Abstract: This circuit is suitable for flow tubes (4) the vibration frequency of which is in the order of 1 kHz. A fluid to be measured flows through the tube (4) vibrating in operation at a frequency determined by the density of the fluid. Attached to the tube (4) are electromagnetic vibration sensors (17, 18) positioned at a given distance from each other delivering sinusoidal sensor signals (x17, x18). Impedance-matching devices (31, 32) are fed by the sensor signals. Inputs of an intermediate switch (35) are connected to the outputs of impedance-matching devices. Additional impedance-matching device (33, 34) are fed by outputs of the intermediate switch. Low-pass filters (37, 38) are connected to the outputs of the additional impedance matching devices. The upper cutoff frequency of low-pass filter (37) differs by about 10% to 15% from the upper cutoff frequency of low-pass filter (38). Zero-crossing detector (39, 40) are fed by the outputs of the low-pass filters.