Electro-Chemical Devices (ECD) L20 C - Manual (Page 7)

Operational Procedures
A. Preparing Standard Solutions
Suitable conductivity standards are available commercially or the
user can prepare them using research grade reagents. Here are
some standard solutions the user can prepare to calibrate the probe
of the Model L20C.
1. Standard solution of 1413uS at 25℃: Accurately weight
out 0.746 grams of research grade dried Potassium
Chloride (KCL). Dissolve in 1000ml of distilled water.
2. Standard solution of 12.90mS at 25℃: Accurately weight
out 7.4365 grams of research grade dried Potassium
Chloride (KCL). Dissolve in 1000ml of distilled water.
3. Standard solution of 111.9mS at 25℃: Accurately weight
out 74.264 grams of research grade dried Potassium
Chloride (KCL). Dissolve in 1000ml of distilled water.
Note: You can store the remaining solution in a plastic container for
one week but the air space between the cap and the solution must
be kept to an absolute minimum. Storing the excess solution below
4℃ can increase the storage life. If you have any doubt of the
accuracy of the stored solution, a fresh batch should be prepared.
B. Calibration
Calibration setup contains six sections: TDS Constant, Temperature
Coefficient, Temperature Reference, Probe Basic Cell Constant, Cell
Constant Calibration and K Value Input. To access these sections:
1. Connect the conductivity probe to the unit and turn the
unit on.
2. Allow temperature reading to stabilize, press “Cal” key
to enter the calibration mode. CAL appears on the LCD.
[Note: Press “Enter” key to accept any values changes in each
section and automatically advance to the next section. If there are
no changes, the unit accepts the current value and proceeds to the
next section.]
TDS Constant
TDS is determined by multiplying conductivity (mS) by a TDS factor.
The default factor value is 0.65. To change the TDS factor, use the
“up” and “down” keys to adjust the value between 0.30 and 1.00.
7