Page 12
5. pH Calibration
5.1 Calibration Procedure
1.
Press the
key if the meter is not already switched on.
2.
Press the
key until the meter is in pH mode. (See section 2.2)
3.
Plug the pH electrode into the
pH
socket. For automatic temperature
compensation, plug the Conductivity sensor into the
Cond
socket. If the
Conductivity sensor is not connected, then the
MC-81
will use manual
temperature compensation.
4.
Ensure that temperature has already been calibrated, or manually set (see
sections 6.1 and 6.4). NOTE: If the decimal point in the temperature reading
is replaced by a
∗
, then the temperature readout is not calibrated.
5.
Remove the wetting cap from the pH electrode.
6.
Rinse the pH and Conductivity electrodes in distilled water and blot them dry.
7.
Ensure that you are using the buffers which have been selected for automatic
buffer recognition. See section 8 for a detailed explanation.
Place both electrodes 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
electrodes directly into the buffer bottle. Discard the used buffer after use.
8.
When the reading has stabilised, press and hold the
key for 2 seconds to
calibrate. If a 1 point calibration has been performed, the
∗
will not be
removed until a full 2 point calibration has been performed.
9.
Rinse the pH and Conductivity electrodes in distilled water and blot them dry.
10.
Place both electrodes 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 electrodes directly into the buffer bottle. Discard the used buffer
after use.
NOTE: pH9.23 and pH10.00 buffers are highly unstable. Avoid using
these buffers if possible. Discard immediately after use
.
When the reading has stabilised, press and hold the
key for 2 seconds to
calibrate. The
∗
will now be replaced by a decimal point, if calibration was
successful.
11.
The
MC-81
is calibrated for pH and is ready for use.