Pressure and pressure measurement

pressure definition.

The easiest and simplest definition of pressure is the force applied on a unit area of an object’s surface where the pressure could be represented as P=F/A where P is the pressure, F is the force, and A is the area. The pressure could be used with solids, gases, and liquids where it represents a crucial role in physics.
As the force unit is Newton and the area is the square meter, the unit of pressure is Newton per square meter which is PASCAL (Pa) in the International System of Units (SI). There are many other units used for measuring the pressure.

Pressure units

what are the measuring units of pressure?

The pressure measuring unit depends on the type of the type of the measured components and the application or the process you need to measure its pressure. These units are:

International System Units (SI).

Pascal (Pa) where 1 Pa = 1 N/m².
Kilopascal (kPa) where 1 kPa = 1,000 Pa. is used in meteorology and other fields.
Megapascal (MPa) where 1 MPa = 1,000,000 Pa. Used in high-pressure applications.

Metric Units.

Bar where 1 bar = 100,000 Pa. used in water and compressed air
Millibar (mbar) where 1 mbar = 100 Pa. normally used in atmospheric pressure

Other Units:

Atmosphere (atm) where 1 atm = 101,325 Pa. It is the average atmospheric pressure at sea level.
Torr where 1 Torr = 1/760 of an atmosphere = 133.32 Pa. It is used in vacuum measurements.
Millimeters of Mercury (mmHg) where 1 mmHg ≈ 133.32 Pa. It is used in medical fields (blood pressure).
Pounds per Square Inch (psi) where 1 psi = 6,894.76 Pa. It is used in tire pressure and hydraulics.

Why do we measure the pressure?

The purpose of measuring the pressure is to know the force distribution over a unit area. Like in engineering, it helps to ensure that any structure like bridges and buildings can hold the force applied to its structure. Pressure measurement in fluid dynamics is essential to control the fluid flow in pipes, pneumatics, and hydraulic systems.
Pressure is used in weather forecasting where atmospheric pressure measurements predict weather patterns. In medical applications, pressure is very important for monitoring blood pressure, ensuring the proper function of ventilators, and maintaining safe conditions in hyperbaric therapies.

Tire pressure

What are the pressure sensors?

A pressure sensor is a device that converts the pressure of liquids or gasses into readable data or an electrical signal. It senses the forces applied per unit area and converts that physical quantity into a form that can be processed or displayed.

The measurement is often based on the deformation of a sensitive element (like a diaphragm or membrane). It monitors and controls the pressure in the instrumentation system to maximize and optimize the system's quality and performance.

What are the Advantages of pressure sensors?

Pressure sensors have many advantages that can support a wide range of applications. The following are the main and important benefits of pressure sensors:

High Accuracy, where pressure sensors provide reliable measurements, precise and, key factors for critical applications like industrial processes that require a high level of control or medical devices (blood pressure).
Real-time Monitoring, where pressure sensors offer continuous and real-time data. This issue is crucial in dynamic systems like water and hydraulic systems, weather forecasting, and engine monitoring.
Pressure process control, where pressure real-time monitoring enables pressure control in pipes and other industrial processes. This control has a significant impact on the production figures and product quality of any process.
Automation, where both the real-time monitor and pressure control offer a great chance to automate the pressure processes to have a cutting-edge automation system.
Safety, where pressure sensors play an important role in equipment and human safety by ensuring safe pressure ranges and limits. It prevents equipment damage and reduces the risk of accidents in industrial applications.

Where pressure sensors are used?

Because of the advantages mentioned of pressure sensors and their ability to monitor and control pressure, many applications use such sensors like

Oil and Gas Industries to monitor the pipeline pressure of fuel industries.
Industrial process control to control and monitor equipment-related pressure like pumps.
Automotive Industry to monitor the pressure of tires. It is also used in fuel system regulations.
HVAC Systems (Heating, Ventilation, and Air Conditioning) to ensure the proper functioning.
Pharmaceutical and Chemical Industries to monitor and control pressure during pharmaceutical production.

What are the types of pressure sensors?

Pressure switch which is used as an ON-OFF switch. It changes its state when a predetermined setting of the pressure is reached.
Digital pressure sensors are devices that measure pressure and convert it into a digital signal that can be processed by computers or microcontrollers.
Analog pressure sensors are devices that measure pressure and output a continuous analog signal (typically voltage or current) that is proportional to the applied pressure.
Strain Gauge Pressure Sensors where these sensors use a strain attached to a diaphragm. When pressure is applied, the electrical resistance of the strain gauge is changed because of the deformation that happened to the diaphragm and converted into a pressure reading.
Piezoelectric Pressure Sensors where electrical charges are generated according to the mechanical stress on a piezoelectric material. This type is used with dynamic pressure measurements in engines or explosions.
Capacitive Pressure Sensors: These sensors use two parallel plates (capacitors) with a gap that changes when pressure is applied. The change in distance alters the capacitance, which is measured and converted into pressure data.
Resonant Pressure Sensors: These sensors measure changes in pressure by observing changes in the resonant frequency of a vibrating element, which varies with applied pressure. They are highly accurate and used in precision instruments.
Optical Pressure Sensors: These sensors use optical fibers to measure pressure changes by detecting variations in light intensity or wavelength due to pressure-induced changes in a diaphragm or another optical element.

The details of the pressure sensor type and how it works will be explained in the coming articles.