baxter ARENA - Overview; Temperature Control and Back Up Temperature Alarm

6. Temperature Control
6. TEMPERATURE CONTROL
6.1 OVERVIEW
The Arena Instrument accurately and safely controls the
temperature of the dialysate using a redundant system. This
redundancy involves two electronic signals that pass through
separate electronic pathways (the UF-Proportioning and the I/O
Controllers) which encompasses two main objectives:
 Control the dialysate temperature to the temperature
selected by the operator and back up temperature alarm
(see Section 6.2)
 Dialysate temperature monitoring and primary temperature
alarm in case there is any failure in the control system (see
Section 6.3)
This redundant system uses a total of three separate temperature
probes in the Instrument delivery system: the heater control
thermistor, and the “B” and Primary conductivity probes.
The “A” temperature sensor, also located in the “A” conductivity
probe, is not used to control the temperature of the dialysate. It is
only used to compensate the conductivity reading due to variations
in temperature.
Another function of the temperature control system is to control
the cabinet (internal) temperature at a level at which the electronic
components are guaranteed to operate properly. This is
accomplished using circuits unrelated to the dialysate temperature
control. The sensors for the cabinet temperature are located on the
Blood Pump Power Board and the I/O Electronics Board (see
Section 6.5).
6.2 TEMPERATURE CONTROL AND BACK UP
TEMPERATURE ALARM
This system is managed by the UF-Proportioning boards. The UF–
Proportioning system measures the dialysate temperature at three
locations in the fluid path. The first location is directly after the
heater, and this thermistor (the heater control thermistor) is used
for the main temperature control feedback. The heater thermistor,
located on the output of the heater housing, signal is biased on the
UF-Proportioning Power board. (There is also a safety thermostat
located within the heater housing.) This signal is passed to the
157-1278-913 Rev A 6-3
November 2003