Tech Briefs Magazine - January 2024 - 22

Sensors
Beyond these characteristics, designers
will need to consider the device form
factor, response time, wiring methods,
and voltage/signaling needs. Small devices
with short response times, flexible
configuration options, selectable operating
modes, and other nice-to-have
features such as laser-marked QR codes
for accessing instructions via a mobile
device provide the best usability for most
applications.
PE sensors often provide the best discrete
detection price/performance ratio
for a wide variety of applications including
machinery, material handling systems, processing/manufacturing,
and many others.
This article was written by Bruce Fink,
Figure 2: IDEC offers a family of PE sensors using various light sources and operating modes incorporating
the latest high-performance technologies and ease-of-use features, so users can find the
optimal device for their discrete detection applications. (Image: IDEC Corporation)
Product Marketing Manager at IDEC Corporation
(Sunnyvale, CA). For more information,
visit https://us.idec.com/.
Optical Concentration Sensor for Liquid Solution
Light scattering approach to precisely measuring solution concentrations.
Kennedy Space Center, Meritt Island, FL
I
nnovators at the NASA Kennedy Space
Center have developed a new optical sensor
for measuring concentration in a liquid
solution. The sensor was designed for
measuring the pretreat solution concentration
within the Universal Waste Management
System (UWMS), a specialized
toilet designed for the International Space
Station (ISS) and other future missions.
The sensor was developed to replace the
current pretreat concentration sensor
within the UWMS that uses electrical conductivity
instead of light-based methods.
Typical concentration sensors, like the
one initially used in the UWMS, rely on
changes in electrical conductivity to
measure the concentration of a solution.
These measurements using conductivity
are prone to voltage drift over time, leading
to unreliable measurements as the
sensor ages. The optical sensor developed
here uses light scattering to measure
the solution concentration without
the issue of voltage drift.
In this sensor, light from a green LED
is passed into the sensor housing where
Reference scattering volume
PFA tube
Scattering
surface
23 mm
Green
LED
Pretreat
scattering
volume
Reference
Photodiode
Pretreat
Photodiode
32 mm
Schematic of the optical sensor for measuring pretreat concentration. (Image: NASA)
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22
it hits a first detector (i.e., a photodiode)
to establish a reference of the amount of
light before scattering. Simultaneously,
the light from the LED scatters through
the pretreat solution and then hits a second
photodiode to measure the amount
of light after scattering. The difference
between the amount of light measured
by the two detectors is used to calculate
the concentration of the pretreat solution
(based upon Beers Law).
The optical concentration sensor has
been demonstrated to effectively measure
pretreat concentrations in both
still and flowing liquid conditions and is
resistant to contamination issues as necessitated
by the UWMS. Using established
methodologies and commercial
components, the new sensor can precisely
measure the concentration or
pretreat within the waste treatment
solution using the light passed through
and scattered by the solution. The optical
sensor can be adapted to measure
the concentration of solutions across
various industries.
NASA is actively seeking licensees to
commercialize this technology. Please
contact NASA's Licensing Concierge at
Agency-Patent-Licensing@mail.nasa.gov
or call at 202-358-7432 to initiate licensing
discussions. For more information, visit
https://technology.nasa.gov/patent/
KSC-TOPS-91.
Tech Briefs, January 2024

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Tech Briefs Magazine - January 2024

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