THz measuring device for measuring at least one layer thickness (d) of a test object conveyed along a conveying direction (v) or axis of symmetry, said THz measuring device comprising: - a main THz sensor for emitting a main THz beam along a first optical axis in a detection plane perpendicular to the conveying direction (v) or axis of symmetry and for receiving THz radiation reflected along the first optical axis, - at least one additional THz sensor (30-i) for emitting an additional THz beam along a second optical axis, for detecting the additional THz beam reflected back along the second optical axis, - an evaluation and control device suitable for = picking up a first signal amplitude of the main THz sensor, determining main reflection peaks (P1, P2, P3, P4) in the first signal amplitude, and, from the main reflection peaks (P1, P2, P3, P4), determining a distance and/or a layer thickness in the detection plane, and = picking up a second signal amplitude of the additional THz sensors (30-i), determining additional reflection peaks in the second signal amplitude, and assigning the additional reflection peaks faults in or on the test object, characterised in that the second optical axis extends outside the detection plane and/or at an angle to the detection plane, wherein the main THz sensor and the at least one additional THz sensor (30-i) are arranged rigidly in relation to one another and on a common measuring head, and where multiple additional THz sensors (30-i) are arranged together with the main THz sensor as a THz sensor array, their optical axes (A1, A2, A3) being arranged fixed in relation to one another and in a manner divergent widening, for detecting multiple material regions of the test object. - a main THz sensor for emitting a main THz beam along a first optical axis in a detection plane perpendicular to the conveying direction (v) or axis of symmetry and for receiving THz radiation reflected along the first optical axis, - at least one additional THz sensor (30-i) for emitting an additional THz beam along a second optical axis, for detecting the additional THz beam reflected back along the second optical axis, - an evaluation and control device suitable for = picking up a first signal amplitude of the main THz sensor, determining main reflection peaks (P1, P2, P3, P4) in the first signal amplitude, and, from the main reflection peaks (P1, P2, P3, P4), determining a distance and/or a layer thickness in the detection plane, and = picking up a second signal amplitude of the additional THz sensors (30-i), determining additional reflection peaks in the second signal amplitude, and assigning the additional reflection peaks faults in or on the test object, = picking up a first signal amplitude of the main THz sensor, determining main reflection peaks (P1, P2, P3, P4) in the first signal amplitude, and, from the main reflection peaks (P1, P2, P3, P4), determining a distance and/or a layer thickness in the detection plane, and = picking up a second signal amplitude of the additional THz sensors (30-i), determining additional reflection peaks in the second signal amplitude, and assigning the additional reflection peaks faults in or on the test object, the second optical axis extends outside the detection plane and/or at an angle to the detection plane, wherein the main THz sensor and the at least one additional THz sensor (30-i) are arranged rigidly in relation to one another and on a common measuring head, and where multiple additional THz sensors (30-i) are arranged together with the main THz sensor as a THz sensor array, their optical axes (A1, A2, A3) being arranged fixed in relation to one another and in a manner divergent widening, for detecting multiple material regions of the test object.