Datex-Ohmeda S/5 Avance Technical Reference Manual page 41

A
C
RS-422 Serial
B
Interface Driver
O
A
R
12.5 VDC
3.3 VDC
D
Regulator
Balance Gas
Valve Drive
Oxygen Valve
Drive
FAN Hi/Lo
Regulator
Oxygen
Balance
Gas
Figure 2-17 • Electronic Gas Mixer block diagram
1009-0357-000 11/03
Desired gas flows are sent from the Anesthesia Control board to the Gas
Mixer.
Gas Mixer operation is controlled through a microcontroller which:
• Opens and closes selector valves for O
• Regulates flow control valves for O
Closed-loop flow control is accomplished through a hot-wire anemometer in
concert with the flow control valves. Gas flow, based on a calibration table, is
on target when the reference measurement equals the flow measurement.
Pressure measurements across each of the flow sensor channels are used as
checks on the flow measurement for hazard mitigation, ambient pressure
compensation, and compensation for back pressure downstream of the
Mixer.
Selector and Bypass Valves
130 ma max.
VDD
5.5 VDC
Regulator fro
Flow Sensors
350 ma max.
Press.
T1 F1
Press.
T2 F2
, N O and Air.
2 2
and balance gas (N
2
Atmel AVR Mega103L
Processor with 124K
Flash, 2K RAM
SPI Port
12 Bit A/D
Self Test Analog
Mutiplexer
Signal
Conditioning
Press.
Temperature, Flow, and
Pressure Sensors
2 Theory of Operation
O or Air).
2
Watchdog
CODE
CPU
RCV
XMIT
VLV1
VLV2
Analog FAIL
References
Diagnostic
Indicators
Vaporizer
2-15