Thermo Fisher Scientific Alpha pH 190 (In the process of updating the brand guideline & product image) - Manual (Page 17)

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6 PH CALIBRATION
IMPORTANT: When Calibration mode is entered, controller
automatically goes into a “HOLD” mode where the 4-20 mA output
freezes and relays are de-activated (if it was in an activated
condition). Upon return to measurement mode, both 4-20mA output
and relay activities resume, depending on settings.
The Alpha pH 190 controller features seven preset buffer values
(pH 1.68, 4.01, 6.86, 7.00, 9.18, 10.01, 12.45) for quick auto-
calibration at one or two points. The first calibration point must
be pH 6.86 or 7.00. When you calibrate this instrument, you need
to use FRESH standard pH buffer solution that matches these
values.
NOTE: If you are in ORP mode, see Program 3.0 for instructions on
switching to pH mode.
1. Press CAL / ENTER key to directly access the Calibration mode
when the unit is in pH measurement mode.
NOTE: Instead of pressing the CAL/ENTER key, you can also enter
the Calibration mode using the password code procedure as
explained in Section 5.
2. The display scrolls BUFF and either pH 7.00 or 6.86. You must
calibrate at one of these two buffers for the first calibration. Use ▲ /
▼ keys to select pH 7.00 or 6.86.
3. Make sure the electrode is in the buffer solution. In ATC mode,
you must also immerse the temperature sensor in the buffer
solution. In the symmetrically high-resistance measurement mode,
you must also immerse the solution ground (potential equalization
pin) in the buffer.
4. Allow the electrode time to stabilize.
5. Press ENTER. The instrument will blink with the un-calibrated
pH value corresponding to the mV output of your pH probe. If the
value displayed differs substantially from the buffer value, this
indicates electrode drift. Consider replacing your electrode.
6. Press ENTER to confirm the buffer value. The display blinks the
calibrated value twice, shows “DONE” and moves to the next buffer.