| 摘要 |
The flowmeter comprises a flow sensor with a flow tube, two electrodes, and two field coils traversed by a first excitation current and a second excitation current, respectively, as well as control and evaluation electronics. The method serves to generate an error signal when the uniform turbulence in the liquid to be measured is disturbed. During a first quarter cycle, the excitation currents are equal, have a constant value, and flow in the same direction, a first direction. During a second quarter cycle, the first excitation current has the constant value and flows in the opposite direction, and the second excitation current is less by a constant amount and flows in the first direction. During a third quarter cycle, the excitation currents have the constant value and flow in the opposite direction. During a fourth quarter cycle, the first excitation current has the constant value and flows in the first direction, and the second excitation current is less by the constant amount and flows in the opposite direction. During each quarter cycle, a voltage is derived from the electrodes, and from these voltages, a first and a second voltage difference and a quotient using the first and the second voltage diffrences are formed. The latter is determined during calibration under uniformly turbulent flow conditions, and stored. In operation, values of the quotient are continuously formed and compared with the stored quotient; in case of deviations, an alarm is triggered and/or the volumetric flow rate signal represented by the first voltage difference is corrected.
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