Medical Design Briefs - December 2022 - 35

Selecting the
1000g
HT
100g
Switch
Accelerometer
10g
nA
uA
Amperes
mA
10g
5 years 6 months 1 day
Time
100g
1000g
HT
Switch
Accelerometer
Right Motion Sensor:
Accelerometer vs.
Zero-Power Motion
Switch
Accelerometers and motion switches
perform some of the same functions,
but there are important differences.
The best choice for an
application depends on the hardware
interface, power budget, data
processing needs, and battery accessibility
for
Wake-up
acceleration in amperes (a) and time (b).
Accelerometer
Capabilities Measures acceleration, tilt,
and vibration. Able to process
large amounts of data
continuously.
Power Consumption Consumes minimal power
while waiting for a signal.
Size World's smallest
accelerometer is about the
size of a letter on a coin.
Developed by Graphene
Flagship, a European research
initiative.
Programming Requires digital programming
to design for drift, noise, and
potentially a separate power
bus.
Ruggedness Not suitable for extreme
temperatures, severe shocks,
or radiation environments.
Zero-Power
Motion Switch
Measures force. Able
to wake up electronics,
detect shock/impact,
and count events.
Consumes no power
while waiting for a signal.
World's smallest
threshold switch by
90% at 3.4 mm2
.
Developed by HT
Micro, a US-based
manufacturer.
Requires no additional
programming to interpret
the defined motion event.
Operates in
temperatures up
to 250 °C, shock
resistant to thousands
of Gs, and suitable for
radiation environments.
Manufacturing
Compatibility
Not rated for higher voltages
without additional circuitry.
Surface mount options
available.
Comparison of accelerometer and zero-power motion switch.
shorter duration impacts are not important,
the switch doesn't waste power logging
them. For example, consider a wireless
x-ray machine jostling on a cart
between locations. Such low-level shocks
are part of normal use and usually not a
cause for concern. A drop to the floor,
on the other hand, requires the unit to
be recalibrated immediately. In this case,
the shock sensor is activated and triggers
an alert such as a flashing LED light.
Winter 2022 Resource Guide
Richard Halstead, CEO of Empire
Magnetics, sees tremendous potential
for this technology in manufacturing
devices of all kinds, medical and otherwise.
" An obvious application for this
product is monitoring electric motors.
As bearings in a motor begin to fail, the
inertial sensor detects the change in acceleration
and alerts the operator. This
would be of particular value in remote
locations, " he says.
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Rated for electrical
requirements up to 48
V. Surface mount for
regular reflow assembly.
recharging or replacement.
" Based
on the application, we
typically evaluate a sensor technology
on several criteria - battery
shelf life, the ability to meet our motion
requirements, and ease of integration
into production at a reasonable
price, " says Matt Bertram,
director of manufacturing operations
at SportsMEDIA Technology
Corp (SMT). " Accelerometers have
come a long way in terms of battery
life, but only HT Micro's inertial
switch checks all the boxes for us. "
Inspiring the Next NextGeneration
Medical Devices
The merging of sensing, motion,
and analytics - in applications like
medical wearables and implantable
devices - was unimaginable to most
people even just a few years ago.
Growth in the medical device market
shows no sign of abating. In 2021
alone, the FDA's Center for Devices
and Radiological Health received
nearly 18,000 conventional premarket
submissions and 2,200 Emergency Use
Authorization (EUA) requests. As devices
incorporate more customization,
advanced analytics, and artificial intelligence,
design engineers will continue
to be challenged to accommodate
more complex features without increasing
the power budget or product
size. The zero-power motion switch is a
valuable tool for meeting these competing
priorities.
This article was written by Danny Czaja,
CEO, HT Micro, Albuquerque, NM. For
more information, visit www.htmicro.com.
Contact: sales@htmicroanalytics.com.
35
Wake Up Acceleration
Wake Up Acceleration
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