DD271369A1

DD271369A1 - CAPACITIVE TILT AND LEVEL MEASUREMENT DEVICE

Info

Publication number: DD271369A1
Application number: DD31445388A
Authority: DD
Inventors: Andreas Budich; Albrecht Lerm; Gerd Mueller; Kurt Nicht; Rolf-Gerd Pfeiffer; Hartmut Rinza
Original assignee: Akad Wissenschaften Ddr
Priority date: 1988-04-06
Filing date: 1988-04-06
Publication date: 1989-08-30

Abstract

Die Erfindung betrifft ein kapazitives Neigungs- und Ebenheitsmessgeraet, welches die Messung von Winkelabweichungen in einer Ebene mit hoher Empfindlichkeit und Genauigkeit ermoeglicht. Die Aufgabe der Erfindung, Aenderung der Dieelektrizitaetskonstanten des fluessigen Mediums und Aenderung der Kammergeometrie im beschriebenen Neigungssensor infolge Temperaturaenderungen zu kompensieren, wird erfindungsgemaess dadurch geloest, dass innerhalb des Neigungsmessbereiches der aufgeteilten Messelektroden zusaetzliche Elektrodenbereiche, die wenigstens teilweise staendig mit der dielektrischen Fluessigkeit bedeckt, mit der Massgabe angebracht sind, dass diese bedeckten Flaechenbereiche flaechenmaessig mindestens so gross sind, wie die Haelfte der ins Dielektrikum eintauchenden Messelektrodenanteile und sie bei kleinstmoeglichem Umfang eine groesstmoegliche Flaeche aufweisen. Fig. 2The invention relates to a capacitive inclination and flatness measuring device, which allows the measurement of angular deviations in a plane with high sensitivity and accuracy. The object of the invention to compensate for alteration of the dielectric constant of the liquid medium and change of the chamber geometry in the inclination sensor as a result of temperature changes, is achieved according to the invention by additional electrode regions which at least partially continuously cover the dielectric fluid within the tilt measuring range of the divided measuring electrodes It is appropriate for these covered areas to be at least as large as half of the measuring electrode portions dipping into the dielectric and to have the largest possible area at the smallest possible circumference. Fig. 2

Description

Anhand beiliegender Figuren soll die Erfindung näher illustriert werden. Die Figuren zeigen dabei maßstäbliche Ausföhrungsbeispiel für einen auf einen bestimmten Winkelbereich von ±4° optimierten Sensor, worauf die Erfindung jedoch nicht beschränkt ist. Die Kammer des kapazitiven Neigungssensors besteht aus zwei Kammerwänden mit den innen aufgebrachten Flächenelektroden und dem volumenbestiminenden Abstandsrahmen. Die Sensorelektroden 1 und 2 und die in diesem Beispiel als geschlossene Fläche ausgebildete Gegenelektrode 3 werden zur Hälfte von einem flüssigem Dielektrikum bedeckt, wobei die waagerechten Zwischenstriche in der Kammermitte dabei das Flüssigkeitsniveau des Dielektrikums in der Nullage bezeichnen. Ddπ h Drehung bzw. Neigung des kapazitiven Sensors ergibt sich eine winkelproportionale Kapazitätsänderung, die durch eine nachgeschaltete Elektronik in ein kalibriertes Spannungssignal umgesetzt wird. Durch die erfindungsgema'Je, vollständig ins Dielektrikum eingotauchte zusätzliche Referenzelektrode 4 werden kapazität&beeinflussende Parameter der Umgebung (Temperatur, Atmosphärendruck) als Kapazitätsänderung gemessen und elektronisch bei ücksichtigt. Auf diese Weise gelingt es, temperaturbedingte Winkelfehler und Langzeitdriften um eine Größenordnung auf 0,003%/Kzu senken.With reference to accompanying figures, the invention will be illustrated in more detail. The figures show scaled Ausföhrungsbeispiel for an optimized to a certain angular range of ± 4 ° sensor, to which the invention is not limited. The chamber of the capacitive inclination sensor consists of two chamber walls with the inside applied surface electrodes and the volume-determining spacer frame. The sensor electrodes 1 and 2 and the counterelectrode 3 formed in this example as a closed surface are half covered by a liquid dielectric, the horizontal intermediate lines in the chamber center denoting the liquid level of the dielectric in the neutral position. Ddπ h rotation or inclination of the capacitive sensor results in an angle-proportional capacitance change, which is converted by a downstream electronics in a calibrated voltage signal. By virtue of the additional reference electrode 4 wholly immersed in the dielectric according to the invention, capacitance & influencing parameters of the environment (temperature, atmospheric pressure) are measured as capacitance changes and taken into account electronically. In this way, it is possible to reduce temperature-induced angular errors and long-term drift by an order of magnitude to 0.003% / K.

Abhängend von den Materialeigenschaften des Dielektrikums, derart der Kammergestaltung und der Einsatzumgebung bringt eine erfindungsgemäße Zusatzelektrode, entsprechend Figur 2 gestaltet, zur Kompensation von meßv/ertverfälschenden Kapazitätsänderungen im Dampfraum und im dielektrikumgefüllten Kammerraum eine weitere Verringerung der Meßfehler.Depending on the material properties of the dielectric, such as the chamber design and the environment of use, an additional electrode according to the invention, designed in accordance with FIG. 2, brings about a further reduction of the measurement errors in order to compensate for changes in capacitance in the vapor space and in the chamber chamber filled with dielectric changes.

Claims

A high sensitivity capacitive tilt and flatness meter using a differential capacitor type electrode pair between which electrodes is at least partially a dielectric liquid having no wettability of the electrodes, characterized in that additional electrode portions within the tilt measuring range of the split measuring electrodes at least partially permanently covered with the dielectric fluid, with the proviso that these covered surface areas are at least as large in area as half of the measuring electrode portions dipping into the dielectric and have the largest possible area at the smallest possible circumference.

2. Capacitive tilt and toenheitsmeßgerät according to claim 1, characterized in that the nonf lüssigkeitsbedeckten electrode areas - are electrically connected to the liquid-covered electrode areas of the same polarity - preferably formed with the same dimensioning dimension, symmetrical to these covered areas.

For this 2 pages drawings

Field of application of the invention

The invention relates to t ^; n capacitive inclination and planeness meter with the inclination, Ebenhoits- and angle measurements relative to the gravitational vector of the earth with high sensitivity and accuracy are possible. Such measurement tasks exist for example in mining and road construction.

Characteristic of the known technical solutions

Measuring devices of the type mentioned are known and there are numerous suggestions. To outline the area of the prior art in which this invention falls, the following patents are to be mentioned by way of example: EP 035,340; DD 212,000; DD 212,001; DD 114,677; SU 794,210; DE 3,608,274; 3,249,101; 3,406,174; US 4,023,278; GB 2,070,774. Closely related to the invention is the solution described in DD 226.C68, in which a nonconductive liquid having a constant dielectric constant, a good wetting property, a low foaming tendency and an optimum viscosity is arranged in the space between two symmetrical pairs of electrodes. The electrode pairs are designed according to the principle of a differential condenser. The problem with this solution is the demands placed on the liquid dielectric medium, which still have to be extended by one essential, namely a medium having a low vapor pressure. Such ideal media do not exist. In particular, when using such a tilt sensor within larger temperature ranges (240-320 K) considerable problems arise as a result of the temperature dependence of the dielectric constant of the liquid medium and the chamber geometry, which, since the use of a differentiulkondensators can not eliminate this effect, leading to erroneous measurements.

Object of the invention

It is the object of the invention to provide an inclinometer which allows high sensitivity and accuracy measurement in large temperature ranges.

Explanation of the essence of the invention

The invention has for its object to compensate for changes in the dielectric constant of a liquid medium and change in the chamber geometry in said tilt sensor as a result of Temperatii changes. According to the invention the object is achieved in that within the Neigungsmeßberfeiches the split measuring electrodes additional electrode areas which are at least partially constantly covered with the dielectric liquid, are provided with the proviso that these covered surface areas in terms of area are at least as large as half of dipping into the dielectric Meßelektrodenanteile and they have the largest possible area with the smallest possible extent, the last measure is not a bi restriction on circular surfaces, but it refers to the, due to the special design of the sensor rea'isk rbaren electrode surfaces. A reference electrode design which is particularly advantageous in the context of the invention is characterized in that the non-liquid-covered electrode regions -electrically connected to the liquid-covered electrode regions of the same polarity-are formed, preferably with the same dimensioning dimension, symmetrically with respect to these covered regions. With the help of the invention, it is possible to reduce temperature-induced bending angle with long-term drift by an order of magnitude relative to the state of the art to 0.003% / K.