The Measured Value Is Lower Than The Actual Value (Higher In The Case Of A Hygrometer); Measured Values Occasionally Show Abnormal Values - YOKOGAWA ZR22G User Manual

12.3.2 The measured value is lower than the actual value
(higher in the case of a hygrometer).
<Cause and remedy>
(1) The pressure of the measured gas decreases.
If the change in the measured value due to pressure fluctuation cannot be ignored, take
measures according to (1) in section 12.3.1.
(2) The amount of water contained in the comparison gas changes greatly (decreases).
If the air at the detector installation site is used as a comparator gas, a large change in
the amount of water contained in the air may result in errors in the measured oxygen
concentration (vol%O
If this error cannot be ignored, use a gas with a constant moisture content, such as instrumented air
that is almost dry, as the comparison gas. Changes in the amount of water in the combustion exhaust
gas can also be considered as an error factor. Normally, this amount of error is negligible.
(3) Calibration gas (zero gas) is leaking into the detector
If zero air leaks into the detector, e.g. due to a defective valve installed in the calibration gas
piping system, the measured value will be lower.
Check the valves in the calibration gas piping system for leaks. For manual valves, check
that the valve is fully closed before checking for leaks.
(4) Combustible components exist in the measured gas.
If there is a combustible component in the measurement gas, it will burn in the sensor and
the O2 concentration will decrease. Check for flammable components.
(5) The detector cell temperature is 750°C or higher.
If the measured gas leaks into the comparison gas side for some reason, the thermocouple
may be corroded and the temperature of the sensor may become 750°C or higher. If the
measured gas leaks into the comparison gas side for some reason, the thermocouple may
be corroded and the temperature of the sensor may become 750°C or higher.
12.3.3

Measured values occasionally show abnormal values

<Cause and remedy>
(1) Noise comes in from the detector output wiring.
Ensure that the transmitter and sensor are properly grounded.
Check that the signal lines are not routed along other power lines.
(2) Affected by power supply noise.
Check that the power is not supplied from the same location as the other power equipment.
(3) Poor contact of wiring.
Poor contact in the wiring may cause the electromotive force of the sensor or thermocouple
to change due to vibration, etc. Check that the wiring connections are not loose and that the
crimped part of the crimp terminal is not loose.
(4) Combustible components in the measured gas enter the sensor.
If the combustible component is dust-like, attach the dust filter K9471UA to improve the
flammability.
(5) There is a crack in the sensor or a leak in the sensor mounting part.
If the indication changes in synchronization with the fluctuation of the furnace pressure,
check that there is no crack in the sensor, that the metal O-ring is firmly crushed, and that
the flange of the sensor is in close contact with the contact surface of the probe.
(6) There is a leak in the calibration gas piping
In the case of negative pressure in the furnace, if the indication fluctuates with fluctuation in
the furnace internal pressure, check the calibration gas piping for leaks.
) and humidity (vol%H
2
<12. Troubleshooting>
O or kg/kg).
2
IM 11M12G01-02EN
12-12
1sh Edition : Mar. 25, 2021-00