i3 - September/October 2016 - 14

By Murray Slovick

A T EC H TO WATC H

Sensors: How the IoT
Knows What's Going On

A

s a critical component of the IoT, sensors collect data and
then relay it over the internet for analysis and appropriate
action. In consumer technology, sensors can detect
movement, measure pressure, proximity or temperature,
and capture images. Sensors also can scan fingerprint and iris
patterns and facial features to ensure secure user access.
Meanwhile ambient light sensors
deliver automatic control of display backlight brightness, enabling backlight LEDs
to operate longer and with substantial
performance improvement.
Perhaps the most common sensor is the
accelerometer, a device that measures the
rate of change of velocity (speed plus the
direction of motion). Accelerometers are
used in phones, tablets and digital cameras
so that images on screens are displayed
upright. Another example is in drop systems
where accelerometers protect laptop hard
drives from damage during a fall.

MEMS Sensors
Starting with the automotive airbag
sensor in the mid-1990s, MEMS
(microelectromechanical systems)
accelerometers now extend to products
like drones, which include several of
these tiny, low-cost, low-power devices.
MEMS are created by etching a sensor
into silicon, using the same fabrication
process as microprocessors. The MEMS
accelerometer consists of little more than
a cantilever beam with a moveable proof
mass surrounded by fixed plates to form
a sensitive motion-responding capacitor.
Under acceleration, the proof mass
moves and the capacitance between the
plates changes by a tiny amount, and this
minute change is sensed, amplified and
converted into a digital representation of
what is happening.
MEMS sensors can be embedded in
wearables to track use motion and pulse
rates. In cars, multiple MEMS sensors can
trigger airbags and also sense impending
14

SEPTEMBER/OCTOBER 2016

rollover, adjust shock-absorber settings to
match load and road conditions, oversee
braking, and monitor other performance
and safety-related systems.
Advances in sensor technology are
making applications possible in home
automation, robotics and health. It's
wearables, however, where sensor technology is really making
its mark. Research firm
IDTechEx predicts there
will be three billion
wearable sensors by
2025. Sensors collect
data about the physical
and chemical properties
of the body and local
environment, and then
wireless connectivity is
used to bring in the analytical power of a
smartphone or tablet.
Recently researchers from UC Berkeley
and Stanford University developed a
wearable sensor that can analyze sweat
and wirelessly transmit the data to a
smartphone to alert users to health
problems such as fatigue, dehydration
and dangerously high body temperatures. The prototype packs five sensors
onto a flexible circuit board. The sensors
measure the metabolites glucose and
lactate, the electrolytes sodium and
potassium, and skin temperature. An app
syncs the data from the sensors to mobile
phones, and the device can be fitted onto
"smart" wristbands and headbands.
Sensors used in medical applications
measure and monitor blood flow, pulse,
blood pressure, blood oxygen levels, muscle

movement, body fat and body weight.
Conductive circuitry for sensors that
measure heart rate and blood pressure can
be woven into garments or hidden in ear
buds. At CES 2016, Seattle startup Levl
showed a device that measures acetone
in your breath to figure out how much fat
versus carbohydrate your body burns when
you exercise. You breathe into the pod and
place it into a reading port. The device displays your score while seamlessly syncing
to a smartphone app via Bluetooth. The
app indicates whether your exercise or diet
plan is working by telling you how many fat
calories your body is burning.
As car capabilities evolve from active
safety to autonomous driving, LIDAR
(Light Detection and Ranging) will
become the predominant automotive
distance measuring technology. LIDAR
sensors work on the principle of radar,
but use light from a laser instead. LIDAR
offers greater precision than radar, but it
can't see as well through
rain, snow and fog. While
LIDAR sensors are
employed in all autonomous research vehicles,
the technology is already
in cars with adaptive
cruise control systems.
When data is extracted
from different sensor
observations and combined to help make decisions or increase
accuracy, the practice is known as "sensor
fusion." Combining multiple "senses" for
an improved result is not a new concept.
When we taste food our brain is combining the input from the taste buds on
our tongue, smell from our nose and the
texture of the food to determine whether
we like what we taste. Sensor fusion works
the same way.
A typical sensor fusion solution might
combine a 3-axis accelerometer (a multiaxis sensor can measure what is happening
in more than one plane), a 3-axis gyroscope
and a 3-axis compass in the same chip.
Multi-axis sensors are ideal for robotics,
drones, gaming and navigation systems. n
Sensors will be one of the product categories
at CES 2017, January 5-8.
I T I S I N N O VAT I O N

PHOTOGRAPH BY PATRICK FOTO/GETTY IMAGES

Tech
http://www.levlnow.com/ http://www.levlnow.com/ http://ces.tech/
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