GE 001C 051D 003A, Service Manual

Page: 46 / 282

Equipment overview: Theory of operation
2-26 Dash 3000/4000/5000 2000966-542D
The DAS block diagram with Nellcor 05 DAS PCB assembly consisting of
three sections:
The DAS design includes the Nellcor MP100 Module technology. Nellcor
SPO2 is classified as motion-resistant. It uses advanced digital signal
processing algorithms to extract very low-level SPO2 signals in the
presence of artifact induced noise.
The DAS contains all circuitry necessary to support the MP100 Module.
The Nellcor MP100 Module contains:

All SPO2 front end circuitry, such as the digitally programmable
photodetector signal conditioning, A/D conversion, digitally
programmable back-to-back LED IR/RED emitter drive and on-board
diagnostic / sensor identification signal processing circuits.

A digital signal processor (DSP), clock circuitry, and program
memory. The Nellcor SPO2 algorithms executes on the DSP. No
external memory interface is provided. The DSP is "reset-able" by the
DAS CPU.

A UART for communication of commands and data.
Parameter functions of the DAS with Nellcor OxiMax SPO2,
four BP channels and Dinamap SuperSTAT NIBP
Except for the SPO2 parameter and additional 2 IBPs, the DAS with the
Nellcor OxiMax SPO2 parameter supports the same parameters as DAS
with the GE Ohmeda SPO2 parameter. Refer to
“ECG” on page 2-20.
Probes and cable
The DAS is intended for use only with Nellcor digital probes. It is not for
use with non-Nellcor probes or with Nellcor R-cal (resistor id) probes. An
adapter cable is used to interface the probes to the DAS front panel
Nicolay connector.
Section Description
ECG/Respiration Separately isolated section includes a 7.3728MHz 68HSC05
microcontroller, A/D conversion, signal processing hybrids and
DC-DC isolation converter.
Main DAS Separately isolated section includes a 22.1184MHz Motorola
MC68332 microcontroller with FLASH and SRAM memory, an
Analog Devices ADSP-21062 32-bit floating point digital signal
processor running at 12.096MHz, A/D conversion, signal
processing hybrids/modules and DC-DC isolation converter.
Non-isolated circuits Includes serial and parallel host interfaces and NBP pump, valves,
and over-pressure circuitry.