Datex-Ohmeda 7900 Service Manual page 22

2/Theory of Operation
During normal operation the GIV (Gas Inlet Valve) is open to allow the supply gas
to flow to the ventilator manifold. This valve provides a shut off of the supply gas
to the ventilator when the ventilator is not in use. The GIV also shuts off supply
gas to the ventilator under failure conditions as the microprocessor or over-pres-
sure switch demands. The output from the GIV remains at the filtered supply gas
pressure.
35 - 100 psi
Supply inlet
Inlet
Filter
Supply
Gas
Hose
Figure 2-5
Non-Relieving Pressure Regulator
The pressure regulator is a Non-relieving Pressure Regulator which regulates
the high pressure filtered supply gas, oxygen or medical air, down to 172 kPa
(25 psi).
35 - 100 psi
Supply inlet
Inlet
Filter
Supply
Gas
Hose
Figure 2-6
Flow Control Valve
The Flow Control Valve is controlled by the microcontroller. Signals are sent to the
Flow Control valve which correspond to the generated flow requirements called for
by ventilator settings and sensor signals. The Flow Control Valve modulates the
incoming 25 psi drive gases to a variable output from 0 to 120 liters per minute at
pressures nominally ranging from minus 10 to plus 100 cmH
2-4 1503-0151-000
Gas
Inlet
Valve
(GIV)
Gas
Inlet
Valve
(GIV)
3/27/97
25 psi
Pressure
Regulator
Outlet
25 psi
Pressure
Regulator
0 - 120 Lpm
O.
2
Flow
Valve