Mindray WATO EX-55Pro, Service Manual

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6.6.7.2 Check the N2O Electronic Flowmeter Accuracy
NOTE

When checking the accuracy of N2O electronic flowmeter, first adjust O2 flow to
sufficiently large (above 5 L/min), so as to make sure that O2 flow does not increase
when the needle valve of N2O supply flowmeter is being adjusted. Otherwise, you
need to increase O2 flow further and do the test again.
Due to the existence of O2-N2O chain linkage and O2-N2O cut-off valve, the method for
checking the accuracy of O2 or Air electronic flowmeter cannot be used for N2O electronic
flowmeter accuracy checking. When checking the accuracy of N2O electronic flowmeter,
eliminate the effect of O2 first.
To check the measurement accuracy of N2O electronic flowmeter:
1. Make sure that checking the O2 electronic flowmeter accuracy is passed.
2. Turn off all the electronic flowmeters.
3. Make sure that the anesthesia machine calibration device is connected to the anesthesia
machine in the same way to that for checking the O2 electronic flowmeter accuracy. For
details, refer to
6.6.7.1 Check the O2/Air Electronic Flowmeter Accuracy.
4. Select N2O for the gas under test of the anesthesia machine calibration device.
5. Turn on O2 electronic flowmeter and set O2 flow to approximately 5 L/min. Record the
reading measured by the calibration device, which is used as the “initial flow” for N2O
measurement.
6. Keep O2 flow control unmoved. Adjust the needle valve of the N2O electronic
flowmeter, causing the reading on the calibration device to increase by (3±1) L/min and
(6±1) L/min respectively based on the “initial flow”. Observe the value displayed by the
N2O electronic flowmeter, which should fall within (1+/-10%) of the increased reading
(current reading minus initial flow) on the calibration device. Otherwise, calibrate the
N2O electronic flowmeter.