All pressure transducers and transmitters convert the pressure in a process line into an electrical signal.

In general, pressure or differential pressure transmitters are vital elements in industrial installations. Most of them can be found installed inside compressors, dryers, mounted on compressed air pipelines, pressurized vessels, accumulator tanks or line filters and in control systems such as PLCs.

Today, industrial plants handle compressed air, liquids, gases or steam. We are not only limited to see the pressure values in a given line, but you have to use that value in integrated control systems that perform jobs or certain actions with that value. To do this, you have to send that pressure measurement to them and it is done by means of an electrical signal.

Pressure transmitters are actually pressure sensors. Other names, such as pressure transducers, are also accepted, but care must be taken with this aspect because some manufacturers call pressure transducer to equipment that send signals in volts and not in mAmp.

The most common electrical value in this type of equipment is 4 to 20 mAmp, using a two-wire cable like the one shown in the photograph.

Although the most commonly used signal is in mAmp, it is also possible to find applications that work with signals in volts. The most frequent are 1-5 volts or 0-10 volts with 3-wire cables, but 0-100 millivolts are also used with 4-wire cables.

In today’s industrial processes and controls, we witness technological advances with the advent of microprocessors and electronic components, Fieldbus technology, the Internet, etc., all to facilitate operations, ensuring the optimization and performance of processes and operational safety. This advance makes it possible today that pressure transmitters, as well as transmitters of other variables, can be designed to guarantee high performance in measurements that until then used only analog technology. Analog transmitters were designed with discrete components, susceptible to deviations due to temperature, environmental and process conditions, with constant adjustments through potentiometers and keys. With the advent of digital technology, simplicity of use became very easy.

Pressure transmitters are widely used in processes and applications with numerous functionalities and resources. The vast majority of industrial processes involve pressure measurements, yet pressure is a basic variable to measure for the control of flow, level, density, etc.

The accuracy of a pressure transmitter

In the last decades, a huge variety of equipment has spread through the market for various applications. The accuracy of transmitters is usually between 0.5% to 0.1%. Every pressure measurement system is composed of the primary element, which will be in direct or indirect contact with the process where pressure changes occur, and the secondary element (the pressure transmitter), which will have the task of translating this change into measurable values for use in indication, monitoring and control.

The static performance or accuracy of a pressure transmitter depends on how well calibrated the instrument is and how long it can maintain its calibration. Keep in mind that accuracy is often confused with precision; accuracy is associated with the proximity to the true value and precision is associated with the dispersion of values resulting from a series of measurements.

Calibration of a pressure transmitter encompasses zero and spam adjustment. Accuracy usually includes nonlinear effects of hysteresis and repeatability. Accuracy is usually obtained in % of the calibrated spam.

Intelligent pressure transmitters

A smart transmitter blends sensor technology to its electronics. It must provide the following features:

• Digital output signal.
• Digital communication interface.
• Pressure compensation.
• Temperature compensation.
• Stability.
• Simple calibration.
• Re-rangeability with and without reference.
• Self-diagnosis.
• Easy installation.
• High reliability; they are very accurate (from 0.5% to 0.01%).
• Low costs and short installation and maintenance times.
• Reduced intrusion / penetration (process).
• Installation space saving.
• Upgrades to Foundation Fieldbus and Profibus PA technology, etc. are possible.

Flexilatina, continuing with its multi-brand strategy, offers the Colombian market different options from simple transmitters to intelligent transmitters. Our brands are Winters, Wika and Noshok; recognized and widely used brands in our country. We also have a Pressure Laboratory with ONAC 09-LAC-031 accreditation in calibration of pressure gauges according to ISO/IEC 17025:2017, with a range from vacuum to 10,000 PSI. This means that the supply of our transmitters can be accompanied by a formal calibration certificate. Likewise, we are able to adjust and scale intelligent pressure transmitters that have HART Protocol (Highway Addressable Remote Transducer) as communication system.