Cheap capacity sensor with unique construction

Cheap capacity sensor with unique construction

14. 05. 2012

Recently, researchers at the Brno University of Technology have announced a unique and very interesting electrical connection of a sensor which enables very small changes in environment permittivity to be converted into a digital electric signal.

Current, generally available sensors are technologically complex, and their production and operation is economically much more demanding. Compared to such sensors, this newly-developed capacity sensor is unique in several ways and thanks to the simplicity of the whole connection, it has outstandingly small dimensions, high sensitivity and a surprisingly low price.

Modern life, which according to some people has become overly technical, cannot survive without measurements and measuring technology. Obtaining information on the amount, position or presence of a thing somewhere in space, or the indication of a body of any material, is highly desirable. However, standing in opposition to the desirability of such parameters is price, which plays a key role in selecting such devices.

levny-a-konstrukcne-unikatni-kapacitni-snimac-02The new miniature capacity sensor has been designed to take into account its potential integration, which enables its rational in various applications. Connection of the miniature capacity sensor, completed with an appropriate electrode system, can indicate the presence of a body made of any materials such as stone, wood, plastics (except for extruded ones), metals, oils, water and loose materials. The possibility to detect such a broad range of materials means that the connection will inevitably be used for constructing numerous different types of applications.

levny-a-konstrukcne-unikatni-kapacitni-snimac-01One example might be providing security for valuable exhibited items, where an electrode system is embedded directly in a desk top or table top. Placement of an item (e.g. statuette or book) is indicated by an input signal. If the item is removed, the signal is interrupted. Since the electrode system is embedded in the board, the whole device is not detectable by sight. In a similar way, e.g. a medium flowing through a plastic tube can be indicated from the outside (liquid or powdery materials of any grain size), the precise number of pieces on a line can be indicated or determined, and countless other applications can be used.

The miniature capacity sensor fulfils all the requirements of so far used sensors, while having considerably smaller dimensions and lower purchase price; it is protected as a utility model and has huge potential for application in various commercial fields.

Capacity sensors

Capacity sensors evaluate a change in capacity caused by an object entering the electric field of a condenser.
This means that capacity sensors can sense not only metal but non-conductive materials with sufficiently high permittivity as well.
When chosen correctly, capacity sensors can “see through” some non-metallic materials. Classical surface level sensors work in the same way, sensing the presence or absence of a liquid or grainy materials through a tank wall.

Title figure legend:
Pole snímače a elektrody - Field of sensor and electrodes, Oscilátor - Oscillator, Demodulátor - Demodulator, Klopný obvod - Trigger circuit, Výstupní obvody - Output circuits

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