baxter ARENA - End-Of-Stroke Sensors; Input Pressure Equalizer, Flow Equalizer, and Output Pressure Equalizer

Arena Service Manual
4.2.10.5 Supply Pressure Regulator
The supply pressure regulator controls the peak input pressure to
the "pre" side of the input pressure equalizer. When the flow
equalizer cavity is filled, the pressure in the pressure regulator
increases to its maximum value (16 psi ±1), overcoming the spring
force of the regulator spring allowing the dialysate to recirculate
back to the “B” mix chamber. The Supply Pressure Regulator is
equivalent to an adjustable pressure relief valve. See also Section
8, Ultrafiltration.
4.2.11 Input Pressure Equalizer, Flow Equalizer, and
Output Pressure Equalizer
Refer to Section 8, Ultrafiltration, for a detailed description of
these components.
4.2.12 End-of-Stroke Sensors
The end-of-stroke (EOS) sensors are infrared optical devices
located in the flow path after the Flow Equalizer and before the
Output Pressure Equalizer. These sensors verify when the Flow
Equalizer compartments have reached the end of the fill cycle.
When the compartments are full, the sensor sends a signal to the
UF-Proportioning Power board. The EOS sensors are used to
minimize the end-of-stroke time of the Flow Equalizer by
controlling the flow rate of the supply pump via feedback from the
sensors.
The Instruments that have temperature-dependent EOS sensors,
work with self-heating thermistors. The temperature of these
thermistors will rise when the flow through them stops.
The Instrument may have optical EOS sensors like the one shown
in Figure 4-9. (The diagrams in this section show the optical
sensor.) The main components are two small PCBs, one on each
side of the assembly, and one diaphragm right in the middle of the
assembly. One PCB has the circuitry for the LED, and the other
for the Detector. On the body of the assembly, the orientation of
the diaphragm is indicated by a raised alignment symbol.
4-12 157-1278-893 Rev A
January 2004