Vibration measuring device designed to measure a viscosity, a density and a mass flow of a fluid conducted in a pipe, said vibration measuring device comprising: - a measuring sensor -- with at least one measuring tube inserted in the pipe, which --- has an interior measuring tube channel conducting the fluid, and --- which is clamped on the inlet end and on an outlet end in a manner that it is capable of vibrating, -- with an exciter arrangement designed to allow the measuring tube to vibrate, wherein - for the purpose of generating viscous frictions in the fluid - the measuring tube oscillates, during operation, at least partially in a lateral vibration mode, particularly in a flexural vibration mode, in relation to a rest position at an adjustable excitation frequency (f exc), and -- with a sensor arrangement reacting to vibrations of the measuring tube, said sensor arrangement being designed to generate a first sensor signal (X s1) representing lateral vibrations, particularly flexural vibrations, of the measuring tube on the inlet side, and designed to generate a second sensor signal (X s2) representing lateral vibrations, particularly flexural vibrations, of the measuring tube on the outlet side, and - a measuring device electronics module -- with an excitation circuit that generates an excitation current (i exc) that feeds the exciter arrangement, and -- with an evaluating circuit --- which generates an estimated value (Xe) for a velocity of a movement of the fluid that causes viscous frictions using the first sensor signal (X s1) and/or using the second sensor signal (X s2), and --- which generates a viscosity measured value (X η), which represents the viscosity of the fluid, using this estimation value (X θ) and using the excitation current (i exc). - a measuring sensor -- with at least one measuring tube inserted in the pipe, which --- has an interior measuring tube channel conducting the fluid, and --- which is clamped on the inlet end and on an outlet end in a manner that it is capable of vibrating, -- with an exciter arrangement designed to allow the measuring tube to vibrate, wherein - for the purpose of generating viscous frictions in the fluid - the measuring tube oscillates, during operation, at least partially in a lateral vibration mode, particularly in a flexural vibration mode, in relation to a rest position at an adjustable excitation frequency (f exc), and -- with a sensor arrangement reacting to vibrations of the measuring tube, said sensor arrangement being designed to generate a first sensor signal (X s1) representing lateral vibrations, particularly flexural vibrations, of the measuring tube on the inlet side, and designed to generate a second sensor signal (X s2) representing lateral vibrations, particularly flexural vibrations, of the measuring tube on the outlet side, and -- with at least one measuring tube inserted in the pipe, which --- has an interior measuring tube channel conducting the fluid, and --- which is clamped on the inlet end and on an outlet end in a manner that it is capable of vibrating, --- has an interior measuring tube channel conducting the fluid, and --- which is clamped on the inlet end and on an outlet end in a manner that it is capable of vibrating, -- with an exciter arrangement designed to allow the measuring tube to vibrate, wherein - for the purpose of generating viscous frictions in the fluid - the measuring tube oscillates, during operation, at least partially in a lateral vibration mode, particularly in a flexural vibration mode, in relation to a rest position at an adjustable excitation frequency (f exc), and -- with a sensor arrangement reacting to vibrations of the measuring tube, said sensor arrangement being designed to generate a first sensor signal (X s1) representing lateral vibrations, particularly flexural vibrations, of the measuring tube on the inlet side, and designed to generate a second sensor signal (X s2) representing lateral vibrations, particularly flexural vibrations, of the measuring tube on the outlet side, and - a measuring device electronics module -- with an excitation circuit that generates an excitation current (i exc) that feeds the exciter arrangement, and -- with an evaluating circuit --- which generates an estimated value (Xe) for a velocity of a movement of the fluid that causes viscous frictions using the first sensor signal (X s1) and/or using the second sensor signal (X s2), and --- which generates a viscosity measured value (X η), which represents the viscosity of the fluid, using this estimation value (X θ) and using the excitation current (i exc). -- with an excitation circuit that generates an excitation current (i exc) that feeds the exciter arrangement, and -- with an evaluating circuit --- which generates an estimated value (Xe) for a velocity of a movement of the fluid that causes viscous frictions using the first sensor signal (X s1) and/or using the second sensor signal (X s2), and --- which generates a viscosity measured value (X η), which represents the viscosity of the fluid, using this estimation value (X θ) and using the excitation current (i exc). --- which generates an estimated value (Xe) for a velocity of a movement of the fluid that causes viscous frictions using the first sensor signal (X s1) and/or using the second sensor signal (X s2), and --- which generates a viscosity measured value (X η), which represents the viscosity of the fluid, using this estimation value (X θ) and using the excitation current (i exc).