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Differential pressure transducers are devices that measure the pressure difference between two points in a system. They are an essential part of fluid mechanics and are widely used in many fields, such as the energy, chemical and oil and gas industries. These sensors are very accurate and can measure very low pressures with great precision. They are often used to monitor and control industrial processes, to measure levels or flows, to detect leaks in pipes and to monitor the performance of motors and pumps.

The FKC high accuracy differential pressure sensor models accurately measure a differential pressure and transmit a proportional 4-20 mA electrical output signal. The transmitter uses a unique and highly reliable micro-capacitive silicon sensor, combined with state-of-the-art digital signal processing, to provide outstanding performance in terms of accuracy and stability.

- Accurate measurement results
- Significant process performance due to GyrationTM 4D characterisation
- High plant availability due to unique high reliability design

- High accuracy and reliability
- Design for minimum stock
- Minimal influence of the environment
- HART communication protocols
- Application flexibility
- Programmable linear or square root output
- Long-term stability
- Available with diaphragm seals for extreme temperatures from -90 °C to +400 °C

Differential pressure (dp) is the difference in pressure between two pressures.

The differential pressure cell compares two pressures:

- a reference pressure on the low pressure side (LP or BP)
- a pressure on the high pressure side (HP)

The differential pressure sensor converts the pressure difference into an electronic signal.

The pressure has two pressure ports: one port for low pressure (LP) and one port for high pressure (HP).

Each of these ports is connected to a metal membrane.

When process pressure is applied through each of these ports, it deforms the metal diaphragm.

The FCX intelligent industrial pressure sensor measures the pressure difference by the change in deformation of two metal diaphragms.

The metal diaphragms will transmit the measured pressure via an internal fluid to the micro-capacitive measuring element.

The pressure exerted on both sides of the element will compress the element. The deformation measured is proportional to the differential pressure to be measured.

The signal is then digitally processed by the electronic unit to obtain an analogue and digital signal.

The unit of measurement for differential pressure is the pascal (Pa).

There are also other differential pressure units that are commonly used, including bar, millibar, mmWC.

Several differential pressure ranges are available for differential pressure transmitters. The measurement ranges available range from 0 to 1 mbar for the lowest to 0 to 30 bar for the highest.

These available pressure ranges meet the requirements of a wide variety of applications for effective monitoring of fluid processes.

Depending on the use of the differential pressure sensor, the output signal can be programmed either as linear (output proportional to differential pressure) or as square root output (output proportional to flow).

The square root output function on a differential pressure sensor is used to measure the velocity of a fluid.

We then use the relationship between the speed of the fluid and the differential pressure which is generated by the flow rate of the fluid (Bernoulli's law),

This relationship is expressed by the following equation:

V = sqrt((P1 - P2) / (1/2 * rho))

P1 = Pressure on the high pressure side -HP) measured upstream of the fluid flow

P2 = Pressure on the low pressure side (LP) measured downstream of the fluid flow

rho = Density of the fluid

V= fluid velocity

V= vitesse du fluide

The different types of differential pressure sensors are used in many applications, from flow measurement to level measurement, through filtration and density measurement, as well as interface measurements. They can be used for:

- Measure a differential pressure, to monitor a pump.
- Measure a pressure drop, to monitor filter clogging.
- Measure a liquid or gas level continuously, for a pressure vessel.

The high pressure (HP) side of the level sensor cell measures pressure.

The low pressure (LP) side of the level sensor cell measures the headspace pressure.

The pressure difference between the high and low pressure sides allows the pressure transmitter to calculate the level.

The density must be constant to guarantee the accuracy of the level measurement. - Measure a volume or mass flow of a fluid (liquid flow, gas flow, water flow or steam flow).

In the latter case, the differential pressure transmitter is associated with a primary element which creates a differential pressure according to the flow rate of a fluid. - Measure an interface or a density.
- For applications with very low or very high temperatures, the differential pressure sensors can be equipped with one or two diaphragm seals.

Differential pressure sensors have many advantages for industrial processes.

- Many applications: flow measurement, level measurement, filtration, density measurement, interface measurement
- Rugged design withstands high static pressures
- Improved measurement accuracy compared to using two relative pressure sensors
- Differential pressure measurement with very low pressure
- Differential pressure measurement with very high static pressures
- Diaphram Seal pressure transmitters for extreme temperatures from -90°C to +400°C and harsh environments

Measuring the pressure difference between two points in a system is simplified by using a differential pressure transmitter.

This measuring instrument is designed to accurately measure differential pressure and provide a corresponding digital pressure signal.

With a differential pressure transmitter, you can accurately measure the pressure difference without having to do manual calculations.

Another way to measure differential pressure is to use two gauge pressure transmitters. You then have to measure the pressure separately and calculate the pressure difference manually.

This process can be laborious and error-prone.

Also, if you are using two gauge pressure transmitters, it is essential to ensure that each transmitter is accurately calibrated for accurate pressure measurements.

Indeed, if one of the pressure sensors is offset, the measurement of the differential pressure may be erroneous.

By using a differential pressure sensor, you get rid of these problems and the risk of measurement errors. You use only one device, specifically designed for this differential pressure measurement application. You get accurate, reliable measurement you can rely on.

Differential pressure transmitter documentation