The device electronically measures fluid viscosity and temperature simultaneously principally for determining the changes in the properties of cervical mucus at the onset of ovulation. Interdigital transducers are used to generate and detect surface and bulk acoustic waves on one side of a slab of fused...http://www.google.es/patents/US4691714?utm_source=gb-gplus-sharePatente US4691714 - Rheological testing apparatus and method
