Duo™ Service Manual 0070-10-0604-01 1 - 5
Theory of Operation Hardware Overview
FIGURE 1-4 CPU/Display Board Block Diagram
1.2.4 NIBP Module Overview
The Duo monitor determines non-invasive blood pressure using the oscillometric method. The
blood pressure cuff is inflated until the pressure in the cuff is sufficient to block blood flow in
the brachial artery. As the cuff begins to deflate, blood beginning to flow through the artery
will cause the artery to pulsate. These pulsations are transmitted through the blood pressure
cuff and connecting hose to the pressure transducer in the NIBP module. The output of the
pressure transducer is an analog pulsating signal. This signal is filtered by a high-pass filter
and then amplified. The amplified analog signal is then converted to a digital signal. The
digital signal is then processed to determine the systolic, diastolic, and mean pressures as
well as heart rate.
CPU Board Test Points
Location Function
VPP in +12 vdc power supply
VDD in +3.3 vdc power supply
BV Battery voltage
5B in +5 vdc power supply
ADV +10.5 vdc ADV out
RST CPU reset line
XT2 11.0592 MHz clock
A/D Converter
Keypad
LED Array
Display
Indicator
LEDs
User Interface
RTC/ E
2
PROM
CPU
FPGA
Serial Interface
To
SpO2
Module
To
NIBP
Module
To
External
Interface
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