Complex viscosity and complex modulus measurement device and method

A viscometer for determining a complex viscosity of a fluid, the viscometer comprising:

• vibrating means for imparting one of a random and a pseudo random alternating movement to a surface of the fluid in a direction substantially perpendicular to the surface to cause a corresponding alternating flow of the fluid, the flow leading the fluid to exert on the vibrating means an alternating reaction force related to the viscosity of the fluid;
• force measuring means for providing a force signal related to the alternating reaction force;
• displacement measuring means for providing a movement signal related to the alternating movement of the surface;
• and
• processing means for using the force signal and the movement signal to compute the complex viscosity of the fluid.

A method for measuring a viscosity of a fluid, the method comprising the steps of:

• imparting an alternating movement to a surface of the fluid to cause a corresponding alternating flow of the fluid, the flow leading the fluid to produce an alternating reaction force related to the viscosity of the fluid;
• providing a force signal related to the alternating reaction force;
• providing a movement signal related to the alternating movement of the surface;
• and
• processing the force signal and the movement signal to compute the viscosity of the fluid by obtaining a Fourier Transform F(.omega.) of the force signal, a Fourier transform H(.omega.) of the movement signal and a ratio F(.omega.)/H(.omega.) of the Fourier transform of the force signal to the Fourier transform of the movement signal.

A method for measuring a viscosity of a fluid, the method comprising the steps of:

• imparting one of a random and a pseudo random alternating movement to a surface of the fluid in a direction substantially perpendicular to the surface to cause a corresponding alternating flow of the fluid, the flow leading the fluid to produce an alternating reaction force related to the viscosity of the fluid;
• providing a force related to the alternating reaction force;
• providing a movement signal related to the alternating movement of the surface;
• and
• processing the force signal and the movement signal to compute the viscosity of the fluid.

A viscometer comprising:

• a fluid sample holder carrying a predetermined amount of fluid, the fluid sample holder having an upper plate spaced from and substantially parallel to a lower plate, the upper plate vibrated at a plurality of frequencies in a direction normal to the plane of the upper plate to produce a reaction force without applying an external magnetic force to the fluid while the lower plate remains substantially motionless;
• a force measuring device responsive to the reaction force to produce a force signal;
• a displacement device to produce a movement signal indicative of the displacement of the fluid sample holder;
• and
• a processing device responsive to the force signal and movement signal to produce the complex viscosity of the fluid.