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Service Manual Functional verification 35
WARNING Eliminate all the possibilities causing errors shown in the following
table before performing the calibration procedure (“MSP Board (MCO2)
calibration” on page 54). Recalibrating the altimeter as described in that
procedure, without adequately eliminating all other possible faults, may result in
inaccurate EtCO
2
readings.
Table 10. Possible sources of CO
2
verification test errors
Error Specification Correction
Incorrect/unknown calibration gas
concentration
4 to 10% certified to within ±0.01% Verify gas supply. Gas must be
between 4% and 10%. Once known,
convert percentage to partial pressure
(mmHg) as instructed in “Partial
pressure of test gas source” on
page 31.
Insufficient/excessive gas flow rate Between 60 and 200 ml/min Verify with flow meter.
Excessive back pressure in cuvette Back pressure should not exceed
1 mmHg
Connect gases as instructed in
verification test.
Air mixed with standard gas Check integrity of test setup.
Gas temperature Gas temperature entering airway
adapter should be at room
temperature
Store gas at room temperature.
Cuvette error Results should not vary more than
0.5 mmHg due to cuvette tolerances
Use another cuvette (airway adapter).
Thermal equilibrium error Sensor not warmed up Allow the sensor/system to warm up
for 15 minutes.
High CO
2
reading with sensor subject
to room air only
CO
2
forced outside of airway adapter
into sensor. This is possible during
demonstration if exhaled gases are
blown through hands cupped around
cuvette and exhaled gases are forced
into sensor.
Contain exhaled breath through the
inside of the cuvette only. Do not allow
gases to be forced outside of the
cuvette and into the sensor housing. If
CO
2
has been forced into the sensor,
allow 24 to 48 hours for the CO
2
to
dissipate.