A torque measuring device for determining properties such as viscosity, shearing force or concentration in liquids or suspensions. The device comprises two elastically connected concentric axles in the form of one external hollow axle through which an inner measuring axle extends, and an element responsive to the measured medium located on a distal end of the measuring axle. The axles are individually propelled by electrical motors. The motors are operated such that the axles rotate at generally constant speed and, simultaneously, the phase between the two are controlled irrespective of applied speed and torque. The torque is measured through the degree of load of the motor propelling the inner axle, which is provided as an output signal.