Thin film pressure sensors utilise a piezoresistive effect to measure pressure changes. They consist of a thin film sensing element, usually made of materials like polysilicon or metal alloys, deposited onto a flexible metal diaphragm. When external pressure is applied, it causes the diaphragm to deflect, inducing strain in the thin film. This strain alters the electrical resistance of the sensing element, which is then measured and converted into a corresponding pressure reading.
The key advantages of thin film technology lie in its miniature size, high sensitivity, and durability, making it suitable for various applications demanding precise pressure measurements in constrained spaces or harsh environments.
Products
DMP334 Hydraulic Pressure Transducer for Very High Pressures - DMP 334 is a high range pressure transducer designed for measuring hydraulic pressures up to 2200 bar (32,000 psi) .
ASMT Miniature Combined Temperature and Pressure Transducer - 1/2 inch diameter sensor for measuring both temperature and pressure in one device.
Applications
M5 thread compact pressure sensor for 30 bar DOT4 brake fluid - Looking for very compact pressure sensor to be installed on M5 thread, measure DOT4 brake fluid between 1-30 bar
10 bar g miniature pressure transducer with integrated PT100 thermometer - This small size pressure & temperature transducer has a PT100 platinum resistance thermometer and a 0 to 10 bar gauge pressure range with a radiometric output of 0.5 to 4.5 volts dc with a supply voltage of 5 volts dc.
20,000 psi g digital pressure gauge with 4 to 20 mA output - 4-20 milliamp loop powered high range pressure gauge for measuring 0 to 20,000 psi gauge.
10,000 psi hydraulic pressure transmitter and panel readout - Pressure transmitter and remote readout for measuring hydraulic fluid from 0-10,000psi.
Mechanical press 1000 bar pressure sensor and panel indicator
High pressure pump 1600 bar water pressure sensor with 4-20mA output
2000 bar high pressure water pump 4-20mA pressure transducer
Injection moulding machine 22000 psig 4-20mA output synthetic hydraulic oil pressure sensor
10 ksi g range 4-20mA out high pressure sensor for pumps and actuators bench test rig use
30000 psig 0-10Vdc output freshwater pressure sensor for high pressure valve test rigs
1600 barg 4-20mA freshwater pressure sensor for hydrostatic testing
All welded wetted parts 10000 psig 0-10Vdc out pressure sensor for hydraulic control use
How It’s Made
Thin-film sensing elements are typically manufactured through microfabrication techniques, such as sputtering or chemical vapour deposition. These processes deposit a thin layer of piezoresistive material, like polysilicon or metal alloys, onto a substrate, often a flexible diaphragm. The deposition process can be precisely controlled to achieve the desired thickness and uniformity of the sensing element.
How it works
The operating principle of a thin-film sensing element relies on the piezoresistive effect. Piezoresistive materials exhibit a change in electrical resistance when subjected to mechanical stress or strain. When external pressure is applied to the diaphragm, it deflects, causing the thin film to stretch or compress. This deformation induces strain within the thin film, which alters its electrical resistance proportionally to the applied pressure.
The resistance change is measured using a Wheatstone bridge circuit, which is usually almost entirely made up of thin-film piezoresistive elements. In some cases, additional electronics such as resistors may be incorporated to balance the bridge and compensate for offsets or temperature variations. The Wheatstone bridge configuration allows for high sensitivity and common-mode noise rejection, making it ideal for converting the small resistance changes of the thin film into a measurable voltage signal. This voltage signal can then be amplified and processed to obtain a precise pressure reading.
Characteristics & Properties
Thin film sensors offer a unique combination of miniature size, high sensitivity, wide pressure range, and excellent durability. These advantages make them a preferred choice for many applications where space constraints, accuracy, and reliability are critical factors.
Miniaturisation
Thin film sensors excel in miniaturisation due to the nature of their fabrication process. The deposition of thin layers onto substrates allows for incredibly small and compact sensor designs, which is not always feasible with bulkier technologies like bonded foil or thick film strain gauge.
High Stability
The strain gauges are created using sputtering techniques, which produces a molecular bond between the diaphragm substrate and the strain gauges, leading to a very stable sensing technology, with very little calibration shift over time.
High Vibration Shock Tolerance
Due to the small size and low mass of thin-film strain gauge sensing diaphragms, they perform very well in high shock and vibration environments with less degradation to the reading accuracy and signal to noise ratio.
Less Complex & More Robust Construction
Thin-film pressure sensors boast a simpler construction compared to other pressure sensor technologies due to their monolithic design. The sensing element, diaphragm, and often signal conditioning circuitry are integrated into a single assembly, reducing the number of components and potential failure points. This streamlined construction not only enhances the sensor’s robustness but also reduces its size and weight, making it more resilient to mechanical shocks and vibrations. Additionally, the materials used in thin-film technology are inherently durable and can withstand harsh environmental conditions, including high temperatures, pressures, and corrosive media. This combination of simplified construction and robust materials makes thin-film pressure sensors highly reliable and well-suited for demanding applications where durability and longevity are critical.
Dynamic High Pressure
Thin-film pressure sensors demonstrate exceptional dynamic high-pressure tolerance due to their robust construction and absence of vulnerable components. The metal diaphragm, typically made of stainless steel or other resilient alloys, can withstand rapid pressure fluctuations and high-pressure spikes without significant deformation or damage. This is a significant advantage over sensors that rely on oil filling or isolation membranes, which can be prone to rupture or leakage under extreme pressure conditions. Moreover, the absence of these components eliminates potential sources of contamination or interference, ensuring the sensor’s long-term stability and reliability in demanding dynamic high-pressure environments.
Specialised Gases
Thin-film pressure sensors are particularly well-suited for measuring specialised gases like hydrogen, oxygen, or helium due to their unique construction features. The utilisation of an all-welded, relatively thicker stainless steel diaphragm provides a robust barrier against gas permeation, preventing contamination of the measured gases and ensuring the integrity of the sensor over time. This is crucial when dealing with reactive gases like hydrogen or oxygen, which can degrade or react with other materials commonly used in sensor construction.
Furthermore, the absence of oil filling eliminates the risk of oil contamination, which can be detrimental to the purity of the measured gases. The all-welded construction also minimises the risk of leaks, preventing the escape of potentially hazardous gases like hydrogen into the electronics or surrounding environment. This enhances safety and ensures compliance with stringent regulations governing the handling of specialised gases.
Overall, the combination of a robust all-welded construction, thicker stainless steel diaphragm, and absence of oil filling makes thin-film pressure sensors an ideal choice for measuring specialised gases like hydrogen, oxygen, or helium. Their ability to prevent contamination, minimise leaks, and withstand harsh environments ensures accurate and reliable pressure measurements, even in demanding applications.
High Operating Temperature Range
Thin-film pressure sensors are capable of withstanding higher operating temperatures due to their robust all-metal construction and molecular bonding techniques. The absence of organic adhesives or epoxies, which are susceptible to degradation at elevated temperatures, contributes to the sensor’s thermal stability. Unlike other pressure sensor technologies that may incorporate temperature-sensitive materials like plastics or elastomers, thin-film sensors rely on materials like high-temperature resistant alloys, which exhibit excellent thermal stability and can maintain their mechanical and electrical properties even at high temperatures.
The molecular bonding process used in thin-film sensor fabrication ensures a strong and durable connection between the sensing element and the diaphragm, further enhancing its high-temperature resilience. This bonding method eliminates the risk of delamination or separation that can occur in sensors that rely on adhesives, which tend to weaken or fail at elevated temperatures.
Additionally, the thin-film sensing element itself is typically made of materials metal alloys that are inherently stable at high temperatures. These materials do not undergo significant changes in their properties or experience thermal degradation, ensuring consistent and reliable performance even in extreme thermal environments.
Applications
Motorsport
Miniature thin film pressure sensors are an ideal choice for high-performance motorsport vehicles due to their unique combination of features. Their low mass and small size are crucial for minimising added weight and optimising space in these highly engineered machines. This allows for streamlined integration into various vehicle systems without compromising performance or aerodynamics.
The ability to withstand high operating temperatures is another critical factor in motorsport, where engines and brakes generate intense heat. Thin film sensors, with their robust construction and absence of temperature-sensitive components, can reliably operate in these extreme environments, ensuring accurate pressure measurements even under intense racing conditions.
Furthermore, thin film sensors exhibit excellent resistance to shock and vibration, which are prevalent in the harsh environment of motorsport. The monolithic design and strong molecular bonding of these sensors minimise the risk of damage or malfunction due to mechanical stress, ensuring consistent and reliable performance even during high-speed manoeuvres and impacts.
In motorsport, precise pressure monitoring is essential for optimising engine performance, managing tire pressure, and ensuring the proper functioning of braking and hydraulic systems. Thin film pressure sensors provide the accuracy, reliability, and durability required to meet the demanding requirements of this high-performance industry. Their ability to deliver accurate pressure data in real-time allows engineers to make critical adjustments to vehicle setups, enhancing performance and safety on the track.
Hydraulics
High-range thin-film pressure sensors are ideally suited for hydraulic applications due to their unique ability to withstand extreme pressure conditions. In hydraulic systems, pressure surges and spikes are common occurrences, especially during rapid changes in flow or sudden valve closures. The robust construction of thin-film sensors, with their thicker metal diaphragms and absence of fragile components like oil-filled chambers or isolation membranes, allows them to endure these dynamic pressure fluctuations without sustaining damage or compromising accuracy.
Furthermore, the miniature size of thin-film pressure sensors is a significant advantage in compact mobile hydraulic packages, where space is at a premium. Their compact footprint allows for easy integration into tight spaces, minimising the overall size and weight of the hydraulic system. This is particularly beneficial in applications like construction equipment, agricultural machinery, and mobile cranes, where portability and manoeuvrability are crucial.
In addition to their high-pressure tolerance and small size, thin-film sensors also offer other benefits for hydraulic applications. Their high accuracy and fast response times enable precise monitoring and control of hydraulic pressures, ensuring optimal system performance and preventing damage due to over-pressure or under-pressure conditions. Their resistance to vibration and shock further enhances their reliability in demanding hydraulic environments, where mechanical stresses are common.
Moreover, thin-film pressure sensors can be customised for specific pressure ranges and output signals, providing flexibility to meet the unique requirements of different hydraulic applications. They can also be integrated with signal conditioning circuitry and digital interfaces, simplifying their integration into complex hydraulic control systems.
Overall, the combination of high-pressure tolerance, miniature size, accuracy, and reliability makes thin-film pressure sensors an excellent choice for a wide range of hydraulic applications, from heavy-duty industrial machinery to compact mobile equipment. Their ability to withstand dynamic pressure surges, provide precise measurements, and operate reliably in demanding environments ensures optimal performance and longevity of hydraulic systems.
Research & Development
Miniature thin film pressure sensors are invaluable tools in research and development, particularly for testing prototype machines and vehicles. Their small size and lightweight nature make them ideal for temporary installation without significantly impacting the overall weight or dimensions of the prototype, thus minimising any potential influence on test results. This allows engineers to obtain accurate and reliable pressure data from critical systems and components without compromising the integrity of the testing process.
The ability to seamlessly integrate these sensors into tight spaces or complex systems further enhances their usefulness in research and development. Thin film pressure sensors can be easily incorporated into various components, such as engines, hydraulic systems, or aerodynamic surfaces, to monitor pressure fluctuations in real-time during testing. This real-time data provides invaluable insights into the performance and functionality of the prototype, allowing engineers to identify potential issues, optimise designs, and validate engineering objectives.
Moreover, thin film sensors’ high accuracy and fast response times enable researchers to capture even subtle pressure variations, providing a comprehensive understanding of the system’s behaviour under different operating conditions. This level of detail is crucial for refining designs, troubleshooting problems, and ultimately achieving optimal performance in the final product.
Furthermore, the durability and reliability of thin film pressure sensors make them well-suited for the demanding conditions often encountered in research and development. They can withstand vibrations, shocks, and temperature fluctuations, ensuring consistent and accurate data collection throughout the testing process.
In summary, miniature thin film pressure sensors play a pivotal role in research and development by providing a non-intrusive, accurate, and reliable means of measuring pressure in prototype machines and vehicles. Their compact size, ease of integration, high accuracy, and durability make them indispensable tools for engineers and researchers seeking to optimise designs, validate performance, and achieve engineering objectives.
Advantages
- Miniaturisation of sensor package for applications requiring low mass and small size
- Good stability of output signal due to molecular bonded strain gauges
- Vibration and shock tolerance due to low mass and simpler robust construction
- Dynamic high pressure tolerant due to tough metal sensing diaphragm without oil filling or thin isolation membranes
- Welded design with thicker diaphragm prevents gas contamination and leaks, ideal for specialised gases.
- All-metal construction and molecular bonding allow for higher operating temperatures without degradation.
Disadvantages
- Less repeatable performance at low pressures and more susceptible to temperature changes.
- Lower output sensitivity than semiconductor strain gauge technologies
- Limited absolute pressure ranges due to design complexity of containing and maintaining a stable vacuum reference
- Less options for differential pressure ranges due to difficulties integrating an additional diaphragm into the reference side and isolation the strain gauges and interconnections from the process media
Checklist for thin film pressure sensor requirements
Define your thin film pressure sensor requirements using this checklist:
- Pressure range?
- Overpressure?
- Output signal?
- Dynamic response?
- Accuracy?
- Electrical connection?
- Process connection?
- Size dimensions?
- Process media type?
- Media temperature range?
- Environment temperature range?
- Environment shock and vibration?
- Shock pressures?