The class is given according to the maximum permissible tolerance or error; but it is very important to emphasize that the class only applies to volumetric material, as is the case of pipettes.
The volumetric material allows us to know the precise measurement of a volume and precisely how real we need that value to be, is what will give us the guideline when choosing the required class. For this it is also essential that you consult the pipette sales section of your trusted manufacturer.
The best known are Class A and B, however there is one more that is good to know: school grade or Tekk
Class A offers the best choice in accuracy because they have narrower or more demanding tolerances, unlike Class B where their tolerances are twice as large as Class A and therefore provide less accurate work. Do you know the kind of pipette sales from your supplier?
On the other hand, the volumetric materials class or grade Tekk do not show tolerances, that is to say that they are not determined, so the resulting volume is inaccurate and we do not know how much.
The class must be printed on the material for easy identification and thus make a good sale of pipettes. Just as in the material with which it is made, the class also has interference with the price, the lower the class is the lower the price; but beware, that if we send to calibrate a flask grade school is very likely that it will not happen. That’s why we have to decide how accurate we need to be when choosing the material.
So how do you see it? It’s simple, isn’t it? But hopefully things will end here, because there is one more factor to consider and that is: the norm under which the volumetric materials were manufactured. Don’t be fooled when they you pipettes sales.
On the one hand, there is the DIN standard (German Institute for Standardization) and on the other hand the ASTM (American Association for Testing and Materials) and the difference between the two lies mainly in two factors:
Maximum permissible tolerances or errors, in some cases, are slightly narrower or stricter in ASTM than in DIN. The materials manufactured under DIN standard are calibrated by batch, while in ASTM they are per part, however nowadays any manufacturer, no matter under which standard it is governed has available calibrations by batch or part as required by the customer.