Yokogawa DO402 Dissolved Oxygen Analyzer - Manual (Page 68)

IM 12J05D02-01E
6-2 Calibration
6-1-2. Diagnostic functions performed during calibration
The calibration is a semi-automatic calibration, which means that the sensor output is used for calcula-
tion of sensor parameters after the readings have stabilized. The criteria for stabilization are set in serv-
ice code 20. If stable readings are not achieved within one hour error E1 message will appear on the
display and the procedure is aborted. The calculated sensor parameters are compared with preset toler-
ances and if these conditions are not met, Error E2 (Zero Error) or E3 (Slope Error) will be signalled.
Notes: 1. Error messages that appear initially indicate inadequate settings of the diagnostic variables in
service codes 01, 20 and/or 22.
2. Patience improves the accuracy of calibration. When the EXA prompts the user that the
preset criteria are met by showing CAL.END message it only means that the minimum criteria
are met. When the signal still changes after this initial acceptance, EXA will automatically
update the sensor characteristics with the new information.
6-2. Calibration procedure using air calibration method
6-2-1. Preparation
Move the sensor to a maintenance site and wash off any dirt on the membrane. Lightly wipe off any
remaining water from the membrane with a soft tissue.
Expose the sensor to the air in an environment where there is no temperature change and no wind. ( A
convenient way to accomplish this environment is to place the sensor in an empty bucket)
Note: If sensors are used without temperature compensating element, the temperature must be adjusted
to ambient temperature in service code 13.
Before zero calibration, see 6-3-1 Preparation