DE3824663A1 - Device for continuous level measurement in liquids, by means of a chain of series- or parallel-connected, temperature-dependent resistors, which are heated by an electrical current - Google Patents

Device for continuous level measurement in liquids, by means of a chain of series- or parallel-connected, temperature-dependent resistors, which are heated by an electrical current

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Publication number
DE3824663A1
DE3824663A1 DE19883824663 DE3824663A DE3824663A1 DE 3824663 A1 DE3824663 A1 DE 3824663A1 DE 19883824663 DE19883824663 DE 19883824663 DE 3824663 A DE3824663 A DE 3824663A DE 3824663 A1 DE3824663 A1 DE 3824663A1
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Germany
Prior art keywords
temperature
resistance
liquid
immersed
case
Prior art date
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Ceased
Application number
DE19883824663
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German (de)
Inventor
Wolfgang Prof Dr Ing Thelen
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Individual
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Individual
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Priority to DE19883824663 priority Critical patent/DE3824663A1/en
Publication of DE3824663A1 publication Critical patent/DE3824663A1/en
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
    • G01F23/246—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid thermal devices
    • G01F23/247—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid thermal devices for discrete levels
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F23/00—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm
    • G01F23/22—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water
    • G01F23/24—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid
    • G01F23/246—Indicating or measuring liquid level or level of fluent solid material, e.g. indicating in terms of volume or indicating by means of an alarm by measuring physical variables, other than linear dimensions, pressure or weight, dependent on the level to be measured, e.g. by difference of heat transfer of steam or water by measuring variations of resistance of resistors due to contact with conductor fluid thermal devices

Abstract

A device is described for level measurement in liquids, which uses the immersion depth of a resistor strip with a positive-temperature-coefficient behaviour (Figure 3) or with a negative-temperature-coefficient behaviour (Figure 4) for the level measurement. The resistor strips are, in this case, heated directly by an electric current. The portion of the resistor which is immersed is held at the temperature of the cooling liquid; the part which is not immersed has a significantly higher temperature than the immersed part, because of its electrical heating and the far poorer cooling effect of the surrounding gas (vapour of the liquid itself or air). In this case, in the case of positive-temperature-coefficient material, the partial resistance (Figure 1) increases in the non-immersed part, in the case of negative-temperature-coefficient material, the partial resistance (Figure 3) decreases in the non-immersed part. If the resistance Ro is known in the case of a fully immersed measuring element, the immersion depth can be determined by a comparison of Ro and the actual resistance. <IMAGE>

Description

Nieveaumessung in Flüssigkeiten gehört zu den häufigsten Meßaufgaben. Als übliche Lösung gelten Schwimmer mit durch die Schwimmerbewegung betätigten Potentiometern, luftgespülten Druckmeßsonden, Ultraschall- Verfahren mit Bestimmung der Flüssigkeitsspiegelhöhe, Wägeverfahren, Verfahren mit Messung der Kapazität eines flüssigkeitsgefüllten Konden­ sators oder mit Messung des Flüssigkeitswiderstandes. Als Grenzwertgeber für Flüssigkeitsstände kennt man auch temperaturabhängige Widerstände. Als Vorteil des hier betrachteten Verfahrens kann gelten, daß die Meßwertgewinnung ohne bewegte Teile, ohne komplizierte Elektronik und ohne größere Verschmutzungsgefahr erfolgt. Dabei wird die Flüssigkeit im Bereich der Widerstandskombination infolge des fließenden Heizstroms nur leicht erwärmt. Der in die Flüssigkeit tauchende Teil der Kaltleiterkette oder der Heißleiterkette hat im wesentlichen die Temperatur (T f ) der Flüssig­ keit und damit einen dieser Temperatur entsprechenden Leitwert G f . Der ausgetauchte Teil der Widerstandskette wird durch den fließenden Heizstrom auf eine Temperatur zwischen 10-30 K oberhalb der Temperatur T f erwärmt.Level measurement in liquids is one of the most common measuring tasks. The usual solution are floats with potentiometers actuated by the float movement, air-flushed pressure measuring probes, ultrasound methods with determination of the liquid level height, weighing methods, methods with measurement of the capacity of a liquid-filled capacitor or with measurement of the liquid resistance. Temperature-dependent resistors are also known as limit switches for liquid levels. One advantage of the method considered here is that the measurement can be obtained without moving parts, without complicated electronics and without a greater risk of contamination. The liquid in the area of the resistor combination is only slightly heated due to the flowing heating current. The part of the PTC thermistor chain or the thermistor chain immersed in the liquid essentially has the temperature (T f ) of the liquid and thus a conductivity G f corresponding to this temperature. The immersed part of the resistor chain is heated by the flowing heating current to a temperature between 10-30 K above the temperature T f .

Somit besteht bei PTC-Verhalten des Widerstandsmaterials der Widerstand (2) der Kaltleiteranordnung aus zwei parallelen Widerständen R f (eingetaucht) und R D (oberhalb des Flüssigkeitsspiegels). Da wegen der üblichen Kalt­ leitercharakteristik Δ R D » Δ R f ist, trägt der Leitwert von Δ R D nur sehr wenig zum Gesamtleitwert bei. In Flüssigkeit ist die Kühlung wesentlich besser und der LeitwertThus, with PTC behavior of the resistance material, the resistor ( 2 ) of the PTC thermistor arrangement consists of two parallel resistors R f (immersed) and R D (above the liquid level). Since Δ R D Δ Δ R f because of the usual PTC characteristic, the conductance of Δ R D contributes very little to the overall conductance. In liquid the cooling is much better and the conductivity

groß.large.

Eine Messung des Gesamtleitwertes erfolgt über den Strom durch den Kon­ standwiderstand (4) und ergibt somit einen von der Eintauchtiefe abhän­ gigen Wert, der direkt zur Niveaumessung verwertet werden kann. Die Temperatur von Flüssigkeit und Dampfraum über Flüssigkeitsniveau lassen sich durch Messen dieser Werte rechnerisch eliminieren.The overall conductance is measured via the current through the resistance resistor ( 4 ) and thus results in a value dependent on the immersion depth, which can be used directly for level measurement. The temperature of the liquid and vapor space above the liquid level can be mathematically eliminated by measuring these values.

ersetzt man R durch den jeweiligen Leitwert, also R is replaced by the respective conductance, i.e.

folgt G = (n-x) Δ G f + Δ G D .
n = Gesamtzahl der Teilwiderstände Δ R,
x = Zahl der ausgetauchten Widerstände. follows G = (nx) Δ G f + Δ G D.
n = total number of partial resistances Δ R ,
x = number of resistors exchanged.

Liegt der Leitwert G (2) in Reihe mit einem Meßwiderstand R o (4) und einer Konstantspannungsquelle U o (3 a), so ist der Spannungsabfall an R (4) proportional zum Strom durch G. Da G eine Funktion der Eintauchtiefe ist, ist auch der Spannungsabfall U Th eine Funktion der Temperatur.If the conductance G ( 2 ) is in series with a measuring resistor R o ( 4 ) and a constant voltage source U o ( 3 a ), the voltage drop across R ( 4 ) is proportional to the current through G. Since G is a function of the immersion depth, the voltage drop U Th is also a function of the temperature.

Bei NTC-Verhalten setzt sich der Gesamtwiderstand R aus einer Reihen­ schaltung von Heißleitern (1) zusammen, von denen die eingetauchten Elemente ihren R f -Widerstand behalten und die ausgetauchten Elemente, beheizt durch den elektrischen Strom, ihren Widerstand stark vermindern.With NTC behavior, the total resistance R is made up of a series connection of thermistors ( 1 ), of which the immersed elements retain their R f resistance and the immersed elements, heated by the electrical current, greatly reduce their resistance.

R = (n-x) Δ R f + Δ R D R = (nx) Δ R f + Δ R D

Wird die gesamte Anordnung aus einer Konstantstromquelle I o (3 b) gespeist, ist die über den Gesamtwiderstand R abfallende Spannung von R und damit von der Eintauchtiefe abhängig.If the entire arrangement is fed from a constant current source I o ( 3 b ), the voltage falling across the total resistance R depends on R and thus on the immersion depth.

Claims (4)

1. Vorrichtung zur stetigen Niveaumessung in Flüssigkeiten, bestehend aus einer Anzahl von temperaturabhängigen Widerständen in einer Serien- oder Parallelschaltung als Kette in die Flüssigkeit hineinhängend, die durch einen elektrischen Strom beheizt, ihren Widerstand ändern, sofern sie sich außer­ halb der Flüssigkeit befinden, ihren Widerstand jedoch nicht wesentlich ändern, sofern sie in die kühlende Flüssigkeit eintauchen.1. Device for continuous level measurement in liquids, consisting of a number of temperature dependent resistors in a series or Parallel connection as a chain suspended in the liquid through a heated electric current, change their resistance provided they are out half of the liquid, but its resistance is not essential change if they are immersed in the cooling liquid. 2. Vorrichtung nach Anspruch 1, bestehend aus einem in der Masse leitenden Band oder Streifen mit temperaturabhängigem Widerstand, durch einen elek­ trischen Strom beheizt, die, teilweise in eine Flüssigkeit eintauchend, dort ihren Widerstand nicht wesentlich ändert, während der Streifenteil oberhalb des Niveaus der Flüssigkeit entsprechend der durch die Beheizung auftretenden Temperatur den Zahlenwert seines Widerstandes vermindert (NTC) oder vermehrt (PTC).2. Device according to claim 1, consisting of a conductive in the mass Band or strip with temperature-dependent resistance, by an elec heated electric current, which is partially immersed in a liquid, their resistance there does not change significantly while the strip part above the level of the liquid corresponding to that caused by the heating occurring temperature reduces the numerical value of its resistance (NTC) or increased (PTC). 3. Vorrichtung nach Anspruch 1 oder 2, durch je einen Widerstand stets unter dem Flüssigkeitsspiegel und einem Widerstand stets über dem Flüssig­ keitsspiegel im Dampfraum mit gleichem Temperaturverhalten wie die Vor­ richtung nach Anspruch 1 oder 2, die beide zusammen zur Kompensation der Temperaturschwankungen der Flüssigkeit und des darüber befindlichen Dampfraumes bei der Auswertung der Widerstandsänderung des Niveaufühlers (Eintauchendes Band oder Streifen) dienen.3. Device according to claim 1 or 2, always by a resistor below the liquid level and a resistance always above the liquid level in the steam room with the same temperature behavior as the previous one Direction according to claim 1 or 2, both together for compensation the temperature fluctuations of the liquid and that above it Steam room when evaluating the change in resistance of the level sensor (Immersing tape or strip). 4. Vorrichtung nach Anspruch 1, 2 und 3, bei der nach Maßgabe der Be­ hältertiefe die beiden Leiter mit dem verbindenden kaltleitenden Wider­ ständen durch einfaches Abschneiden und nachfolgendes Isolieren auf die Meßlänge eingestellt werden können.4. Apparatus according to claim 1, 2 and 3, in which according to the loading deep the two conductors with the connecting cold conducting counter by simply cutting them off and then isolating them Measuring length can be set.
DE19883824663 1988-07-15 1988-07-15 Device for continuous level measurement in liquids, by means of a chain of series- or parallel-connected, temperature-dependent resistors, which are heated by an electrical current Ceased DE3824663A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
DE19883824663 DE3824663A1 (en) 1988-07-15 1988-07-15 Device for continuous level measurement in liquids, by means of a chain of series- or parallel-connected, temperature-dependent resistors, which are heated by an electrical current

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE19883824663 DE3824663A1 (en) 1988-07-15 1988-07-15 Device for continuous level measurement in liquids, by means of a chain of series- or parallel-connected, temperature-dependent resistors, which are heated by an electrical current

Publications (1)

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DE3824663A1 true DE3824663A1 (en) 1989-01-05

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0477851A2 (en) * 1990-09-25 1992-04-01 Alcatel Cit Circuit for processing a heat loss dependent signal of a resistor and application thereof
DE19849706A1 (en) * 1998-10-28 2000-05-04 Walther Menhardt Level measurement system with digital signal output has individual sensors at different levels with signals output via common signal line using resistance value dependent time offsets
EP1310631A2 (en) * 2001-05-26 2003-05-14 Services Petroliers Schlumberger Apparatus and method for locating a fluid interface
EP1600747A1 (en) * 2004-05-29 2005-11-30 ITW Automotive Products GmbH & Co. KG A thermoelectric device for measuring the level and/or the temperature of a liquid in a container
WO2015144627A1 (en) * 2014-03-27 2015-10-01 Carrier Corporation Device and method for determining the filling height of liquid in a container
US11048279B2 (en) * 2016-05-31 2021-06-29 Pointwatch Systems Llc Liquid handling system monitoring systems and methods

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Publication number Priority date Publication date Assignee Title
DD155207A1 (en) * 1980-12-10 1982-05-19 Bernd Wuschko DEVICE FOR THE ELECTRIC REMOTE DISPLAY OF THE GROUNDWATER LEVEL IN THE LOCKER MOUNTAIN
US4350968A (en) * 1981-01-29 1982-09-21 The United States Of America As Represented By The United States Department Of Energy Liquid level detector
DE3116987A1 (en) * 1981-04-29 1982-11-18 Draloric Electronic GmbH, 8672 Selb Electrothermal filling level display device
DE3125591A1 (en) * 1981-06-30 1983-01-20 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Level meter
DE3148533A1 (en) * 1981-12-08 1983-06-16 Siemens AG, 1000 Berlin und 8000 München Device for measuring the level in a vessel containing a liquid
DE3148383A1 (en) * 1981-12-07 1983-06-16 Siemens AG, 1000 Berlin und 8000 München Device for measuring the filling level
DE3315592A1 (en) * 1982-04-30 1983-11-03 Jaeger, 92303 Levallois-Perret, Hauts-de-Seine DEVICE FOR STATICALLY MEASURING THE LEVEL OF A LIQUID
DE3341630A1 (en) * 1983-11-17 1985-05-30 Kraftwerk Union AG, 4330 Mülheim Measuring device for the liquid level in a container
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US4724415A (en) * 1983-09-21 1988-02-09 Jaeger Level measuring probes

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DD155207A1 (en) * 1980-12-10 1982-05-19 Bernd Wuschko DEVICE FOR THE ELECTRIC REMOTE DISPLAY OF THE GROUNDWATER LEVEL IN THE LOCKER MOUNTAIN
US4350968A (en) * 1981-01-29 1982-09-21 The United States Of America As Represented By The United States Department Of Energy Liquid level detector
DE3153284C2 (en) * 1981-04-18 1987-01-02 Telefunken Electronic Gmbh, 7100 Heilbronn, De Thermoresistive filling level measurement device
DE3116987A1 (en) * 1981-04-29 1982-11-18 Draloric Electronic GmbH, 8672 Selb Electrothermal filling level display device
DE3125591A1 (en) * 1981-06-30 1983-01-20 Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt Level meter
DE3148383A1 (en) * 1981-12-07 1983-06-16 Siemens AG, 1000 Berlin und 8000 München Device for measuring the filling level
DE3148533A1 (en) * 1981-12-08 1983-06-16 Siemens AG, 1000 Berlin und 8000 München Device for measuring the level in a vessel containing a liquid
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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0477851A2 (en) * 1990-09-25 1992-04-01 Alcatel Cit Circuit for processing a heat loss dependent signal of a resistor and application thereof
EP0477851A3 (en) * 1990-09-25 1993-04-28 Alcatel Cit Circuit for processing a heat loss dependent signal of a resistor and application thereof
DE19849706A1 (en) * 1998-10-28 2000-05-04 Walther Menhardt Level measurement system with digital signal output has individual sensors at different levels with signals output via common signal line using resistance value dependent time offsets
EP1310631A2 (en) * 2001-05-26 2003-05-14 Services Petroliers Schlumberger Apparatus and method for locating a fluid interface
EP1310631A3 (en) * 2001-05-26 2004-03-10 Services Petroliers Schlumberger Apparatus and method for locating a fluid interface
EP1600747A1 (en) * 2004-05-29 2005-11-30 ITW Automotive Products GmbH & Co. KG A thermoelectric device for measuring the level and/or the temperature of a liquid in a container
US7258483B2 (en) 2004-05-29 2007-08-21 Itw Automotive Products Gmbh & Co. Kg Device for measuring the level and/or the temperature in a container
WO2015144627A1 (en) * 2014-03-27 2015-10-01 Carrier Corporation Device and method for determining the filling height of liquid in a container
CN106461301A (en) * 2014-03-27 2017-02-22 开利公司 Device and method for determining the filling height of liquid in a container
US11048279B2 (en) * 2016-05-31 2021-06-29 Pointwatch Systems Llc Liquid handling system monitoring systems and methods

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