Vibrating fork level switches

Patent metadata

Field	Value
Publication number	US-10982991-B2
Application number	US-201716322582-A
Country	US
Kind code	B2
Filing date	Aug 2, 2017
Priority date	Aug 3, 2016
Publication date	Apr 20, 2021
Grant date	Apr 20, 2021

Abstract

The invention provides a method for configuring for use a vibrating fork level switch having a dry fork frequency DFF. The method involves establishing a wet fork frequency WFF and combining this with the DFF to configure the switch for use in media of differing densities.

First claim

The invention claimed is:

1. A method of configuring for use in different media a vibrating fork level switch, said method comprising the steps of:
establishing for said switch a relationship between wet fork frequency (WFF) and density;
establishing a relationship between density and switching frequency at a given point for said switch;
determining a frequency of vibration of the switch in air (DFF);
determining a frequency reading (WFF) obtained from fully immersing said switch in a medium with which said switch is to be used;
combining measures of DFF and WFF to determine a density of said medium; and
from the determined density establishing a switching frequency for said switch in said medium.

2. The method as claimed in claim 1 comprising establishing the switching frequency (SF) for said switch from the DFF and WFF based on a polynomial.

3. The method as claimed in claim 2 wherein said polynomial is a 6 th order polynomial.

4. The method as claimed in claim 1 wherein said measures of DFF and WFF are classified into bands, the combination of two bands being used to establish a density classification for said medium.

5. The method as claimed in claim 4 further comprising allocating a switching frequency to each density classification at a given switch point.

6. The method as claimed in claim 1 when applied to the determination of the content of one medium suspended in a carrier liquid of density ρ o , said method comprising measuring the WFF of a combination of said medium in said carrier liquid to derive a combination density ρ and comparing ρ o and ρ to derive an indication of the amount of medium in said carrier liquid.

7. The method as claimed in claim 6 wherein the percentage of medium (PCM) in said carrier liquid can be calculated according to the expression:
PCM =((ρ−ρ o )/ρ o )×100

8. The vibrating fork level switch configured to undertake and/or apply the methods set forth in claim 1 .

Assignees

• Rosemount Tank Radar Ab

Inventors

• Sears Jeffery Allan
• Zhang Jingdong
• Tzegazeab Tadewos
• Thomas Kevin

Classifications

• G01F25/20 Primary

  of apparatus for measuring liquid level · CPC title

• G01F15/02

  Compensating or correcting for variations in pressure, density or temperature · CPC title

• G01F23/2967 Primary

  for discrete levels · CPC title

• G01N9/002

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

• G01N2009/006

  vibrating tube, tuning fork · CPC title