Instrument for use with fluid

1. An instrument in a milking machine for measuring viscosity of gels formed from mixing milk with a reagent in order to determine a somatic cell count for a particular milk sample, comprising:

a mixing element, wherein the mixing element is a shuttle and contains a magnet or ferromagnetic material which assists in measuring a viscosity by a fall time of the mixing element in the milk and reagent to be mixed;

a container to hold the milk to be mixed, the container including a chamber for the mixing element;

a driving means for the mixing element positioned exterior to an inner surface of the container and the mixing element and the milk with the reagent to be mixed;

wherein the driving means is not physically connected to the mixing element, and the mixing element is not attached to the container;

wherein the driving means is an electromagnetic coil which drags the shuttle up through the milk and can be turned off to enable the shuttle to drop down, or which is provided near the base of the container and repels the shuttle upwards, and which is configured to sense changes in the magnetic field;

wherein the shuttle includes guides in the form of fins that are substantially straight and aligned with the sides of the container into which the shuttle is to be placed,

and wherein the chamber includes an inlet for the milk and an inlet for the reagent, and wherein at least one inlet opens into the chamber from the upper side of the instrument.

2. The instrument as claimed in claim 1 wherein the driving means is positioned on an exterior surface of the container.