The densimeter core is an undamped oscillating-hollow tube with constant inner volume (0.6 mL). The tube filled with different fluids changes its natural oscillation frequency, and the square of the oscillation period with the fluid density presents a linear behaviour. A calibration curve is obtained measuring the period for two or more fluids of accurately known densities, and the unknown fluid density is then obtained easily. The frequency measurement is obtained with a frequency counter. High temperature control ( ±0.001°C) allows anyone to determine the density with a precision of ±1*10-6 g/cm3.

Measurement principle

The measurement principle of the flow digital densimeter is based on the properties of a mechanical oscillator. The natural vibration frequency of a reed, consisting in a tube firmly anchored at one end, is related to its mass per unit length and to a restoring force constant. The resonant frequency of this tube oscillator is thus a function of the density of any fluid it contains. Measurement of the resonance period (Ï„) yields the density (d) of the fluid according to the relationship:

Where A and K are constants of the system, which may be determined by straightforward calibration using fluids of known density, typically nitrogen gas and water.

The density apparatus allows density measurements with part per million precision to be carried out in a few minutes, using as little as 1 cm3 of liquid.


Parts list