Method for determining an inner diameter of a sounding tube by a fill-level measuring device

Patent metadata

Field	Value
Publication number	US-10753783-B2
Application number	US-201715464825-A
Country	US
Kind code	B2
Filing date	Mar 21, 2017
Priority date	Mar 23, 2016
Publication date	Aug 25, 2020
Grant date	Aug 25, 2020

Abstract

A method for determining an inner diameter of a sounding tube, which, for measuring the fill level of a fill substance located in a process space of a container, extends in the process space, or is placed alongside the container and connected with the process space. The method can be implemented in the case of a fill-level measuring device working according to the FMCW-principle. Besides the intermediate frequency of the difference signal, also its phase shift is ascertained, wherein the exact tube inner diameter can be determined based on the phase shift. An advantage of the method is that the fill-level measuring device with the help of the then exactly known tube diameter can be recalibrated and accordingly the fill level determined more exactly. The exact tube inner diameter does not have to have been previously known.

First claim

The invention claimed is:

1. A method for determining an inner diameter of a sounding tube, wherein, for measuring a fill level of a fill substance located in a process space of a container, the sounding tube extends in the process space, or wherein the sounding tube is placed alongside the container and connected fluidically with the process space, the method comprises method steps as follows:
by means of a periodic electrical signal, a microwave signal is produced, wherein the electrical signal has a periodic frequency change in the region of a center frequency;
the microwave signal is transmitted along the sounding tube in a direction of a surface of the fill substance;
an echo signal, which, after reflection of the microwave signal on the surface of the fill substance, is reflected along the sounding tube in opposite direction, is received and converted into an electrical, received signal;
by mixing the received signal with the electrical signal, a difference signal with an difference frequency is produced;
as a function of the fill level, a phase shift between the difference signal and the electrical signal is ascertained;
a phase difference between the phase shift and a previously known, base phase shift, which is based on a reference inner diameter, is ascertained; and
based on the phase difference, a tube inner diameter is determined;
wherein the tube inner diameter (D) is calculated based on the formula

D
=

D
0

*

f
c

f
r

*

1
-

(

β
α

)

2

⁢

⁢
with

⁢

β
=

1
-

(

f
c

f
r

)

2

⁢

⁢
and

⁢

α
=

1
+

c
⁢

⁢
β

8
⁢
π
⁢

⁢

f
r

*

d
⁢

⁢
Δ
⁢

⁢
ϕ

d
⁢

⁢
L

and wherein the change

(

d
⁢

⁢
Δ
⁢

⁢
ϕ

d
⁢

⁢
L

)

is ascertained by linear regression;
wherein:
c=speed of light;
π=Archimedes' constant;
D 0 =reference inner diameter;
f c =limit frequency in a tube with diameter D 0 ;
fr=reference frequency; and

d
⁢

⁢
Δ
⁢

⁢
ϕ

d
⁢

⁢
L

=change of the phase difference as a function of the fill level.

2. The method as claimed in claim 1 , wherein:
the periodic frequency change is a sawtooth-shaped or triangular change of the electrical signal.

3. The method as claimed in claim 1 , wherein:
the fill level is measured based on the difference frequency and/or the base phase shift.

4. The method as claimed in claim 3 , wherein:
the measuring of the fill level is recalibrated based on the tube inner diameter.

5. The method as claimed in claim 1 , wherein:
the phase shift is ascertained by means of a fast Fourier transformation of the difference signal.

6. The method as claimed in claim 1 , wherein:
the tube inner diameter is determined based on the change

(

d
⁢

⁢
Δ
⁢

Assignees

• Endress Hauser Gmbh Co Kg
• Endress+Hauser Se+Co Kg

Inventors

• Malinovskiy Alexey
• Gorenflo Stefan
• Merle Jens
• Vogel Markus

Classifications

• G01B21/14 Primary

  internal diameters {(of boreholes or wells E21B47/08)} · CPC title

• G01F25/20 Primary

  of apparatus for measuring liquid level · CPC title

• G01S7/4004

  of parts of a radar system · CPC title

• G01S7/03

  Details of HF subsystems specially adapted therefor, e.g. common to transmitter and receiver · CPC title

• G01S13/88

  Radar or analogous systems specially adapted for specific applications (electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00) · CPC title