1. Field of the Invention
The present invention relates to a method of determining the time of modification of the physical state of a fluid medium and, in particular, determining the coagulation time of blood, of the kind in which a ferromagnetic ball is placed in the bottom of a cup containing the fluid to be studied and driven with a periodic movement under the effect of an external magnetic field, and in which the modifications of the movements of this ball due to the modification of the physical state are detected. The invention also relates to a device for implementing this method.
2. Description of the Prior Art
Such a method is described more particularly in the European patent n.degree. 90 192 in which the ball thus driven moves freely over the flat and horizontal bottom of a cup. When the modification of the physical state of the fluid which is contained in the cup, and which is here blood plasma to which reagents have been added, occurs, the ball moves over a curve directed towards the inside because, so it seems, of the increase of mechanical resistance opposed by the contents of the cup, and its radial movement is detected by means well known in themselves.
The accuracy of measurements thus made leaves much room for improvement, since the radial movement of a ball towards the center of a cup of very small size is a physical magnitude which is difficult to detect and to evaluate satisfactorily. Furthermore, the reproducibility of such measurements is not good, because, particularly, of the complexity of the phenomena on which they are based.