quality Industrial Pressure Transmitters & Differential Pressure Transmitter factory

New York, United States, Oct. 10, 2024 (GLOBE NEWSWIRE) -- Valve positioners are utilized to regulate the precise position of a valve in process control systems. Controlling the flow of fluids (like gases or liquids) through fluids is a common function of valves in numerous industrial settings. A valve positioner ensures precise valve placement to maintain the specified flow rate, pressure, or other process parameters.   The fundamental function of a valve positioner is to systematically regulate the valve's position in response to a signal received from a controller, such as a programmable logic controller or distributed control system. Such a system ensures that the valve responds precisely to the control signal and facilitates the achievement of precise command over the operation.   Market Dynamics   Increasing Urbanization and Industrialization in Developing Economies Drive the Global Market   In numerous sectors, including energy and power, water and wastewater management, pharmaceuticals, metals and mining, chemicals, food and beverages, and energy and gas, the rapid process of industrialization and urbanization in developing economies such as China, India, Brazil, and South Africa has increased the demand for valve positioners.   In these sectors, valve positioners are essential for regulating the flow of fluids, gases, and steam to preserve quality, safety, and productivity. According to projections by the United Nations, the global urban population will increase from 4.2 billion in 2018 to 6.7 billion in 2050, with 90% of this surge occurring in Asia and Africa. The lucrative prospects identified in these geographical areas indicate a considerable capacity for expansion within the market for valve positioners.   Advancements in Valve Positioner Create Tremendous Opportunities   Significant industry participants have recently advanced in developing valve positioners to improve their efficacy. For instance, in January 2021, PMV developed a modular, user-friendly, and extremely sophisticated digital positioner. The PMV D30 digital positioner is an advanced technological advancement that offers precise and reliable valve regulation while being straightforward to set up and calibrate. Rotary and linear valves powered by double-action or single-action spring return actuators are compatible.   Similarly, Spirax Sarco, the preeminent provider of equipment and services for steam system control, announced the EP500's release in February 2017. The ergonomics of this first electro-pneumatic valve positioner are its primary consideration. This positioner offers exceptional accuracy and unmatched dependability; additionally, it requires no effort to set up, calibrate, or operate. A cast aluminum exterior intended for outdoor installations is featured on the EP500. These developments are anticipated to generate market expansion opportunities.   Regional Analysis   North America is the most significant global valve positioner market shareholder and is estimated to expand substantially during the forecast period. It is anticipated that established industries such as water and wastewater, electricity and energy, oil and gas, and chemicals will have a significant presence in North America, contributing to the region's dominant market share throughout the forecast period. Moreover, the increasing adoption of automation technologies and the development of sophisticated industrial infrastructure drive robust growth for valve positioners in the North American market.   Furthermore, an increasing number of North American businesses are adopting valve positioners to improve the accuracy and productivity of their manufacturing processes. According to research by the National Association of Manufacturers, American investments in manufacturing technologies surpassed USD 243 billion in 2022, showcasing an unwavering commitment to technological advancement. The substantial investment signifies the region's readiness to integrate and integrate state-of-the-art technologies, including valve positioners, into its industrial framework. Key Highlights   Based on type, the global valve positioner market is bifurcated into pneumatic valve positioner, electro-pneumatic valve positioner, and digital valve positioner. The digital valve positioner segment dominates the global market. Based on actuation, the global valve positioner market is divided into single-acting and double-acting. The single-acting valve positioner segment is the highest contributor to the market. Based on industry, the global valve positioner market is bifurcated into energy and power, chemical, oil and gas, pharmaceutical, metal and mining, food and beverage, water and wastewater treatment, paper and pulp, and others. The oil and gas segment is the largest contributor to the market. North America is the most significant global valve positioner market shareholder and is estimated to expand substantially during the forecast period. Competitive Players   The key players in the global valve positioner market are Emerson, Metso, General Electric, Flowserve, Siemens, ABB, SAMSON AG, Honeywell International Inc., Azbil, SMC, Rotork, Schneider Electric, Nihon KOSO, GEMU, Yokogawa, Chongqing Chuanyi Automation, IMI STI, Festo, Jordan Valve, VRG Controls, Circor International, Crane, ContRoLAir, Gemu Group, Dwyer Instruments, and others.   Market News   In March 2023, Valworx officially introduced its latest collection of flange valves, which are designed to have low emissions and provide fire safety. Valworx stainless steel flange valves are certified for use in pipelines, and they also meet standards for low fugitive emissions and fire-safe design. Valworx offers stainless steel flange valves that can be operated in electric explosion-proof (On-Off/ Positioner), electric (On-Off/ Positioner), pneumatic, or manual modes. In September 2023, Samson Controls Pvt. Ltd., a German firm, marked the commencement of construction for their new facility with a significant ceremony at their Ranjangaon plant premises. The company is a prominent maker of various valves, intelligent positioners, and smart valves and systems powered by artificial intelligence. Segmentation   Global Valve Positioner Market: Segmentation   By Type Pneumatic Electro-Pneumatic Digital   By Actuation Single-Acting Double-Acting   By Industry Energy and Power Chemical Oil and Gas Pharmaceutical Metal and Mining Food and Beverage Water and Wastewater Treatment Paper and Pulp Others   By Regions North America Europe Asia-Pacific Latin America The Middle East and Africa  

The pressure of the measured fluid is applied to an internal measuring element through a fitting and then a mechanical interface – measuring membrane. The electronic measuring element converts the pressure into a raw signal. There are different measurement technologies: The piezoresistive pressure sensor measures the force applied to a metal diaphragm. The pressure exerted deforms the diaphragm which transmits the pressure variation via an intermediate incompressible fluid (oil or water). This deforms a piezoresistive silicon element (Wheatstone bridge). This element is a variable electrical resistance which converts the strain into an ohmic value. The capacitive pressure sensor measures the force applied to a metal or ceramic membrane. The pressure exerted distorts the membrane, which transmits the pressure variation via an intermediate incompressible fluid (oil or water). This deforms a capacitive silicon element. This element is a variable capacitor that converts deformation into a capacitive value. The frequency resonant pressure sensor The voltage gauge sensor The signal from the measuring element is then filtered, amplified, temperature compensated and then formatted into an analog signal. The analog output signal is transmitted via an electrical connector. How to calibrate a pressure transmitter: Industrial pressure transmitters require periodic calibration to ensure accurate pressure measurement. The calibration period is defined by the manufacturer. Zero (Zero) and full-scale sensor (Span) should be calibrated. Calibration involves applying a reference pressure to the sensor’s mechanical interface, checking the output signal and then applying a compensation. The sensor can be calibrated using an external adjustment screw, a local digital indicator, a programming interface or programming software. In order to perform the various manipulations, it may be necessary to have an isolated faucet or manifold on the pressure transmitter. How to install a pressure transmitter: The pressure sensor can be fixed with a mechanical connection to the measuring organ or to the piping where the pressure is to be measured. Special precautions should be taken depending on pressure and temperature conditions. The sensor output signal can be connected to a display system (display, recorder or supervision) or an PLC to drive a control device. How to check a pressure transmitter: A pressure sensor can be tested by applying a reference pressure to the process connection and by checking the signal of the measured analog output or the value displayed on the indicator. How to set up a pressure transmitter: There are different ways to set up pressure sensors. Pressure sensors can have a local digital indicator that can be adjusted to adjust the parameters. They can also be configured remotely with a programming interface (hand held communicator) or a configuration software via the digital signal and HART protocol.

1.Signal output Pressure Transmiter. A pressure transmitter outputs a standardized signal, which is usually a 4-2omA or o-10V signalThis makes it easy to connect directly to a control or monitoring system without needing additional processingequipment. Pressure Transducer: A transducer typically provides a raw signal, such as a voltage or current, which may requireadditional amplifcation or signal conditioning to make it useful for monitoring or control systems 2.Signal Conditioning Pressure Transmitter. A transmitter has built-in signal conditioning components that convert the output into astandardized form. This ensures that the device is immediately usable for industrial control applications.Pressure Transducer. A transducer usually requires additional sional conditioning to convert its output into a usableform, This makes the transducer more flexible but also more complex to intearate. 3. Accuracy Pressure Transmitter: Pressure transmitters are generally more accurate due to their built-in processing systems. Theadditional signal conditioning helps to filter out noise and ensure reliable readings.Pressure Transducer: While transducers are accurate in terms of pressure measurement, they can be moresusceptible to noise or fluctuations in the sianal unless additional components are used to condition the output 4. Cost and Complexity Pressure Transmitter. Typically, pressure transmitters are more expensive than pressure transducers because theycome with built-in electronics for signal processing and conditioning. However, this makes them easier to integrate intocomplex systems. Pressure Transducer. Transducers are usually less expensive but require additional components or systems to processthe raw signal. This can make installation more complicated. 5.Integration Pressure Transmitter: These devices are designed for easy integration into control systems, providing a simpleinterface that requires minimal additional processing. Pressure Transducer. While a transducer can be integrated into a system, it usually reauires more work to adapt theraw signal into a usable form for monitoring or control.

A pressure transmitter is a mechanical device that measures the expansive force of a liquid or gaseous sample. Also known as a pressure transducer, this type of sensor is typically composed of a pressure sensitive surface area made of steel, silicon, or other materials depending upon the analyte’s composition. Behind these surfaces are electronic components capable of converting the applied force of the sample upon the pressure sensor into an electrical signal. Pressure is generally measured as a quantity of force per unit of surface area, and is expressed as the value required to stop a liquid, gas, or vapor from expanding. Various derived units are used to quantify pressure, including: As a proportion of / relation to a pascal (Pa), or a single newton per square meter (1 N/m2); A value of pounds per square inch (psi). Pressure sensitive environments such as the gas, petrochemical, laboratory, and pharmaceutical industries often require pressure transmitters to monitor the applied force of liquids and gasses as a value of either Pa or psi. This necessitates the precise integration of pressure transmitters into rapid electrical conversion equipment, to ensure results are accurate and delivered in real-time. More often however, industrial professionals rely on comprehensive gauge systems with incorporated pressure transmitters to maintain optimal pressure levels for gas, oils, and high temperature liquids.   Gauge Pressure Transmitters Gauge pressure transmitters are equipped for absolute pressure measurements with industry-specific considerations to support severe process monitoring. Steel diaphragms fitted to pressure vessels or pipework can register minute deformations relating to applied force, which is in turn swiftly translated into an electrical signal by a pressure sensor within the gauge transmitter. This can be measured remotely, or monitored through intuitive, user-friendly displays at the site of measurement. Applications of Pressure Transmitters Pressure transmitters are routinely used in a wide range of industrial sectors. Offshore drilling and oil exploration commonly utilize pressure sensors to measure differential values between the interior and exterior of pressure sensitive equipment. Distinct parameters must be maintained to ensure drilling and acquisition processes are carried out to an ethical and efficient standard. This is also true of on-shore petrochemical, gas, and chemical facilities. Numerous industries use pressure-sensitive transportation and storage devices to maintain optimal product conditions, which must be accurately monitored to ensure safe delivery and eventual application. Laboratories also use pressure sensors to measure the relative pressure of vacuum chambers to the atmosphere, supporting a limitless range of emerging studies.

In almost every type of engineering, having knowledge on how to use pressure measurement tools is crucial to the safety and integrity of projects. According to the International Society of Automation (ISA), pressure measurement is the second-most common in processing plants and is usually coordinated with that of temperature. The ISA defines pressure as a force applied over a surface measure in force per unit area using the formula in which pressure is equal to the unit of force divided by that of an area. Traditional tools like manometers pale in comparison to today's techniques for measuring and transmitting pressure. Modern tools are highly precise and take advantage of a variety of modern technologies. Despite the new tools involved in the processes used today, their use is still reliant on the user understanding the unchanged physics behind how pressure works. Gas laws of physics are considered in many pressure management systems because they involve gases, and this means they have a direct effect on the overall reaction. The Four Types of Pressure and their Measurement For pressure measurement, Applied Measurements LTD states there are four main methods to get the most accurate readings for the four types of pressure involved. These four types of pressure measurements are gauge, sealed, absolute and differential. Gauge: In a vented environment with ambient atmospheric pressure, this measure uses sensors to gauge the input pressure into the system. These setups are vulnerable to humidity. Applications could include chamber pressure, hydraulics, tyre pressure. Sealed: The measure of pressure applied to a sealed chamber closed with atmospheric pressure. Some application examples would be food and beverage, also used in aggressive media. Absolute: These types of measurements are conducted in areas in a vacuum chamber removed of air (generating absolute pressure) for a reading of input pressure. An absolute pressure meter is the most recommended tool for this measurement. According to Pneumatic Tips, this is often confused with gauge pressure. The difference between the two in terms of measurement is that the latter uses atmospheric pressure as its zero point, while absolute uses absolute zero. Using the two incorrectly in calculators will lead to extremely inaccurate readings. Differential: Unlike the others, differential pressure measurement is the difference between two pressures, usually between ambient and those internal to a sensor. For this measurement, you'll be sure to need a differential pressure gauge. Some common applications include filter monitoring, HVAC, clean rooms. Other pressure measurements important to industries such as HVAC are those for absolute pressure, overpressure, negative pressure and differential pressure. With proper and regular pressure management, accidents resulting from leaky pipes and damage to refrigeration or ventilation systems can be negated. Measurement Tools You Can Use and How they Can be Applied Today's modern tools are easily applied to a variety of situations. They offer convenience and efficiency in the workplace, such as using a pressure monitor to test leaky pipes without the need to shut off the system. Even aggressive media, such as refrigeration and heating systems, can be dealt with safely using manometers and pressure sensors for measurement. Vacuum gauges and manifolds are very useful for evacuating refrigeration systems, while digital barometers can be used by those in the industrial sector to assist in reducing overpressure and keep clean rooms free of undesirable air particles and germs. Differential pressure measurement devices also play a role in the maintenance of cleanrooms and HVAC in general, and also heating systems. Testo offers a range of products and solutions that can be used for these types of pressure measurements, as well as tools that can help record, save, and store readings for further use… all accessible via smartphone, making them highly efficient and simple to implement into your business's workflow. These tools provide a wide array of applications for many businesses- even for overall facilities management. For example, routine applications to check refrigeration systems can use Testo's electronic manifold, which features an acid-resistant, ceramic pressure sensor that also functions as a manometer. Our fast and high-precision leak detectors may also come in handy, as they are easy to handle in spaces seemingly inaccessible for measurement. It cannot be overstated the importance of having a measurement instrument that enables fast and simple measurements of all the important parameters required for your business's operation. With Testo, you can rest assured that you always have the right measuring instrument that provides all the accurate data for pressure measurement and other important measurement parameters at your side.

Pressure gauges, which are devices that measure the internal pressure of media within a system, are among the most often used instruments in any given industrial facility. Pressure measurement is, along with temperature measurement, one of the most important measurements for operations in a wide variety of applications – especially industrial applications – and it is essential in ensuring both the quality of a product and the safety of a facility and its personnel. Pressure gauges are used to monitor and control pressure – which is often a necessity in industrial processing. Without pressure gauges, industrial processing systems would be both unpredictable and unreliable. Pressure gauges are used by industry professionals to troubleshoot fluid power machines – which are designed to work within a set pressure range. With properly installed gauges, leaks and unwanted pressure changes can be monitored and addressed immediately. Types of Pressure Gauges and How They Work Often, the terms pressure gauge, sensor, transducer, and transmitter are used interchangeably. The term pressure gauge usually refers to a self-contained indicator that converts the detected process pressure into the mechanical motion of a pointer. Pressure gauges can either be mechanical or digital. The first pressure gauges used flexible elements as sensors. As pressure changed, the flexible element moved, and this motion was used to rotate a pointer in front of a dial. In these mechanical pressure sensors, a Bourdon tube, a diaphragm, or a bellows element detected the process pressure and caused a corresponding movement.

Emerson Process Management has launched a new icon-based user interface for the industry-leading 475 Field Communicator that simplifies the work of field maintenance technicians. The new interface features graphical menus that are easy to use and understand, and Device Dashboards that provide a clear view of a device’s operating health. The 475 also includes the ValveLink™ Mobile software application, which delivers advanced control valve diagnostics in the field for Fisher® FIELDVUE™ instruments. The icon-based interface functions like popular consumer products with a touch screen for one-finger selection of various tasks, including quick connection to field devices and ValveLink Mobile. Once a field device is identified, task-based menus enable technicians to easily carry out maintenance or troubleshooting routines. Device Dashboards, popular on other Emerson products, are now incorporated in the 475 Field Communicator. These intuitively designed interfaces provide an instant view of all essential information needed to evaluate, diagnose and configure a field device. The clear, concise presentation of device data helps reduce guesswork and shortens the time required for maintenance in the field. Issues are not only identified, but detailed troubleshooting information indicates where and how repairs should be made. The ValveLink Mobile application uses the icon-based interface to simplify access to HART® control valve data and is easily navigated with the commonly-used flick, zoom in and zoom out capabilities. For example, users can select an icon to initiate a series of valve tests, including a total check of the configuration, calibration, diagnostics and other key parameters. Diagnostic data can be viewed and stored in the 475 Field Communicator or uploaded to Emerson’s AMS Suite for additional evaluation. The icon-based interface is pre-installed in 475 Field Communicators purchased since January 2011 and can be downloaded without charge by current users of 475 and 375 Field Communicators who hold Easy Upgrade licenses. With Easy Upgrade, users can quickly and easily update their communicators with the latest capabilities via the Internet. ValveLink Mobile software has come pre-installed on all 475 Field Communicators since January 2010.  

The report "Pressure Transmitter Market by Technology, Type (Absolute, Gauge, Differential, Multivariable), Design & Functionality (Diaphragm, Hygienic, Wireless), Fluid Type (Liquid, Gas, Steam), Measurement Application, Industry - Global Forecast to 2030" The global pressure transmitter market is expected to be USD 3.84 billion by 2030 from USD 3.21 billion from 2025, at a CAGR of 3.7% during the forecast period. The pressure transmitter market is growing due to several important factors. One major reason is the increasing need for energy-efficient solutions to help reduce energy use and lower operating costs. The growing use of automation in pressure systems is also boosting the market, as automated systems improve performance and reduce the need for manual work. Additionally, industries are now focusing more on improving manufacturing efficiency while meeting strict environmental regulations. This has led to higher investment in advanced pressure transmitter technologies that support sustainability goals. Differential pressure transmitter is expected to register the largest market share during forecast period. The differential pressure transmitter segment is expected to hold the largest market share in the pressure transmitter market during the forecast period, driven by its critical role in measuring flow, level, and pressure variations across industries. These transmitters are widely used in oil & gas, chemicals, power generation, and water & wastewater treatment, where precise measurements are essential for maintaining operational efficiency. Their ability to perform reliably in high-pressure and extreme environments makes them vital for complex industrial applications. In the oil & gas sector, differential pressure transmitters are extensively used for pipeline flow measurement, tank-level monitoring, and subsea operations, ensuring both safety and performance optimization. They also play a crucial role in steam flow monitoring for power plants, enhancing energy efficiency and process control. Additionally, in the chemical industry, these transmitters support production by maintaining accurate pressure levels, which is essential for quality assurance and regulatory compliance. With industries increasingly adopting automation and digitalization, demand for differential pressure transmitters continues to grow. As businesses focus on improving efficiency, safety, and reliability, these devices are expected to remain a key component in modern industrial operations. The liquid fluid type segment is expected to exhibit highest CAGR in the pressure transmitter market during the forecast period. The liquid fluid type segment is expected to exhibit highest CAGR in the pressure transmitter market during the forecast period. Pressure transmitters are essential for accurately measuring and monitoring liquid, gas, and steam pressure across various industries, including oil & gas, chemicals, power generation, and water treatment. Among these, liquid applications dominate due to the widespread need for precise pressure measurement in water management, fuel monitoring, and industrial processing. Advanced pressure transmitter technology enhances operational efficiency by ensuring real-time data accuracy, optimizing process control, and improving safety. In particular, digital advancements in pressure measurement enable seamless data integration across industrial systems, facilitating better decision-making and process automation. By enabling consistent monitoring, pressure transmitters help industries maintain regulatory compliance, reduce downtime, and enhance productivity. The growing demand for smart pressure transmitters with IoT capabilities further strengthens their role in liquid-based applications, making them an indispensable part of modern industrial operations. The level measurement application segment is expected to hold major share in the pressure transmitter market. The level measurement segment is expected to hold the largest share in the pressure transmitter market during the forecast period. This growth is driven by the increasing demand for accurate and reliable level monitoring across industries such as oil & gas, chemicals, water & wastewater, and power generation. Pressure transmitters play a vital role in ensuring precise liquid level measurements in storage tanks, processing units, and industrial vessels, helping maintain safety and operational efficiency.With stricter regulations on process safety and environmental compliance, industries are adopting advanced pressure transmitters to enhance monitoring accuracy and prevent overflows, leaks, and equipment failures. Modern pressure transmitters, equipped with digital communication and remote monitoring capabilities, improve process control and reduce maintenance costs by enabling early issue detection. Additionally, the growing integration of automation and smart monitoring systems further boosts the demand for high-performance level measurement solutions. As industries focus on efficiency, safety, and regulatory compliance, pressure transmitters for level measurement will continue to dominate the market, driving overall growth in the measurement application segment. North America is expected to hold the second largest share of the pressure transmitter market. The North American market holds the second-largest share in the pressure transmitter market, driven by several key factors. The region is home to major industries such as oil & gas, chemicals, food & beverages, and pharmaceuticals, all of which rely on pressure transmitters for accurate monitoring and process control. Additionally, North America has a well-developed infrastructure for power generation and advanced manufacturing facilities that require reliable pressure measurement solutions to ensure operational efficiency and automation. Moreover, stringent regulations on safety, environmental protection, and energy efficiency further drive the adoption of high-precision pressure transmitters, helping industries enhance performance, reduce emissions, and improve overall sustainability. The key companies in the pressure transmitter market include Emerson Electric Co. (US), Yokogawa Electric Corporation (Japan), Honeywell International Inc. (US), ABB (Switzerland), Schneider Electric (France), Endress+Hauser Group Services AG (Switzerland), Fuji Electric Co., Ltd.(Japan), Azbil Corporation (Japan), Ashcroft, Inc(US), Danfoss (Denmark), Huba Control (Switzerland), Siemens (Germany),. Don’t miss out on business opportunities in Pressure Transmitter Market. Speak to our analyst and gain crucial industry insighs that will help your businessgrow. About MarketsandMarkets™ MarketsandMarkets™ is a blue ocean alternative in growth consulting and program management, leveraging a man-machine offering to drive supernormal growth for progressive organizations in the B2B space. We have the widest lens on emerging technologies, making us proficient in co-creating supernormal growth for clients. The B2B economy is witnessing the emergence of $25 trillion of new revenue streams that are substituting existing revenue streams in this decade alone. 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Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure mechanically are called pressure gauges, vacuum gauges or compound gauges (vacuum & pressure). The widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge. A vacuum gauge is used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (for instance, −1 bar or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. For very low pressures, a gauge that uses total vacuum as the zero point reference must be used, giving pressure reading as an absolute pressure. Other methods of pressure measurement involve sensors that can transmit the pressure reading to a remote indicator or control system (telemetry). Absolute, gauge and differential pressures — zero reference     Natural gas pressure gauge   Silicon piezoresistive pressure sensors Everyday pressure measurements, such as for vehicle tire pressure, are usually made relative to ambient air pressure. In other cases measurements are made relative to a vacuum or to some other specific reference. When distinguishing between these zero references, the following terms are used: Absolute pressure is zero-referenced against a perfect vacuum, using an absolute scale, so it is equal to gauge pressure plus atmospheric pressure. Absolute pressure sensors are used in applications where a constant reference is required, like for example, high-performance industrial applications such as monitoring vacuum pumps, liquid pressure measurement, industrial packaging, industrial process control and aviation inspection. Gauge pressure is zero-referenced against ambient air pressure, so it is equal to absolute pressure minus atmospheric pressure. A tire pressure gauge is an example of gauge pressure measurement; when it indicates zero, then the pressure it is measuring is the same as the ambient pressure. Most sensors for measuring up to 50 bar are manufactured in this way, since otherwise the atmospheric pressure fluctuation (weather) is reflected as an error in the measurement result. Differential pressure is the difference in pressure between two points. Differential pressure sensors are used to measure many properties, such as pressure drops across oil filters or air filters, fluid levels (by comparing the pressure above and below the liquid) or flow rates (by measuring the change in pressure across a restriction). Technically speaking, most pressure sensors are really differential pressure sensors; for example a gauge pressure sensor is merely a differential pressure sensor in which one side is open to the ambient atmosphere. A DP cell is a device that measures the differential pressure between two inputs. The zero reference in use is usually implied by context, and these words are added only when clarification is needed. Tire pressure and blood pressure are gauge pressures by convention, while atmospheric pressures, deep vacuum pressures, and altimeter pressures must be absolute. For most working fluids where a fluid exists in a closed system, gauge pressure measurement prevails. Pressure instruments connected to the system will indicate pressures relative to the current atmospheric pressure. The situation changes when extreme vacuum pressures are measured, then absolute pressures are typically used instead and measuring instruments used will be different. Differential pressures are commonly used in industrial process systems. Differential pressure gauges have two inlet ports, each connected to one of the volumes whose pressure is to be monitored. In effect, such a gauge performs the mathematical operation of subtraction through mechanical means, obviating the need for an operator or control system to watch two separate gauges and determine the difference in readings. Moderate vacuum pressure readings can be ambiguous without the proper context, as they may represent absolute pressure or gauge pressure without a negative sign. Thus a vacuum of 26 inHg gauge is equivalent to an absolute pressure of 4 inHg, calculated as 30 inHg (typical atmospheric pressure) − 26 inHg (gauge pressure). Atmospheric pressure is typically about 100 kPa at sea level, but is variable with altitude and weather. If the absolute pressure of a fluid stays constant, the gauge pressure of the same fluid will vary as atmospheric pressure changes. For example, when a car drives up a mountain, the (gauge) tire pressure goes up because atmospheric pressure goes down. The absolute pressure in the tire is essentially unchanged. Using atmospheric pressure as reference is usually signified by a "g" for gauge after the pressure unit, e.g. 70 psig, which means that the pressure measured is the total pressure minus atmospheric pressure. There are two types of gauge reference pressure: vented gauge (vg) and sealed gauge (sg). A vented-gauge pressure transmitter, for example, allows the outside air pressure to be exposed to the negative side of the pressure-sensing diaphragm, through a vented cable or a hole on the side of the device, so that it always measures the pressure referred to ambient barometric pressure. Thus a vented-gauge reference pressure sensor should always read zero pressure when the process pressure connection is held open to the air. A sealed gauge reference is very similar, except that atmospheric pressure is sealed on the negative side of the diaphragm. This is usually adopted on high pressure ranges, such as hydraulics, where atmospheric pressure changes will have a negligible effect on the accuracy of the reading, so venting is not necessary. This also allows some manufacturers to provide secondary pressure containment as an extra precaution for pressure equipment safety if the burst pressure of the primary pressure sensing diaphragm is exceeded. There is another way of creating a sealed gauge reference, and this is to seal a high vacuum on the reverse side of the sensing diaphragm. Then the output signal is offset, so the pressure sensor reads close to zero when measuring atmospheric pressure. A sealed gauge reference pressure transducer will never read exactly zero because atmospheric pressure is always changing and the reference in this case is fixed at 1 bar. To produce an absolute pressure sensor, the manufacturer seals a high vacuum behind the sensing diaphragm. If the process-pressure connection of an absolute-pressure transmitter is open to the air, it will read the actual barometric pressure. A sealed pressure sensor is similar to a gauge pressure sensor except that it measures pressure relative to some fixed pressure rather than the ambient atmospheric pressure (which varies according to the location and the weather).

For much of human history, the pressure of gases like air was ignored, denied, or taken for granted, but as early as the 6th century BC, Greek philosopher Anaximenes of Miletus claimed that all things are made of air that is simply changed by varying levels of pressure. He could observe water evaporating, changing to a gas, and felt that this applied even to solid matter. More condensed air made colder, heavier objects, and expanded air made lighter, hotter objects. This was akin to how gases really do become less dense when warmer, more dense when cooler. In the 17th century, Evangelista Torricelli conducted experiments with mercury that allowed him to measure the presence of air. He would dip a glass tube, closed at one end, into a bowl of mercury and raise the closed end up out of it, keeping the open end submerged. The weight of the mercury would pull it down, leaving a partial vacuum at the far end. This validated his belief that air/gas has mass, creating pressure on things around it. Previously, the more popular conclusion, even for Galileo, was that air was weightless and it is vacuum that provided force, as in a siphon. The discovery helped bring Torricelli to the conclusion: We live submerged at the bottom of an ocean of the element air, which by unquestioned experiments is known to have weight. This test, known as Torricelli's experiment, was essentially the first documented pressure gauge. Blaise Pascal went further, having his brother-in-law try the experiment at different altitudes on a mountain, and finding indeed that the farther down in the ocean of atmosphere, the higher the pressure.