The invention relates to a rheometer having a rotatable shaft (1) on which a rotor plate (2) is fastened, and having a measuring instrument (10) for measuring torques exerted on the rotor plate (2) by a substance (6) to be studied during rotation of the shaft (1), a first measurement gap (5) for holding the substance (6) to be studied being formed between a first side (3) of the rotor plate (2) and a first shear face (4) and a second measurement gap (9) for holding the substance (6) to be studied being formed between a second side (7) of the rotor plate (2), opposite the first side, and a second shear face (8). The rheometer contains a magnet for generating a magnetic field in the first and second measurement gaps (5, 9).
