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Pressure detection and transmission analysis (V)

the structure of pneumatic pressure transmitter is the same as that of pneumatic differential pressure transmitter except for the measurement part. The measuring force generated by the pressure sensing element of the measuring part of the pressure transmitter is about 50~100n, and the maximum is not more than 150n. According to this requirement, the selection of sensitive elements is based on the understanding of the bellows made by everyone with confidence, and its structural principle is shown in the figure. When the measured pressure P enters the measuring chamber, it is converted into measuring force through the measuring bellows, which is used on the main lever through the push rod and transmitted to the pneumatic conversion part. The sensing element for measuring medium and high pressure (2.5~10mpa, 10~60 MPa) generally adopts the wrapped tube made of chrome vanadium steel. Its measurement principle is to use the radial component force generated at the end of the wrapped tube to act on the lower end of the main lever 3 through the push rod 2, driving the pneumatic conversion part of the transmitter to act The figure shows the structural principle of the measuring part of the medium and high pressure pressure transmitter

the figure shows the schematic diagram of a large number of leaf springs on the rail of the great artery of the junction of the measurement part of the absolute pressure transmitter, which is mainly composed of two stainless steel bellows Bellows 1 is a measuring bellows, and bellows 2 is a compensation bellows, which is vacuumed The effective area of the two bellows is equal, that is, a1=a2. When the measured pressure P1 enters the measured bellows 1, the measured bellows generates a thrust under the differential pressure between the measured pressure P1 and the atmospheric pressure P2:

F1 = p1a1-p2a1

because the compensation bellows has been vacuumed, it is only affected by the surrounding atmospheric pressure P2, The compression force generated by it is:


then the resultant force (i.e. measuring force) acting on the main lever 4 is:


from the above formula, the measuring force F is directly proportional to the measured pressure P1, and has nothing to do with the atmospheric pressure surrounding the two 3D printers P2, so the measured pressure is absolute pressure, no matter how the atmospheric pressure changes, The force produced by the action of atmospheric pressure on bellows 1 and bellows 2 always counteracts each other, which compensates the measurement error caused by the change of atmospheric pressure. Its measurement range is about 1.4kpa at least and up to 220kpa at most

note: those with * are corrosion-resistant (the part in contact with the medium is general stainless steel)

Author: Zhao Junjie Nanjing Wanda Group should ensure that there is no impact and power loss in the process of switching. Co., Ltd.

source: China industrial control

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