# US 10,119,895 B2 · Method, circuit and flexural resonator for measuring the density of fluids

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,119,895 B2
- Document ID: US10119895B2
- Status: Granted
- Kind: B2
- Application number: 14/887,811
- Filed: 2015-10-20
- Published: 2016-04-21
- Granted: 2018-11-06
- Earliest claimed: 2014-10-20
- Assignees: Anton Paar GmbH
- Applicants: Anton Paar GmbH
- Inventors: Andreas Rechberger; Robert Amsuess
- Web page: https://patentgrep.com/patent/US10119895B2

## CPC

- G01N 9/002: {using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis (G01N9/34 takes precedence)}
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## 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.

## Claims

### Claim 1

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.

### Claim 2 (depends on 1)

The method according to claim 1, which further comprises:
evaluating the free damped oscillation in terms of at least one parameter selected from the group consisting of phase and amplitude; and
making a viscosity correction of a determined density value with the parameter.

### Claim 3 (depends on 1)

The method according to claim 1, which further comprises determining a period of an oscillation frequency by carrying out a comparison with a local oscillator.

### Claim 4 (depends on 2)

The method according to claim 2, which further comprises carrying out an amplitude determination directly by means of coordinate transformation of a measuring signal.

### Claim 5 (depends on 1)

The method according to claim 1, which further comprises performing a periodic switching on and off of the excitation amplifier circuit for predetermined, fixed, equal length, time intervals and/or that the switching on and off of the excitation amplifier circuit is regulated by means of amplitude values of a damped oscillation and/or an undamped oscillation.

### Claim 6 (depends on 5)

The method according to claim 5, wherein the time interval Δt1 of the excitation amplification is in a fixed relationship to the time interval Δt2 of a period measurement, wherein a ratio Δt1: Δt2 lies in a range of between 1:1 to 1:3.

### Claim 7 (depends on 1)

The method according to claim 1, wherein:
the excitation amplifier circuit remains closed until a forced resonant oscillation of the oscillator reaches its maximum amplitude; and/or
both a period and an amplitude of the forced undamped oscillation are determined after a decoupling of an exciter.

### Claim 8 (depends on 1)

The method according to claim 1, wherein:
a decay is interrupted:
after a predetermined time interval; or
when a predetermined amplitude value is reached; and
the quality factor is calculated through extrapolation of obtained amplitude values; and/or
a width of a decay window is selected or held constant; or
the time interval selected for the decay is selected or held constant.