surface 20 the platens are maintained in a spaced relationship with the surfaces 20 facing each other so that a fluid sample 12 can be held between the surfaces 20 to provide a fluid bridge the actuator 28 is controlled by control and measurement devices 19 to control the displacement of the carriage 17 along the track 14 to elongate the fluid bridge a diameter measuring system 23 is located so as to provide diameter measurements of a fluid bridge formed between the platens 15 16 at the midpoint of the fluid bridge the measuring system is moved and controlled by control and measurement devices 19 so as to be maintained at the midpoint of the fluid bridge and provide a measurement of the diameter in real time referring to fig3 a a fluid sample 12 is placed between opposed surfaces 20 of the platens 15 16 to form a fluid bridge as the platens separate as shown in fig3 b the fluid sample 12 between the platens 15 16 is stretched to elongate the fluid bridge the fluid bridge has an initial length l 0 and an initial diameter do typically corresponding to the diameter d of the platens 15 16 to measure the elasticity of the fluid sample 12 the.