A hollow glass tube vibrates at a certain frequency. This frequency changes when the tube is filled with the sample: the higher the mass of the sample, the lower the frequency. This frequency is measured and converted into density. Calibration is carried out with air and distilled water. A built-in Peltier thermostat controls the temperature very precisely, without using a water bath.

Advantages:	Disadvantages:	Main applications:
built-in thermostat	relatively expensive	high accuracy measurements
quick measurement (Approx 1 min.)		GLP measurements, where protocols are required
very high accuracy		perfumes, fragrances: where small sample volume required
small sample volumes (1,2 ml)		soft drinks, cola drinks: BRIX measurements
GLP: operator independent		alcoholic beverages: Alcohol measurement
special instruments with direct readings in Alcohol%, Sugar% (BRIX) or other density related values available		petroleum: API measurements