Mallinckrodt NELLCOR NPB-4000, Service Manual

Page: 90 / 219

Section 10: Introduction and System Description
10-2
Figure 10-1: NPB-4000/C System Block Diagram
10.2.1 Isolated Front End
The Isolated Front End section includes all the circuitry to convert ECG, SpO
2
,
and temperature measurements to digital format and to connect this information
to the processor. The respiration detection is obtained from two of the three
electrodes of the ECG connections.
Galvanic isolation of these circuits from the remainder of the monitor is
accomplished by utilizing an isolated power supply and by incorporating
opto-isolators between the Front End outputs and inputs to the microprocessor
computation and control circuitry.
10.2.2 NIBP Front End
The NIBP section contains the pumps, valves, pressure measurement circuitry,
and control circuitry for the noninvasive blood pressure measurement. Pressure
data is converted to digital format and conveyed to the processor section.
10.2.3 Power System
The power system section contains a power supply capable of operating the
monitor and charging the battery from either an AC source of 100 to 240 volts
AC at 50 to 60 Hz or a 10 to 16 volt DC input. This section also contains the
battery, battery monitoring circuitry, and battery charging circuitry. The battery
provides the operating power for the monitor.
Power system outputs of
±
12 volts DC, +5 volts DC, and -24 volts DC are
developed for use throughout the non-isolated portions of the monitor.