Method, circuit and flexural resonator for measuring the density of fluids
AssigneeAnton Paar GmbH
InventorsANDREAS RECHBERGER, ROBERT AMSUESS
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Abstract
A method for determining a density of a fluid medium with a flexural oscillator whose oscillator tube is filled with the measurement fluid. Accordingly, reference is made to a period of oscillation of a free and damped oscillating flexural resonator for density determination. For this purpose, the excitation of the excitation amplifier is interrupted alternately by a switch and then switched back into the oscillating circuit. The period of the damped oscillation, together with the amplitude and/or phase, is used for the output of a viscosity-corrected density.
Claims15
A method for measuring a density of fluids from a period of a resonant oscillation mode of a flexural resonator, which further comprises:
- operating an oscillator in a resonant undamped oscillation with an excitation amplifier circuit;
- operating the oscillator in a forced undamped oscillation during a time interval Δt1 via an excitation amplifier;
- periodically interrupting an excitation of the forced undamped oscillation for a time interval Δt2, the oscillator is left free and allowed to oscillate damped as a function of its quality factor during the time interval Δt2 of an interruption, in the time interval Δt2, a period of a free damped oscillation is used for a density determination;
- and
- exciting the oscillator again into the resonant undamped oscillation after a measurement of the period of the free damped oscillation.
A control and/or regulating circuit for a flexural resonator, comprising:
- an excitation circuit provided for switching on the flexural resonator, said excitation circuit, which excites an oscillator of the flexural resonator to an undamped oscillation;
- a switch for repeating an excitation of the flexural resonator for undamped oscillation, or interrupts the excitation for periodically-defined time intervals, in said time intervals damped free oscillation of the flexural resonator takes place without specifying an excitation;
- and
- a measurement and evaluation unit for measuring a period of a damped free oscillation for determining a density of a fluid to be examined.
Dependencies are inferred from the claim text.