In order to calibrate a Conductivity Probe, or to confirm that a saved calibration is accurate, you should have a supply of standard solutions that cover the range of values you will be measuring. There are multiple ways to obtain these solutions:

We sell three different concentrations of Conductivity Standard. Each standard contains 500 mL.
Low Range Setting 150 uS/cm Conductivity Standard Solution (Low) (CON-LST)
Medium Range Setting 1413 uS/cm Conductivity Standard Solution (Middle) (CON-MST)
High Range Setting 12880 uS/cm Conductivity Standard Solution (High) (CON-HST)

You can prepare your own solutions with the following recipes:
200 uS/cm = 0.0905 grams of NaCl per Liter of distilled water
2000 uS/cm = 1.05 g NaCl/L
20,000 uS/cm = 11.53 g NaCl/L