The positive pressure of a pressure transmitter is the state of a gas at a pressure higher than that of a gas at normal pressure (often called one atmosphere).For example, when you pump air into a bicycle or car tire, the outlet of a pump or pump creates positive pressure.

Usually in the industry, especially the micro pump (such as micro booster pump, micro air pump, micro air pump, micro gas circulation pump, micro air pump, micro air pump, etc.) often involved in the selection of this concept.

Beam tube positive pressure gas transmission is the gas transport mode used in coal mine spontaneous combustion fire beam tube positive pressure gas transmission monitoring system.The pump station is arranged underground by the system. During the operation of the pump station, the gas from the underground monitoring point is transported to the well, which is monitored and analyzed by the special gas chromatograph of the coal mine. According to the change of the gas content, the system will report the prediction of spontaneous combustion of the coal mine.In the process of gas transport, the pressure in the beam tube is moderate than the outside atmospheric pressure, so it is called positive pressure transport.

Based on the advantages of the positive pressure transport gas pressure is not restricted by vacuum degree and is greater than the environmental pressure, the ambient gas cannot enter the beam pipe during the transport process, the positive pressure is proposed as the transport method to detect the gas, and a positive pressure beam pipe monitoring system is developed.The experiment and theoretical calculation results show that the positive pressure transport power is 4~3 times as much as the negative pressure transport power. The positive pressure transport power not only reduces the transport time of the gas, but also ensures the constant gas concentration.The data measured by positive pressure beam tube can reflect the spontaneous combustion state of coal.

The measuring part of pressure transmitter usually adopts differential capacitance structure.The center movable plate and the two fixed plates form two planar capacitors H and L.The H end represents positive pressure, and the movable plate and the fixed plate on both sides form two pressure Chambers. The medium pressure is acted on the central movable plate through the filling liquid in the two Chambers.The ideal liquid such as silicon oil is generally used as the filling liquid, and the measured medium is mostly gas.The function of the isolating diaphragm is to transfer pressure and avoid damage to the capacitive plate.

When the positive and negative pressure (differential pressure) by negative pressure guide pressure on the isolated patch on both sides of the bellows, through cavity indoor silicone oil liquid is passed on to the center measuring diaphragm, displacement of the center of pressure sensitive film, the movable plate and left and right amount of space between two plates is not relative, the formation of differential capacitance, were it not for the edge electric field, the differential capacitance can be seen as flat capacitance.The relative variation of differential capacitance is proportional to the measured pressure and has nothing to do with the dielectric constant of the filling fluid, so the measurement error caused by the variation of dielectric constant is eliminated in principle.

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