Tech Briefs Magazine - June 2021 - ST-24

Applications
based on software changes. For example,
there's a new breed of refrigerants
that are low global warming. But many
of these new refrigerants, used in air
conditioning units and refrigerators,
etc., are flammable. Therefore, all residential
air conditioners are going to
require flammability sensors to prevent
an unsafe condition. Based on the thermodynamic
properties of those refrigerant
molecules NevadaNano was able to
come up with a product uniquely suited
to that particular species of gas or multiple,
just by making a software change.
So, within about a month they had a new
Alpha product and started taking it out
and showing it to people.
Calibration
I asked Rogers if they needed to calibrate
each sensor for a particular gas.
He replied that it depends upon which
gas needs to be detected. For the standard
flammable gases, they use methane
as the calibrant gas at the factory. " Once
we've shown the sensor methane, we
don't have to then calibrate it to hydrogen,
butane, propane - it intuitively
senses all the other gases as well. " So, for
example, they don't necessarily have to
use hydrogen at the factory to calibrate a
hydrogen-specific sensor.
Applications
I then asked Rogers about typical
applications. " We're just the sensor -
we're that that little bucket-shaped
device that gets plugged into a detector
system. For example, if you were to go
to a refinery today and look around on
the walls, you would see many dozens of
devices that kind of look like utility
power meters. " They have multiple sensors
plugged into them, probably
including a hydrogen sulfide sensor, an
oxygen sensor, a carbon monoxide sensor,
and a flammable gas sensor such as
the MPS.
Smart Sensors Are Improving Medical Care
ver the last 75 years, sensors have
played an increasingly significant
part in the advancement of medicine.
Medical sensors for monitoring people's
vital signs, including temperature,
blood pressure, heart rate, and respiration
rate have become increasingly
sophisticated. But sensors are also useful
for measuring the vital signs of medical
equipment.
Temperature Monitoring
Glass bulb thermometers have been
used for decades to take body temperature.
In the 1970s, they were
replaced by electronic versions with
digital displays. These were minimally
invasive devices and were required to
be inserted somewhere into the
patient's body.
Today, the most common devices are
thermopile-based non-contact temperature
sensors, which operate like a tiny
infrared camera. They measure the radiated
thermal energy of the skin and provide
an output signal proportional to
skin temperature. They can take a reading
in just a few seconds, and being noncontact,
can help to avoid the spread of
bacteria and viruses.
Packaged in a small TO-5 or TO-18
hermetically sealed enclosure, they can
easily be mounted on a PC board. The
24
Cov
Figure 1. Today, the most common thermometers are thermopile-based non-contact temperature
sensors. (Image by Iana Aibazova/Shutterstock)
www.techbriefs.com
ToC
Sensor Technology, June 2021
O
thermopile is a miniature array of
dozens or hundreds of thermocouple
elements on a silicon chip. The chip is
designed so the junctions on its topside
are exposed to the incoming IR radiation
while the backside is attached to a
metal header and remains at ambient
temperature. The thermocouples are
connected in series so that their outputs
add. The sum of the signals provides a
usable output with an amplitude in the
tens of millivolts.
A cutaway view of a typical thermopile
is shown in Figure 2. The chip is
mounted so it " looks " through a window
that is transparent only to infrared
wavelengths. This helps eliminate interference
from visible light. As thermal
energy from a heated (or cooled)
object enters the window, it impinges
Firemen and other first responders
running into a building typically wear
what's called a four-gas sensor - a little
cell phone-sized device that sort of sits
on their shoulder and has four gas sensors
in It, including an MPS.
Summing it Up
According to Rogers, the MPS is the
most innovative technology for gas
detection in over 30 years. It overcomes
the shortcomings of existing technologies;
it is stable across broad operating
ranges, including rapid temperature
and humidity changes; it is accurate for
a list of common flammable gases
(including hydrogen). Furthermore, the
MPS can be used for environments with
multiple or unknown gases present and
is intrinsically safe, robust, and immune
to poisoning.
This article was written by Ed Brown, Editor
of Sensor Technology. For more information,
visit http://info.hotims.com/79414-162.

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Tech Briefs Magazine - June 2021

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