IM 12D03D02-01E
5-4
5
.
Maintenance
5.4 Calibration with Standard Solution
Note:
Calibration with standard solution means to measure a standard solution of accurately-
known conductivity and to adjust SC72 meter so that the displayed measured value is
the same as the known conductivity value of the standard solution.
If the sensor has been used for a long time, and does not look clean despite washing,
recalibrate the SC72 meter with standard solution to check if cell constant is normal.
If “
” occurs during calibration with standard solution, replace the sensor.
Note that if calibration with the standard solution shows that the cell constant has
changed, update the cell constant value on the sensor cable with the new data.
Notes for calibration with standard solution:
Types of standard solution
Use NaCl (sodium chloride) or KCl (potassium chloride) solutions.
(1) NaCl (sodium chloride) solution
When NaCl solution is used, the temperature coefficient of NaCl is built into the
temperature compensation functions of the meter so conductivity converted
to 25°C can be readily obtained regardless of liquid temperature. Standard
NaCl solution of 0.1 mol/l (normal unit expressing concentration of solution) is
available as an option from Yokogawa. For more details, see Section 1.7.
When the sensor for high purity water measurement is used, dilute the standard
solution with pure water to obtain 0.001 ml/l solution of conductivity 1 µS/cm.
Conductivity is as follows:
0.1 mol - NaCl solution:
conductivity 10.67 mS/cm at 25°C
0.001 mol/l - NaCl:
conductivity 123.9 µS/cm at 25°C
(2) KCl solution
Table 5.2 describes how to make KCl solution of different concentrations, and
lists their conductivities.
Table 5.2 How to make KCl solutions, and their conductivities (based on JIS
K 0102)
KCl
solution
How to make
KCl standard solution, µS/cm
0°C
18°C
25°C
A
Dissolve 74.2460g of KCl in water to get
1l at 20±1°C.
65176
97838
111342
B
Dissolve 7.4365g of KCl in water to get
1l at 20±1°C.
7138
11167
12856
C
Dissolve 0.7440g of KCl in water to get
1l at 20±1°C.
773.8
1220.5
1408.8
D
Dissolve 100ml of standard solution C
avobe in water to get 1l at 20±1°C
146.93
