Pressure Measurement

Pressure measurement is the process of measuring and quantifying the force (i.e. pressure) exerted by a gas or liquid by means of specific instruments and methods. Pressure is the vertical force exerted by the molecules of a substance per unit area and is an important concept in fluid mechanics and thermodynamics.

Apure pressure transmitters do more than just provide accurate and reliable data for process control. Apure pressure instrumentation helps achieve enhanced product quality, reduced total cost of ownership, and increased plant availability.

Pressure transmitters do more than just provide accurate and reliable data for process control. Apure pressure instrumentation helps achieve enhanced product quality, reduced total cost of ownership and increased plant availability.

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Pressure gauge refers to the elastic element as a sensitive element, measuring and indicating higher than the environmental pressure of the instrument, the application is very common, it almost throughout all industrial processes.

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Types of Pressure Measuring Instruments

Elastic element type manometers

The deformation of an elastic element under pressure is utilized to indicate the pressure value.

Resistive Pressure Sensor

Measures pressure by utilizing the characteristic of the material’s resistance to change with strain or pressure.

Piezoelectric Pressure Sensor

Piezoelectric pressure sensors measure pressure by utilizing the property of piezoelectric materials to generate an electric charge when a force is applied. Suitable for measuring transient pressures such as shock waves.

Capacitive Pressure Sensor

Utilizes the change of capacitance to measure pressure. Characterized by high accuracy and good long-term stability.

Digital Manometer

Converts analog signals to digital signals, featuring high accuracy and easy readability.

Intelligent pressure sensor

Integrated sensor, signal conditioning circuit, microprocessor, etc., with self-diagnosis, self-calibration and other functions, can directly output digital signals.

Units of Pressure Measurement

  • Pascal (Pa): The unit of pressure in the International System of Units.
  • bar: Commonly used in industrial measurements.
  • kilopascal (kPa): Commonly used for smaller pressures.
  • Megapascal (MPa): Commonly used to express larger pressures.
  • Kilogram force per square centimeter (kgf/cm²): traditional unit of pressure.

Application Scenarios for Pressure Measurement

  • Fluid Transportation: Measurement of fluid pressure in pipelines to control flow.
  • Vessel pressure: Measurement of the pressure of gases or liquids in vessels to ensure safety.
  • Process control: Measurement of pressure to control production parameters in industrial processes.
  • Scientific research: Measure the pressure of various substances under different conditions to study their properties.

Factors affecting pressure measurement

  • Temperature: Temperature variations can affect the measurement results.
  • Medium properties: Corrosivity, viscosity, etc. can affect sensor selection.
  • Vibration: Vibration can interfere with measurement accuracy.
  • Overload: Excessive pressure can damage the sensor.

Considerations for pressure measurement

  • Selection of the right sensor: According to the measurement range, accuracy requirements, media properties, etc. to choose the right sensor.
  • Calibration: Regularly calibrate the sensor to ensure measurement accuracy.
  • Installation: Install the sensor correctly to avoid external interference.
  • Maintenance: Maintain the sensor regularly to prolong its service life.

FAQ

Gauge pressure Indicates fluid pressure based on atmospheric pressure, which can be measured with a manometer and is called gauge pressure, that is, absolute pressure – atmospheric pressure = gauge pressure.

Also called pressure transmitter, it is a kind of pressure into pneumatic signals or electric signals for control and remote transmission equipment. It can change the physical pressure parameters such as gas and liquid felt by the load cell sensor into the standard electrical signal (such as 4~20mADC, etc.), to supply indicating alarm, recorder, regulator and other secondary instruments for measurement, indication and process adjustment.

The pressure on the gauge, measured in absolute terms, is equal to the gauge pressure plus one atmosphere.

The theory is: the gauge pressure, is the indicator value of the pressure gauge, it is absolute pressure and atmospheric pressure difference.

Pressure transmitter, also known as pressure sensor, is composed of measuring diaphragm, insulation sheet, electrode and so on. The working process of pressure transmitter is relatively simple, it has a varistor inside, the varistor resistance changes after being subjected to pressure, this current change is amplified by the amplifier, and then the standard pressure calibration, through the pressure detection signal to achieve the operation control of the system.

When the pressure on both sides of the insulation slices inconsistent, pressure through the direct effect on the surface of the diaphragm, make measuring diaphragm displacement, the displacement is proportional to the internal medium pressure difference, which can lead to both sides unequal, capacitance measuring diaphragm with a high precision circuit on these subtle changes can be transformed to voltage signal, again through the link of oscillation and demodulation, Have a dedicated chip convert a voltage signal into a current signal.

The measuring diaphragm of pressure transmitter is made of standard integrated circuit with linear and temperature compensation circuit mechanism, which can ensure the high precision and high stability of the working process, so as to ensure that the special chip of the transmitter circuit can realize the output of two-line current signal.

Pressure gauge through the elastic deformation of the sensitive elements (Bourdon tube, diaphragm box, bellows), and then the pressure deformation is transmitted to the pointer by the conversion mechanism of the movement in the table, causing the pointer to rotate to display the pressure.

  1. pressure detection, check the method is: supply power to the sensor, blow the pressure sensor’s air hole with the mouth, detect the voltage change at the output end of the sensor with the voltage file of the multimeter. If the relative sensitivity of the pressure transmitter is large, this variation will be significant. If there is no change, pressure will need to be applied using a pressure source.Through the above method, the basic condition of a transmitter can be detected. If accurate detection is required, it is necessary to use a standard pressure source, pressure to the sensor, according to the size of the pressure and output signal changes, the transmitter calibration. And when conditions permit, the relevant parameters of temperature detection.
  2. zero detection, with a multimeter voltage profile, detection in the absence of pressure, the transmitter zero output. This output is generally mV level voltage, if it exceeds the technical index of the sensor, it means that the zero deviation of the transmitter is beyond the range.
  3. bridge detection, the main detection of the transmitter circuit is correct, is generally wheatstone full bridge circuit, the use of multimeter ohm file, the amount of impedance between the input end, and the impedance between the output end, the two impedance is the input and output impedance of the pressure sensor. If the impedance is infinite, the bridge is disconnected, indicating that the transmitter is faulty or the pin definition has not been judged correctly.

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