pressure detection and transmission
First, an overview of
pressure in industrial production is one of the important parameters in order to ensure the production of political parties running, pressure must be monitored and controlled, but noted that the pressure we are talking about here is actually the concept of physical pressure, that is, vertical In the role of the force per unit area.
in the measurement of pressure, the pressure is used, the pressure on the table, the negative pressure or vacuum division. The so-called absolute pressure measured is the role of the media in the container per unit area on the full pressure of pj that used symbols. Used to measure the absolute pressure instrument known as the absolute pressure gauge. On the ground of the column of air generated by the average pressure as the atmospheric pressure, with signs that pq. Used to measure the atmospheric pressure on the gas meter called the barometer. Absolute pressure and atmospheric pressure difference. As the pressure on the table, with symbols that pb. That is, pb = pj-pq. When the pressure is less than atmospheric pressure, the pressure on the negative list (that is, negative pressure), the absolute value of negative pressure, known as the vacuum, and use symbols that pz. Used to measure the degree of vacuum instruments known as a vacuum table. Not only can the value of measuring pressure vacuum measurement instrument called a vacuum pressure on the table.
Second, the pressure and the pressure gauge measuring the choice of
pressure measuring principle can be divided into the column-and-elastic, resistive, capacitive, inductive-frequency vibration and so on. Pressure gauge measuring pressure from a broad range of ultra-vacuum such as 133 × 10-13Pa up to ultra-high pressure 280MPa. Pressure from the structure can be divided into laboratory and industrial-type applications. A wide variety of pressure gauge. According to the detected object is therefore a good choice of pressure on the pressure gauge is very important.
1. Direct pressure locally
when the pressure in the 2.6Kpa, the patch can type pressure gauge, bellows pressure gauge and pressure gauge pipe Bolden. As close to the low atmospheric pressure testing, the patch can be used bellows-type pressure gauge or pressure gauge.
2. Pressure on long-range display
if it shows the need for long-range pressure, which tends to be used for electric or pneumatic pressure on transformers, electrical pressure sensor can also be used. When the pressure in the range of 140 ~ 280MPa, should be heavy-handed pressure-receptor. When the high-vacuum heat can be measured when the vacuum gauge.
3. More pressure measurement
multi-point measurement of pressure, the pressure detector can tour.
if the measured pressure to reach the limit required to report to the police, should be chosen with alarm the various types of pressure gauge.
gauge the right choice In addition to the above points into account, need to consider the following points.
(1) range of choices under the pressure measured to determine the size of the instrument range. The flexible-pressure gauge in determining the stability of the pressure, the pressure should not exceed the value of full-scale 3 / 4; measuring pressure fluctuations, the value of the maximum pressure should be less than the full-scale 2 / 3. The lowest pressure measurements should not be less than the value of the entire range of 1 / 3.
(2) the production of precision choose the maximum allowed under the measurement error to the economy, the principle of cost-effective instrument to determine the accuracy level. General industrial pressure gauge with 1.5 or 2.5 is sufficient, scientific research or to use precision measuring 0.5 or 0.35 of precision pressure gauge or standard gauge.
(3) environment and the use of media properties to consider adverse environmental conditions, such as high temperature, corrosion, moisture, vibration and so on, measured the performance of media, such as the high and low temperature, corrosive, easy crystallization of flammable, explosive, etc. And so on, as a means of pressure gauge to determine the type and model.
(4) pressure gauge size of the scene on the spot to choose the general direction of the pressure gauge on the surface with a diameter of 100mm, a higher standard in lighting conditions or poor clearance occasion with a diameter of the surface of 200 ~ 250mm, disk diameter loading gauge 150mm, rectangular or pressure gauge. Flexible-pressure gauge specifications used in table 2-1-13.
three, the pressure sensor
pressure sensors detect pressure system is an important part of the pressure from a variety of sensitive components to the measured pressure signals into electrical signals for easy measurement of output, to show that pressure on the value of the instrument display, or for the control and use the report to the police.
1. Strain-pressure sensors
strain pressure sensor is to convert the pressure changes in the value of the resistance to the changes in the measure, by the strain gauge metal conductors or semiconductors made of resistance, the resistance with the pressure generated by the strain of change.
2. Piezoelectric pressure sensors
piezoelectric sensors is based on the principle of the piezoelectric crystal materials some of the effects of the current widespread use of piezoelectric material, such as quartz and barium titanate, when the pressure of these crystals by mechanical deformation, in its relative of the two On the side of the opposite sex have a charge, a phenomenon known as the "piezoelectric effect."
3. Fiber-optic pressure sensor
fiber-optic pressure sensor with the traditional pressure sensor, has its unique advantages: the use of pressure wave transmission of information, free from electromagnetic interference, electrical insulation, corrosion-resistant, non-electrical discharge, high pressure can, of flammable and explosive Environment pressure measurement, flow, level, and so on. It is highly sensitive, small and flexible, and can insert a narrow space is measured, be given due attention and rapid development.
IV pressure transmitter
in the control room need to show that the pressure of the instrument, the selection of the general pressure transmitter or pressure sensors, for the risk of explosion sites, often optional pneumatic pressure transmitter, explosion-proof electric or -pressure transmitter; for Micro-pressure measurement, may be micro-differential pressure transmitter; on the sticky, blocking easy, easy crystallization of the corrosion and strong media, should be chosen with the flange diaphragm pressure transmitter; place in the atmosphere corrosion and strong corrosion Such as media measurement, the 1151 series is also available, or 820 series pressure transmitter.
some of the pressure transmitter measurement of pressure-sensitive components generated by measuring the size of the force range of about 50 to 100 to a maximum of not more than 150N. In response to this request, based on the choice of sensor made by the bellows, the structure of the principle shown in Figure 2-1-12. When measured pressure p into the measuring room, measurement by the bellows into force measured by putting to use the main lever, delivered to the aerodynamic part of the conversion. Measurement, high-voltage 2.5 ~ 10MPa, 10 ~ 60 MPa) of the sensitive components generally made of chrome vanadium steel tube-end package, and its measuring principle is the use of packet-side end of the tube have a radial play, putting the role of 2 At the lower end of the 3 main lever to stimulate the conversion transmitter of the aerodynamic part of the action.
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