RS20080063A - Horizontal capacitance sensor - Google Patents

Abstract

Invention herewith described refers to a horizontal capacitance sensor consists of two electrodes which are in one plane and most frequently is achieved on a printed plate as two planes made of conductors. When there is no object for detection, as the distance between the electrodes is relatively high, capacity that the unit value of electrodes make is approximately equal to zero. As the electrodes are extremely thin, smaller than 0.1 mm, the distance between them is relatively large in the unit value of 1 cm the capacitance made by electrodes is considered to be a zero value. When there is no object the plane of the equivalent condenser is in the unit value of 0.1 mm x 1cm and the distance between the electrodes has the unit value of 1 cm then capacitance (C), relatively, proportionally 0.0001 times dialectric constant of air plus parasite capacitor which make two plates in one plane that at one side have an insulator (printed plate) and at the other side a thin polish applied onto the conductor and air. Figure 1 and Figure 2 when the object is in the vicinity of electrodes, it has the unit value of 1 cm and less, between the first electrode E1 and the object and also between the body of the second electrode E2. The total capacity between E1 and E2 is a serial connection of these two capacitors. As the plane existing between electrodes and the object has the unit value of 1 cm x 1 cm and the distance of 1 cm, the capacity of the equivalent capacitor is proportional 0.01 times dialectric constant of air or some other insulating material if the electrodes are positioned in some insulator. From Figure 1 it can be seen that the growth of capacity has the order of magnitude of 100 times. The growth can be even higher when the distance between the object and the electrodes is smaller and has the order of magnitude of 1 mm then the growth of capacity is 1000 times. The equivalent capacity Cx has the unit value of 1 pF. Such an equivalent capacitor is tied to an easily actuating oscillator which oscillates in a frequency proportional to 1/(R1 x Cx) or SQR(LCx)). Depending on the frequency the output is logical, in Figure 4 when the sensor can be used as a switch, Vi analogous tension when the sensor is used as a measuring instrument.