The world today has become increasingly mobile with advances in powerful and portable technologies, such as smartphones and wearables. These trends aren’t exclusive to the consumer market. Medical devices traditionally used in hospitals and clinics are also evolving to become more portable, creating possibilities to be used in home healthcare.

Fig. 1 – Medical devices, such as CPAP machines, are evolving to become more portable and thus driving innovation in sensing technologies that are small, accurate, and reliable.

A market study by RNR Market Research, entitled Homecare Medical Equipment Markets Market Share Analysis: Market Shares, Analysis, and Index, Bundle, Worldwide, 2006 to Current, Quarterly, which can be found at , estimates that the homecare medical equipment market could be worth nearly $26 billion by 2022. As a result of these market influences, medical device manufacturers are designing solutions in smaller form factors, as smaller medical devices can be more practical and valuable today.

By the same token, the demand is growing for smaller component parts, such as the sensors that are used in more portable medical devices. However, device functionality and reliability cannot be sacrificed for smaller form factors. And for most manufacturers, budgets aren’t unlimited, meaning low-cost components are ideal. This is why new sensor innovations reaching the market need to feature smaller form factors while maintaining high functionality and affordability.

Sensing Market Trends

Embedded devices such as pressure sensors are advancing in many ways to better meet the needs and challenges of designing smaller medical devices. For example, advanced low-cost basic pressure sensors have become a valuable commodity, specifically with engineers who need to design and create lowcost, high-volume assemblies in sectors such as industrial manufacturing and healthcare. Original equipment manufacturers (OEMs) in these industries are experiencing a greater demand for products in these applications, and need components that meet their strict design requirements.

In the healthcare market, for example, the focus on designing technology that is less intrusive and more portable for home use has led to a demand for smaller devices, such as oxygen concentrators, CPAP machines, and others. (See Figure 1)

Additionally, the growing adoption of wearable devices to track a person’s health and fitness is also having an impact. A 2016 report by Gartner, Inc., which can be found at , estimates that more than 109 million units of fitness wearables will be sold in 2017 alone.

Even as devices become smaller for increased portability, users still expect that these systems maintain functionality and accuracy. And, to design small yet accurate medical devices, component parts, such as sensors, must also offer robust features at a low cost. Yet, higher degrees of accuracy usually mean higher price tags, which isn’t ideal for low-cost, high-volume applications.

For example, certain ventilators can cost tens of thousands of dollars to design and build. At that cost, it’s easier to justify using a more expensive $15 sensor because it represents less than 1 percent of the total cost of the unit. It’s harder to justify that $15 sensor on a blood pressure monitoring application that only costs $40 to $120 for design and build. The extra cost for 1.5 percent full scale span (FSS)—the difference between output signal measured at the upper and lower limits of the operating pressure range—of Total Error Band (TEB) improvement is not as easily justifiable.

Staying within budget is a priority. And if lower-cost components are the only available option to a design engineer, how does one best evaluate lowcost sensors for use in these types of highly functional systems? Deriving value from these types of applications requires designers to view these components not purely as commodities, but as critical technology enablers that can offer a competitive advantage to the systems that design engineers create.

Accuracy Is King

Fig. 2 – Shown is a new series of pressure sensors designed to better meet the needs and challenges of designing smaller medical devices.

Functionality and reliability are important qualities for all medical devices. Improving accuracy of a component device, like a sensor, can result in higher functionality and accuracy for these systems. For a low-cost, high-volume application, innovation in small, affordable sensing technology has helped bolster measurement accuracy that can rival some premium solutions. (See Figure 2)

Innovations in these low-cost sensor technologies have become especially important as factors including lower power consumption, repeatability, and reliability have become popular among design engineers looking to maintain tighter error budgets and improve system specifications.

Let’s look at an oxygen concentrator as an example. Low- and ultra-low pressure silicon sensors may be used in these systems to detect when a patient begins to inhale so that oxygen can then be delivered efficiently in order to minimize oxygen waste when the patient isn’t inhaling. This allows the oxygen concentrator to be smaller and to operate more efficiently. And smaller equipment size also means lower power consumption, as well as greater portability.

In order to improve accuracy in lowcost applications, it is important to retain the benefits of easier-to-install components, such as compensated or amplified compensated pressure sensors. Less-accurate sensing technology could negate some of the benefits achieved by using plug-and-play technology, such as the ability to help relax specifications in other parts of the system. This benefit may be of greater value, particularly for engineers struggling to meet design requirements. For example, being able to more accurately measure pressure inside an oxygen concentrator may negate the need to regulate down to the minute details, or overcompensate elsewhere in the system.

The desire for more “plug-and-play” components in part explains the growing popularity of amplified compensated vs. uncompensated pressure sensors. Amplified compensated sensors can typically be used without the need for additional modifications, and can provide part-to-part interchangeability, calibration, and temperature compensation. A non-amplified compensated sensor may require the use of amplification circuitry, assuming that an application-specific integrated circuit (ASIC) with an mV-input analog-to-digital converter (ADC) is not being used. By contrast, uncompensated sensors provide raw sensor output, and usually require some form of compensation to be used in many applications.

Using plug-and-play solutions, such as a fully amplified compensated sensor, eliminates the need for additional circuitry and design time to develop, and therefore, provides greater value. Again, though, a plug-and-play solution that doesn’t provide accurate data defeats the overall purpose. Poor performance could potentially negate any savings gained through the easier installation.

Let’s examine a scenario that can help design engineers choose the ideal sensing solution. An uncompensated sensor that has a TEB of greater than 30 percent FSS costs $9, and a compensated sensor with a TEB of about 10 percent FSS costs $10. A fully amplified plug-and-play sensor with a TEB of 1.5 percent costs $13. Knowing that low cost and high accuracy is important for their system design, the best option would be to implement additional circuitry to improve the accuracy of the less-expensive sensors if the component costs less than $4, not to mention design and calibration time involved. In doing a similar upfront analysis, design engineers can better understand the advantages and benefits of a component device’s price and performance value.

Evolving Functionality

Portable medical devices aren’t new, but these devices continue to be designed smaller and easier for patients who prefer to receive higher quality healthcare in the comfort of their own homes. However, neither the design engineer nor the patient can afford to sacrifice functionality for the benefits of size and portability. Recent innovations have helped transform low-cost components into valuable, highly functional technologies that are often ideal for the medical device’s current technology renaissance. Advancements in smaller sized and highly accurate low-cost components will continue to help design engineers address some of the strictest design parameters in today’s medical device industry.

This article was written by Tomoko Fujiwara, Product Marketing Manager, Honeywell Sensing & Productivity Solutions, Golden Valley, MN. For more information, Click Here .