p/n 18603-001, Rev. C LTV
®
1200/1150 Ventilator Service Manual Page 6-25
Flow Valve Calibration
The flow valve should not normally require recalibration from its factory set values. However,
some circumstances, such as mechanical shock, may cause the flow valve calibration to
change from its factory-set condition. This flow valve calibration procedure can be used to
adjust the flow valve calibration setting to compensate for improper flows measured during
the Performance Checkout procedure.
LTV
®
software includes an adjustable VHOME option to allow for field calibration of the flow
valve. Specifically, the location of the flow valve HOME position Flag can be set relative to
the position sensor.
Proper ventilator flow performance depends on several conditions, such as transducer
calibration and lack of leaks in the airway passages, in addition to flow valve calibration.
Flow valve recalibration should only be performed after all other factors affecting flow
performance are verified to be correct. This procedure is designed so that it checks the
other factors contributing to flow performance before adjusting the flow valve calibration. For
this reason, it is important to follow this flow valve calibration procedure completely, and in
the stated order. Enter the measurements on the flow valve Calibration Worksheet at the
end of this section.
CAUTION
Recalibration of the flow valve - When recalibrating the flow valve this procedure must be
followed completely, and in the listed order of events.
Calibration of the valve differential (see page 6-13) and motor drive (see page 6-19) must be
performed prior to performing flow valve calibration.
1) Determine the current configuration of the flow valve.
• Turn on the LTV
®
in the VENT CHECK mode. (Push and hold the Select button
while the unit powers on).
• Turn the Set Value knob to the VENT OP menu and push the Select button.
• Turn the Set Value knob to the VHOME XXX display and record the value.
2) Warm the ventilator up by running it at the following settings on a test lung for
approximately 1 hour; Mode: Volume, Assist/Control, Rate:12 bpm, Tidal Vol:500 ml,
Insp Time:1.5 sec. Measure the flow in Vent Maintenance / Servo mode at 4000 rpm
and 10 Lpm. The measured flow should be 9.5 Lpm – 10.5 Lpm. If the measured flow is
within this range, then the flow is within specification, and there is no need to continue
with flow valve calibration; otherwise power down the ventilator and proceed to step 3.
3) Place the ventilator in an ESD-safe environment, and use ESD controls. Remove the
back panel from the ventilator. Perform a visual inspection of the flow valve:
• Is the Motor bracket interfering with the turbine manifold?
• Is the Motor bracket interfering with the side weldment?
• Are any of the screws loose, including the screws for the Drive Band, Motor
bracket, Sensor PCB, and Flag?
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