Airflow Module (Afm) - Respironics BiPAP Vision Service Manual

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Chapter 3: Description and Theory of Operation

3.6 Airflow Module (AFM)

The AFM is a submodule of the Pressure Control (PC). The AFM receives power from the PC and provides the
following analog signals to the PAS:
a. Gas flow indication
b. Pressure indication
c. Temperature indication
To provide indications accurate enough for system requirements, the AFM must be calibrated. Calibration data is
stored in a nonvolatile memory that is part of the AFM. The flow, pressure, and temperature indications are for the
ventilator gas stream flowing through a "flow body" attached to the AFM circuit board.
3.6.1 Flow Body
The flow body, with laminar flow element, is added to the ventilator gas stream, creating a small pressure differen-
tial to short a fraction of the flow through the AFM sensor. Inlet, outlet, and pressure ports are part of the flow body
for tubing attachment to the AFM electronic sensors. Also, a hole is molded into the flow body to position the
temperature sensor. The body has molded feet for attaching it to the AFM circuit board assembly.
And/Or Oxygen Supply
1015010
Figure 3-6
AFM Block Diagram
BiPAP Vision Service Manual