Drop Counter reservoirs and tips are calibrated differently than other Vernier sensors. The volume of the drop is actually a function of the reservoir, the tip, the height of the liquid in the column, and the properties of the liquid (such as viscosity or density). This value is used by the software during a lab session to report the volume along with the sensor data being collected.
Drop Counter calibrations cannot be stored on the Drop Counter in the same way as other Vernier sensors. When a new experiment is started, the drops/mL value may need to be determined or entered into the software. Otherwise, the default value of 28 drops/mL will be used. If the calibration value for the reservoir and tip are known for a particular liquid, you can manually enter this value in the calibration window.
For low viscosity liquids, such as aqueous solutions of low concentration, where the density can be assumed to be close to that of water, once a reservoir and tip are calibrated, the value of drops/mL can be written on the side of the reservoir and tip combination. For future experiments using this type of titrant, when the calibration window is opened, the known number of drops/mL can be manually entered for that experiment.
For higher titrant concentrations or for better accuracy overall, the Drop Counter should be calibrated whenever a new titrant is being used.