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Aquaprobe
®
AP-5000 Instruction Manual
10401-00906 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 side (see photograph in section 12). 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 side of the electrode by the
four stainless steel contacts. The sleeve forms part of the EC cell. Temperature is also
measured in this electrode.
14.2. DO Measurement Technique
The AP-5000 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's Sleeve removed as the Sleeve
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 300mL 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.
Bang the probe against the bottom of the cup several times to dislodge any air
bubbles. 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. T
he following screen will be
displayed.
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®
Ltd.
www.aquaread.com
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