Datex-Ohmeda S/5 B-GAS, Technical Reference Manual

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Datex-Ohmeda S/5 Anesthesia Monitor
Document No. 800 1005-1
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2.2.5 ASX agent identification bench
The ASX-200 agent identification bench has one measuring chamber. Background compensation
is done by subtracting the background spectrum from the measured signal. Background spectrum
is measured simultaneously with the zeroing of the ACX-200 unit. The resulting spectrum is
analyzed to identify the agent.
The ASX unit requires two calibrations. One is the time between synchronization pulse and
measured spectrum (time offset) of the ASX-200 and the other is the peak wavelength of the
narrow bandpass filter. The former is calibrated automatically together with the gas calibration of
the ACX and the latter is calibrated at the factory.
ASX Bord
Preamplifier
ASX Unit
Figure 12 ASX measuring unit
ASX preamplifier board
The absorption of infrared light is measured with a lead selenide detector. The signal is amplified
and then led to the measuring board.
2.2.6 ASX measuring board
The measuring electronics can be divided into a few functional blocks, which are described below
(See the block diagram in figure 13).
The ASX measuring board controls the measurement. It converts the ASX photometer signal to
digital data, calculates results and communicates with the main CPU through a serial channel. The
board contains, in addition to the 80C196 processor, EPROM, RAM, and EEPROM, several analog
and digital I/O functions.
Processor section
Processor is a 80C196 and works at 12 MHz. It has an internal A/D-converter with a multiplexer.
One channel is used for converting temperature signal. Two others are for the measurement signal
from preamplifier board.
The processor uses an internal bus to access EPROM (64k x 8 bit), SRAM (8k x 8 bit) and two D/A-
converters. It communicates with the Gas mother board through a serial channel (RXD, TXDB).