In medical devices, precise pressure and flow measurements are central to diagnostic accuracy and therapeutic safety. Transducers, sensors that convert pressure into electrical signals, are indispensable components in these systems, especially for applications involving liquids and gases.

Merit Sensor Systems, leveraging advanced MEMS technology, provides high-performance medical-grade transducers engineered for use from the benchtop to the clinic.

Pressure and Flow: Taking the Pulse Through Medical Applications

Medical equipment is routinely employed to monitor pressure within fluid delivery systems as well as the human body. By utilizing Bernoulli’s principle, in which pressure reductions across a restriction are proportional to the square of the flow rate, pressure measurements can be used to approximate flow, provided the system geometry is known. Accordingly, devices like infusion pumps can detect pressure to identify occlusions, and ventilators are able to calculate airflow based on pressure changes.

Merit Sensor’s transducers measure both gas and liquid pressure across applications, such as digital inflation devices, depth/crossflow filtration, gas detection, bioreactor monitoring, peristaltic pumps and many more.^1,2 To deliver consistent measurements, Merit’s transducers are designed with high-frequency response and analog signal output for fine-grained signal processing. This ensures even subtle pressure fluctuations, such as pulsating displacements, are captured with high fidelity.

MEMS Technology for Sensing: The Heart of Effective Metrology

Merit Sensor’s medical-grade transducers use silicon-based MEMS (micro-electro-mechanical systems) technology. These sensors incorporate a minute diaphragm with a Wheatstone bridge that flexes under pressure, converting mechanical force into an electrical signal.³ Through proprietary laser-trimmed resistors, each device guarantees low offset error and stable zero-points, achieving a temperature-compensated zero drift (TCZ) of under 2 % full scale, maintaining accuracy across typical hospital and lab environments without needing external compensation electronics.⁴

A standout feature is the wide pressure range, from -15 psi (full vacuum) to over 1000 psi. This allows use across diverse medical needs, including blood pressure monitoring and high-pressure injection systems. Despite their compact dimensions, these transducers are mechanically robust, with burst tolerance up to 1000 psi, allowing safe operation even under demanding conditions.

Purpose-Built: Medical-Grade Durability and Compatibility

Sterilization and biocompatibility are critical in medical design. Merit Sensor’s transducers use carefully selected wetted materials—such as silicon sensing elements—that are inert to common fluids like blood, saline, and medications. Many models also include silicone gel barriers that isolate internal components, enhancing fluid resistance and safety.³

Importantly, these components tolerate standard sterilization processes such as ethylene oxide (ETO) gas and gamma irradiation, making them suitable for both single-use and reusable devices. Whether embedded in a bedside monitor or integrated into a sterile fluid path, Merit Sensor transducers meet strict safety and cleanliness standards.⁵

Our Portfolio: Trusted Solutions for Medical Pressure Sensing

AP Series – Compensated Pressure Sensor Assemblies

Merit’s AP Series is a compact, passively compensated sensor line used widely in medical and pharmaceutical devices. With customizable packaging options, these assemblies provide accurate, analog millivolt output with low offset error, ready for external signal amplification.

Designed for digital inflation devices, AP Series sensors are built with sterilizable materials, extending their utility to any low to medium pressure medical application.³

Amplified Pressure Transducer Assemblies

For plug-and-play integration, our portfolio includes transducers with onboard electronics that amplify and condition the signal. These assemblies use the same core sensing element as the AP Series but add real-time compensation for pressure and signal linearity. Luer lock connections ensure simple fluid interfacing, while a standard 3 pin Molex or an optional RJ11 connector make them compatible with hospital-grade systems. Their robust construction and sterilization tolerance suit applications, including diagnostic and analysis equipment.⁶

Meritrans^® Disposable Blood Pressure Transducers and Flush Devices

Our range of Meritrans® Blood Pressure Transducers, including the Meritrans® DTXPlus, are a range of disposable, single-use pressure transducers designed for arterial blood sampling. Commonly found in surgical and critical care settings, they translate blood pressure within the body into a real-time signal displayed on bedside monitors.^6,7

These sterile transducers connect via Luer locks and include integrated flush devices for line maintenance. A manual flush clears blood, while a continuous low-rate flush (e.g., 3 mL/hour) keeps the line open. For safety, overpressure valves automatically vent excess pressure back into the IV bag, preventing device or patient harm.⁸

Core Advantages of Merit Sensor Transducers

• Accuracy and Stability: The MEMS elements deliver precise readings with low temperature drift, ensuring long-term reliability without complex compensation electronics.
• Wide Pressure Range: From vacuum conditions to 1000 psi, the same sensor platform handles a range of medical use cases, from suction to high-pressure fluid delivery
• Mechanical Robustness: With high burst resistance, our transducers offer operational safety and durability, even in disposable formats.
• Sterilization Compatibility: ETO- and gamma-compatible materials ensure safe reuse or single-use deployment in sterile environments.
• Flexible Signal Output: Devices can choose between uncompensated millivolt signals for low-cost integration or fully conditioned analog outputs for quick deployment.
• In-House Customization: Vertically integrated wafer-fab allows for tailored performance and packaging to meet unique medical design requirements.

Conclusion: Trustworthy Data in Life-Critical Applications

Pressure transducers play a major role in modern medical technology, transforming critical physical parameters into actionable digital signals. Whether tracking blood pressure or monitoring inflatable devices, Merit Sensor’s transducers empower healthcare professionals with accurate, reliable data.

By combining rugged design, sterilization readiness, and customizable performance, these sensors meet the exacting standards of the medical industry. Merit Sensor’s solutions span from OEM elements to complete disposable transducers, offering broad utility for diagnostic, monitoring, and therapeutic systems. For manufacturers and clinicians alike, these transducers provide a dependable foundation for improving patient care through precision measurement.

If you’re looking to find out more, contact a member of the Merit Sensor’s team today!

References and Further Reading

1. Merit Medical. [Online] Inflation Devices. Available at: https://www.merit.com/solutions/inflation-devices/ (Accessed on 23 April 2025).
2. Merit Medical. [Online] Meritrans® Pressure Transducers. Available at: https://www.merit.com/product/meritrans-pressure-transducers/ (Accessed on 23 April 2025).
3. Merit Sensor. Data Sheet: AP Series. Available at: https://meritsensor.com/assets/documents/pdf/AP-series.pdf (Accessed on 23 April 2025).
4. Merit Sensor. [Online] AP Series. Available at: https://meritsensor.com/products/AP-Series/ (Accessed on 23 April 2025).
5. Merit Sensor. [Online] Merit Sensor AP Series in Pharmaceutical and Medical Applications. Available at: https://meritsensor.com/merit-sensor-ap-series-in-pharmaceutical-and-medical-applications/ (Accessed on 23 April 2025).
6. Merit Sensors. Merit OEM Transducers.
7. Merit Medical. [Online] Meritrans DTXPlus Disposable Transducers. Available at: https://www.merit.com/product/meritrans-dtxplus-disposable-transducers/ (Accessed on 23 April 2025).
8. Merit Medical. Meritrans DTXPlus™ Disposable Pressure Transducer Sets Safedraw™ Blood Sampling System. Available at: https://manualzz.com/doc/81931887/merit-medical-meritrans-dtxplus-disposable-transducers-in… (Accessed on 23 April 2025).

During the COVID-19 pandemic, several medical papers exposed the risk of barotrauma from mechanical ventilation, bringing into focus the value of precise pressure sensor technologies.^1,2,3 Yet the utility of pressure sensors extends beyond medical applications, complementing pneumatic systems, electronics, and dry, non-corrosive gas pressure tools.

The CMS Series of pressure sensors, manufactured by Merit Sensor, provides high-performance solutions for all these applications. This article explores these sensors in the context of analyzers and ventilators, explaining why they represent the preferred choice for medical professionals, engineers, scientists, and industry leaders worldwide.

Analyzers and Ventilators: In a Nutshell

Analyzers encompass a broad range of devices used to measure and profile various substances, such as gases, liquids, and blood samples. These devices play a crucial role in diagnostic, environmental monitoring, and quality control applications. Some key examples include blood gas analyzers, gas chromatographs, ECMO machines and other systems like  air quality monitors equipped with analyzers to track pollutants and ensure optimal indoor air quality. To ensure these systems operate within ideal parameters, pressure sensors are incorporated to monitor and regulate airflow and pressure levels.⁴

On the other hand, mechanical ventilators are specialized devices designed to assist with a patient’s breathing. These machines deliver positive pressure ‘breaths’ to the lungs, ensuring effective oxygen circulation and carbon dioxide expulsion. Ventilators carefully regulate airflow based on patient-specific settings, such as pressure, volume, and breathing rate, to fully support or augment spontaneous breathing. Precise pressure sensors are also critical to their operation, maintaining the correct air pressure and preventing complications such as barotrauma.⁵

Enter the CMS Series by Merit Sensor

The CMS Series by Merit Sensor is a high-performance pressure sensor designed for precision and reliability. Utilizing an ASIC for calibration and thermal compensation, this sensor guarantees long-term, accurate pressure responses. It features a piezoresistive Wheatstone bridge with glass bonded to a chemically etched silicon diaphragm, which allows the sensor to maintain stability across various environmental conditions. Its compact size, wide operating voltage range, and low power consumption make it valuable across numerous applications. With absolute and gage pressure options, the CMS Series is suitable for a range of pressure-sensing needs, offering both I²C and SPI digital outputs.

Merit Sensor, based near Salt Lake City, Utah, designs, engineers, and manufactures its products in-house, assuring quality control from start to finish. The company’s proprietary Sentium^® technology provides best-in-class temperature stability, allowing sensors like the CMS Series to perform steadfastly under challenging conditions. This comprehensive approach to development and production positions Merit Sensor as a leader in high-precision pressure sensing solutions.^6,7

CMS Series: Specification Breakdown

The unique profile of the CMS Series sets it apart from other pressure sensors on the market, making it the go-to choice for both analyzers and ventilators.

1. High Precision
   

   Whether using analyzers or ventilators, extreme precision is required to generate data that reliably reflects sample conditions. With an accuracy of ±0.25 % full-scale output, the CMS Series offers pinpoint pressure measurements and peace of mind in situations where minor deviations affect performance and patient outcomes.⁴

2. Durability and Stability
   

   Engineered with a robust silicon piezoresistive element, these sensors provide long-term repeatability and can operate in demanding outdoor conditions and healthcare environments. Their stable performance over time reduces the need for frequent maintenance or recalibration.⁶

3. Wide Pressure Range
   

   The CMS Series covers a broad spectrum of pressures—from  -2 to 150 psi—accommodating the needs of both high- and low-pressure applications. This versatility makes it suitable for a wide variety of devices and industries.⁴

4. Compact Design
   

   At only 6.8 mm x 6.8 mm, the CMS Series is small enough to be easily integrated into compact devices without compromising on performance. This is a significant advantage for manufacturers designing portable or space-constrained equipment, such as hand-held analyzers.⁴

5. Temperature Compensation
   

   CMS Series sensors are equipped with temperature compensation over a range of -40 °C to 85 °C, making them reliable even in fluctuating environmental conditions.⁷

6. Low Power Consumption
   

   Efficient power use is essential in devices like ventilators that need to operate continuously and for battery-powered analyzers that are used in the field. The CMS Series’ low power mode ensures minimal energy consumption without sacrificing performance.⁶

7. Domestic Manufacturing
   

   All CMS Series products are proudly manufactured in the US, ensuring the highest standards of quality and compliance with local regulations.⁴

8. RoHS Compliant
   

   All products are Restriction of Hazardous Substances (RoHS) compliant, meeting the specific environmental safety standards set by the European Union.⁶

The CMS Series by Merit Sensor: A Benchmark for Precision and Performance

The CMS Series harnesses the latest pressure-sensing technology, blending innovation with precision, to deliver unrivaled performance. With its advanced design, offering temperature compensation and energy efficiency, it serves as a critical component in life-saving medical devices like ventilators as well as environmental analyzers.

Manufactured in the US with a commitment to superior quality, the CMS Series is engineered to adapt to evolving needs. Its versatility ensures that professionals worldwide, from engineers to healthcare providers, can trust it to perform under the most demanding conditions.

Contact a member of the Merit Sensor Systems team today to learn more!

References and Further Reading

1. Serck, N., et al. (2023). Barotrauma in COVID-19 acute respiratory distress syndrome: retrospective analysis of the COVADIS prospective multicenter observational database. BMC Anesthesiology. doi.org/10.1186/s12871-023-02093-1
2. Belletti, A., et al. (2021). Predictors of Pneumothorax/Pneumomediastinum in Mechanically Ventilated COVID-19 Patients. JVCA. doi.org/10.1053/j.jvca.2021.02.008
3. Rajdev, K., et al. (2021). Pulmonary Barotrauma in COVID-19 Patients With ARDS on Invasive and Non-Invasive Positive Pressure Ventilation. Journal of Intensive Care Medicine. doi.org/10.1177/08850666211019719
4. CMS Series technical datasheet
5. Hickey, S.M., et al. (2024). [Online] Mechanical Ventilation. StatPearls [Internet]. Available at: https://www.ncbi.nlm.nih.gov/books/NBK539742/ (Accessed on 21 October 2024).
6. Merit Sensor. CMS Series: Data Sheet. Available at: https://meritsensor.com/assets/documents/pdf/CMS-Series.pdf
7. Merit Sensor. [Online] CMS Series – Available Now! Available at: https://meritsensor.com/products/cms-series/ (Accessed on 20 October 2024).

In this interview, AZoSensors speaks to Merit Sensor’s Rick E. Russell about the critical role MEMS pressure sensors will play in water conservation efforts.

Could you describe the role of water in the MEMS pressure sensor manufacturing process and the key reasons behind implementing a water-conservation initiative?

Deionized water is the main ingredient for wafer fabrication processing and is similarly the largest waste product that we have to deal with. We have been prioritizing the sustainability of our operations for a number of years, and both reducing water usage and minimizing water waste have been central to this initiative.

This work also links into our wider organizational goals around sustainability. We believe that as a global leader in healthcare technology, Merit Medical has a major role to play in contributing to a sustainable future. Improving our organization’s sustainability is also key to the success of our overall business strategy.

In what ways does the water-recycling program address the challenges associated with wastewater treatment and disposal during the sensor fabrication process?

Many of our sites are based in desert environments where available water is at a premium, so we strive to conserve as much water as possible.

Our waste naturalization system already balances the wastewater’s pH before we send it down the drain, so we thought it would be worth the investment to see if we could recycle this water instead.

Can you walk us through the steps involved in recycling and reusing wastewater to produce MEMS pressure sensors?

We utilized the Water Risk Filter tool provided in collaboration between the World Wildlife Fund for Nature (WWF) and KFW DEG, and this helped us to understand basin water risk at our operating locations.

Since then, we have identified three manufacturing locations (Tijuana, Mexico; Salt Lake City, Utah; and Pearland, Texas) as water-stressed sites and invested capital over the past three years at these drought-vulnerable operations to allow us to better conserve and store water.

To recycle and reuse wastewater, we essentially pass it through additional filtration cycles and add chemicals to strip away any unnecessary contaminants.

In 2022, we implemented two successful projects of this nature at our Salt Lake City site: a cooling-water recirculation project and a process-water recirculation project within our sensor operations. We are also working on a similar project at our facility in Tijuana, Mexico, which is our second largest site for water consumption and another where a risk of water scarcity has been identified.

Considering the involvement of acids and bases in manufacturing, what measures have been implemented to treat and neutralize wastewater before discharge?

Our waste neutralization system continuously monitors the pH of the contaminated water and balances the pH with the necessary acid or base before discharging the water down the drain.

How does Merit Sensor’s water-saving initiative align with the broader regional efforts to mitigate water usage?

As reported by our CEO in our 2023 Sustainability Report, Merit completed its third year of progress toward our 2030 Operational Sustainability Goals, and we are seeing more evidence of momentum as we consistently reach and surpass each of our targets for energy, water, and greenhouse gas emissions.

Efforts to mitigate water use vary between regions. Water is one of our main environmental challenges and opportunities, so we have worked to better understand the impact of water use at each of our operating facilities and to implement water efficiency programs on a regional level.

These goals and initiatives are addressed at the individual site level, and we can do this by understanding the local and regional water basin activity and stress.

Achieving a ninety percent water recycling efficiency is an ambitious goal. What innovative approaches or technologies are Merit Sensors exploring to reach this objective?

As pointed out in our 2023 Sustainability report, we have other ongoing projects, such as closed-loop water cooling and xeriscaping, that will help us reach our goal. The water recirculation project will also be instrumental in our success in this area.

We have already seen a 17 % decrease in water withdrawal per dollar of revenue earned since 2020, already surpassing our global 2030 targets. This water intensity improvement was primarily driven by water-reduction and efficiency projects, including the use of xeriscaping and installing water-recirculation systems at our largest site in Salt Lake City, Utah.

Can you share some of the critical lessons your team learned throughout the process and how these experiences have influenced your approach to sustainability in other aspects of the company’s operations?

Merit was initially focused on xeriscaping because it was the most straightforward. We knew that fabrication was the biggest culprit for water consumption, but the cost of water does not provide any payback. We learned very quickly that you must spend money to save water. If water costs more than gasoline, then everyone would be focused on saving water.

Does the water-recycling program offer any other potential environmental benefits besides conserving water?

We at Merit believe that spending money to save water would, in turn, save lives. Water is essential for drinking, farming, firefighting, reservoirs and dams, wildlife, and much more. This is also important because several of our sites are located in regions prone to droughts, and any water saved can potentially be used by local communities or amenities.

How do you envision the long-term impact of this initiative on the company’s operations and its contribution to sustainable manufacturing?

Merit is committed to our long-term goals of maintaining our ISO14001 and ISO50001 certifications. This includes not only water but also energy consumption and emissions.

For example, 50 % of our manufacturing sites (Salt Lake City, Utah; Galway, Ireland; Venlo, the Netherlands; and Paris, France) are certified to ISO 50001, and we continually seek to improve our energy management systems.

By implementing this system in our sensor operations and fine-tuning its performance, we are paving the way for similar solutions at other Merit sites to continue reaping the benefits of using water efficiently.

MEMS pressure sensors find applications in various industries. can you elaborate on the quality control measures to ensure recycled water meets the required standards for diverse applications?

Further testing has proven that recycled water does not affect the quality of our MEMS pressure sensors or the operation of our fab. We currently deliver pressure sensors to monitor the pressure in various water applications, such as water meters and tank levels.

Apart from the current water-recycling project, has Merit Sensor integrated other sustainable practices into its manufacturing process?

Merit is focused on three major sustainability goals: decreasing water intensity by 10 %, decreasing energy intensity by 10 %, and decreasing GHG emissions by 15 % by 2030. We are also working towards increasing the proportion of Merit’s energy from renewable sources to 50 % of total usage.

Increasing our use of renewable and carbon-free energy is a key part of our long-term strategy. We have already committed to purchasing 50 % of our total energy from renewable and carbon-free sources by 2030, and given the large amount of energy required by our operations, we also plan to explore opportunities around installing solar panels and the potential of carbon offset credits.

Wider goals include reducing product packaging, transitioning to paper-free systems where possible, and increasing the percentage of waste at our facilities that is recycled.

About the Speaker

Rick joined Merit Sensor in October of 2009 where he managed worldwide sales and business development until he became President of the group in 2013.  He brings many years of organizational management and technical expertise in the area of MEMS silicon fabrication. With more than 25 years of experience managing sales to product development across multiple industries, his knowledge has enabled him to expand the operations to accommodate a number of new customers in their state-of-the-art wafer fab located in Salt Lake City.

Rick studied mathematics and computer science at Eastern Michigan University and received a Bachelor of Science in Electrical-Engineering from Lawrence Technological University.

This article was published by AZo Network.

In this interview, AZoSensors talks to Scott Sidwell, Engineering Manager at Merit Sensor Systems, about MEMS piezoresistive pressure sensors, silicon dies, and how these are all utilized across a range of industries.

Could you provide us with some background information on pressure sensors and their significance in various industries?

Pressure sensors are vital components that play a crucial role in various industries. The pressure sensor market is projected to see remarkable growth, as indicated by recent research, and it is expected to reach nearly 24.5 billion dollars by 2028.

They find applications in automotive, industrial automation and process control, consumer products like diving, e-bikes, and, importantly, in the medical field.

Pressure sensors work based on the principle of the force of a fluid divided by area. To put it into perspective, consider a syringe – a smaller one can generate more pressure than a larger one with the same force applied. Understanding this concept is crucial when dealing with pressure sensors.

Atmospheric pressure is a term we often hear. Could you explain what it is and its relevance in the context of pressure sensors?

Atmospheric pressure is essentially the weight of the air pressing down on us. As you ascend in an airplane or spacecraft, the air becomes less dense, with fewer molecules and less oxygen. It is important to consider atmospheric pressure when measuring the pressure in your application, because it will determine the type of pressure sensor needed.

What other applications besides the automotive industry benefit from pressure sensors, and how are they used?

Pressure sensors find applications across a diverse spectrum of industries, expanding far beyond their traditional use in the automotive sector. One of the sectors where pressure sensors play a critical role is the diving industry. In this field, pressure sensors are employed to monitor the depth of divers underwater, enabling them to calculate ascent and descent times accurately. The hostile underwater environment necessitates reliable pressure measurements to ensure diver safety.

Pressure sensors have made their way into the consumer product market. For instance, in the realm of bicycles, especially the emerging category of e-bikes, pressure sensors are integrated into various components. These sensors may be utilized on bike shocks, tires, and other critical parts to enhance the overall performance and user experience.

What are the typical applications of piezoresistive pressure sensors, and how do they work?

Piezoresistive pressure sensors are a subtype of pressure sensors known for their versatility and use in various applications. Piezoresistive sensors function on a principle involving doped, semiconductor silicon crystal, which allows them to measure pressure more repeatably than other technologies.

To understand their typical applications, it is worth highlighting that piezoresistive pressure sensors are not constrained to a single field. They are used in an array of industries, including the medical sector. In medical procedures like angioplasty, where surgeons inflate balloons inside arteries, pressure sensors play a crucial role. In these procedures, the pressure sensor’s output helps the surgeon monitor the level of inflation inside the balloon, and assess the overall status of the procedure.

Can you explain what MEMS technology is and its advantages in the context of pressure sensors?

MEMS stands for Micro-Electrical-Mechanical Systems, and there are many different types of MEMS. The deposition, ion implantation, and diffusion steps are all fundamental to semiconductor manufacturing, as well as the photolithography and etching of MEMS pressure sensors. MEMS pressure sensors feature an elastic silicon diaphragm, which means they are free from hysteresis and creep.

This elasticity benefits the sensor because it allows it to undergo repeated pressure cycling without altering its properties. When things tend to creep or change, it is almost always a result of how they are packaged, not necessarily the silicon chip itself. Putting thousands of pressure sensors onto one wafer also significantly helps to reduce costs.

Merit Sensor has its wafer fab in Utah. There are many advantages to working with a vendor that has its wafer fab. When it comes to developing a new product, having your wafer fab is a huge advantage, as it allows you to control the supply chain. Keeping the design in-house is often considered the key to the successful development and launch of any product.

Can you give us a basic understanding of the MEMS pressure sensor?

The key design characteristic of a MEMS pressure sensor is the Wheatstone bridge diffused into the silicon diaphragm. The change in output from this bridge corresponds to a change in applied pressure.  When a customer needs a higher pressure range, the sensor requires a thicker diaphragm to handle the increased pressure. Conversely, for measuring low pressures, like inches of water or low pascals, a thin diaphragm suffices.

After the manufacturing process, the silicon is bonded to a piece of glass. The glass may have a hole to create a vent for various pressure applications, or it can be sealed without a hole. In the latter case, the glass and silicon are bonded together in a vacuum.

When there is no hole in the glass, it is known as an absolute sensor because the space between the silicon and glass represents zero pressure absolute.

There are two types of absolute sensors made from MEMS dies. The traditional type has no hole in the back glass, creating a sealed vacuum reference for absolute pressure. However, this design requires protection for the circuitry on the top side to prevent corrosion and shorts from humidity or moisture.

Alternatively, there is the absolute sensor with backside pressure. In this design, a piece of glass is added to the top of the silicon, creating a sealed vacuum reference on the top side and allowing for backside pressure on the MEMS element. This type is commonly used in automotive and high-temperature applications, as well as with liquids.

Can you tell us more about offset pressure and other factors like pressure non-linearity and hysteresis?

Offset pressure is the zero pressure measurement at room temperature. Pressure non-linearity measures how linear or nonlinear the sensor’s output is from zero pressure to full-scale pressure, and hysteresis reflects the difference between the initial zero and return zero, when pressure is applied and then relieved. The MEMS sensing element is designed to minimize these sources of error.

How do temperature-related factors, such as TCR and TCS, influence the behavior of pressure sensors?

It is possible to use the TCR, the Temperature Coefficient of Resistance, in conjunction with the pressure sensing to determine the temperature, because the TCR changes significantly with temperature. The Temperature Coefficient of Span/Sensitivity, or TCS, is important to take into account, especially in applications for wide operating temperature ranges. The TCS is negative, and when using the MEMS piezoresistive pressure sensor, the sensitivity or span decreases as the temperature rises.

Can you explain the importance of accuracy in pressure sensors and how it can be achieved?

Accuracy in pressure sensors is often measured as the total error band, which includes errors related to temperature and pressure. Achieving accuracy involves calibration, and fully compensated sensors with onboard ASICs simplify this process and provide higher accuracy. Accuracy is vital, especially in applications where precise measurements are critical.

How do stress and other external influences impact pressure sensors?

We take great pride in understanding and characterizing the sources of error that our customers can’t compensate for:  thermal hysteresis and long-term stability. The last thing our customers want is a part failure in their hands, which can occur due to long-term stability issues.

It’s important to keep in mind, that the MEMS sensing element is also a good stress sensor.  For example, a torque, or bending moment on the MEMS element will change the output of the Wheatstone bridge.  Stress can be induced during packaging and assembly processes, impacting sensor performance. Over time, any package-related stresses will relieve themselves and come back to equilibrium.  This stress-relief will manifest as a change in the offset of the sensor, in other words, offset drift and long-term stability. Careful handling and packaging are essential to maintain sensor stability.

Could you explain how MEMS dies are suitable for a wide range of applications, both specific and general, and what factors should customers consider when selecting a pressure sensor?

MEMS dies are common in pressure transducer or pressure transmitter applications where the MEMS die is on a header. The header gets welded into a stainless-steel housing with a stainless-steel diaphragm. Stainless steel is an excellent choice since it is very media-friendly, and most people are usually very familiar with stainless steel’s capabilities. This package is suitable for many industrial applications.

After welding the stainless-steel diaphragm and package together, there’s a back-filling of oil into this housing. A clean silicon oil surrounds the MEMS die, transmitting pressure between the stainless-steel diaphragm and the silicon diaphragm of the MEMS element.

In the HVAC industry, the MEMS die can be purchased separately or packaged into our LP series and placed on a control board. These control boards are found in large buildings, either atop the building near the air intake or in the building’s utility room, where heat exchangers and air airflow systems are located.

Another common application is in transportation. Pressure sensors are widely used in various types of automobiles. This area continues to grow as legislation drives the demand for higher efficiency and cleaner emissions.

To learn more, watch the full webinar below:

Understanding MEMS Piezoresistive Pressure Sensors: A Close Look at a Silicon Die from Merit Medical on Vimeo.

 

About the interviewee

Scott joined Merit Sensor in September of 2003. Before joining Merit Sensor, he worked in a variety of engineering roles with semiconductor companies, such as ON Semiconductor and Motorola. In his current role he works closely with customers to provide pressure-sensing solutions and technical support.

Scott received a chemical-engineering degree and MBA from Brigham Young University. He speaks Spanish and enjoys volunteering his time.

In the medical industry, blood pressure monitoring is essential. Readings are used to evaluate general health and diagnose diseases. High blood pressure, otherwise known as hypertension, is a serious health risk and can also be indicative of other health problems.¹

Thus, accurate and reliable blood pressure monitoring data is essential to ensure positive health outcomes for patients. Blood pressure monitoring is not only necessary for standard use but is critical when it comes to monitoring a patient’s condition online during critical surgical operations.

Extracorporeal membrane oxygenation (ECMO) is a crucial medical application that necessitates precise online monitoring. ECMO is used throughout certain surgical procedures where the patient’s heart and lung functions are compromised or for critically ill patients.

In an ECMO machine, blood is pumped outside the body for carbon dioxide removal and reoxygenation before returning it to the patient.²  ECMO is a feasible substitute for mechanical ventilation as it is able to reduce lung damage invoked by the positive pressure used in these methods.

Blood pressure monitoring equipment is essential when it comes to monitoring a patient’s condition and the ECMO machine itself.³ A typical healthy blood pressure level is traditionally lower than 120/80 mmHg. However, low blood pressure can be seen to fall as low as 90/60 mmHg.

In applications such as ECMO, blood pressure monitors with an extended reading range can be highly beneficial.

ECMO Machine featuring the BP Series extended range pressure sensor.

Merit Sensor Systems

Merit Sensor Systems is a globally renowned, industry-leading company with experience designing and producing highly accurate, piezoresistive technology-based pressure sensors. The company provides pressure sensors for blood pressure monitoring applications and a range of medical equipment.

The patient’s blood pressure measurements can be significantly impacted by the resting environment. One way in which data quality can be improved is by ambulatory blood pressure testing, in which portable devices are used to record blood pressure measurements throughout the day.⁴

MEMS piezoresistive sensors and assemblies, such as the BP Series, are ideally suited for portable blood pressure monitoring applications due to their compact sensor footprints.

Merit Sensor has a variety of sensors available for blood pressure monitoring applications. These include the BP Series, which operates in normal pressure ranges, and an extended range version suited for applications such as ECMO, where measurements must be taken over a wide range of -500 – 1000 mmHg.

The BP + T is designed for ultra-compact applications which additionally measure temperature ranges.

BP Series Sensors

Blood pressure monitoring sensors from Merit Sensor are ideal for invasive blood pressure monitoring applications and measurements, such as ECMO.

The standard BP Series configuration BP0001 covers the pressure range of -30 to 300 mmHg, providing a reliable signal that does not need any temperature correction (operating temperature 15-40 °C).

An ultra-compact sensor with an extremely robust design, the sensor is suitable for burst pressure readings up to 800 psi. Additionally, it is compliant with AAMI BP22 and RoHS standards.

Sensors provided by Merit Sensor Systems can be easily integrated into a range of medical devices, with standard solder pads providing connectivity. The standard seal diameter is 4.8 mm (BP0001), and a smaller seal diameter of 3.2 mm (BP0002), which minimizes the device’s overall footprint.

The small seal diameter in the sensors lowers the amount of blood in contact with the sensor, minimizing the risk of clotting or coagulation, which can decrease overall blood flow and cause problems with readings.

Alongside the sensor, a media-compatible medical dielectric gel is utilized for medical applications. The BP Series also includes an IMDS file for rapid and easy media compatibility verification, minimizing the time required to develop device prototypes.

       

BP Series 4.8mm Standard Seal Diameter               BP Series 3.2mm Small Seal Diameter

Extended Range

The BP Series Extended configuration provides measurements in the range of -500-1000 mmHg and can be used in applications such as ECMO. The system operates at a broader pressure range than the standard configuration.

The blood pressure monitoring sensors from Merit Sensor Systems are designed to handle high-pressure conditions and provide accurate readings over their entire operational range.

With an extended product shelf life of up to three years, the solutions offered by Merit Sensor Systems extend the lifespan of medical devices and ensure that pressure monitors remain functional, whether they are used as short-term or long-term solutions.

BP Series Extended Pressure Range Statistics

The graph below shows the over-pressure specifications limits for the BP Series Extended between -500 to 1000 mmHg. The test results are available in the Overpressure/Accuracy Report.

The BP + T sensor, which integrates pressure and temperature measurements in one device, is available as an upgrade option. The BP + T sensor is a direct in-flow measurement sensor that can monitor pressure and temperature at a single location.

The temperature reading is directly proportional to the Ohmic reading of the embedded thermistor, which is coated with a media-compatible substance. Two additional pads provide the temperature-measuring electrical connection (Kelvin-Point).

The BP + T sensor is also geometrically compatible with the BP0001 and overall BP Series configurations. The 3D-Model files are available for the verification of this integration capability.

Blood Pressure + Temperature Series

Applications

Merit Sensor’s devices are currently used in several novel lung support therapies and blood pressure sensors as part of lightweight and portable emergency response cardiopulmonary support systems.

The blood pressure sensors from Merit Sensor Systems are high quality and can handle the pressure peaks encountered in ECMO applications. Additionally, the sensors are cost-effective, even for disposable medical devices.

Contact Merit Sensor to find out which of its pressure sensors is the best option for your blood pressure monitoring application and how to benefit from its technical expertise and support.

Merit Sensor’s robust, reliable sensors offer clinical experts the highest quality assurance for medical applications.

References and Further Reading

1. Elliott, W. J. (2003). The Economic Impact of Hypertension. The Journal of Clinical Hypertension, 5(3), 3–13. https://doi.org/10.1111/j.1524-6175.2003.02463.x
2. Patel, A. R., Patel, A. R., Singh, S., Singh, S., & Khawaja, I. (2019). Applied Uses of Extracorporeal Membrane Oxygenation Therapy Different modes of ECMO therapy. Cureus, 11(7), e5163. https://doi.org/10.7759/cureus.5163
3. Mossadegh, C. (2017). Monitoring the ECMO. In: Mossadegh, C., Combes, A. (eds) Nursing Care and ECMO. Springer, Cham. https://doi.org/10.1007/978-3-319-20101-6_5
4. Turner, J. R., Viera, A. J., & Shimbo, D. (2015). Ambulatory Blood Pressure Monitoring in Clinical Practice: A Review. The American Journal of Medicine, 128(1), 14–20. https://doi.org/10.1016/j.amjmed.2014.07.021