Mallinckrodt NELLCOR NPB-4000, Service Manual

Page: 97 / 219

11-1
SECTION 11: ISOLATED FRONT END FUNCTIONS - THEORY OF
OPERATION
11.1 Block Diagram
11.2 Overview
11.3 Interface Circuit
11.4 ECG
11.5 Respiratory Circuit
11.6 Temperature Circuit
11.7 Optocouplers
11.8 Controls
11.9 A/D Converter
11.10 Isolated Power Supply
11.11 SpO
2
Board
11.12 Isolation
11. ISOLATED FRONT END FUNCTIONS - THEORY OF OPERATION
11.1 BLOCK DIAGRAM
See Figure 11-1. The simplified block diagram of the previous section has been
reproduced and highlighted to indicate the circuit block that will be described in
some detail in the paragraphs that follow. As shown, the selected block is the
isolated Front End circuitry. This block contains the interfaces with the patient
connections at the input, and delivers an isolated output to the microprocessor
and controller. An expanded block diagram for this circuitry is shown in
Figure 11-2.
Figure 11-1: NPB-4000/C Simplified Block Diagram