Tech Briefs Magazine - April 2024 - 10

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INSIDE STORY
Accelerometers play an integral role in condition monitoring programs that reduce unplanned
downtime and reduce maintenance costs. However, the technologies and chipsets for vibration
sensing have required tradeoffs in power consumption, sensor performance, and cost. Wilcoxon
Sensing Technologies has developed an ultra-low power embeddable accelerometer to reduce or
eliminate these performance compromises. In this interview, Chris Kramm, Director of Sensing
and IoT Solutions at Wilcoxon Sensing Technologies, discusses the latest innovations in embeddable
sensing elements for wireless accelerometers.
Tech Briefs: The vibration monitoring market has been asking
for wireless sensors for more than two decades. Why
haven't they broken into the mainstream yet?
Chris Kramm: Wilcoxon actually released
a wireless product more than
20 years ago, but it was ahead of its
time. At that time, battery technology
was far more limited than it is today,
and we did not fully understand the
benefits that wireless could offer. When
it came to accelerometer technology,
the sensors that were most effective
for condition monitoring, Integrated
Electronic Piezoelectric (IEPE) accelerometers, had high power
requirements and a long startup and settling period. They were
not practical for battery-powered wireless applications. But this
is something we were able to solve through innovation. Take
our low-voltage embedded pellet for example, it operates on as
little as 3V while drawing only60 µA. Furthermore, its power-up
time is significantly reduced from around 3 seconds to 350 µs.
We reduced settling time - the time we need to wait before
taking a measurement - by 1000 times. With these innovations,
we were able to reduce power consumption to a point where it
becomes negligible when compared to the power consumption
of the wireless radio.
Tech Briefs: What about size constraints of piezo sensors?
Kramm: After we solved the constraints around startup and
power consumption, we had to solve the integration problem.
There are two main problems to solve here, one mechanical
and one electrical. When it comes to electrical integration,
the MEMS chips have an advantage. Most give a digital output
that can interface with a simple processor or radio. With
piezo, we provide an analog output, so the digitization needs
to happen on the radio board. But it can still be fairly simple
with the right selection of a processor that has the digitizing
capability built in. The second challenge is around mechanical
mounting. A vibration sensor must couple mechanical energy
into the sensor and convert it to an electrical signal. Getting
good mechanical coupling is one of the most challenging
design challenges and the one that is most often overlooked
by wireless designers. Poorly packaged sensors result in poor
vibration coupling. This means the sensor is less sensitive.
It won't detect a defect in a machine component until much
Tech Briefs: What other designs use embedded accelerometers?
Kramm:
Wilcoxon has provided high-quality, reliable, premium-performance
accelerometers for industrial vibration monitoring
applications for more than 35 years, and we are excited
to participate in the evolution of IIoT and smart manufacturing.
In the factories of the future, production assets will have built-in
self-testing capabilities and real-time condition monitoring. Our
LVEP-TO5 accelerometers can be embedded into critical rotating
equipment such as pumps, motors, fans, and compressors
to enable early fault detection and predictive maintenance. This
is another reason the LVEP-TO5 had to match the performance
and condition monitoring capabilities of existing industrial accelerometers
in a low-cost, easily integrated package.
To learn more about Wilcoxon Sensing Technologies embeddable
accelerometers, visit https://wilcoxon.com/LVEP.
later in time. We looked at some of the packages common on
the market and selected a TO-5 package. The TO-5 package
is small enough to embed in one- and three-axis wireless
accelerometer designs. Another advantage is its ability to be
mounted in a way that provides a high coupling of the vibration
energy into the piezo sensing element while not introducing
sub-resonances that contaminate the vibration signal. The
other thing we needed to take care of was the sealing. This
was achieved using a technology already known in the market
called hermetic sealing.
Tech Briefs: Can you explain more about the significance of
vibration coupling on a wireless sensor performance?
Kramm: The coupling goes back to achieving the stated sensor
specifications. Without rigid coupling, the vibration from the
machinery is dampened before it reaches the sensor, and data
that is critical to fault diagnostics is lost. When high- or low-frequency
vibrations are not captured, the vibration practitioners
lose the data necessary for condition-base maintenance, like
early detection of bearing or gearing faults. This is where IEPE
accelerometers truly excel compared to MEMS. In the LVEP-TO5
accelerometers, we've translated that industrial accelerometer
performance into a small, low-power, easily integrated package.
We can offer the same resolution, noise performance, bandwidth,
and flat response as our traditional vibration sensors at
a fraction of the power consumption.
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