Automatic Ph Buffer Recognition Feature; Testing A Ph Electrode For Automatic Buffer Recognition - Thermo Scientific Orion Dual Star User Manual

Section 10 Advanced Meter Features
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90 Orion Dual Star pH/ISE Benchtop Meter User Manual
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Automatic pH Buffer Recognition Feature

The Orion Dual Star meter is capable of automatically recognizing pH 1.68, 4.01, 7.00, 10.01
and 12.46 buffers or pH 1.68, 4.01, 6.86, and 9.18 buffers during a pH calibration, depending
on the pH buffer set that is selected in the setup menu. During a calibration, the meter uses the
selected buffer set and the raw mV reading of the pH electrode in the buffer to recognize and
display the buffer value at the measured temperature. The raw mV reading of the pH electrode
in the buffer must be about ± 30 mV from the theoretical mV reading of the buffer in order for
the meter to automatically recognize the buffer.
USA pH Buffer Set
Buffer mV Range
1.68 +285 to +345 mV
4.01 +207 to +147 mV
7.00 - 30 to + 30 mV
10.01 -207 to -147 mV
12.46 -293 to -353 mV

Testing a pH Electrode for Automatic Buffer Recognition

To verify that the raw mV reading of the pH electrode in use is ± 30 mV from the theoretical mV
reading of the buffer, and therefore verify that the pH electrode in use is capable of performing
automatic buffer recognition, perform the following procedure.
1. Set the measurement mode to mV in the setup menu. Prepare the pH electrode according
to the instructions in the pH electrode user guide. Ensure that the pH electrode is connected
to the meter input that corresponds with the channel that will be measured.
2. Rinse the pH electrode with distilled water, blot it dry with a lint-free tissue and place the pH
electrode into a pH 4.01 buffer at 25 °C.
3. Wait for the measurement to stabilize and record the mV value of the pH 4.01 buffer when
the measurement is stable. The read type selected in the EZ Startup menu or setup menu
will determine how the mV measurements are displayed by the meter.
4. Remove the pH electrode from the pH 4.01 buffer, rinse the pH electrode with distilled
water, blot it dry with a lint-free tissue and place it into a pH 7.00 buffer at 25 °C.
5. Wait for the measurement to stabilize and record the mV value of the pH 7.00 buffer when
the measurement is stable.
6. The mV reading of the pH electrode in pH 4.01 buffer should be +207 to +147 mV and the
mV reading of the pH electrode in pH 7.00 buffer should be -30 to +30 mV. If the mV
readings are in the correct ranges, the pH electrode is capable of performing automatic
buffer recognition. If the mV readings of the pH electrode are not in the correct ranges, the
values of the pH buffers will need to be manually entered during a pH calibration.
EURO pH Buffer Set
Buffer mV Range
1.68 +285 to +345 mV
4.01 +207 to +147 mV
6.86 +38 to -22 mV
9.18 -99 to -159 mV
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