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SENSOR PREPARATION / ACTIVATION
pH Preparation
Remove the shipping cap from the pH sensor. If the shipping cap does not contain any liquid, pour
HI70300 into shipping cap, place it back on the sensor and soak for at least 1/2 hour before use. If
HI70300 is not available, pH 4.01 buffer may be substituted.
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 response.
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 pH mV pH mV pH mV pH mV
0 990 1 920 2 860 3 800 4 740
5 680 6 640 7 580 8 520 9 460
10 400 11 340 12 280 13 220 14 160
For reducing pretreatment: immerse the electrode for at least five minutes in HI7091.
For oxidizing pretreatment: immerse the electrode for at least five minutes in HI7092.
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.
• With the sensor facing down screw the membrane cap counterclockwise to the end of the threads.
Some electrolyte will overflow.
• Rinse outside of sensor with deionized water.
• Invert sensor and inspect. There should be no bubbles or debris between the membrane and
sensor body.
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