2-1 
2 Theory of Operation 
 
 
 
2.1 Electrical Part 
The hardware system of WATO EX-55/65 includes: mother board, power sub-system, main unit 
sub-system, display sub-system, gas parsmeters module sub-system, electronic flowmeter 
sub-system, pneumatic accessories, and others. The introductions of the modules are as follows: 
1.  Mother board: connects to the related parts of cards and hardwares, and transfers related 
signals to corresponding cards and components. 
2.  Power sub-system: includes power board, battery adapter board, lithium battery, AC 
input, auxiliary electrical outlet, etc. It supplies power to anesthesia machine and its 
external equipments. 
3.  Main unit sub-system: includes main control board and monitoring module. Main 
control board realizes the human-machine interaction function of the anesthesia machine 
and the data exchange with monitoring module and electronic flowmeter sub-system, 
and it extends with USB, network port, RS-232 series port, VGA port, calibration port, 
etc. Monitoring module controls the parameters of the anesthesia machine and realizes 
monitoring function, and it includes ventilation control board and ventilation protection 
board. 
4.  Display sub-system: includes key control board, encoder board (main encoder), EFCS 
flowmeter encoder board, alarm light board, screen, touchscreen, touch key board, etc. 
Key control board realizes the functions of EFCS flowmeter encoder, encoder 
recognition, touchscreen recognition, touch key recognition, backlight control, etc, and it 
also transfers the signal of alarm light controlled by main control board and the 
backlight enable signal, and send data to main control board through series port. 
5.  EFCS flowmeter sub-system: includes EFCS flowmeter control board, flow sensor 
board, proportional valve, three-way valve, NC valve, and NO valve. EFCS flowmeter 
control board monitors and controls the flow of fresh gas in real time, and exchanges 
data with master through series port. 
6.  Gas parsmeters module sub-system: includes infrared backlight board, parameter 
module, fan of module rack, and interior AG module. 
7.  Except the modules and cards above, the hardware system of WATO EX-65/55 also 
includes several components related to hardware, for example, valve, position switch, 
heater, speaker, heat-sink fan, etc.