Page 17
5. pH Calibration
5.1 Calibration Procedure
1. Plug the pH sensor into the
pH/mV
socket. The Dissolved Oxygen
sensor (or a Temperature sensor) should be plugged into the
Dissolved Oxygen
socket.
2. Switch the meter on.
3. Select pH Mode. (
→
F3:Mode
→
F4:pH
).
4. Ensure that temperature has already been calibrated (see section 7).
NOTE:
If the decimal point in the temperature reading is shown by a
∗
, then the temperature readout is not calibrated.
5. Remove the wetting cap from the pH sensor.
6. Rinse the pH and Dissolved Oxygen/Temperature sensors in distilled
water and blot them dry.
7. Ensure that you are using the primary buffer for which the
WP-91
has been set (see section 17).
Place both sensors into a small sample of pH6.88 (or pH7.00) buffer,
so that the bulb and reference junction are both covered, as per the
diagram over the page.
DO NOT
place the sensors directly into the buffer bottle.
To reduce the amount of pH buffer that is consumed, the Dissolved
Oxygen sensor may be placed into a separate beaker of water that is
at the same temperature as the buffer
.