Method and measuring system for ascertaining density of a fluid

Patent metadata

Field	Value
Publication number	US-9377387-B2
Application number	US-201213716637-A
Country	US
Kind code	B2
Filing date	Dec 17, 2012
Priority date	Dec 23, 2011
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

A method for producing at least one oscillation measurement signal, which has vibrations of a vibratory body are registered. A temperature sensor is applied thermally attached with a non fluid contacting, second surface of the vibratory body for producing a temperature measurement signal representing a time curve of a variable temperature of the vibratory body. The temperature measurement signal can follow, however time delayed, a change of the temperature of the vibratory body from a beginning temperature value, to a new temperature value. Based on the oscillation measurement signal as well as the temperature measurement signal, density, measured values are produced representing the density, wherein, during such, discrepancies possibly occurring between the time curve of the temperature of the vibratory body and the temperature measurement signal are taken into consideration, respectively at least partially compensated.

First claim

The invention claimed is:

1. A measuring system for ascertaining density of a fluid, said measuring system comprising:
a measuring transducer including:
at least one vibratory body, said vibratory body being held oscillatably and adapted to be contacted on a first surface by fluid to be measured in such a manner that said first surface assumes a fluid temperature, namely a temperature of the fluid contacting said first surface, and to be caused to vibrate in such a manner that it executes, at least partially, resonant oscillations, namely mechanical oscillations with a resonant frequency, dependent on the density of the fluid, and said vibratory body exhibiting a specific thermal conductivity, consequently a therefrom dependent, thermal conductivity, effective for heat transfer from said first surface to a non fluid contacting, second surface, and a heat capacity;
at least one oscillation sensor for registering vibrations of said vibratory body and for producing an oscillation measurement signal, which includes at least one signal component with a signal frequency dependent on the density of the fluid; and
a temperature sensor thermally coupled with said second surface of said vibratory body for registering a temperature on said second surface of said vibratory body dependent on the fluid temperature, and for producing a temperature measurement signal representing a time curve of a temperature of said vibratory body, namely a temperature dependent on the fluid temperature of said vibratory body, said temperature measurement signal, following a change of the temperature of said vibratory body from a beginning first temperature value, to a second temperature value, only time delayed, so that the temperature measurement signal corresponds consequently to said second temperature value only time delayed;
and said measuring system comprising: an electronics electrically connected with said measuring transducer for processing the oscillation measurement signal and the temperature measurement signal as well as for generating, based on both the oscillation as well as also the temperature measurement signal, a density measured value, representing the density of the fluid, said electronics being adapted, to generate the density measured value taking into consideration an occurrence of a discrepancy between the time curve of the temperature of the vibratory body and the temperature measurement signal
wherein: the electronics is adapted to produce a sampled sequence of frequency, namely a sequence of digital frequency values ascertained at different points in time based on the at least one oscillation measurement signal, said sampled sequence approximating a time curve of the resonant frequency of the vibratory body;
the electronics is adapted to apply the sampled sequence of frequency for producing a delayed sampled sequence of frequency, namely a sequence of digital frequency values ascertained at different points in time based on the sampled sequence of frequency, in order to approximate the time curve of the resonant frequency of the vibratory body, in such a manner that said delayed sampled sequence of frequency more slowly approaches a time curve of the resonant frequency following on a change of the resonant frequency;
the electronics is adapted to apply the delayed sampled sequence of frequency for producing a frequency measured value representing the resonant frequency of the vibratory body contacted by the fluid; and
the electronics is adapted to apply the frequency measured value for producing the density measured value.

2. The measuring system as claimed in claim 1 , wherein:
said vibratory body is adapted to carry fluid, respectively to be flowed through by fluid.

3. The measuring system as claimed in claim 1 , wherein:
the change of the temperature results from a change of the temperature of the fluid contacting said vibratory body on its first surface.

4. The measuring system as claimed in claim 1 , wherein:
the change of the temperature results from a change of the fluid.

5. The measuring system as claimed in claim 1 , wherein:
said discrepancy between the time curve of the temperature of the vibratory body and the temperature measurement signal is time dependent.

6. The measuring system as claimed in claim 1 , wherein:
the electronics is adapted to take into consideration said occurrence of the discrepancy between the time curve of the temperature of the vibratory body and the temperature measurement signal in such a manner that said discrepancy is at least partially compensated.

7. The measuring system as claimed in claim 1 , wherein:
the vibratory body exhibits a specific thermal conductivity greater than 5 W K−1 m−1.

8. The measuring system as claimed in claim 1 , wherein:
the vibratory body is of metal.

9. The measuring system as claimed in claim 1 , wherein:
the electronics is adapted to apply the temperature measurement signal for producing a temperature measured value representing the temperature of the vibratory body; and
the electronics is adapted to apply both, the frequency measured value as well as also the temperature measured value for producing the density measured value.

10. The measuring system as claimed in claim 1 , wherein:
the electronics is adapted to apply the sampled sequence of frequency for producing the frequency measured value.

11. The measuring system as claimed in claim 1 , wherein:
the change of the resonant frequency is a jump-like change of the resonant frequency.

12. The measuring system as claimed in claim 1 , further comprising:
at least one electro-mechanical oscillation exciter in actuating connection with the vibratory body adapted.

13. The measuring system as claimed in claim 12 , wherein:
the measuring electronics includes a driver-circuit serving for activating the measuring transducer; and
the electro-mechanical oscillation exciter is adapted to convert an electrical excitation power fed from the driver circuit of the electronics by means of at least one electrical driver signal into exciter forces, which act correspondingly on the vibratory body.

14. The measuring system as claimed in claim 1 , wherein the measuring electronics includes a measuring- and evaluating-circuit serving for processing the at least one oscillation measurement signal of the measuring transducer.

15. The measuring system as claimed in claim 14 , wherein the measuring- and evaluating-circuit includes at least one of: a microprocessor and a digital signal processor.

16. The measuring system as claimed in claim 1 , wherein:
said vibratory body is an oscillatably held measuring tube exhibiting a lumen surrounded by a tube wall.

17. The measuring system as claimed in claim 16 , wherein:
said measuring tube is adapted to be immersed in fluid; and
said first surface of said vibratory body contacting the fluid is formed by an outer surface of the tube wall and the non fluid contacting, second surface of said vibratory body by an inner surface of the tube wall facing the lumen.

18. The measuring system as claimed in claim 16 , wherein:
said measuring tube is adapted to carry fluid; and
said first surface of said vibratory body contacting the fluid formed by an inner surface of the tube wall facing the lumen and the non fluid contacting, second surface of said vibratory body by an outer surface of the tube wall.

19. The measuring system as claimed in claim 1 , wherein:
said vibratory body is adapted to be immersed in fluid, or flowed on by fluid.

20. The measu

Assignees

• Flowtec Ag

Inventors

• Dijk Coen Van
• Momente Omar
• Hagenmeyer Heinerich

Classifications

• G01F1/8472

  having curved measuring conduits, i.e. whereby the measuring conduits' curved center line lies within a plane (G01F1/8481 takes precedence) · CPC title

• G01N2009/006

  vibrating tube, tuning fork · CPC title

• G01N9/002 Primary

  using variation of the resonant frequency of an element vibrating in contact with the material submitted to analysis (G01N9/34 takes precedence) · CPC title

• G01F1/8477

  with multiple measuring conduits · CPC title

• G01F1/74

  Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid · CPC title