Arena Service Manual
13.1 BLOOD/SALINE DETECTOR
The Blood/Saline Detector is an optical source (LED) of pulsed
green light and a phototransistor (detector) that will allow the
Instrument to differentiate between the presence of blood and the
presence of saline in the venous blood line tubing. This
information is used to automatically activate the Air Detector. The
Air Detector can also be activated manually.
The Saline/Blood Detector is adjusted to the optical properties of a
specific blood tubing during calibration. See Section 18.5.12..
When the detector senses constant light pulses (saline), the
extracorporeal alarms may be disarmed in the Prime Mode and the
Instrument state may be changed from Dialyze Mode or Standby
Mode to Rinse Mode. If the detector senses either no pulse
(blood) or constant light (ambient light error), the extracorporeal
alarms are armed in the Prime Mode and the change from the
Dialyze Mode or Standby Mode to the Rinse Mode is prohibited.
13.2 AIR DETECTOR
13.2.1 Functional Description
The air detector monitors the venous blood line via the I/O
Electronics Power Board for the presence of air bubbles by
continuously emitting an ultrasonic signal of a known intensity.
This ultrasound is monitored by the air detector receptor for any
change in characteristics. If the passing blood contains air bubbles
equal to or larger than the sensitivity value set in Calibration Mode
(see Section 17.3.1.2), the sound reaching the receiver will change
enough to cause the Instrument to trigger an alarm.
Warning
The Air Detector housing and blood line must be clean and dry
for proper operation. Do not wet or apply other liquids to the
Air Detector or external surface of the blood line in the Air
Detector. Wetting or the use of other liquids (including
ultrasonic gel) could result in reduced air detector sensitivity.
During an air detector alarm the audio alarm sounds, the blood
pump stops, the venous line clamp occludes the venous blood line,
and the UF rate goes to 0 mL/h. The blood and dialysate pressures
will slowly equalize across the dialyzer membrane.
13-4 157-1278-920 Rev A
April 2004
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