5. Electronics
second thermistor uses thermal dilution to sense the fluid flow.
The voltage outputs from the thermistors on the I/O Hydraulics
Power board drive A/D input channels on the I/O Controller board
where they are converted to 10 bit digital values. A software
algorithm in the I/O Controller code uses these inputs to determine
the flow condition. The design of the voltage divider guarantees
that the output remains within the A/D input range of 0 to +5 VDC
over the input temperature/flow range and over all component
tolerances.
5.8 I/O ELECTRONICS POWER BOARD
This board is also controlled directly by the Input/Output
Controller board. The I/O Electronics Power board in turn
controls the operation of some of the analog devices related mostly
to the extracorporeal circuit (see Figure 5-1):
• Air & Saline/Blood Detector
• Venous Line Clamp Driver
• Membrane Panel Switches
• Sonalert Control
• Power Fail Alarm. The power fail alarm circuitry is
located on the I/O Electronics Power board. See next
drawing:
157-1278-912 Rev A 5-39
November 2003
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