Magnetics Business & Technology - September/October 2020 - 6

FEATURE ARTICLE

Paramagnetic Sensors from Hummingbird at the Heart of Respiratory Ventilators Battling
Covid-19
"This technology is non-depleting and requires no reference gas,
so paramagnetic cells supplied with a clean dry non-condensing
sample gas never need replacement. The performance does
not deteriorate over time, giving significant benefits to ongoing
maintenance costs and sensor lifespan."
Applications for these sensors are mainly medical, including
neo-natal incubators, anesthesia delivery systems and cardiopulmonary function testing, notes Cox. "However, with the current pandemic, critical care ventilators are where these sensors
are being used the most right now."

Unseen but close at hand to patients and medical staff battling
Covid-19 are tiny, highly sensitive paramagnetic sensors from
Hummingbird Sensing Technology that perform a crucial role
inside respiratory ventilators. They can detect and assess paramagnetism, a characteristic of certain materials such as oxygen
which have a weak attraction to magnetic fields.
Critical care ventilators (pictured above, courtesy medscape.
com) form an essential part of any treatment for severe respiratory diseases and disorders. They have been vital for patients
unfortunate enough to develop the more severe complications of
the Covid-19 coronavirus.

Paracube Modus sensor is vibration resistant, designed for transportable medical and analytical applications.

"Our Paracube sensor is used in the control and safety system
of the ventilator, to ensure the oxygen mixture that respiratory
therapists select on a ventilator control panel is correctly delivered to the patient," explains Martin Cox, Hummingbird business
unit director. Inside the protective housing of each sensor is a
tiny, paramagnetic cell.
"Paramagnetic cells consist of two nitrogen-filled glass spheres,
mounted on a thin wire suspension within a strong magnetic
field. Oxygen is naturally paramagnetic, so is attracted to the
magnetic field, creating a force on the spheres - the torque acting
on the suspension is directly proportional to the concentration of
oxygen within the gas mixture," relates Cox.

Magnetics Business & Technology * September/October 2020

Based in Crowborough, England, Hummingbird is the sensing
technology division of Servomex, which makes gas analysis
instruments for medical and industrial applications. Hummingbird supplies its sensors to equipment manufacturers around the
world. Its Paracube products are an innovative range of compact
paramagnetic oxygen sensors for use in industrial and medical
sectors. The range consists of the Micro, Modus, and Sprint.
The Modus is the world's first vibration-resistant paramagnetic
oxygen sensor, designed for transportable medical and analytical
applications.
How It Works

Auto-balance system within a Hummingbird paramagnetic cell
The company's Magnetodynamic Paramagnetic technology
provides fast, accurate and sensitive
measurement of percentage levels
of oxygen. Two nitrogen-filled glass
spheres are mounted within a magnetic field, on a strong, noble metal
taut-band rotating suspension, with a
centrally placed mirror. Light shines on
the mirror and is reflected onto a pair of
photocells. As oxygen is attracted into
the magnetic field, it displaces the glass
spheres, causing suspension rotation
which is detected by the photocells.

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Magnetics Business & Technology - September/October 2020

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