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LeveLine
®
Instruction Manual
10401-01026 Rev D
4.10. Calibrating the Electrical Conductivity Cell on - CTD Probe Models
4.10.1. EC Calibration Standards
EC calibration is always carried out at a single point. There is a choice of two Aquaread
®
calibration standards, or you can use any third party calibration standard value between
100µS/cm and 99,999µS/cm.
The Aquaread
®
standards are: Aquaread
®
RapidCal
™
(EC value 2570µS/cm at 25°C) for
general use, and Aquaread
®
SC-35 (EC value 53,065µS/cm at 25°C), which is specifically
for use when measuring EC and salinity in sea water.
The calibration solution value you use to calibrate EC should always be chosen to be as
near to the readings you expect to see in the field as possible.
If you are not sure what values to expect, RapidCal
™
is a good choice as this will give
reasonably accurate readings across a wide range of EC values.
For best results, calibrate as close to 25ºC as possible. The Probe will compensate for
temperature variation in the Calibration Standard during calibration.
4.10.2. Recognising the EC Cell
The -CTD Probes all have an elongated nose sleeve covering the EC cell contacts.
The black plastic nose sleeve (shown removed on the right of the photo) forms an
integral, working part of the Probe’s EC measurement system, and MUST be fitted
during calibration and measurement for correct operation.
4.10.3. EC Calibration Technique
1. Remove the nose sleeve from the Probe, wash the EC cell and the sleeve in
clean water, dry thoroughly, then replace the nose sleeve.
2. Drop the Probe into a calibration bottle filled with EC Calibration Standard and
agitate to remove any air bubbles from inside the sleeve.
3.
Ensure the liquid level is above the top row of holes in the nose sleeve.
Low liquid level will result in erroneous EC calibration
.
4. Watch the temperature and EC readings on the Meter and wait until they are
completely stable.
5. Ensure the temperature of the solution is between 5ºC and 40ºC (41ºF
-104ºF).
6. On the Meter, press 'Menu' key then select 'Probe & Meter Setup' followed by
'Calibrate EC'. The following screen will be displayed:
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®
Ltd.
www.aquaread.com
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