmitter, it is necessary to fully consider the pressure range, accuracy and stability.

2, pressure medium:

What we need to consider is the medium that the pressure transmitter measures. Viscous liquids and mud will block the pressure interface. The solvent or corrosive substances will not destroy the materials that are directly contacted by these mediums. These factors will determine whether to select the direct isolation membrane and the material directly in contact with the medium. The material of the contact pressure medium part of the general pressure transmitter is made of 316 stainless steel. If your medium is not corrosive to 316 stainless steel, then basically all pressure transmitters are suitable for your measurement of medium pressure. If your The medium is corrosive to 316 stainless steel. Then we must use a chemical seal. This not only can measure the pressure of the medium, but also can effectively prevent the medium from contacting the wetted part of the pressure transmitter, thus protecting the pressure from changing. The transmitter extends the life of the pressure transmitter.

3, accuracy level:

The accuracy, nonlinearity, hysteresis, non-repeatability of electromechanical business network, temperature, zero-offset calibration, and temperature effects are all decisive. But mainly by non-linear, hysteresis, non-repeating, the higher the precision, the higher the price.

4, temperature range:

A transmitter typically calibrates two temperature ranges, the normal operating temperature range and the temperature compensated range.

The normal operating temperature range refers to the temperature range when the transmitter is not destroyed in the working state. When the temperature is exceeded, the application performance index may not be achieved.

The temperature compensation range is a typical range that is smaller than the operating temperature range. Working within this range, the transmitter will definitely reach its proper performance. Temperature changes affect its output in two ways. One is zero drift; the other is affecting full-scale output. Eg +/-X%/°C of full scale, +/-X%/°C of reading, +/-X% of full scale when out of temperature range, +/-X% of reading when within temperature compensation range , without these parameters leads to uncertainty in use.

5, signal output:

The pressure transmitter output signal has many kinds, mainly has 4...20mA, 0...20mA, 0...10V, 0...5V and so on, but more commonly used is 4...20mA and 0...10V two kinds, among these output signals, only 4...20mA is two-wire system, Others are three-wire system

The signal output mainly has mV, V, mA and frequency output digital output. The choice of output depends on various factors in the production process of the enterprise, such as the distance between the transmitter and the system controller or display, whether there is an electronic interference signal, whether it is transmitted in Greater noise and vibration. For OEM devices that have a short distance between the transmitter and the controller, the most economical and effective solution is to use a mA output transmitter. If it is necessary to amplify the output signal, it is best to use a transmitter with built-in amplification. For long-distance transmission or presence of strong electronic interference signals, it is best to use a mA-level output or a frequency output.

If you want to select mA or frequency output in an environment with high RFI or EMI specifications, consider special protection or filters.

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