Instruction manual

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Current pH
(only appears if pH Control Mode is selected as Direct pH Sensor)
Displays the current pH reading from the electrode.
Status
This menu is for information only, and displays whether the pH output is “Off” or “On” and if on,
for how much time, or if any alarm conditions exist. Possible status messages are Off,
Off/Manual, On/Time counting up (for adds based on pH input signal) and On/Time counting
down/Hand (for manual activation). Possible error messages are Time Out (output has been on too
long), No Flow and Interlock. See section 8.1 for a complete description of error messages.
Reset Timeout
There is also a button called “Reset Timeout” which is used to reset the output if it has been
activated for longer than the time limit imposed in the “Output Time Limit” menu described
below.
Custom Name
This menu allows you to call the output another name if desired. Type the new name in the text
box.
Set Point
Type in the text box the pH value at which the pump will turn on in order to correct it. Any value
between –2 and 16 is acceptable (if based on direct pH sensor). If the control mode is based on a 4-
20 mA input, then the set point value is limited to the range of the 4-20 mA input. Click on the
link called Scaling to set the range of the 4-20 mA input.
.
Dead Band
Type in the text box the pH value away from the set point at which the pump will stop running.
For example, if you are forcing the pH lower, your set point is 7.50, and your dead band is 0.05,
then the acid pump will start at 7.51 and stop at 7.45. The purpose of the dead band is to prevent
rapid cycling of the relay open and closed, which can shorten its life. The dead band should be set
for the lowest value that still prevents the relay from chattering.
Control Direction
Click on the radio button that describes which direction you want to move the pH. If you plan on
adding an acid to lower the pH, select “Force Lower”. If you plan on adding caustic to raise the
pH, select “Force Higher”.
Interlock Outputs
Click the check boxes to select or de-select the relays that you want to be forced OFF if this output
relay is turned ON. If you do not need any other output to shut off when this relay turns on,
UNCHECK all boxes. The selection is mutually exclusive, meaning that if the Feed output has the
pH output interlocked, the feed won’t turn on if the pH output is on, and the pH output won’t turn
on if the Feed output is already on. This feature should be used with caution since it can
potentially delay a chemical addition for a long time. Typical uses are to prevent inhibitor feed
during a biocide addition, or to prevent bleed and pH control during inhibitor feed.