Frequently there is a need in the process industry to measure several properties at the same time. This is most often the case with pressure and temperature, as there is often a direct connection between them. A combined sensor, which can measure both properties, would be ideal. It would reduce the number of openings that must be made in a system for installing sensors and so reduce the hygiene risks.
Food production and processing requires above all, cleanliness and hygiene. Filling levels and pressures are important factors, but temperature is the most frequently measured property in the food industry. It is often required at the same points where level and pressure are measured, in containers, reactors, fermenters and ponds.
Up to now, pressure and level were recorded with pressure transmitters, and temperatures with temperature sensors. In the food industry, pressure transmitters must be installed so that they are absolutely flush with the surface of the process vessel. Any gap increases the risk of contamination and the threat of bacterial growth. Every sealed joint must be maintained; every process connection must be designed and manufactured; and every sensor whether for pressure or temperature is a cost factor.
Vega, a specialist in measurement and sensor technology, recognised the need for a dual-purpose sensor and has developed pressure transmitters that can measure both pressure and temperature.
The pressure transmitter supplies the values for pressure and temperature digitally through a simple 2-core cable and works on Profibus PA. Digital technology makes it possible not only to supply power, but also to transmit the pressure and temperature values from seven pressure transmitters over this single 2-core cable.
Before the temperature signal can be used, the question of accuracy must be considered. Generally temperatures are measured using NTCs, PTCs, temperature crystals or Pt100s. In pressure transmitters, NTCs are frequently employed. Unfortunately, they are not very linear and have even less long-term stability. Attempts to compensate for these factors in the microprocessor meet with only limited success.
However, in the oil-free Vega Multisensors, linear and long-term stable silicon double-diodes are employed. An oil-free sensor was developed because the oil in an oil-filled pressure transmitter is a severe hindrance to the flow of heat from the sensing diaphragm to the measuring cell. A silicon double-diode temperature sensor in the measuring cell records the temperature of the cell in the range -30 to +150°C.
Vega's dual-purpose sensor concept has been successfully adapted for aseptic installations for food industry-approved variants. The sensor has been approved by the EHEDG (European hygienic equipment design group) and the American FDA. The diagram shows a section through the flush-mounting Vega D84 pressure transmitter.
For more information contact Alan Wynn, Vega Instruments SA, 011 958 1901, alan.wynn@za.vega.com
Sitrans P320/P420 pressure transmitters with PROFINET over Ethernet-APL
Pressure Measurement & Control
Siemens’ Sitrans P320/P420 pressure transmitters are now available with PROFINET over Ethernet-APL, enabling data transmission at 10 Mb/s over cable lengths of up to 1 000 m with built-in intrinsic safety for use in hazardous areas.
Read more...Pressure sensor for robust measurement and clear communication ifm - South Africa
Pressure Measurement & Control
ifm’s G1/2 PF pressure sensor monitors highly viscous or abrasive media directly on the system, with a robust ceramic measuring cell, a rotatable display and a flush design that prevents clogging.
Read more...Precision solutions for extreme conditions VEGA Controls SA
Pressure Measurement & Control
VEGA’s VEGAPULS radar sensors, VEGABAR pressure transmitters and VEGASWING level switches deliver reliable measurement in chemical storage environments handling corrosive acids, alkalis and volatile hydrocarbons, with ATEX and IECEx certification for hazardous zones.
Read more...The hydrogen economy is moving from concept to industrial reality VEGA Controls SA
Editor's Choice Pressure Measurement & Control
Scaling the hydrogen economy requires safe, efficient and tightly controlled processes across generation, storage, distribution and end use, underpinned by accurate instrumentation for pressure, temperature, level and flow measurement.
Read more...VEGA leads Africa’s next mining era VEGA Controls SA
Level Measurement & Control
Africa’s mines demand instrumentation that performs under extreme conditions, and VEGA’s level, pressure, point-level and density solutions are engineered to deliver exactly that. From flotation circuits to tailings management, its technologies help operations convert reliable process data into measurable gains in productivity, safety and control.
Read more...VEGA pressure instrumentation supports resilient water network management VEGA Controls SA
Pressure Measurement & Control Flow Measurement & Control
As rapid urbanisation and climate pressures strain water networks across Africa, accurate real-time pressure monitoring has become a strategic necessity. VEGA’s pressure instrumentation helps utilities reduce losses, protect infrastructure and meet sustainability targets.
Read more...Where corrosion meets control VEGA Controls SA
Level Measurement & Control
Reliable level measurement is essential in copper and cobalt processing, and at KCC, VEGA Controls is helping ensure uninterrupted operations with robust vibrating level switch technology.
Read more...Safety, hygiene and quality management for Africa’s pharmaceutical manufacturing industry VEGA Controls SA
Level Measurement & Control
VEGA sensors support critical processes in pharmaceutical manufacturing such as fermentation, purification, formulation, filling, storage and CIP/SIP cleaning cycles. Their design ensures that pharmaceutical manufacturers can maintain sterility, reduce downtime and achieve consistent batch quality, even in demanding production environments.
Read more...Measuring what matters in oilfields VEGA Controls SA
Mass Measurement
In the oil and gas industry, enhanced oil recovery addresses key industry challenges. However, the extraction process often results in a mixture of materials that is hard to characterise.
Read more...Reinventing grain silo management VEGA Controls SA
Editor's Choice
The VEGAPULS 6X radar sensor is designed for continuous level measurement to help overcome the challenges faced by storage in grain silos.
While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.
printer friendly version