DE2645743C2

DE2645743C2 - Liquid level measuring device

Info

Publication number: DE2645743C2
Application number: DE19762645743
Authority: DE
Inventors: Wolfgang Ing.(grad.) 6230 Kriftel Stark
Original assignee: Mannesmann VDO AG
Current assignee: Mannesmann VDO AG
Priority date: 1976-10-09
Filing date: 1976-10-09
Publication date: 1985-11-07
Also published as: JPS5346766A; DE2645743A1; GB1537809A

Description

g Die Einrichtung umfaßt vier Widerstandselemente 1, £ 2, 3 und 4, die jeweils aus einer Halterung und einem J?" darauf frei gespannten Nickeldraht bestehen und in ver- i? schiedenen Behälterquerschnittsebenen am Behälter jl selbst oder auf einem in den Behälter ragenden starren je oder flexiblen Halter angebracht sind. Die einzelnen £ Widerstandselemente sind elektrisch in Reihe geschali?i tet und von einer Konstantstromquelle 5 gespeist
f3 Die Konstaulstromquelie 5 enthält einen Transistor 6, :| in dessen Emitter-KoIIekior-Kreis die Widerstandsele-Ü mente 1,2,3 und 4 liegen, und einen Operationsverstär- §j ker 7, von dem der Transistor 6 angesteuert wird. Der jg eine Eingang des Operationsverstärkers 7 ist an einen |> Spannungsteiler 8 angeschlossen, in dessen einem Ü Zweig eine Diode 9 liegt. Der andere Eingang des Ope- ψ rationsverstärkers ist an den Emitter des Transistors 6 y angeschlossen. Die Temperaturregelung der Konstantin stromquelle 5 erfolgt über den Temperaturgang der Dir.; ode 9. Aus diesem Grunde empfiehlt es sich, zumindest !''■ die Diode 9 oder aber die gesamte Konstantstromquelle ρ möglichst in unmittelbarer Nähe der widerstandspjei| mente anzuordnen, damit die Diode 9 der gleichen Um-Il gebungstemperatur ausgesetzt ist, wie die Widerstands-Is elemente.g The device comprises four resistance elements 1, £ 2, 3 and 4, each consist of a holder and a J? "it freely tensioned nickel wire and ks in comparable i? different container cross-sectional planes of the container projecting itself or on the container rigid The individual resistance elements are electrically connected in series and fed by a constant current source 5
f3 The Konstaulstromquelie 5 contains a transistor 6,: | in the emitter-KoIIekior-Kreis the resistance elements 1, 2, 3 and 4 lie, and an operational amplifier 7, from which the transistor 6 is controlled. The jg one input of the operational amplifier 7 is connected to a |> voltage divider 8 in whose one U branch a diode 9 is located. The other input of OPE ψ rationsverstärkers is connected to the emitter of the transistor 6 y. The temperature control of the constantine power source 5 takes place via the temperature range of the Dir .; ode 9. For this reason it is advisable to at least! '' ■ the diode 9 or the entire constant current source ρ as close as possible to the resistance pjei | to arrange elements so that the diode 9 is exposed to the same ambient temperature as the resistance Is elements.

I Die an den einzelnen Widerstandselementen abfallenb den Spannungen werden jeweils einem als Komparator |! geschalteten Operationsverstärker 10 bzw. 11, 12, 13 ί ■ zugeführt und dort mit einer Referenzspannung verglil;_? chen. Die Ausgänge der einzelnen Operationsverstärker p stehen jeweils mit einem ihnen zugeordneten Anzeige- β element 14,15,16 bzw. 17 in Verbindung. Die Anzeigest elemente sind in einer Reihe hintereinander, ein Leucht- ]■■ band bifdend in einem Gehäuse 18 untergebrachtI The voltages dropping across the individual resistance elements are each used as a comparator |! switched operational amplifier 10 or 11, 12, 13 ί ■ supplied and verglil there with a reference voltage; _? chen. The outputs of each operational amplifier are each connected to a p their associated display element β 14,15,16 or 17 in conjunction. The display elements are arranged in a row one behind the other, a luminous ] ■■ band bifdend in a housing 18

Hierzu 1 Blatt Zeichnungen1 sheet of drawings

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Claims

1 2 corresponds to such a change in resistance of a patent claim:. Resistance element between an immersed and non-immersed state in the liquid

1. Device for measuring the liquid level device has the disadvantage that the respective environment in a container, in particular a force temperature or the temperature of the liquid Material container of a motor vehicle, with several, is included in the measurement. For example, it can be Resistance arranged at different heights that at low ambient temperatures the Stand elements whose temperature-dependent Wi-Fi facility is available when an empty container is present the change in level between in and exchanged nevertheless indicates a high level, while with State detected and used to control a display of high ambient temperatures and a full container level is used, thereby identifying the device indicates an empty container because draws that the resistance element by the heated liquid

has a high resistance value, which increases the

a) the individual resistance elements (i to 4) in stör iii controls its blocking state

Series connected in series 15 This disadvantage is also known to another

b) a depending on the Umgebungstem- device own (DE-OS 24 28 778), which consists of a Parperatur Regulated constant current source (5), above all, a PTC thermistor with a series of arms is that the resistance elements (1 to device from a Zener diode and a light emitting diode 4) feeds and whose temperature-dependent EIe- exists. Also with this device, the change ment JS) in the immediate vicinity of the resistance 20 of the resistance of the PTC thermistor between the liquid level elements (1 to 4) is arranged, and speed immersed and non-immersed state for

c) a control of the display element is used for each resistance element (1 to 4).
Comparator (10 to 13) is assigned, the same disadvantage of which has another known one input with the respective resistance device for monitoring a fill level element (1 to 4) and the other input 25 (DE-OS 24 23 415) , at which the filling level is assigned a PTC thermistor with a reference resistance and its off, which is operated in a voltage divider circuit with a fixed resistance output connected to a display stage (14 to 17). The voltage divider controls three threshold levels, one of which signals that the level has fallen below, and

2. Device according to claim 1, characterized by a further, whether the PTC thermistor records a short circuit because each resistance element (1, 2, 3, 4) has

contains a freely tensioned resistance wire. These disadvantages of the known devices are intended

3. Device according to claim 1 or 2, thereby being overcome by the invention. It is therefore characterized in that as annealing jurgregelte Kon the object of the invention to create a device constant current source (5) a transistor (6) is provided 35 in which the ambient temperature is not or at most that of an operational amplifier (7) is included in the measurement to a negligible extent controls, one input of which receives a display and display (9) as a temperature-dependent element contain measures that cause costs that are as low as possible Voltage divider (8) and its other inches.

output of the transistor (6) connected 40 This task is based on a device

the type described above is solved by the features of the characterizing part of claim 1

This inventive measure is how

It has been shown that the level accurately measures and displays the level in an extremely wide 45 temperature range.

The invention relates to a device for de device, which is due, among other things, to the tem-measurement of the liquid level in a container, temperature-dependent current storage of the resistance, in particular a fuel tank of a motor vehicle element The indicated temperature thus leads to a change in the current flowing through the arranged resistance elements, their temperature-dependent current flowing through the resistors and thus to a dependent change in resistance between in and out - exercise - air or liquid - heat to be dissipated,
display level is used. In a preferred embodiment of the invention there is already a device of this type, each resistance element contains a freely tensioned known (DE-OS 21 12 220), in which each resistance element 55 resistance wire can, for example, a element with a further fixed resistance the base - Wire made of nickel or a nickel alloy or the voltage divider of a transistor forms, in whose emit the same are used.

A display element is arranged on the collector line as a temperature-controlled constant current source is on. As long as the resistance element is provided outside of the most expedient a transistor, which is from egg-liquid, the transistor is blocked and the μ nem operational amplifier is activated, one of which does not light up the display element. However, as soon as the input of a diode as a temperature-dependent resistance element is immersed in the liquid, element containing voltage divider and its changes due to the better heat dissipation of the input with the output of the transistor ver-resistance value of the resistance element and that is connected. In this embodiment the tempo indicator lights up. The display elements are used in the temperature response of the diode for temperature-dependent communication in the same order as the resistance elements for the constant current source,
arranged so that they form a display tape whose The invention will be explained in more detail with reference to the drawing, which shows a luminous part of the respective liquid level circuit diagram of the device.