where c is an elastic constant, M is the mass of the body, V is the filled volume, and ρis the density of the sample liquid. Therefore the period, T, can be calculated as
where A and B are temperature dependent coefficients to be calibrated using reference liquids. At the same temperature, the density difference between two fluids is
The densimeter manufacturer claims that the fractional uncertainty for the density of the water at room temperature is 6510−⋅, provided that the temperature instability is less than 0.01 K. This uncertainty includes 6210−⋅due to the temperature instability and 6310−⋅ due to deviation of the oscillator.