72-900-06 Rev. F
Page 22 of 38
Step 2 – Draw a sample of the process flow water and measure the conductivity
using a calibrated meter. Be certain the meter being used to measure
conductivity is temperature compensated.
Do not allow the sample to sit for any length of time after being drawn as this may
cause the reading of the sample to be different from the probe.
Step 3 – Enter the calibrated conductivity value into the Probe Calibration screen.
If the conductivity reading varies more than 25 counts from the reading of the
calibration meter verify the sample temperature is within 1 C of the probe
temperature.
Step 4 – Return to the Home Screen and verify the proper conductivity reading is
displayed.
4.7.2 pH and ORP
From these menus configure the parameters that trigger the pH and ORP control output.
Additionally, the probe calibration, alarm set points, and the limit timer functions are also
configured in this section.
Set point Type - A Set point is a setting at which the controller activates an output,
such as a solenoid valve or a metering pump on the relay outputs or dry contact
outputs. The type – Rising or Falling defines which side of the set-point the relay
activates. A Rising type means that the output activates when the input goes above
the set point. A Rising set point is commonly used in pH control where it is desirable
to keep pH below a certain value. A Falling type activates the output when the
value goes below the set point. A common example of this is ORP control, where
maintaining a certain minimum level of an oxidizer in the system is required.
Set point –This is the point where a control relay will activate. Once the ph or ORP
has reached this value the control relay output will turn on.
Differential – The differential setting controls when the control relay deactivates.
This value subtracted from the set point causes the relay to stop.
Example: Set point=7.00, Differential=1.00, the pH begins when the pH reaches 7.0
and ends when the pH reaches 6.0.
Limit Timer – Set this value to the maximum amount of time the output can stay
energized before a pH or ORP Limit Alarm is reported. If the next control cycle
completes without an alarm the limit alarm will clear itself on the next cycle. Setting
this value to 00:00 turns off this function.
Limit Alarm- Use this option to turn the control relay off on a limit alarm or to keep
it on in automatic mode during a limit alarm. (default is “Turn relay off” for the pH
and ORP relay)
Probe Calibration – Use this function to calibrate the probe.
Alarm Setp’t – Use this menu to specify the upper and lower values for alarm
reporting.
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