DE4118170A1

DE4118170A1 - Electrical capacitive level meter esp. for water - has copper@ strip inserted into conducting tube from which it is insulated by styroflex foil or ceramic insulation

Info

Publication number: DE4118170A1
Application number: DE19914118170
Authority: DE
Inventors: Hans Wittkowski
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-06-03
Filing date: 1991-06-03
Publication date: 1992-12-17

Abstract

An electrical capacitance level sensor consists of two mutually insulated conducting surfaces arranged so that the capacitance is varied by a medium on or around one of them. An insulated copper strip can be inserted in an uninsulated conducting tube and insulated by a styroflex foil or ceramic insulation. The tube forms one capacitor pole and a good noise screen. The capacitance is electrically charged and charging and discharging measured using a timer. The charging time corresp. to the water level and the capacitor is charged via a defined resistor. After reaching a defined charge level the capacitor is discharged ready for the next measurement. USE/ADVANTAGE - Esp. for measuring water level. The sensor is capable of measuring level changes of less than one hundredth of a millimetre if the water's dielectric value is constant.

Description

Der Erfindung liegt die Aufgabe zu Grunde, als Sensor, auf Veränderungen oder dem Vorhandensein von verschiedenen Medien, seinen kapazitiven Wert zu ver ändern.The invention is based on the object, as a sensor, for changes or the presence of different media to verify its capacitive value to change.

Der elektrisch kapazitive Pegelmesser soll seine Kapa zität bei Füllhöhenschwankungen ändern. Insbesondere soll der kapazitive Pegelmesser bei Wasser spiegeländerungen, seine Kapazität ändern.The electrically capacitive level meter should be its Kapa Change the level in the event of level fluctuations. In particular, the capacitive level meter for water mirror changes, change its capacity.

Der elektrisch kapazitive Pegelmesser besteht grundsätzlich aus zwei elektrisch leitenden Polen, bei denen mindestens ein Pol so isoliert sein muß, daß ein dazwischen befindliches Medium, die beiden Pole nicht kurzschließen kann. Die Pole des elektrischen Pegelmessers, sind eine Kapazität, die sich entsprechend des zwischen den kapazitiven Polen befindlichen Mediums, z. B. Wasser, im Wert verändert.The electrically capacitive level meter basically exists from two electrically conductive poles, in which at least a pole must be insulated so that an interposed one Medium that cannot short-circuit the two poles. The poles of the electrical level meter, are a capacitance that can corresponding to that between the capacitive poles Medium, e.g. B. water, changed in value.

Der elektrisch kapazitive Pegelmesser kann außen aus einem elektrisch isolierten Metallrohr bestehen, und stellt einen Pol der Kapazität dar. Im Mittelpunkt des Rohres kann ein unisolierter Draht als zweiter Pol der Kapazität zwischen den Rohrenden an einer entsprechenden Aufhängung, gespannt sein.The electrically capacitive level meter can be made from one outside electrically insulated metal pipe exist, and represents one Pole of capacity. At the center of the tube can be a uninsulated wire as the second pole of the capacitance between the pipe ends on a corresponding suspension, tensioned be.

Die beiden Pole des elektrisch kapazitiven Pegelmessers werden durch zwei voneinander isolierten Drähten, an einem Ende des Rohres, welches den oberen Teil des Sensors darstellt, zu einer elektronischen Kapazitätsauswertung geleitet.The two poles of the electrically capacitive level meter are made by two insulated wires, at one end of the tube, which represents the upper part of the sensor, to one electronic capacity evaluation.

Befindet sich der untere Teil des Sensors in einer Flüssigkeit z. B. Wasser, so bewirkt das Wasser je nach Höhe innerhalb des Rohres als Hilfskapazität eine Kapazitätsveränderung des elektrisch kapazitiven Pegelmessers.The lower part of the sensor is in a liquid e.g. B. water, the water causes depending on the height within the tube a change in capacity of the electrical as auxiliary capacity capacitive level meter.

Wird nun an den äußeren Pol der Minuspol und an den Inneren Pol der Pluspol einer Spannungsquelle angeschlossen, so läd sich der Kapazitive Pegelmesser bis zu Sättigung auf. Die Ladezeit wird durch die Größe der Kapazität mitbestimmt. Die Kapazität wird durch die Hohe des Wasserspiegels mitbestimmt. Dadurch verhält sich die Ladezeit der Kapazität propotional zur Wasserhöhe.Now the minus pole on the outer pole and on the inside The positive pole of a voltage source is connected, so it charges the capacitive level meter up to saturation. The loading time is determined by the size of the capacity. The capacity is determined by the height of the water level. Thereby behaves the loading time of the capacity is proportional to the water level.

Claims

1. The sensor consists of two electrically insulated from each other conductive surfaces (e.g. copper). The two areas form a capacitance (sensor capacitance). The two capacitive sensor surfaces must be in relation to each other be arranged that a medium rising on or around it, in this explanation water that changes capacity.

There can be an insulated copper strip in an uninsulated one (conductive) metal tube can be pushed.

The insulation of the copper strip can be done with a styroflex film, depending on the application, also with ceramic insulation respectively.

The tube is a pole of capacity and at the same time one very good shield against interference.

The sensor capacity is electrically charged for measuring, the one pole of the capacitance to a plus voltage and the other pole a negative voltage is connected.

Charging and discharging can be done by a timer module, e.g. B. a IC (NE 555).

The charging time of the sensor capacity corresponds to the water level. The capacity size is determined by the water level, because that Water "connects" the capacity areas with each other.

The relative dielectric constant of air = 1, of distilled water = 80.

The sensor capacity is charged via a defined one Resistance.

If the charging voltage reaches a defined "threshold value", then the duration of this loading process is a size that in proportion the capacity is the water level.

Then the sensor capacity is discharged again to a new one Measure.

Basically, the sensor can measure changes in water level, that are less than a hundredth of a millimeter. However, this measurement is only realistic if the water has correspondingly constant dielectric values.