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Aquaprobe
®
AP-7000 Instruction Manual
10401-00894 Rev M
14. DO/EC Electrode Calibration and Maintenance
14.1. Recognising the DO/EC Electrode
The DO/EC electrode is easy to recognise because it has a screw-on cap and four
stainless-steel EC sensor contacts on the inside facing the wiper. Dissolved Oxygen (DO)
is measured at the end of the electrode by the components behind the removable cap.
Electrical Conductivity (EC) is measured on the inside edge of the electrode by the four
stainless steel contacts. The flat on the wiper forms part of the EC cell.
14.2. DO Measurement Technique
The AP-7000 features an optical DO sensor. This sensor does not use a liquid electrolyte
and has a black rubber gas-permeable membrane. See
Aquaread’s Optical DO Measurement System
14.3. Precautions During Use
EC measurement is not possible with the Probe central wiper removed as the central
wiper forms an integral part of the measurement system
.
Never immerse the Probe without the DO Cap fitted. If the components at the end of
the DO/EC electrode come into contact with the liquid being tested, serious damage
can occur to the DO/EC electrode circuitry.
14.4. Calibrating the DO/EC Electrode
Calibration of the EC section of the electrode is normally carried out during RapidCal (see
). EC can be calibrated separately using different EC
Calibration Standards, this is covered after the DO calibration section (
The DO section of the electrode should be calibrated at the Zero saturation point at least
once a month. Before each day’s use, the 100% saturation point should be checked in
moist air and re-calibrated if necessary. For optimum
accuracy, calibrate the DO100% point
as near to your sample temperature as possible (within the calibration temperature limits of
5
C - 40
C).
If you are going to calibrate both the Zero and 100% points at the same time,
ALWAYS
calibrate the Zero point first
, then the 100% point.
14.5. Calibrating the DO Zero Point
1.
Pour 400mL of DO Zero calibration solution into a calibration up, remove the
storage cap from the pH electrode if fitted, wash the Probe in distilled water, then
gently lower the Probe in all the way.
2.
Activate the probe cleaning feature in order to remove any air bubbles that may be
clinging to the electrodes. Wait until the temperature and DO measurements are
completely stable.
3.
Ensure the temperature of the solution is between 5
C and 40
C (41
F - 104
F).
4.
Press the
MENU
key then select
Calibration.
The following screen will be
displayed.
© 2017 Aquaread
®
Ltd.
www.aquaread.com
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