Method and device for measuring fat in milk

A measuring arrangement for determining a fat content of milk in a pipeline, comprising:

• a densimeter having at least one oscillatable measuring tube and configured to determine a first eigenfrequency of a first bending oscillation mode and a second eigenfrequency of a second bending oscillation mode;
• a pressure sensor for measuring a static pressure in the pipeline;
• a microwave sensor for ascertaining a propagation velocity and/or an absorption of microwave signals in the milk;
• and
• a computer unit for calculating the fat content of the milk, wherein the computer unit is configured to:
• calculate a velocity of sound in the milk and calculate an average density for the milk based on the first and second eigenfrequencies;
• read the static pressure in the pipeline using the pressure sensor;
• calculate a gas volume fraction of the milk based on the velocity of sound in the milk, the average density, and the static pressure;
• calculate a density of the milk without gas content based on the average density and based on the gas volume fraction;
• measure the propagation velocity and/or the absorption of microwaves in the milk using the microwave sensor;
• calculate an effective permittivity of the milk from the propagation velocity and/or absorption;
• and
• calculate a fat fraction of the milk based on the density of the milk without gas content and on the effective permittivity.