Devices and methods for capacitive foam detection in liquid containers

Patent metadata

Field	Value
Publication number	US-11360040-B2
Application number	US-201917258370-A
Country	US
Kind code	B2
Filing date	Jul 9, 2019
Priority date	Jul 13, 2018
Publication date	Jun 14, 2022
Grant date	Jun 14, 2022

Abstract

Devices and corresponding methods for capacitive foam detection in liquid containers are disclosed. The device has a sensor with a measurement electrode having a plurality of sub-electrodes, a bottom plate that is used as a counter electrode for arranging a liquid container, a sensor electronic unit that is connected to the measurement electrode and the bottom plate and is adapted to determine an impedance, in particular a capacitance, between the measurement electrode and the bottom plate, and an evaluation unit, the measurement electrode being arranged substantially perpendicularly to the bottom plate.

First claim

The invention claimed is:

1. A device for capacitive foam detection in liquid containers ( 1 ) comprising:
a sensor ( 2 ) having a measurement electrode ( 3 );
a conductive bottom plate ( 4 ) suitable for arranging at least one liquid container ( 1 ) or a carrier unit ( 5 ) having at least one receptacle ( 6 ) for receiving a liquid container ( 1 );
a sensor electronic unit ( 7 ) which is connected to the measurement electrode ( 3 ) and the conductive bottom plate ( 4 ) and is adapted to determine an impedance, between the measurement electrode ( 3 ) and the conductive bottom plate ( 4 ); and
an evaluation unit (A),
wherein
the measurement electrode ( 3 ) is arranged substantially perpendicularly to the conductive bottom plate ( 4 ), in particular is arranged vertically to the horizontally arranged conductive bottom plate ( 4 );
the sensor electronic unit ( 7 ) comprises a signal generator with which a first signal for exciting the measurement electrode ( 3 ) at a first frequency and a second signal for exciting the measurement electrode ( 3 ) at a second frequency can be generated; and
the evaluation unit (A) is adapted to detect, based on the impedance, a presence of foam (S) in the liquid container ( 1 ) if a difference between a first measurement signal in the case of exciting the measurement electrode ( 3 ) with the first signal and a second measurement signal in the case of exciting the measurement electrode ( 3 ) with the second signal or a ratio of the first and second measurement signals exceeds a predetermined threshold value,
characterized in that the measurement electrode ( 3 ) comprises a plurality of sub-electrodes ( 31 , 32 , 33 ) which are arranged one above the other in the vertical direction and of which simultaneously a plurality can be selectively connected to the sensor electronic unit ( 7 ).

2. The device according to claim 1 , further comprising a multiplexer (MUX) with which the selected at least two sub-electrodes ( 31 , 32 , 33 ) can be connected to the sensor electronic unit ( 7 ).

3. The device according to claim 1 , wherein the measurement electrode ( 3 ) is arranged on a front side (V) of a sensor carrier ( 8 ) above a guard electrode ( 9 ), wherein the guard electrode ( 9 ) is located in particular between the measurement electrode ( 3 ) and the conductive bottom plate ( 4 ).

4. The device according to claim 1 , wherein the measurement electrode ( 3 ) is arranged on a front side (V) of a sensor carrier ( 8 ) between a first and a second guard electrode ( 91 , 92 ).

5. The device according to claim 4 , wherein a third guard electrode ( 93 ) is arranged on a rear side (H) or an intermediate layer (Z) of the sensor carrier ( 8 ), wherein the third guard electrode ( 93 ) covers at least the measurement electrode ( 3 ).

6. The device according to claim 1 , wherein the first frequency lies in a range from 1 kHz to 1 MHz, and the second frequency lies in a range from 1 MHz to 50 MHz, wherein both the first and the second frequency are in particular differently adjustable, and wherein the first and second signals are in particular sinusoidal signals.

7. A method for capacitive foam detection in a liquid container ( 1 ) comprising the steps of:
providing a conductive bottom plate ( 4 ), which is arranged horizontally, and a sensor ( 2 ) having a measurement electrode ( 3 ), which is arranged vertically, and a sensor electronic unit ( 7 ), which is connected to the measurement electrode ( 3 ) and the conductive bottom plate ( 4 );
arranging the liquid container ( 1 ) or a carrier unit ( 5 ) having at least one receptacle ( 6 ) for accommodating the liquid container ( 1 ) on the conductive bottom plate ( 4 ) next to the measurement electrode ( 3 );
exciting the measurement electrode ( 3 ) with a first signal at a first frequency in particular in a range from 1 kHz to 1 MHz;
determining a first measurement signal depending on an impedance, between the measurement electrode ( 3 ) and the conductive bottom plate ( 4 );
exciting the measurement electrode ( 3 ) or a second measurement electrode ( 3 ′), which is connected to the sensor electronic unit ( 7 ) and the conductive bottom plate ( 4 ), with a second signal at a second frequency, in particular in a range from 1 MHz to 50 MHz;
determining a second measurement signal depending on the impedance, between the measurement electrode ( 3 ) or the second measurement electrode ( 3 ′) and the conductive bottom plate ( 4 ); and
outputting an identifier signaling the presence of foam (S) in the liquid container ( 1 ) if a difference between the first and second measurement signals or a ratio of the first and second measurement signals exceeds a predetermined threshold value,
characterized in that the measurement electrode ( 3 ) comprises a plurality of sub-electrodes ( 31 , 32 , 33 ) arranged one above the other in the vertical direction, and exciting the measurement electrode ( 3 ) with the first and second signals comprises selecting at least two sub-electrodes ( 31 , 32 , 33 ) and exciting only the at least two selected sub-electrodes ( 31 , 32 , 33 ).

8. The method according to claim 7 , wherein the selection of the at least two sub-electrodes ( 31 , 32 , 33 ) is effected via a multiplexer (MUX) which connects the at least two selected sub-electrodes ( 31 , 32 , 33 ) to the sensor electronic unit ( 7 ).

9. The method according to claim 7 , further comprising the step of:
moving a carrier unit ( 5 ) with a plurality of receptacles ( 6 ) for accommodating sample tubes ( 1 ) in a horizontal direction past the measurement electrode ( 3 ),
wherein the determination of the measurement signal is performed during the movement of the carrier unit ( 5 ) past the measurement electrode ( 3 ).

10. An alternative device for capacitive foam detection in liquid containers ( 1 ) comprising:
a sensor ( 2 ) having a measurement electrode ( 3 ), which is arranged coplanar on a horizontal bottom plate ( 4 ) or integrated in the horizontal bottom plate ( 4 );
an at least partially conductive carrier unit ( 5 ) having at least one receptacle ( 6 ) for accommodating a liquid container ( 1 ), wherein the at least partially conductive carrier unit ( 5 ) is in particular grounded;
a sensor electronic unit ( 7 ) which is connected to the measurement electrode ( 3 ) and the at least partially conductive carrier unit ( 5 ) and is adapted to determine an impedance between the measurement electrode ( 3 ) and the at least partially conductive carrier unit ( 5 ); and
an evaluation unit (A),
wherein
the at least partially conducive carrier unit ( 5 ) is arranged on the horizontal bottom plate ( 4 ) in such a way that the receptacle ( 6 ) lies above or on the measurement electrode ( 3 ), and the at least partially conductive carrier unit ( 5 ) is electrically insulated from the measurement electrode ( 3 );
the sensor electronic unit ( 7 ) comprises a signal generator with which a first signal for exciting the measurement electrode ( 3 ) at a first frequency and a second signal for exciting the measurement electrode ( 3 ) at a second frequency can be generated; and
the evaluation unit (A) is adapted to detect, based on the impedance a presence of foam (S) in the liquid container ( 1 ) if a difference between or a ratio of a first measurement signal in the case of exciting the measurement electrode ( 3 ) with the first signal and a second measurement signal in the case of exciting the measurement electrode ( 3 ) with the second signal exceeds a predetermined threshold value.

11. The device according to claim 10 , wherein the measurement electrode ( 3 ) is arranged on or in a sensor carrier ( 8 ) and is surrounded by a guard electrod

Assignees

• Tecan Trading Ag

Inventors

• Ott Philipp

Classifications

• G01F23/265

  for discrete levels · CPC title

• G01N27/226 Primary

  Construction of measuring vessels; Electrodes therefor · CPC title

• G01F23/268

  mounting arrangements of probes · CPC title

• G01F23/266

  measuring circuits therefor · CPC title

• G01F23/26 Primary

  by measuring variations of capacity or inductance of capacitors or inductors arising from the presence of liquid or fluent solid material in the electric or electromagnetic fields · CPC title