Method and Apparatus for Monitoring a Predefined Filling Level of a Medium in a Container

Patent metadata

Field	Value
Publication number	US-2016018248-A1
Application number	US-201414771841-A
Country	US
Kind code	A1
Filing date	Feb 17, 2014
Priority date	Mar 1, 2013
Publication date	Jan 21, 2016
Grant date	—

Abstract

A method and an apparatus for monitoring a set fill level of a medium in a container using a fill level measuring probe that is designed to operate as a conductive fill level measuring probe in a conductive operating mode and as a capacitive fill level measuring probe in a capacitive operating mode, with a control/evaluation/output unit that is designed to alternately trigger conductive operating mode and capacitive operating mode, and with a control/evaluation/output unit that determines whether the set fill level of the medium in the container has been reached on the basis of the measured values from the two operating modes, and which generates a message when the set fill level is exceeded and/or undershot.

First claim

1 - 14 . (canceled)

15 . A method to monitor a set fill level of a medium in a container, with a filling level meter, comprising the steps of:
operating the filling level meter in a conductive operating mode as a conductive filling level measuring probe; and operating the filling level meter in a capacitive operating mode as a capacitive filling level measuring probe, wherein: said conductive operating mode and said capacitive operating mode being alternately triggered; and the measured values from the two operating modes being used to determine whether the set filling level of the medium in the container has been reached, and with a message being generated when the set filling level is exceeded and/or undershot.

16 . The method according to claim 15 , wherein:
the filling level measuring probe is assigned information that establishes a functional relationship between the measured values of the fill level measuring probe, or variables derived from the measured values of the fill level measuring probe; and at least one medium-specific characteristic of the medium, with switch points being defined by the functional relation that correspond to an exceeding and/or undershooting of the set fill level.

17 . The method according to claim 15 , wherein:
the media-specific characteristic being determined in conductive operating mode (II); and the associated switch point being determined on the basis of the determined media characteristic and the functional relation.

18 . The method according to claim 15 , wherein:
the electrical conductivity or the permittivity being used as the medium-specific characteristic.

19 . The method according to claim 17 , wherein:
the measured values of the fill level measuring probe being provided for monitoring the set fill levels and the associated switch point depending on the determined medium-specific characteristic in conductive operating mode and/or in capacitive operating mode.

20 . The method according to claim 18 , wherein:
the measured values that have been determined in said capacitive operating mode are used for non-conductive media to be monitored or media with a low electrical conductivity; the measured values obtained in said conductive operating mode are used for the media to be monitored with electrical conductivity; and those measured values that are determined in said capacitive operating mode and in said conductive operating mode are used for media to be monitored with a conductivity in an intermediate range (Ill), with the measured values being assigned an appropriate weighting factors depending on the conductivity of the medium.

21 . The method according to claim 20 , wherein:
the measured values obtained in said capacitive operating mode are compared to the measured values obtained in said conductive operating mode for the intermediate range (Ill), and with a plausibility check being performed by this comparison.

22 . An apparatus for monitoring a set fill level of a medium in a container, comprising:
a fill level measuring probe that is designed to operate as a conductive fill level measuring probe in a conductive operating mode and as a capacitive fill level measuring probe in a capacitive operating mode, with: a control/evaluation/output unit that is designed to: alternately trigger the conductive operating mode and the capacitive operating mode, wherein: said control/evaluation/output unit determines whether the set fill level of the medium in the container has been reached on the basis of the measured values from the two operating modes, and which generates a message when the set fill level is exceeded and/or undershot.

23 . The apparatus according to claim 22 , wherein:
said fill level measuring probe is assigned a memory unit in which information is saved that provides a functional relation between at least one media-specific characteristic of the medium and the measured values of the fill level measuring probe or variables derived from the measured values of the filling level measuring probe, with the functional relation determining the switch points for the control/evaluation/output unit.

24 . The apparatus according to claim 22 , wherein:
said fill level measuring probe having a sensor electrode and a guard electrode, with a first electronic unit being provided that is designed to operate said fill level measuring probe in said conductive operating mode, with a second electronic unit being provided that is designed to operate said fill level measuring probe in said capacitive operating mode; and wherein: a switching unit is provided that is used by said control/evaluation/output unit to alternately activate conductive operating mode and capacitive operating mode of said fill level measuring probe.

25 . The apparatus according to claim 22 , wherein:
said first electronic unit or said second electronic unit supplying said sensor electrode with a control signal or said guard electrode with a guard signal depending on the triggered operating mode (I, II).

26 . The apparatus according to claim 25 , wherein:
said control/evaluation/output unit determines whether the set filling level is exceeded and/or undershot on the basis of a tappable signal resulting from said sensor electrode and said control signal and/or the guard signal.

27 . The apparatus according to claim 26 , wherein:
at least one measuring resistor is provided that is used to tap the ratio of guard current to sensor electrode current.

28 . The apparatus according to claim 26 , wherein:
control/evaluation/output unit determines at least a gain from the guard signal and/or the control signal and the current signal, and/or a voltage signal depending on the current signal, and determines whether the fill level of the medium in the container is exceeded or undershot on the basis of the gain.

Assignees

• Endress & Hauser Gmbh & Co Kg
• Endress & Hauser Gmbh & Co Kg

Inventors

• Wernet Armin
• Bechtel Gerd
• Uppenkamp Kaj
• Ferraro Franco

Classifications

• G01F23/263 Primary

  by measuring variations in capacitance of capacitors · CPC title

• G01F23/241 Primary

  for discrete levels · CPC title

• G01F23/266

  measuring circuits therefor · CPC title

• G01F23/243

  Schematic arrangements of probes combined with measuring circuits · CPC title

• G01F23/265

  for discrete levels · CPC title