Aquaprobe
®
AP-700, AP-800 & AP-2000 Instruction Manual
10401-00870 Rev R
The sponge within the storage cap should be moistened with a few drops of pH
Electrode Storage Solution each time it is removed and replaced.
If a pH/ORP
electrode is inadvertently allowed to dry out, it must be re-hydrated by soaking in storage
solution for at least one hour prior to use.
13.4. Calibrating pH
pH electrodes should be calibrated fully at least once a week to ensure optimum accuracy.
Full calibration involves calibrating at pH 7.00 first, then at pH 4.01 and/or pH 10.00. The
Aquaprobe
®
allows for both two and three point pH calibration. Should you decide to carry
out just a two point calibration, the probe will automatically calculate and save a calibration
value for the uncalibrated third point in order to maintain the electrode's linearity over the
full range of 0 – 14.
For best results, calibrate all three points as close to 25
C as possible.
13.5. Special Notes Concerning ISE Electrodes
The high ionic concentration of pH calibration
solutions (buffers), including RapidCal, can
cause significant offsets in ISE electrodes.
These offsets are temporary, but best avoided
because they can cause significant errors
during both calibration and normal operation.
For this reason all ISE electrodes are supplied
with a red rubber sealing cap.
The caps should be fitted to all ISE
Electrode during pH calibration
in order to
protect the ISE electrodes from the effects of
the buffer solution.
At all other times, the ISE electrodes should be left uncovered.
13.5.1.
Calibrating the First Point (pH 7.00)
Due to the way in which pH calibration works,
the Probe must be calibrated at pH7.00
before calibrating at pH 4.01 or pH 10.00
.
Never calibrate at pH 4.01 or pH 10.00
before first calibrating at pH7.00.
To calibrate the pH electrode follow these steps:
1. Fill a calibration bottle with fresh pH 7.00 solution or RapidCal, remove the storage
cap from the pH electrode, wash the Probe in distilled water, then drop the Probe in
all the way.
2. Switch the Aquameter
®
on and wait until the temperature and pH measurements are
completely stable.
3. Ensure the temperature of the solution is between 5ºC and 40ºC (41ºF - 104ºF).
4. Press the
MENU
key then select
Calibration.
The following screen will be displayed.
© 2017 Aquaread
®
Ltd.
www.aquaread.com
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