Pressure Measurement Why is it important?. Pressure Measurement Asses the situation –What is the...
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Transcript of Pressure Measurement Why is it important?. Pressure Measurement Asses the situation –What is the...
![Page 1: Pressure Measurement Why is it important?. Pressure Measurement Asses the situation –What is the range of pressures to be measured? –Is pressure dynamic.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d945503460f94a7c1f0/html5/thumbnails/1.jpg)
Pressure Measurement
• Why is it important?
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Pressure Measurement
• Asses the situation– What is the range of pressures to be
measured?– Is pressure dynamic or static?– What is more important: absolute accuracy or
good repeatability?– How much overpressure protection is
required?
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Types of Measurement
• Mechanical– U-tube manometer, Bourdon tube, Diaphragm
and Bellows
• Electrical– Strain Gauge, Capacitive sensor,
Potentiometric, Resonant Wire, Piezoelectric, Magnetic, Optical
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Mechanical
• Mechanical pressure measurement devices are large and cumbersome.
• Not suited for automated control loops typical in industry.
• Mechanical devices:– U-tube Manometer– Bourdon tube– Diaphragm and Bellows element
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U-tube Manometer
• Measures difference in pressure between two points in a pipe.
• Typical in laboratories.
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Bourdon Type
• Flexible element used as sensor.• Pressure changes cause change in element
position.• Element connected to pointer to reference
pressure.
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Diaphragm and Bellows Element
• Similar concept to Bourdon type.• Widely used because they require less space
and can be made from materials that resist corrosion.
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Electrical
• Have become more common with increased reliance on computerized control systems.
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Strain Gauge
• Measures deflection of elastic diaphragm due to pressure difference across diaphragm.
• Widely used in industry.• Used for small pressure ranges.• Measurements tend to drift.
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Capacitive Sensor
• Measures changes in capacitance of electrically charged electrodes from movement of metal diaphragm due to pressure difference across diaphragm.
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Capacitive Sensor, cont.
• Can be operated in balanced or unbalanced mode.– Balanced always has capacitance of zero.
Measures pressure indirectly by measuring drift in capacitor arms.
– Unbalanced measures ratio between output voltage and excitation voltage.
• Widely used in industry.• Large rangeability.
![Page 12: Pressure Measurement Why is it important?. Pressure Measurement Asses the situation –What is the range of pressures to be measured? –Is pressure dynamic.](https://reader035.fdocuments.us/reader035/viewer/2022062320/56649d945503460f94a7c1f0/html5/thumbnails/12.jpg)
Resonant Wire
• Wire is oscillated at resonant frequency by oscillator circuit.
• Pressure changes cause change in wire tension which changes oscillatory frequency.
• Generates digital signal.• Very precise, used for low differential
pressure measurements.• Sensitive to temperature variation and
has non-linear output
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Piezoelectric
• Measures the charge developed across quartz crystal due to change in pressure.
• Charge decays rapidly making unsuitable for static pressure measurements.
• Sensors are very rugged. Pressure can be applied longitudinally or transversally.
• Used to measure dynamic pressure changes associated with explosions and pulsations .
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Magnetic• Measures induced current caused by movement of
magnetic components from pressure changes. • Used in applications where high resolution in small range is
desired due to very high output signals.• Sensitive to stray magnetic fields and temperature
changes.
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Optical• Detects effects of minute motions due to process pressure changes
through partial blocking of an LED.• Immune to temperature effects.• Excellent stability and long-duration capability.
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Various types of pressure gauges
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Questions?