Page 18
5. pH Calibration
5.1 Calibration Procedure
1.
Plug the pH sensor into the
Sensor
socket.
2.
Switch the meter on.
3.
Ensure that you are using buffers which have been selected for automatic
buffer recognition. See section 16 for a detailed explanation.
4.
Select pH Mode (
→
→
F3:Mode
→
→
F2:pH
).
5.
Ensure that temperature has already been calibrated, or manually set (see
sections 8.1 and 8.4). NOTE: If the decimal point in the temperature reading
is shown by a
∗
, then the temperature readout is not calibrated.
6.
Remove the wetting cap from the pH sensor.
7.
Rinse the pH and Temperature sensors in distilled water and blot them dry.
8.
Ensure that you are using the primary buffer for which the
WP-90
has been
set (see section 16).
Place both sensors into a small sample of pH6.88 (or pH7.00) buffer, so that
the bulb and reference junction are both covered.
DO NOT
place the sensors directly into the buffer bottle.
9.
Select pH Calibration (
→
→
F1:Cal.
→
→
F1:pH
).
10.
When the reading has stabilised, press the
key to calibrate. If a 1 point
calibration has been performed, the
∗
will not be removed until a full 2 point
calibration has been performed.
11.
Rinse the pH and Temperature sensors in distilled water and blot them dry.
12.
Place both sensors into a small sample of pH4.00, pH9.23 or pH10.00
Buffer, so that the bulb and reference junction are both covered.
DO NOT
place the sensors directly into the buffer bottle.
NOTE: pH9.23 buffer is highly unstable. Avoid using this buffer if
possible. Discard immediately after use
.
13.
Select pH Calibration (
→
→
F1:Cal.
→
→
F1:pH
).
14.
When the reading has stabilised, press the
key to calibrate. The
∗
will
now be replaced by a decimal point, if calibration was successful.
15.
The
WP-90
is now calibrated for pH and is ready for use. Discard the used
samples of buffer.