Patent ID: 7219537

Claim:
An apparatus for controlling the shear rate at which viscosity is being measured, the apparatus utilizing an Acoustic Wave Device (AWD) sensor having an input and an output, the apparatus comprising: a controlled power source having an output coupled to said sensor input; an input power detecter coupled to said sensor input, for generating an input power level signal representative of said sensor input power; an output power detector coupled to said sensor output, for generating an output level signal representative of said sensor output power; an error measurement circuit having an input, for producing an error signal reflective of the difference between at least said output power level signal and a set point; an averaging circuit coupled to said input power level signal and to said output power level signal, and operative to generate an average signal therefrom; wherein said average signal is coupled to said input of error measurement circuit; and wherein said error signal is used to control the input power to said sensor via said controlled power source.