Capacitive fill level measurment device

• US 20010037680A1
• Filed: 02/22/2001
• Published: 11/08/2001
• Est. Priority Date: 02/22/2000
• Status: Active Grant

• Current Assignee: I F M Electronic GmbH
• Original Assignee: I F M Electronic GmbH
• Inventors: Buck, Bernd, Palata, Jaromir, Gundlach, Jochen
• Granted Patent: US 6,823,730 B2
• Time in Patent Office: Days
• US Class Current: 73/304C
• CPC Class Codes: G01F 23/265 for discrete levels
• CPC Class Codes: G01F 23/266 measuring circuits therefor
• CPC Class Codes: G01F 23/268 mounting arrangements of probes

Abstract

A capacitive fill level measurement device with a fill level sensor having a plurality of sensor fields, electrical wires for electrically connecting the plurality of sensor fields to a multipole side of a selector switch, and a power supply and evaluation circuit electrically connected to a monopole side of the selector switch. The capacitive fill level measurement device can be made with simple production technology and thus economically for a host of different applications using a matrix of printed conductors which extend vertically and horizontally such that each horizontally extending printed conductor on one side is connected to one sensor field and on the other side connected to a vertically extending printed conductor. Each horizontally extending printed conductor is connected with a respective vertically extending printed conductor to form an electrical line or a part of an electrical line.

Claims

1. A capacitive fill level measurement device comprising:

a fill level sensor having a plurality of sensor fields, said plurality of sensor fields being composed of metal and mounted on top of one another;

a selector switch electrically connected on a multipole side to said plurality of sensor fields;

a power supply and evaluation circuit electrically connected to a monopole side of said selector switch; and

a matrix of vertically extending printed conductors and horizontally extending printed conductors so as to electrically connect said selector switch to said plurality of sensors,

wherein each horizontally extending printed conductor is connected at one end to a respective one of said plurality of sensor fields and at an opposing end to a respective one of said vertically extending printed conductors.

2. The capacitive fill level measurement device as claimed in

claim 1

, wherein a plurality of said horizontally extending printed conductors are connected to a respective one of said vertically extending printed conductors.

3. The capacitive fill level measurement device as claimed in

claim 1

, wherein said vertically extending printed conductors are provided with widened areas for use as solder surfaces.

4. The capacitive fill level measurement device as claimed in

claim 1

, wherein at least one of said plurality of sensor fields and said printed conductors are mounted on a flexible conductor support.

5. The capacitive fill level measurement device as claimed in

claim 4

, wherein said fill level sensor is rolled around a vertical axis.

6. The capacitive fill level measurement device as claimed in

claim 5

, wherein said horizontally extending printed conductors are at least partially surrounded by said plurality of sensor fields.

7. The capacitive fill level measurement device as claimed in

claim 6

, wherein said vertically extending printed conductors are at least partially surrounded by said plurality of sensor fields.

8. The capacitive fill level measurement device as claimed in

claim 7

, further including a cylindrical hollow body having a longitudinal slot and wherein said plurality of sensor fields are located on the outer periphery of said cylindrical hollow body, said horizontally extending printed conductors are located at least partially in the inner periphery of said cylindrical hollow body and said vertically extending printed conductors are located in the inner periphery of said cylindrical hollow body.

9. The capacitive fill level measurement device as claimed in

claim 8

, wherein said cylindrical hollow body is electrically conductive and is composed of metal.

10. The capacitive fill level measurement device as claimed in

claim 7

, further including a cylindrical carrier rod, and wherein said conductor support is wound around the outer periphery of said cylindrical carrier rod.

11. The capacitive fill level measurement device as claimed in

claim 10

, wherein said conductor support is electrically conductive at least in an area proximate to said plurality of sensor fields on a side facing away from said plurality of sensor fields.

12. The capacitive fill level measurement device as claimed in

claim 11

, wherein said conductor support is electrically conductive in an area proximate to said printed conductors on a side facing away from said printed conductors.

13. The capacitive fill level measurement device as claimed in

claim 12

, wherein said conductor support is provided with at least one electrically conductive which is made in the form of a Faraday surface.

14. The capacitive fill level measurement device as claimed in

claim 13

, wherein said vertically extending printed conductors are constricted at least once.

15. The capacitive fill level measurement device as claimed in

claim 14

, wherein the width over each of said vertically extending printed conductors in an area proximate to said constriction corresponds at most to one half the width over each of said vertically extending printed conductors in a non-constricted area.

16. A starting material for a fill level sensor of a capacitive fill level measurement device, said fill level sensor having a plurality sensor fields, said starting material comprising:

a conductor support;

a plurality of sensor fields mounted on top of one another in one plane parallel to a plane of said conductor support and also mounted on said conductor support; and

a matrix of horizontally extending printed conductors and vertically extending printed conductors mounted proximate to said plurality of sensor fields sensor fields,

wherein said horizontally extending printed conductors is electrically connected to said vertically extending printed conductors.

17. The starting material as claimed in

claim 16

, wherein said plurality of sensor fields and said matrix of horizontally and vertically extending printed conductors are made as a continuously bonded lining on said conductor support.

18. The starting material as claimed in

claim 17

, wherein said conductor support on a side opposite to said plurality of sensor fields and said matrix of horizontally and vertically extending printed conductors are provided with at least one electrically conductive shield.

19. The starting material as claimed in

claim 18

, wherein said electrically conductive shield is made in the form of a Faraday surface.

20. The starting material as claimed in

claim 19

, wherein said electrically conductive shield is made as a copper bonded lining.

21. A process for producing a fill level sensor used for a capacitive fill level measurement device having a plurality of sensor fields from a starting material, said process comprising the steps of:

providing a starting material including a conductor support, a plurality of sensor fields mounted on top of one another in one plane parallel to a plane of said conductor support and also mounted on said conductor support, and a matrix of horizontally extending printed conductors and vertically extending printed conductors mounted proximate to said plurality of sensor fields sensor fields, wherein said horizontally extending printed conductors is electrically connected to said vertically extending printed conductors; and

separating said horizontally extending printed conductors from said plurality of vertically extending printed conductors such that only respective ones of said plurality of horizontally extending printed conductors and said vertically extending printed conductors which are to be connected to one another remain.

22. The process as claimed in

claim 21

, wherein said a matrix of horizontally and vertically extending printed conductors are separated using a laser beam.

23. A capacitive fill level measurement device comprising:

a fill level sensor including a plurality of sensor fields that are composed of a metal and are mounted on top of one another;

a selector switch electrically connected on a multipole side to said plurality of sensor fields;

a power supply and evaluation circuit electrically connected to a monopole side of said selector switch for delivering a high frequency power supply voltage that is frequency-spread by a noise signal originating from a noise source;

wherein said frequency-spread power supply voltage leads to at least one of a frequency-spread measurement quantity, a measurement voltage and a measurement current,

wherein the frequency-spread power supply voltage is placed at a first input of a correlator and said at least one of a frequency-spread measurement quantity, a measurement voltage and a measurement current is placed at a second input of said correlator, and

wherein said correlator supplies an output signal to said power supply and evaluation circuit.

24. A capacitive fill level measurement device comprising:

a fill level sensor including a plurality of sensor fields that are composed of a metal and are mounted on top of one another;

a selector switch electrically connected on a multipole side to said plurality of sensor fields;

a power supply and evaluation circuit electrically connected to a monopole side of said selector switch;

a first electrically conductive shield is assigned to at least one of said plurality of sensor fields and said selector switch;

wherein said first electrically conductive shield is always at a potential which corresponds essentially to a potential of said plurality of sensor fields and said selector switch.

25. The capacitive fill level measurement device as claimed in

claim 24

,

wherein said first electrically conductive shield is connected via a current measurement circuit to said plurality of sensor fields and said selector switch, and wherein said current measurement circuit has an essentially negligibly internal resistance.

26. The capacitive fill level measurement device as claimed in

claim 25

,

wherein said current measurement circuit includes a synchronous rectifier, a lowpass filter connected downstream of a synchronous rectifier, and a current-voltage converter connected downstream of said lowpass filter.

27. The capacitive fill level measurement device as claimed in

claim 26

, wherein said power supply and evaluation circuit supplies a power supply voltage between a frame potential and a ground potential.

28. The capacitive fill level measurement device as claimed in

claim 27

, wherein a power supply circuit portion of said power supply and evaluation circuit is connected dc-decoupled to said ground potential by a decoupling capacitor.

29. The capacitive fill level measurement device as claimed in

claim 28

, wherein a evaluation circuit portion of said power supply and evaluation circuit is connected ac-decoupled to said ground potential by a plurality of current-compensated interaction limiting reactors.

30. The capacitive fill level measurement device as claimed in

claim 29

, wherein a frequency of a power supply voltage is controlled by a microprocessor.

31. The capacitive fill level measurement device as claimed in

claim 30

, wherein a gain of said evaluation circuit portion of said power supply and evaluation circuit is controlled by a microprocessor.

32. The capacitive fill level measurement device as claimed in

claim 31

, further including a second electrically conductive shield for shielding said first electrically conductive shield.

33. The capacitive fill level measurement device as claimed in

claim 32

, wherein said second electrically conductive shield is at the ground potential.

34. The capacitive fill level measurement device as claimed in

claim 33

, wherein said plurality of sensor fields are used as transmitters such that said power supply circuit portion of said power supply and evaluation circuit is electrically connected via said selector switch to said plurality of sensor fields.