Instruction Manual
α
lpha-pH2000D
- 14 -
5.2
pH Calibration
If the unit of measure is in pH (default), then the calibration is also carried out in pH. This
transmitter features a one-point or two-point calibration for pH with five preset buffer sets.
Buffer values refer to 25
o
C. A standard pH buffer solution that matches one of these values is
required to calibrate the instrument.
Two point calibration
SETUP
HOLD
PH
CAL
HOLD
PH
P
H
CAL
HOLD
P
H
P
H
CAL
MEAS
P
H
O
C
atc
CAL
CAL
One point calibration
1.
Enter Calibration mode as described in section 5.1. The display shows “CAL PH” (for pH
calibration).
Note: If the display reads “CAL ORP”, see section 6.9 for procedures on how to switch from ORP to
pH readings.
2.
Press the ENT key to start calibration. The “CAL” indicator appears at the top of display and
the buffer indicator appears in the bottom corner of the display. The display shows the actual
pH reading (upper value) and the buffer value for zero point (lower value). For the offset
(zero point) calibration, there are two values to choose from. They are pH 7.00 or pH 6.86.
Using the
▲
and
▼
keys, choose the value that matches with the buffer used.
3.
Place the electrode in the first buffer solution. In ATC mode, you must also immerse the
temperature probe in the buffer solution.
4.
You can conduct either a one-point or a two-point calibration: Press the ENT for two point
calibration or the CAL key for one point calibration. The electrode indicator and CAL indicator
both flash for a few seconds. The controller automatically adjusts the reading to match the
buffer value.
5.
If one-point calibration was selected, the display will show the zero point in the lower section of
the display and the slope (default or using previous two-point calibration) in the upper section of
the display. Proceed to step 7 after zero point display. If two-point calibration was selected, the
lower section of the display will now show its next lower “pH” buffer. Use
▲
and
▼
keys to
select the second buffer from one of these preset value: - pH 1.68, pH 4.01, pH 9.00, pH 9.18
and pH 10.01. Remove the electrode from the first buffer, wash and then immerse it into the
second buffer. Press the ENT key, the electrode indicator and CAL indicator will flash for a few
seconds. The controller adjusts the reading to the second buffer.
6.
After calibrating the second buffer value, the controller will automatically display the slope in the
upper and the zero point in the lower section of the display.
Note: You can also view the values for zero point and slope without calibration (see section 5.5 for
instruction). The zero point and slope are pre-determined after each calibration.
7.
Press the ENT key to return to the Measurement mode.
Note: If you entered the Calibration mode from the Setup mode, the controller will return to the
setup menu.