Hach Lange sensION+ EC71 Manual page 12

4. Operation
4.5. Calibration
This process involves adjusting the values read by a conductivity
measuring system (instrument and cell) according to the values
of standard solutions.
Calibration is very important for highly accurate readings.
The equipment is capable of one-, two- and three-point calibration
using147µS/cm, 1413 µS/cm, 12.88 mS/cm and 111.8 mS/ cm
standards.
The calibration parameters are stored in the memory until a new
calibration is performed.
Normally the calibration is performed with molar standards.
Nevertheless, the instrument offers other options for calibration.
One-point calibration
This form of calibration is acceptable when measuring conduc-
tivity values around that of the standard used.
This is the most common type of calibration. In this type,
1413 µS/cm is the most commonly-used standard.
Two-point calibration
This type of calibration is recommended for work in high or low
conductivity regions where accuracy is required.
If you are calibrating with more than one standard, we recom-
mend that you start with the one with the lowest conductivity to
avoid contamination problems.
Three-point calibration
This type of calibration is recommended when the conductivity
of the samples to be measured ranges from low to high.
If you are calibrating with more than one standard, we recom-
mend that you start with the one with the lowest conductivity to
avoid contamination problems.
Calibration with molar standards
Standards 147uS/cm, 1413 uS/cm and 12.88 mS/cm (25˚C) are
supplied with the instrument.
Preparation
Fill the flasks with the corresponding standard solutions (50 ml)
The times of re-use of these liquids depends on the cell cleaning.
Hach recommend to use the same portion of standard 2 or 3
times.
Every calibration flask is supplied with a magnetic bar.
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sensION+ EC71 HACH LANGE 7010.indd ANG:8 sensION+ EC71 HACH LANGE 7010.indd ANG:8
Diagram for calibration
10-04-2010 17:15
EC CALIBRATION
Calibrate EC
Molar standards
...
Start calibration
EC CALIBRATION
Molar standards
Use standard 147 uS
Continue...
EC CALIBRATION
147 uS/cm
1st standard OK
147 uS/cm
EC CALIBRATION
Molar standards
Use standard 1413 uS
Continue...
EC CALIBRATION
1413 uS/cm
2nd standard OK
1413 uS/cm
EC CALIBRATION
Molar standards
Use standard 12.88 mS
Continue...
To modify the
standard calibra-
tion see page 9.
Modify stirring
with
22.6˚C
@25˚C
The instrument
controls automati-
00:23
cally the start/stop
of the stirrer.
22.6˚C
@25˚C
00:25
22.6˚C
@25˚C
00:40
22.6˚C
@25˚C
00:55
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