Air Detector
The air detector is designed to detect air in the outlet tubing fluid path. The air detector is detachable if not needed. The
When the optional air detector is installed, the Biomed Toolbox feature allows the air detector to be “required” or “not required.” When the air detector is not required, it can be “turned on” or “turned off” using the Options menu. When the air detector is required, the option for turning the air detector on or off will not be available. When the air detector is turned on, the pump will detect the presence of air in the outlet tubing fluid path. If the air detector settings are “not required” and “turned off,” it will default to “turned on” each time the pump powers up in Lock Level 0.
The air detector is compatible with all of the reservoirs and sets indicated for use with the
Specifications
The air detector will alarm when it senses a single air bubble greater than 100 microliters (0.1 milliliters.)
Construction
The air detector housing is made of a special high impact plastic and has a metalized film coating on the inside surface to reduce interference from electromagnetic fields. The air detector is composed of a single base compartment with a detachable door. It is sealed against the pump housing to ensure the overall assembly is water resistant. The air detector is mounted to the pump housing with two screws, and electrically connected with a ten pin connector.
Theory of Operation
The air detector consists of sensor electronics and two ultrasonic transducers positioned on opposite sides of the tubing. One transducer acts as an acoustic transmitter and the other as an acoustic receiver. Air detection occurs when air in the fluid path causes a reduction in the signal level to the receiver. When the signal is interrupted for a preset length of time, the sensing circuitry sends a signal to the microprocessor indicating air in the fluid path. To maximize the reliability of the system and to reduce false alarms, the transmitted signal is swept over a frequency range. This accommodates varying resonance frequencies of the transducer and reduces sensitivity to tubing tolerances and other mechanical variations.
Upstream Occlusion Sensor
Theory of Operation
The upstream occlusion sensor is a strain gauge device capable of detecting pressure changes in the disposable tubing set. This is accomplished by using a loading ball or sphere located on the bottom of the pump. This loading ball contacts the pump tubing when a tubing set is attached to the pump. Under normal operation, the pump tube pushes outward and applies a specified force on the sensor. When an upstream occlusion is present, the upstream tubing collapses pulling away from the sensor reducing the force on the sensor. It is this change of the force that indicates an upstream occlusion.
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