44
45
pH CALIBRATION
ISE Significant Digits
Accessing this option, the number of ISE significant digits can be
set, with one (X), two (XX) or three (XXX) significant digits.
To set the ISE Significant Digits:
• Press
while in
ISE Measure
mode.
• Press
.
• Use
or
to select the ISE Significant Digits
option.
• Press
and use
or
to highlight the
desired option.
• Press
to confirm your selection or press
to
cancel operation.
Calibrate the instrument often, especially if high accuracy is required.
The instrument should be recalibrated:
• Whenever the pH electrode is replaced.
• At least once a week.
• After testing aggressive chemicals.
• When “
Electrode Cond. Unknown
”, “
Default Calibration
” or “
pH Calibration Expired
” message
appears on the LCD, in the Reminder messages area.
PREPARATION
Pour small quantities of the buffer solutions into clean beakers. If possible, use plastic beakers to minimize
any EMC interferences.
For accurate calibration and to minimize cross-contamination, use two beakers for each buffer solution. One
for rinsing the electrode and one for calibration.
If you are measuring in the acidic range, use pH 7.01 or 6.86 as first buffer and pH 4.01/3.00 or 1.68 as
second buffer. If you are measuring in the alkaline range, use pH 7.01 or 6.86 as first buffer and pH
10.01/9.18 or 12.45 as second buffer.
For extended range measurements (acidic and alkaline), perform a five-point calibration by selecting five of
the available buffers.
CALIBRATION PROCEDURE
There are 8 standard pH buffers that are temperature-compensated during pH calibrations: 1.68, 3.00,
4.01, 6.86, 7.01, 9.18, 10.01 and 12.45. If these are in the buffer group, the buffers are temperature-
compensated during calibration. Custom buffers require the user to use the actual buffer value at the
temperature of use.
A minimum of a two-point calibration is required to determine the pH electrode condition. The buffers should
bracket the sample measurement pH.
An extended pH measurement range will require calibration at multiple points. The meter is capable of
calibration with 5 pH buffers. For improved measurement accuracy, perform a multiple buffer calibration
bracketing and including the pH range the sample measurements.
The buffer group that will be available during calibration was set in pH setup >Calibration Buffer Entry
type. The following example demonstrates pH electrode calibration if Manual selection was selected. In this
case all of the 8 standard buffers will be available for calibration.
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