Chapter 3
Theory of Operation
REF 1029568 Rev A BiPAP® Focus™ Ventilator Service Manual © Respironics, Inc. 3-3
Flow valve (FV) The flow valve (valve assembly) is a mechanical sliding
assembly driven by an electromagnetic coil. Valve
commands from the PCB control current (-125mA to
675mA) to the coil. Movement of the flow valve is
proportional to the current through the coil. The flow
valve operates as a closed-loop system, using feedback
from the flow sensor and pressure transducers.
Air Flow Sensor The air flow sensor measures flow from the flow valve.
The ventilator uses this measurement to provide closed
loop control of the flow valve and to compute the flow
and volume delivered to the patient.
Air Delivery System Components (Continued)
Table 3-1: Air Delivery System Components
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