Mallinckrodt NELLCOR NPB-4000 Service Manual page 162

Section 14: Main Color Board Digital Theory of Operation
14.15.1.1 The pneumatic assembly
14.15.1.2 NIBP Hardware
14-22
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 14-12. The pump output is connected to the cuff and to two valves: a
two-way and a three-way valve, 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 14-12: Pneumatic Assembly Block Diagram
Control valve V2 is used to control the rate of deflation. The smoothly variable
opening of the valve is controlled by the valve excitation current.
3-Way valve V1 is either fully ON or fully OFF. It performs two functions:
1. It dumps the remaining pressure from the cuff at the end of the
deflation cycle;
2. It connects the pressure transducers directly to the atmosphere for
calibration purposes.
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.