Pressure transducers used in the marine industry are designed to operate reliably in severe environments. Pressure transducers are used in storage tanks, reservoirs, flood alarms, cooling systems, and hydraulic systems. Marine sensors are intended to be resistant to everything from mechanical shocks, through hydraulic spikes (originating from pumps and valves), to high temperatures. Pressure transducers enable all of these applications to operate efficiently always.
In order for the pressure transducers to operate reliably under severe conditions, they must be designed well, with well-considered electronics and diaphragms. Modern devices offer powerful performance, with a high accuracy and optimal hysteresis behavior, using a combination of ASIC electronics and CVD-based technology. These sensors are produced for operations over millions of cycles and are designed for submersion.
Pressure transducers are sensors that convert pressure variations in a fluid (i.e. a liquid or gas) into an electrical signal. The signal delivered by the pressure transducers can be continuous; therefore, they feed constant readouts to relevant control systems. This enables the installation of smart control systems where falling pressure levels can trigger a series of alarms, which are customized to the readout, with the most serious leading to system shutdown.
Marine pressure transducers can be used in any part of a ship since they are uniquely designed to function under unfavorable conditions (for example, in liquid interfaces and at high temperatures/pressures). Transducers can enhance performance and efficiency in systems like propulsion units and gearboxes, or in the measurement and management of temperatures, clutch pressure, or oil systems.
Pressure transducers are designed to be resistant to the vibrations that happen on ships. Although these transducers are highly sensitive and accurate systems, they can still offer accurate readings even in conditions involving huge amounts of motion. Transducers include multiple components and are made up of a wide variety of materials. They can provide uncorrupted outputs even in sub-optimal operating conditions. Modern transducer manufacturers have designed systems that can ensure higher performance levels whilst at sea.
Three technologies are crucial to the outstanding performance of modern transducers: chemical vapor deposition (CVD) technology, sputtered thin-film technology, and application-specific integrated circuits (ASIC) electronics packaging. The combination of these mechanical and electronic advancements has led to an increasing desire for their use in the marine sector.
Chemical Vapor Deposition (CVD)
CVD is a high-specification technique of manufacturing pressure transducers. CVD enables the production of accurate devices with good hysteresis behavior in a compact form. The CVD process takes place through an economical batch process, which includes the deposition of polysilicon on a stainless steel surface and then chemical milling of the strain gauge patterns.
Once the milling is done, the wafer is cut into individual sensor beams that are mounted onto a stainless steel summing diaphragm and pressure port, through laser welding. The wafers are linked to electronics that perform signal amplification and conditioning.
CVD enables sensor manufacturers to mass-produce robust and accurate pressure sensors in a cost-effective manner.
Sputtered Thin-Film Technology
For measuring pressure, transducers have a thin sealed sensing diaphragm that is in contact with the media being measured. When the diaphragm is moved, the strain gauge is flexed (either by compression or tension), producing an electrical signal proportional to the displacement. The sensors’ output is transmitted through on-board electronics, with the whole system compactly contained within stainless steel housing.
Sputtered thin-film technology is a recognized manufacturing technique for the production of integrated electronic circuits, which was established three decades ago. The process entails the bombardment of a solid material with energized particles, leading to the sputtering of atoms. The sputtered atoms are subsequently deposited onto a sensing substrate in a controlled electronic pattern.
With sputtered thin-film technology, a sensitive and strong sensor can be created that operates while in direct contact with most of the fluids, including oils and gases. This suggests that these sensors can be used in a wide range of applications.
The use of the sputtered thin-film layer at the time of manufacture leads to a robust, sensitive sensor that is ideal for direct contact with nearly all liquids, gases, and oils, providing the ease of use that has been established to be one of the greatest advantages of pressure transducers.
The development of sophisticated electronics packaging is key in producing custom pressure sensors for the marine sector. Modern pressure transducers often use integral electronic signal conditioning, and this is rendered possible only with improved ASIC technology.
ASIC enables the performance and function of individual transducers to be fine-tuned for various applications. Analogous to CVD, the use of ASIC technology also brings down manufacturing costs, which is making pressure sensors even more prevalent in the marine sector.
Gems Sensors and Controls create a broad range of adaptable and powerful pressure sensors using CVD. These include the capacitive Gems 5000 Series transducer with duplex stainless steel housing, which is resistant to seawater corrosion. The 5000 Series has been proven to be greatly useful in on-board applications for low-pressure sensing, such as the gauging of large but shallow tanks. Another notable sensor is the 2600 Series, which is a submersible sensor rated at IP65. This sensor offers accurate and stable measurements that can be employed in various custom enclosures.
The effect of integrating an improved electronics system with modern pressure sensors results in some robust statistics. Pressure responses may happen below 1 ms, and the accuracy of the sensor does not drift over time. This exceptional performance is maintained over a large number of cycles (over 100 million) and offers useful data for shipboard systems at an affordable price, without requiring any maintenance.
These innovations in transducer and sensor technologies mean that solutions to particular issues faced by marine engineers can be accessed in standard units, meaning that custom solutions are no longer required. The increasing popularity of marine pressure inducers has resulted in greater knowledge-transfer among marine manufacturers, enabling them to design systems that satisfy the requirements and demands of the marine industry at large.
This information has been sourced, reviewed and adapted from materials provided by Gems Sensors and Controls.
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