Mass flowmeter according to the Coriolis principle with at least two measuring tube pairs

摘要

A Coriois mass flowmeter (100) comprises two pairs of measuring tubes, each having two measuring tubes (110a, 110b, 110c, 110d) mounted in mutually oscillatory manner, with a bending mode useful mode of different useful natural frequencies f1, f2; each with an electrodynamic exciter (140a, 140c) for exciting the bending vibrations of a pair of measuring tubes; and each having a pair of vibration sensors including a first inlet side vibration sensor (142a-1, 142c-1) and a first outlet side vibration sensor (142a-2, 142c-2) for detecting bending vibrations respectively at two positions of a first pair of measuring tubes (110a, 110b); an operation and evaluation circuit (160); for driving the exciters (140a, 140c) and for detecting signals of the vibration sensors (142a-1, 142a-2, 142c-1, 142c-2); for determining phase difference-dependent mass flow measurements; wherein an excitation signal path is adapted to transmit the excitation signal to the first and second electrodynamic exciters; wherein inlet side and outlet side sensor signal paths are adapted to transmit signals of the vibration sensors superimposed on both pairs of measuring tube; wherein the sensor signals having the first Nutzmodeeigenfrequenz f1 a first relative signal amplitude difference delta ₁ between the signals of the inlet side sensors and the signals of the outlet side sensors, wherein the sensor signals having the second Nutzmodeeigenfrequenz f2 a corresponding second relative Signalalmplitudendifferenz delta ₂ , wherein the amount of Difference deviation D = | delta ₁ - delta ₂ | the second relative signal amplitude difference from the first relative signal amplitude difference delta _{1 is} not more than a tolerance value D _T.