Abstract: A rheological measurement method and device (e.g., a viscometer or rheometer) for measuring rheological properties are disclosed. A rheological property such as viscosity is determined by detecting data corresponding to torque between a drive shaft and a measurement shaft, producing an optical signal corresponding to the detected data, sending the corresponding optical signal with an optical transmitter supported by a rotational structure coupled to the drive shaft, receiving the optical signal from the optical transmitter with an optical receiver supported by a stationary structure of the rheological measurement device, producing an electrical signal corresponding to the received optical signal, and generating a measurement signal based on the electrical signal that corresponds to the torque between the drive shaft and the measurement shaft.