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4.5 TEMPERATURE COMPENSATION OPTIONS
4.6 pH SLOPE ADJUSTMENT
MODEL 54e pH/ORP SECTION 4.0
CALIBRATION
Automatic Temperature Compensation is a standard option for pH equip-
ment and is used in virtually all pH measurement situations. If compen-
sation is not desired, the temperature signal from the sensor can be
ignored by placing the controller in the manual temperature compensa-
tion mode.
Manual mode allows the input of a fixed value that will be used instead of
the sensor value. The manual temperature value need only be entered if
the temperature compensation setting is manual. In this case, a value
may be entered between -15 and 120°C (5 and 248°F).
To change these settings, obtain the top screen by pressing Enter (F4)
when Calibrate is highlighted in the main menu and then press the arrow
key. Press Enter (F4) again to obtain the lower screen. Highlight the
desired item and press Edit (F4) and change the value as needed.
Options are Auto or Manual temperature compensation and the temper-
ature values listed above. Press Save (F4) to save the change. Esc (F3)
will cancel the change.
NOTE
When the temperature compensation setting is manual, all tem-
perature specific faults are disabled.
The slope of the glass electrode is normally calculated during buffer cali-
bration. It can, however, be entered directly (if known) using this proce-
dure. A new electrode has a slope of about 59 mV/pH but as it ages the
slope will decrease. A slope value below 47 mV/pH unit is a sign of an
aged electrode and is not considered adequate for calibration. The pH
slope can also be viewed on the diagnostic variables screen.
Use the procedure in Section 4.5 to obtain the screen to the left with "pH
slope" highlighted. Press Enter (F4) to display the slope value now being
used. Press Edit (F4) for editing and then change the value as needed.
Save the new value with Save (F4).
Acceptable slope values are between 45.0 and 60.0 mV/pH.
NOTE
Before exiting the calibration mode, if the Hold Mode is ON, be
certain to change the setting to OFF to resume normal operation.
Adjust temperature
Temp compensation
pH slope
Exit Enter
Temp comp: Auto
Manual temp:
025.0°C
Exit Enter
pH slope: 59.16 mV/pH
Exit Enter
Temp compensation
pH slope
Output trim
Exit Enter