Yokogawa DO402 Dissolved Oxygen Analyzer User Manual

Page 80

IM 12J05D02-01E

8-2 Troubleshooting

8-2. Measures in the case of failure (Error) detection

If a failure is detected through the self-diagnosis of the DO402G dissolved oxygen converter, the FAIL

contact is closed. The FAIL lamp on the operation panel lights up and an error number appears in the

data display.

Note:

If an error is detected during configuration, the FAIL contact signal is output immediately but the

error number is displayed after that action or operation is completed.

When a FAIL contact signal is output, take measures according to Table 8-1.

Table 8-1.

Countermeasures in the case of failure (Error) detection

Error

No.

Generation

Mode

Error Content and Causes

Countermeasures

AIR.CAL mode

H2O. CAL mode

Stability failure

Even after an hour has elapsed, the measured value

change does not decrease within the set value of (mg/l)

• Sensor temperature changes.

• Dissolved-oxygen of the calibration solution changes.

• The value of A (mg/l) is not suitable.

Eliminate the causes and press the

(NO) key to perform re calibration.

H2O. CAL mode

Zero point error failure

The zero point error exceeds the set range

• Dirt sticks to the tip of the sensor.

• Membrane abnormality. Electrolyte degradation.

Clean the sensor membrane, sensor

cap, and recalibrate. If the error is

detected again, replace the electrolyte

and the membrane, sensor cap.

AIR.CAL mode

H2O. CAL mode

MAN.CAL mode

Slope failure

The slope exceeds the range of 40 to 200 % of the

theoretical value.

• Dirt sticks to the tip of the sensor.

• Membrane abnormality. Electrolyte degradation.

Clean the sensor membrane, sensor

cap, and recalibrate. If the error is

detected again, replace the electrolyte

and the membrane. Check that the

connection between sensor and

sensor cable is fit, and LED emission

of the optical dissolved-oxygen sensor.

When error occurred again, replace

the sensor cap, sensor cable or sensor

itself.

Measuring mode

Sensor membrane failure

Replace membrane

Check for wet O-rings in the

membrane assembly or wet sealing

face.

Wipe off wet areas and dry out.

All modes

Measured temperature failure (too high)

It exceeds 50.0 °C (122.0 °F).

• Measuring solution temperature is high

• CODE 10 setting is not correct

• Sensor cable wiring failure

• Temperature sensor has failed

Examine the temperatures of the

measuring solution and sensor and the

CODE 10 setting

Examine the sensor cable connection

status.

If the temperature sensor fails

(abnormal resistance), replace the

sensor.

All modes

Measured temperature failure (too low)

It falls below 0 °C (or 32.0 °F).

• Measuring solution temperature is low

• CODE 10 setting is not correct

• Sensor cable wiring failure

• Temperature sensor has failed.

Examine the temperatures of the

measuring solution and sensor and the

CODE 10 setting.

Examine the sensor cable connection

status.

If the temperature sensor fails

(abnormal resistance), replace the

sensor.

All modes

Input current failure

It does not satisfy the following equation:

input current < 50 µA for galvanic sensor

< 500 nA for polarographic sensor and optical sensor

Examine the setting for CODE 01, 02