devices can also be exposed to elements in daily life, including
sweat and chlorinated water. While both elements seem harmless,
electronic devices and sensors could experience corrosion issues
and electrical shorts if not properly protected. To protect against
these conditions, specialty coatings can be applied to sensing de-
vices while still allowing for accurate detection and measurement.Miniaturization
Another major trend to consider is miniaturization. In 2018, TE
Connectivity conducted a survey on a variety of topics related
to IoT design. The survey explored IoT applications and design
methods and then identified common challenges that exist across
this space. On the topic of miniaturization, 85% of survey partici-
pants overwhelmingly agree that this should be an area of focus. At
the same time, 15% believe that sensor miniaturization has already
gone as far as needed. The miniaturization of sensors is not unique
to the medical market, but it is increasing in importance.
With the increase in wearable connected devices, the ability
to create lightweight, compact designs becomes necessary. Even
though watches, chest-mounted heart-rate monitors, and jewel-
ry are monitoring health factors with varying accuracy, they are
providing more information than was available in the past. As
the consumer focus on healthy living grows, the drive to have
more precise data increases sensor demand and the need to fit
more sensors into the same-sized package.
Beyond healthy-living wearables, miniature sensors can be
built into electronic robotic prostheses. The force and control
of fingers is a meticulous skill requiring precise measurements.
When considering force measurement, the difference between
holding a grape and crushing it can be significant. Therefore,
it demands accurate data for the fingers to perform seemingly
simple tasks. Applying magnetic sensors to the finger joints at the
point of rotation and strain gages allow for the precise contactless
control and movement needed.Digital signal processing
Greater accuracy is a key objective in choosing a sensor for med-
ical applications, which makes digital sensors a more desirable
option due to their more precise and robust outputs. For exam-
ple, digital thermopile temperature sensors can deliver high-ac-
curacy ±1°C readings of temperature ranges from 0°C to 100°C.
When customized to accommodate a wider range of applications
for intensely harsh environments, these sensors can deliver high
accuracy of ±4.5°C at 300°C.
While analog products are often less expensive, digital sen-
sors, by virtue of their design and configuration, do not require
the purchase of additional electrical components, including
low-offset/low-noise amplifiers and associated filters. Certain
sensor technologies, when packaged with digital outputs, can
offer multiple output signals from the same device, thus eliminat-
ing the overall platform and real estate of the circuit board.
Sensors can be designed for more consumer-based medical
devices by adopting digital signal processing. This would allow
for lower current consumption, as well as the capability to
“sleep” while not in use and operate with lower supply voltages,which would enable the use of smaller batteries on board.Digital signals and scalability
Digital signal processing also plays a role in scalability. Traditional
analog output signals require some level of conversion for modern
electronics to read and process the data. However, on-board digital
signal processing reduces the calibration time during system or
device manufacture, which leads to greater accuracy. Because the
sensor manufacturer’s calibration equipment is designed to test
and qualify the sensor, it requires less investment by the OEM to
duplicate the system requirements to manage the signal processing
from analog to digital. In addition, sensor manufacturers can cus-
tomize mechanical tooling, sensor programming, and calibration
to customer requirements to enable plug-and-play designs.SMT technology and scalability
According to the American Hospital Association, over 5,
U.S.-registered hospitals experienced over 35 million admis-
sions in 2017. While the medical industry in the U.S. is pivoting
to reduce hospital visits, admissions, and admission times, the
demand to support the patient and the need for monitoring
equipment remains consistent. Therefore, designing sensors
for scalable, automated production has become a more desired
option in the medical space to keep up with demand.
Surface-mount technology (SMT) for sensors enables design
engineers to embed the sensor within the electronics of the as-
sembly. Photo-optic sensors offer traditional lead-frame designs
that are hand-soldered into assemblies and are now packaged for
SMT designs. The reflow solderable packaging allows engineers
to design sensors into assemblies that are embedded through
pick-and-place machines, increasing overall quality while reduc-
ing manufacturing time and cost.
With the flexibility to be mounted vertically or horizontally,
AMR sensors are designed for SMT packages as well. Depending
on the design of the system, this can play an important role to
ensure that the sensor can fit within the system and give more
flexibility on the magnet placement.
With the right size and design, sensors can also be utilized
in environmental conditions not possible in years past. Sensors
will continue to enable new capabilities in medical devices and
equipment. Through sensor design trends like scalability in
manufacturing, digital signal processing, and miniaturization,
medical-office–based equipment can lead to improved and more
accurate home-based medical monitoring devices. ☐TE Connectivity’s family of medical sensors (left to right): the KMXP
Series AMR position sensor, the TSD Series digital thermopile
sensor, and the ELM 5000 Series SMT photo-optic sensors.12 FEATURE Overcoming Challenges in Connected Medical Devices
JANUARY 2019 • electronicproducts.com • ELECTRONIC PRODUCTS