Aquaprobe
®
AP-700, AP-800 & AP-2000 Instruction Manual
10401-00870 Rev R
2. Moisten a clean cloth or piece of tissue paper with fresh water and wrap it around
the open end of the probe ensuring all the holes are covered. Place the probe on a
flat surface. Do not hold the probe, the heat from your hands will warm the probe up
and interfere with calibration.
3. Switch the Aquameter
®
on and wait until the temperature measurement is
completely stable
.
This is very
important
.
4. Referring back to the screens shown in item 6 above, select
DO100%
5. Wait while the Aquameter
®
carries out the calibration procedure.
6. When calibration is complete, the Calibration Report will be displayed.
The top line will display the voltage output from the DO cell in millivolts (mV). This value
should be over 20.0 (at 25°C). If the value returned is less than 20.0, the DO Cap should be
replaced.
These values are not stored in memory so should be noted down in a calibration record
book for the probe. If a problem occurs during calibration, an error message will be
displayed. Refer to
Calibration Error Messages
in section 10.4 for error message handling.
14.5. Replacing a Galvanic DO Electrode Membrane Cap
The Galvanic DO electrode membrane is a very thin sheet of special plastic, which is
permeable to oxygen. Oxygen molecules pass through this membrane into the Oxygen
sensor. The membrane is extremely delicate and is factory fitted into the DO Membrane
Cap. To ensure optimum performance, the DO Membrane Cap must be replaced every 1-2
months.
Never touch the plastic membrane as the oils in your skin will block the pores in the
membrane and stop it from working correctly.
To replace the DO Membrane Cap, follow these simple steps.
1. Remove the Probe sleeve.
2. Unscrew the DO Cap from the end of the DO
electrode by rotating it anti-clockwise.
3. Gently brush away any scaly grey deposits
from the zinc shaft of the electrode with a soft
toothbrush, taking care not to damage the
electrode in the process.
4. After removing the deposits, rinse the
electrode with DO Electrode Filling Solution.
5. Rinse a new DO Membrane Cap with DO
Electrode Filling Solution then tap it out so that
it is completely empty.
6. Using the DO Electrode Filling Solution dropper bottle, half fill the DO Membrane
Cap. Gently tap the cap to ensure any trapped air bubbles are released.
7. Holding the Probe so that the DO electrode is facing downwards,
slowly
screw the
half-filled DO Membrane Cap back onto the DO electrode then tighten the cap.
Do
not over-tighten
. Finger tight is fine. Some solution will overflow. This is normal.
8. Wash the DO electrode with fresh water then replace the lower Probe sleeve.
9. Wait at least six hours (preferably over-night) to allow any oxygen dissolved in the
filling solution to be consumed.
10. Carry out both Zero point and 100% point DO calibration as described earlier.
© 2017 Aquaread
®
Ltd.
www.aquaread.com
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