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Appendices
January 2009 UDA2182 Universal Dual Analyzer Product Manual 231
15.16 Appendix O – Auto Clean and Auto Cal Examples
Automatic Cleaning and Calibration
Overview
Although the Honeywell probe accuracy is unaffected by inert fouling, there are two
conditions where probe cleaning may be required. (These conditions affect all
conventional dissolved oxygen probes as well.)
The first is where the fouling is so thick that the response time of the probe becomes
unacceptably long. The second is where organic fouling is consuming oxygen before it
reaches the surface of the probe.
A feature allowing automatic cleaning at preconfigured times is included in the
UDA2182 analyzer. Cleaning may be initiated with a frequency of every few minutes to
monthly.
Cleaning
Functionally, relays within the analyzer are tripped, allowing withdrawal of the probe
from the sample, turning on a cleaning spray, turning off the spray, and reinserting the
probe into the sample. Execution of automatic cleaning and calibration requires you to
install a drive unit, a solenoid valve, and mounting hardware. See
Figure 15-9
Calibration
Similarly, all probes drift with time. Although the Honeywell probe is very stable,
included in the analyzer is a feature that allows withdrawal of the probe into air for
automatic air calibration at user-configured times.
The sequence of calibrations and cleanings are user-configurable.
Low Dissolved Oxygen
One symptom of the need for cleaning is a low dissolved oxygen reading. The UDA2182
dissolved oxygen analyzer can be configured to execute a cleaning cycle if the measured
dissolved oxygen falls below a user-selected value. An alarm can be configured to alert
you if the cleaning fails to restore the dissolved oxygen to a higher level. The alarm will
indicate either a true decrease in dissolved oxygen concentration or unsuccessful
cleaning.