Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 169)

IM 11M12A01-05E 12-6
12.2.2.3 Alarm 7: Span Calibration Coefficient Alarm
In calibration, this alarm is generated when the span gas ratio is out of the range of 0
6 18% (refer to Section 9.1.3, “Compensation”).
The following are suspected as the cause:
(1) The oxygen concentration of the span gas does not agree with the value of the span
gas set “Calibration setup.”
(2) The flow of the span gas is out of the specified flow value (600 6 60 mL/min).
(3) The sensor assembly is damaged and the cell voltage is abnormal.
<Locating cause of failure, and countermeasures>
(1) Confirm the following and carry out calibration again:
If the items are not within their proper states, correct them.
a. If the display “Span gas conc.” is selected in “Calibration setup,” the set value
should agree with the concentration of span gas actually used.
b. The calibration gas tubing should be constructed so that the span gas does not leak.
(2) If no alarm is generated as a result of carrying out re-calibration, it is suspected that
improper calibration conditions were the cause of the alarm in the preceding calibra-
tion. In this case, no specific restoration is necessary.
(3) If an alarm is generated again as a result of carrying out re-calibration, deterioration
of or damage to the cell (sensor) is suspected as the cause of the alarm.
Replacement of the cell with a new one is necessary.
However, before replacement, carry out the procedure described in step (3) and later
of <Search for cause of failure and taking measure> in Section 12.2.2.2, “Alarm 6:
Zero-point Calibration Coefficient Alarm.”
12.2.2.4 Alarm 8: EMF Stabilization Time Over
This alarm is generated if the sensor (cell) voltage has not stabilized even after the
calibration time is up for the reason that the calibration gas (zero gas or span gas) has
not filled the sensor assembly of the detector.
<Cause of alarm>
(1) The flow of the calibration gas is less than normal (a specified flow of 600 6 60
mL/min).
(2) The length or thickness of the calibration gas tubing has been changed (lengthened
or thickened).
(3) The measuring gas flows toward the tip of the probe.
(4) The sensor (cell) response has deteriorated.
<Locating cause of failure, and countermeasures>
(1) Carry out calibration by passing the calibration gas at the specified flow (600 6 60
mL/min) after checking that there is no leakage in the tubing.
(2) If calibration is carried out normally, perform a steady operation without changing
the conditions.
If the error occurs again, check whether or not the reason is applicable to the
following and then replace the sensor assembly.
• A lot of dust and the like may be sticking to the tip of the sensor. If dust is found,
clean and remove the dust (see Section 11.1.1).
In addition, if an error occurs in calibration even after the sensor assembly is
replaced, the influence of measured gas flow may be suspected. Do not let the
measured gas flow toward the tip of the detector probe, for example, by changing the
mounting position of the detector.