Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 176)

<12. Troubleshooting>
12-6
IM 11M12A01-02E
12.2.2 Remedies When Alarms are Generated
12.2.2.1 Alarm 1: Oxygen Concentration Alarm
This alarm is generated when a measured value exceeds an alarm set point or falls below it.
For details on the oxygen concentration alarm, see Section 8.3, Setting Oxygen Concentration
Alarms, in the chapter on operation.
12.2.2.2 Alarm 6: Zero-point Calibration Coefficient Alarm
In automatic or semi-automatic calibration, this alarm is generated when the zero correction ratio
is out of the range of 100 ± 30% (refer to Section 9.1.3, Compensation).
The following are possible causes of this alarm.
(1) The zero-gas oxygen concentration does not agree with the value of the zero-gas
concentration set in Calibration setup. Otherwise, the span gas is used as the zero gas.
(2) The flow rate of zero gas is out of the specified flow (600 ± 60 ml/min).
(3) The sensor assembly is damaged and so cell voltage is not normal.
<Locating cause of failure, and countermeasures>
(1) Check that the following have been set up correctly. If not, correct them. Then, recalibrate.
a. Check the preset zero gas concentration on the Calibration setup display. The displayed
concentration value has agreed with the concentration of the zero gas actually used.
b. The piping for calibration gases has been constructed so that the zero gas does not leak.
(2) If the alarm is not generated during the recalibration, improper calibration conditions are
considered as the cause of the alarm generated in the previous calibration. In this case, no
particular restoration is necessary.
(3) If the alarm is generated again during the recalibration, deterioration of or damage to the
sensor assembly is considered as the cause of the alarm. It is necessary to replace the cell
with a new one. Before replacement, carry out the following.
Check the cell voltages when the zero gas and span gas are introduced.
a. From the Basic panel display, move to the Detailed-data display of the channel where the
alarm is being generated.
b. When the [▼] key is pressed once, the cell voltage should be indicated on the top line
(Figure 12.5).
c. Check whether or not the displayed cell voltage is very different from the theoretical value
at the oxygen concentration of the relevant gas. See Table 12.3 for the theoretical cell
voltages. Although the tolerance to the theoretical value cannot be generally specified, a
reasonable one may be approximately ±10 mV.
Table 12.3 Oxygen Concentration and Cell Voltage
Oxygen concentration
(vol%O2)
Cell voltage
(mV)
1% 67.1
21% 0
8th Edition : Jan.13,2012-00