Mallinckrodt NELLCOR NPB-4000, Service Manual

Page: 111 / 219

Section 12: NIBP - Theory of Operation
12-3
12.2 THE PNEUMATIC ASSEMBLY
The pneumatic assembly, consisting of the pump, two controlling valves, and
tubing to connect the various pneumatic components together are illustrated in
the schematic diagram that follows.
See Figure 12-4. The pump output is connected to the cuff and to two valves: a
two-way proportional control valve (V2) and a three-way valve (V1), as well as
to two pressure transducers. Operation of the valves and of the pump control are
defined as described in the following text.
Figure 12-4: Pneumatic Assembly Block Diagram
Valve V1 is a three-way valve. In the V1 deenergized position, the portion of
the pneumatic system encompassing the cuff and pump are open to the
atmosphere, thus preventing the cuff from being pressurized. In the V1
energized position, the cuff and pump are connected to V2 and the pressure
transducers. When V2 is closed, action of the pump will pressurize the cuff.
Control valve V2 is used to bleed pressure from the cuff during an NIBP
measurement, at a controlled deflation rate.
12.3 NIBP HARDWARE
See Figure 12-5. The NIBP analog control hardware is highlighted in the block
diagram. It includes the Front End NIBP circuitry, as well as the pressure
transducers and pump. Refer to the main PCB schematic drawing, Sheet 2,
Figure 17-6, in connection with the circuit operation descriptions.
Figure 12-5: NIBP Hardware Block Diagram