Arena Service Manual
equalizer. This probe set is identical to the other conductivity
probe sets. It measures the total conductivity of the dialysate
before it enters the artificial kidney. This temperature-
compensated conductivity value is displayed in the
CONDUCTIVITY window. The primary conductivity alarm
circuit also uses the signal from this probe.
As mentioned previously, a thermistor is built into one of the
electrodes. This thermistor supplies information for the
temperature display and the primary high and low temperature
alarm limits. For more information on temperature monitoring,
refer to Section 6, Temperature Control.
4.2.13.2 Dialysate Pressure Transducer
This pressure transducer senses the dialysate pressure and changes
the pressure reading into an analog electrical signal proportional to
pressure. This signal is used for the transmembrane pressure
display and alarms.
4.2.14 Dialysate Bypass Valve and Sensor
4.2.14.1 Bypass Valve
The bypass valve protects the patient in the event of a temperature
or conductivity alarm by diverting unacceptable dialysate away
from the dialyzer. The diverter is a +24 VDC three-way solenoid
valve, controlled by the I/O Hydraulics Power board. During a
dialysate temperature or conductivity alarm, an electronic signal
causes the bypass valve to close the fluid path leading to the
dialyzer and shunt the dialysate to the drain.
On the I/O Hydraulics Power Board, LED DS6 indicates Bypass
(off) or Flow (on). See Figure 4-13 for location.
Figure 4-13. Bypass/Flow LED
4-16 157-1278-893 Rev A
January 2004
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