Sensors for Medical Pump Applications
PAGE 5 MEDICAL SENSORS / WHITE PAPER
Bubble Detection in Infusion Pumps
Bubble detection is critical in applications such as infusion pumps, hemodialysis and
blood flow monitoring where interruption in performance can be life-threatening.
Ultrasonic bubble detectors are non-contact acoustic bubble and liquid detectors
used to identify air bubbles and liquids in infusion tubes. They are widely used in
applications such as liquid transfer and infusion in medical pumps, pharmaceuticals,
industrial and scientific research. TE's AD-101 air bubble detector for non-invasive,
continuous monitoring of fluid for air bubble detection, uses ultrasonic technology
to positively identify the presence of a break in flow of any type of liquid. With
continuous self-diagnosis and flexibility in packaging, these sensors provide reliable
and accurate bubble detection for critical applications such as infusion pumps.
Bubble Detection Technology
As shown below, an air bubble detector such as TE's AD-101, is designed to be installed directly onto the tubing
that is used to infuse the liquid into the patient. The bubble detector contains an embedded piezo transducer that
emits a tone burst ultrasonic signal. The signal passes through the tubing and it's contents. A piezo receiver listens
for the ultrasonic signal. Liquids transmit ultrasound efficiently, so a strong signal passes when only liquid is present
in the tubing. Air bubbles do not transmit ultrasound waves efficiently, so the signal is weakened by any bubble in
the liquid. An internal circuit measures the amplitude of the receiver signal and provides the appropriate output.
The ultrasonic air bubble detector is non-invasive and has no direct contact with the liquid.
The AD-101 can handle tube sizes from 3mm to 10mm and can be custom-designed to fit
unusual tube sizes. The response time is less than 2ms, provides a 3.3V TTL output logic level
and has an integrated LED that provides a visual indication if a bubble is detected.
The AD-101 also has a built-in self-diagnostic capability that continuously monitors the
operation of the sensor. The sensor can be operated in any position with liquid flowing upward,
downward, or at any angle. Gravity has no effect on the detection capability.
AD-101 AIR BUBBLE DETECTOR
ULTRASONIC AIR BUBBLE DETECTOR - HOW IT WORKS
