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January 2009 UDA2182 Universal Dual Analyzer Product Manual 235
rinse/cleaning
solution
process
sample
pH
electrode
to process
to drain
9782
S4
S1
Items outside this area
provided by user
Figure 15-11 Automatic Electrode Wash Setup
Select valves and fittings with appropriate pressure ratings
Make the process connections as shown in Figure 15-11. Be sure that valves and fittings
(S1) have sufficient pressure ratings to withstand pressure peaks which will occur when
process flow is blocked.
Minimize liquid volume in system
Keep pipe sizes small and couplings close to minimize the liquid volume in the system.
Smaller volumes require less time to rinse.
15.17.1 AutoCal Sequence and Piping
Introduction
AutoCal can include one-point calibration (standardization) to adjust zero to compensate
for electrode drift, or two-point calibration (standardization and slope adjustment) to also
adjust span to match the gain of the Analyzer/Controller to the electrode response.
Standardization and slope each depend on the electrode measuring a reference solution
(buffer) of known pH.
Rinse and one-point calibration sequence
The AutoCal operation automatically occurs at the configured intervals. It always
includes AutoClean rinsing of the pH electrode, in addition to any other AutoClean
sequences that are configured to occur between standardization operations. The sequence
is described below.
1 All alarm action is held at existing levels. The output(s) can be held or be active, depending on
configuration. Even if the outputs are not held, “HOLD ACTIVE” is displayed on the alarm stripe
because alarms are always held.
Also, “AUTOSEQUENCE” is displayed. Pressing the DISPLAY key will call up a special display
that shows how much time is left in the operation
2 In preparation for the calibration, Relay 1 activates 3-way solenoid valve S1 (see Figure 15-12) to
direct rinsing fluid to the electrodes for the configured rinse duration (1 to 1999 seconds). If the
measured sample is normally returned to the process but quantities of rinsing fluid cannot be
tolerated there, use an additional 3-way solenoid valve S4. It is activated simultaneously with S1 to