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14
MODEL 54e pH/ORP SECTION 4.0
CALIBRATION
SECTION 4.0
CALIBRATION
The following procedures are described in this section:
• Temperature Calibration (Section 4.1)
• Auto Buffer (Two-Point) Calibration (Section 4.2)
• Manual Two-Point Calibration (Section 4.3)
• Single-Point pH Calibration (Section 4.4)
• Temperature Compensation Options (Section 4.5)
• pH Slope Adjustment (Section 4.6)
• Hold Mode (Section 4.7)
INTRODUCTION
Calibration is the process of adjusting or standardizing
the controller to a lab test (such as free acid titration) or
a calibrated laboratory instrument, or standardizing to
some known reference (such as a commercial pH
buffer). Calibration ensures that the controller shows
an accurate, and therefore, repeatable reading of pH or
temperature.
Since pH measurements are affected by temperature,
the Model 54e pH/ORP reads the temperature at the
sensor and compensates for the changing temperature
by referencing all pH measurements to 25°C (77 °F).
This compensates for temperature-related changes in
the response of the glass pH electrode which would
affect the pH measurement. The pH temperature com-
pensation does not account for changes in chemical
activity which affect the actual pH value of the solution
being measured. See Section 7.0 for information on
solution temperature compensation.
To ensure the controller's accuracy, it is important to
perform all the calibration procedures provided in this
section if you are:
• installing this unit for the first time
• changing or replacing electrodes or sensor ele-
ments
• troubleshooting
IMPORTANT
Before attempting to calibrate, inspect the
pH sensor assembly. It must be clean,
undamaged and free from cracks or other
signs of leakage or wear.
WARNINGS
Before performing any of these procedures, be sure to disable or disconnect the chemical feed pumps or
other external devices (see placing controller in hold, Section 4.7)
Perform the calibration procedures in this section only in the order they are given.
Do not attempt to calibrate the controller if the fault LED is lit or the display is showing fault messages.