It may not be necessary to perform a calibration when using and of the Vernier ethanol sensors in the classroom.
If your experiment or application is evaluating the rate of ethanol production, such as determining fermentation rates with yeast, or the relative change in ethanol concentration, the stored calibration should work well.
For quantitative analysis of ethanol samples, it is best to use a two-point calibration to improve accuracy. The two points you choose for your calibration will depend on the expected amount of ethanol in your sample.
For best results at low concentrations (0.1–1%), calibrate using 1% and 0.1% ethanol.
For best results at high concentrations (1.0–3.0%), calibrate using 3.0% and 1% ethanol.
If you are measuring an intermediate range you can also calibrate using 0.2% and 2.0% ethanol.