A
s new developments in personal devices and medical
equipment are established, sensor technology continues
to evolve to meet the demanding needs of the growing
connected medical industry. With trends such as the IoT
and enhancements in data analytics and artificial
intelligence, sensors are becoming more crucial
to collect accurate data.
To collect this critical data, invasive and
non-invasive sensor technology can be used.
Invasive sensors are designed for applications
such as arterial blood pressure monitoring
during surgical procedures and temperature
measurement through micro-thermocouples
in catheter assemblies. These sensors require
specialized compatibility and packaging,
typically in a miniature disposable package.
Non-invasive and non-contact sensor technologies have a
broader use case and have both mechanical and electrical de-
sign considerations to support the growth in medical devices
and equipment. In this article, we will explore these sensor
design considerations for non-contact medical applications
and review key trends to keep in mind.Survivability
One of the first essential concepts to consider is the survivability,
or ruggedness, of these devices. The sensing elements that measure
properties such as temperature, vibration, and position are relatively
small and delicate. For example, a thermopile sensor is comprised of
a precise array of miniature thermistors to measure the temperature
within its field of view. These sensors are packaged in a way to pro-
tect the sensing element from external environments. This becomes
crucial in applications such as ventilation equipment, wherein a
thermopile is designed to measure surface temperature and mass
airflow sensors measure the airflow temperature to compensate for
condition changes and provide a baseline temperature measurement
for other sensors on board. Encapsulated in a stainless-steel hous-
ing, the sensing element is hermetically sealed to protect against
external conditions such as humidity and other harsh factors.
Similarly, sensors can be packaged within an assembly through
non-contact measurement for position sensing. The demand
for anisotropic magneto-resistive (AMR) position sensors has
increased with its ability to be packaged and sealed within a device
while measuring a magnetic scale external to the assembly.
Prosthetic joints are an interesting example. Within this applica-tion, AMR sensors can measure rotation of a joint such as a knee or
ankle to compensate for movement and create a more natural gait
pattern. Because the sensor is packaged within the knee assembly,
it protects it from environmental conditions such as water, impact,
and general wear. Therefore, it allows independent rotational move-
ment between the sensor and moving limb without physical contact.
Packaging sensors and electronics in sealed assemblies ad-
dresses sterilization concerns as well. Sterilization
in medical applications can be accomplished in a
variety of ways, including the use of steam or
exposure to ethylene oxide. With a sensor
encapsulated within a device, it is protected
against extreme temperatures or moisture
at the component level.
Non-contact sensors used for motion con-
trol can be installed in assemblies with the
sensor submerged in non-conductive hy-
draulic oil. This further allows the sensor to
be embedded within the assembly without
external components exposed. WearableFive design considerations for medical sensors
When selecting sensors for medical applications, design engineers should consider survivability,
miniaturization, digital signal processing, scalability, and surface-mount technologyBY GREG MONTROSE
Senior Manager, Integrated Marketing, Sensor Solutions,
TE Connectivity
http://www.te.comThe ELM-5000 series
photo-optic sensors, designed for surface-
mount technology, is specifically designed
for medical applications.High-quality precision
stamping since 1986
Na Bob Precision Metal Industry Ltd
Homepage: http://www.nabobind.com
Email: [email protected]* 200 pressing machines, Robotic arms and EDMs
* 30 QC technicians perform IQC, IPC and QA
* Clients in the US, Japan and EuropeEET201803_Na Bob.indd 3 2018/3/1 上午9:Overcoming Challenges in Connected Medical Devices FEATURE 11
ELECTRONIC PRODUCTS • electronicproducts.com • JANUARY 2019