4. Hydraulic Theory
Figure 4-8. "B" Probe/Thermister Set
The second conductivity probe in the flow path is located at the
outlet of the “B” mix chamber in the dialysate supply recirculation
loop. The probe/thermistor set is identical to the “A” conductivity
probe/thermistor set. In addition to compensating for temperature
effect on the conductivity reading, the “B” thermistor is also the
source of the temperature reading for the redundant high
temperature alarm as well as fine-tuning the dialysate temperature
control. Refer to Section 6, Temperature Control, for more
information on temperature control.
The “B” probe monitors the total conductivity of the dialysate
solution after both concentrates are mixed. The UF-Proportioning
Controller board subtracts the “A” conductivity probe reading
from the “B” conductivity probe reading and compares the
difference to the expected result. In the acetate therapy mode, the
result of this calculation should be zero and is used to recheck the
“A” conductivity probe reading. When bicarbonate dialysate is
used, the UF-Proportioning Controller board calculates whether
the conductivity contribution of the “B” portion of the solution is
acceptable for the type of bicarbonate concentrate used.
4.2.10.4 Supply Pump
The supply pump fills the flow equalizer with fluid. The supply
pump pumps at a rate slightly higher than the dialysate flow rate
set by the operator. This extra flow ensures an adequate supply of
solution to fill the flow equalizer. For more information on the
speed control of the supply pump, refer to Section 7, Dialysate
Preparation.
157-1278-893 4-11
January 2004
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