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4.2 SENSOR PREPARATION / ACTIVATION
4.2.1 pH Preparation
Remove the shipping cap from the pH sensor. If the shipping cap does not
contain any liquid, pour HI 70300 into shipping cap, place it back on the
sensor and soak for at least 1/2 hour before use. If HI 70300 is not available,
pH 4.01 buffer may be substituted.
4.2.2 ORP Activation
For improved redox measurements, the surface of the sensor must be clean and
smooth. A pretreatment procedure should be performed to ensure quick re-
sponse.
The pretreatment of the sensor is determined by the pH and the ORP potential
values of the sample. Use the table below to determine the treatment required.
First locate the typical sample pH. If the corresponding ORP value (mV) is higher
than the values in the table below, an oxidizing pretreatment is necessary. If the
value is lower, a reducing pretreatment is necessary.
pH mV
0
990
5
680
1 0 400
For reducing pretreatment: immerse the electrode for at least five minutes in
HI 7091.
For oxidizing pretreatment: immerse the electrode for at least five minutes in
HI 7092.
4.2.3 D.O. Sensor Activation
The D.O. probe is shipped dry. To prepare the sensor for use:
• Remove the black & red plastic cap. This cap is used for shipping purposes
only and can be thrown away.
• Insert the supplied O-ring in to the membrane cap.
• Rinse the membrane with some electrolyte solution. Refill with clean electrolyte.
Gently tap the membrane cap to dislodge air bubbles. To avoid damaging the
membrane, do not touch it with your fingers or directly tap the membrane.
pH
mV
pH
1
920
6
640
11
340
1 2
mV
pH
2
860
3
7
580
8
280
13
21
mV
pH
800
4
520
9
220
14
mV
740
460
160
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