7-5
7.3.1.1 Flow Calibration Principles
This calibration item is used to calibrate only the flow sensors and inspiration valve in the circuit.
The built-in flow measurement base source of the machine is utilized to calibrate the inspiratory
flow sensor and expiratory flow sensor on the breathing system. The VCM opens the inspiration
valve based on inspiration valve DA values obtained from service calibration, to inflate the circuit
of the breathing system, records the flow of the built-in flow sensor, and uses the measured value
of the built-in flow sensor as well as AD values collected by the inspiratory flow sensor and
expiratory flow sensor as the data of one calibration point for flow sensors, and uses the measured
value of the built-in flow sensor as well as the DA value of the inspiration valve as the data of one
calibration point for the inspiration valve. Change the DA value of the inspiration valve to obtain
calibration data under a series of flows, forming a flow calibration data table. The flow should be
in the range from 0 L/min to 120 L/min when the inspiration valve is opened during flow
calibration.
If the inspiratory flow sensor and expiratory flow sensor have been used for months, for example,
three months after calibration, the measured tidal volume greatly deviates from the settings (with
the deviation of more than 9%) due to sensor aging or environmental factors; or a flow sensor is
replaced. In this case, the flow sensor needs to be calibrated. The flow calibration (user) can be
adopted.
FIGURE 1 Schematic Diagram of Flow Calibration (User)
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