YOKOGAWA av550g, Руководство пользователя

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< 12. Troubleshooting >
12-15
IM 11M12D01-01E
NOTE
Data such as cell robustness displayed in the [Detailed data] display should also be used for deciding
sensor quality as references .
12.3.2 Measured Value Lower Than True Value
<Causes and Countermeasures>
(1) The measuring gas pressure becomes lower.
Where an increment of the measured value due to pressure change cannot be neglected, take
measures referring to Subsection 12.3.1 (1).
(2) Moisture content in a reference gas changes (decreases) greatly.
If air at the detector installation site is used for the reference gas, large change of moisture
content in the air may cause an error in measured oxygen concentration value (vol% O
2
).
When this error is not ignored, use a gas in which moisture content is constant such as
instrument air in almost dry condition as a reference gas.
In addition, change of moisture content in exhaust gas after combustion is also considered as a
cause of error. However, normally this error is negligible.
(3) Calibration gas (zero gas) is mixed into the detector due to leakage.
If the zero gas is mixed into the detector due to leakage as a result of failure of the valve provided
in the calibration gas tubing system, the measured value shows a value a little lower than
normal.
Check valves (needle valves, check valves, solenoid valves for automatic calibration, etc.) in the
calibration gas tubing system for leakage. For manual valves, check them after confirming that
they are in fully closed states.
(4) Combustible components exist in the sample gas.
If combustible components exist in the sample gas, they burn in the sensor and thus oxygen
concentration decreases.
Check that there are no combustible components.
(5) Temperature of the detector cell reaches 750°C or more.
12.3.3 Measurements Sometimes Show Abnormal Values
<Causes and Countermeasures>
(1) Noise may be mixing in with the converter from the detector output wiring.
Check whether the converter and detector are securely grounded. Check whether or not the
signal wiring is laid along other power cords.
(2) The converter may be affected by noise from the power supply.
Check whether or not the converter power is supplied from the same outlet, switch, or breaker as
other power machines and equipment.
(3) Poor wiring contact.
If there is poor contact in the wiring, the sensor voltage or thermocouple e.m.f. (voltage) may
vary due to vibration or other factors. Check whether or not there are loose points in the wiring
connections or loose crimping (caulking) at the crimp-on terminal lugs.
(4) Combustible components in the sample gas may be getting into the sensor.
If the combustible components show signs of dust, the abnormality may be improved by
mounting a dust filter K9471UA.