DE2215950C

DE2215950C - Method for measuring a liquid level according to the conductivity principle

Info

Publication number: DE2215950C
Application number: DE19722215950
Authority: DE
Inventors: Heino Dipl.-Ing.; Hansemann Heinrich; 2800 Bremen Zimmermann
Original assignee: Gustav F. Gerdts Kg, 2800 Bremen
Filing date: 1972-04-01
Publication date: 1973-09-06

Description

und fürand for

a
Die Erfindung betrifft ein Verfahren zum Messen L₂ — Ln · , a
The invention relates to a method for measuring L ₂ - Ln · ,

eines Flüssigkeitsstandes nach dem Leitfähigkcits- 1 -r α
prinzip unter Verwendune von drei Elektroden. 45 ., „ .. ,. „■ ,,· , ,, · , ■
wobei die eine Elektrode ständig in der elektrisch !ei- ^d:uiil f ^a ^{das Μ3}1?^Γ.d'e E'ntaucht.efe. L₁ w,rd ,m tenden Flüssigkeit eingetaucht ist, die zweite Elektrode -gezahngenerator ^G in eine penodjsche Sagezahnals Meßelektrode je nach Niveauhöhe mehr oder spannung ί , der Periode Γ umgewandelt, so daß fur weniger in die Flüssigkeit eintaucht, während die derenMomentanwertg.lt
dritte Elektrode als Gegenelektrode für die ersten 50 /,Ii
beiden dien!, wobei sich zwischen der ersten und der £■■',= L₁ · -— = Lp. · — · — ·
dritten Elektrode ein elektrischer Widerstand in 1 -r a
Abhängigkeit von der spezifischen Leitfähigkeit der y_s _sowj_e Jj₂ werden auf den Komparator KO ge-Flüssigkcit ergibt, während sich zwischen der zweiten geben. Der Komparator ändert immer dann das Vor- und dritten Elektrode ein Widerstand ausbildet, der 55 zeichen seiner Ausgangsspapnung, wenn die Differenz durch die Eintauchtiefe und die spezitische Leit- (j_s _ ι; nahe Null wird:
fiihigkeit bestimmt ist, und daß beide Widerstandswerte Teilspannungcn ergeben, die unter Knmpen- jj_b ■ ..-_ . ..-.. = (J_n · -—-—.
sation von Leilfähigkeitsschwankungen miteinander 1 -j- a T If"
verglichen und zur Anzeige gebracht werden. 60 _{Hicrmit e jbt} ^ _{dann dn Tastverhältnis} a liquid level according to the conductivity kit 1 -r α
principle using three electrodes. 45., "..,. "■ ,, ·, ,, ·, ■
where one electrode is constantly in the electrical! ^{ei- d: uiil} f ^a ^{das Μ3} 1? ^Γ .d'e E'ntaucht.efe. L ₁ w, rd, with the liquid is immersed, the second electrode - tooth generator ^ G is converted into a penodjsche saw tooth as a measuring electrode depending on the level or voltage ί, the period Γ, so that for less is immersed in the liquid, while its momentary value. according to
third electrode as a counter electrode for the first 50 /, Ii
both serve !, whereby between the first and the £ ■■ ', = L ₁ · -— = Lp. · - · - ·
third electrode an electrical resistance in 1 -ra
Depending on the specific conductivity of the y _{s as} _{well as} j _e Jj ₂ are given on the comparator KO ge liquid, while between the second give. The comparator always changes the upstream and third electrodes to form a resistance that is 55 characters of its initial value when the difference due to the immersion depth and the specific guide (j _s _ ι; is close to zero:
ability is determined, and that both resistance values result in partial voltages below Knmpen- jj _b ■ ..-_. ..- .. = (J _n · -—-—.
sation of weakness fluctuations with one another 1 -j- a T If "
can be compared and displayed. 60 _{Hicrmit e jbt} ^ _{then dn duty cycle}

Bei den bekannten Verfahren dieser Art werdenIn the known methods of this type

üblicherweise beide Widerstände der eingetauchten t _usually both resistances of the immersed t _

Elektroden in Reihe geschaltet und bilden dann den ~γ —ο,
einen Zweig einer Brückenschaltung, während derElectrodes connected in series and then form the ~ γ -ο,
a branch of a bridge circuit, during the

andere Zweig durch zwei weitere gleichwertige Wider- 65 das also ein lineares Maß der Eintauchtiefe α ist.other branch through two further equivalent cons 65 which is therefore a linear measure of the immersion depth α .

stände gebildet wird. Die Verstimmung der Brücke Selbstverständlich besteht die Möglichkeit, das be-stands is formed. The detuning of the bridge Of course, there is the possibility to

durch unterschiedliche Eintauchtiefen wird durch schriebene Auswerteverfahren auch bei kapazitiv ar-Due to the different immersion depths, written evaluation methods are also used for capacitive

Messen der Brückendiagonalspannung; angezeigt. beitenden Meßsonden anzuwenden.Measuring the bridge diagonal tension; displayed. used measuring probes.

Hierzu 1 Blatt Zeichnungen1 sheet of drawings

Claims

ι 2 Dies -'- known method, as it is, for. B. in the claims: deir <chen patent specification S42 554 is described. has

1. A method for measuring a Flüssickeits- the '"disadvantage" that the displayed values are not in accordance with the prior Leitfähiakeitsprinzip under Ver linear to Einiauchiiete behave Herner k ,, .in hei wendune of three electrodes, wherein the one 5 groi.'en Fluctuations in the conductivity of the j \.: .- h-Elektrede constantly bridging the electrical conductors / ueie are so low-resistance that the liquid is breathed in. The zv.cite Ekkiroue to errr.-idliehe internal resistance of the feeding Spanais measuring electrode depending on the level height more or nunas. ^

third electrode as a counter electrode for the first ic. It St. -Was dur.h the German Oiieniegun-.ssenntt serves both, whereby the first and 2 ic ":>? Become known, through a special third electrode an electrical resistance geometric design of the tlektrodenuachen e: r- · in Depending on the specific conductivity, linearization is to be achieved, however, the liquid arises in this way, while between the measures ^: .λ can be used in all cases, / wide and third electrode has a resistance of 15 D ^; e invention has set them the task, which is determined by the depth of immersion and the specific conductivity, and that "· both ne-.ei : igcn. and before .lücin a way to linearize resistance values for partial voltages. To propose the one that does justice to all application cases, with compensation for conductivity fluctuations . \ ί . are brought, thereby ae ken η / calibrated and t, acirennt \ on each other are measured and net. that both partial voltages T ₁ and L, as well as partial voltage L ₁ , are measured in a sawtooth generator / v, run '... one inside the other and various sub-voltages are fed, whose voltage amplitude Jn bias voltage C _{1 can be assigned to} a sawtooth generator (SG) Time T equals ί, and that the saw is guided, the voltage amplitude of which in preload L "becomes equal to Γ" with the partial voltage L ₂ in a correctable time 7 and that the saw parameters are compared the output of which is a tooth tension L _s with the partial voltage ί '., in square-wave voltage, the duty ratio of which is compared in a comparator {«()) , to a linear value: the immersion depth.
the output of which is a square wave voltage. The duty cycle is a linear measure "the duty cycle of the square wave voltage can be counted immersion depth is also used to achieve an analog measured value

2. The method according to claim 'characterized in that the calculating leakage voltage is cingeclättet,
shows that to achieve a digital measurement, the pulse duty factor of the square-wave voltage scheme according to FIG. 1 and the graphic representation can be viewed. 35 according to E 1 g. 2 is the formulaic one below

3. The method according to claim 1 characterized by the context of the method explained.

shows that in order to achieve an analog measurement, the result is partial voltages to be measured separately

value the square-wave voltage is smoothed. for