Mallinckrodt NELLCOR NPB-4000, Service Manual

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12-1
SECTION 12: NIBP - THEORY OF OPERATION
12.1 NIBP System Overview
12.2 The Pneumatic Assembly
12.3 NIBP Hardware
12. NIBP - THEORY OF OPERATION
12.1 NIBP SYSTEM OVERVIEW
See Figure 12-1. The NPB-4000/C noninvasive blood pressure (NIBP)
measurement and display operations described in this section include the
pneumatics of the inflatable cuff and control valves, the specialized Front End
NIBP circuitry, some of the microprocessor memory and control circuitry, some
of the power system, and specific switches on the keypad. These are highlighted
in the main system block diagram, as shown, with a distinction among the
different shades of background tint to identify those that are only partly involved
from the major circuitry dedicated to the NIBP functions.
3-Lead ECG
Temp 1
Isolated Front
End
EKG, Resp,
Temp, & SpO
2
Circuitry
SpO
2
uP, Memory,
and Control
Circuitry
Keypad
(Switches)
Display
Front End
NIBP Circuit
NIBP
Defib. Sync
RS-232 I/O
Speaker
Printer I/O
Power System
Battery
DC In
AC Line In
LNA
Power
Figure 12-1: NPB-4000/C System Block Diagram
The major blocks involved from the cuff to the microprocessor are shown in the
simplified block of the NIBP see Figure 12-2. The pump and motor, mounted on
the power system assembly, are driven by a pulse-width-modulated (PWM)
signal from the digital hardware section of the main board assembly. That signal
is gated by an enabling signal originating in the microprocessor of the section of
the main board. The pumped air is ducted through tubing and valves mounted on
the main board and made available at the Front End connection to the cuff.