KR920002623Y1 - Electric capacitor type sensor for very small difference measuring - Google Patents

Abstract

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Description

Capacitive Sensor for Small Displacement Measurement

1 is a cross-sectional structure diagram of a capacitive sensor for small displacement measurement.

The present invention relates to a capacitive sensor (CAPACITIVE TYPE SENSOR) for measuring a small displacement (0-25mm) using a change in capacitance (CAPACITANCE).

Sensors that measure displacement using the change of capacitance have a method of using a single capacitor and two capacitors. Sensors using a single capacitor have more accuracy, linearity, etc. than sensors using two capacitors. Not good.

CAPACITIVE DISPLACEMENT SENSOR, which uses two capacitors, increases the capacitance output from one capacitor of the sensor constituting the two capacitors when the input changes. The capacitance output from the instrument decreases and appears as the difference between the capacitance outputs from these two capacitance groups.

The reason why the capacitive sensor for displacement measurement is used as two capacitive sensors is that the electrodes of the capacitive capacitor are changed in the same way with respect to changes in the surrounding environment, so that the stability, the linearity and the output are high.

In practice, however, it is composed of two or more electrodes, a support supporting them, an insulator for insulation between electrodes, and a moving body of electrodes for generating capacitance, and thus thermal expansion, vibration, pressure, and humidity. It is difficult to have the same response characteristics for each other's influences such as and geometric distortion.

The design of the present invention basically consists of two capacitive displacement sensors, but due to the asymmetry of the electrode support, the parallelism and straightness between the electrodes, and the moving body of the electrodes, the output value of the sensor appears as a nonlinear characteristic. In order to improve, the mechanical displacement of the sensor generated by the input displacement is sensed through the GUARD electrode.

Therefore, two capacitors are designed symmetrically so as not to be greatly influenced by external influences, and instead of changing the distance between the electrodes, the displacement area of the electrode is changed by the movement of the guard electrode, so that the displacement measuring electricity has excellent characteristics. The capacitive sensor was created.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 shows a cross-sectional structure of a capacitive sensor for microdisplacement measurement, in which the two external electrodes constituting the sensor, the capacitors 1 and 1 ', are all composed of cylinders, and both Each is separated and fixed, and the internal electrodes 3 of the capacitor 1 and 1 'are commonly used.

The guard electrode 4 was moved between the capacitor 1 and the internal electrode 3 to show the difference in capacitance generated in the two capacitors 1 and 1 '.

At this time, the capacitance generated in one capacitance fixed in the cylinder (2) is always output the same value, and the capacitance generated in the other capacitance is proportionally due to the movement of the guard electrode (4). The capacitance value changes.

The electrodes of the capacitor 1 and 1 'are made of stainless steel (SUS304) having a temperature coefficient of 20 × 10 ^-6 mm / ° C except for the guard electrode 4, which is a moving body. The support for the electrodes is all made of polystyrene, and the insulator uses a 0.1 mm Maca washer (5).

In order to reduce the edge effect at the front part, the inner electrode 3 digs an arc 6 having a diameter of 7 mm and has an epoxy mold 7 with the guard electrode that surrounds the outside for support so as to be symmetrically coupled.

A mica washer (8) (8 ') was inserted between two external electrodes to insulate and a conductor was placed between the mica washers to reduce the edge effect generated between the two external electrodes.

The outer end of the moving guard electrode is inserted with a sapphire ball (diameter: 3 mm) (F) to maintain a constant contact with the object to be measured, and the spring 10 is attached to the outside of the guard electrode to The elasticity ensures that the guide electrode always returns to the same point and the jaws 11 are placed inside the electrode so that the guard electrode does not come out.

For the electrostatic shielding to the outside, the electrode structure is placed in a stainless steel tube and fixed. At the same time, the lead 12, 12 ', and 12' 'wires of each electrode are pulled out and connected to the coaxial cable.

The electrode length of the measured capacitance of the external electrodes was 49.5 mm, the electrode length of the reference capacitor was 14.5 mm, both electrodes were 7.4 mm inner diameter, and the moving guard electrode was processed to 80 mm long, 7 mm outer diameter, and 6.1 mm inner diameter. And by assembling the capacitance difference value generated in the two capacitors to 0-5pF.

Therefore, the microdisplacement capacitive sensor according to the present invention has the function of a sensor using two capacitives as one unit, and has the effect of eliminating the disadvantages of the sensor using two capacitives.

Claims (1)

Two external electrodes, a cylindrical capacitor 1 (1 ') are installed in the cylinder 2, and a fine internal electrode 3 of the groove 6 is inserted between the capacitors 1 and 1'. Capacitance sensor for microdisplacement measurement, characterized in that the guard electrode (4) installed between the capacitive (1) (1 ') and the internal electrode (3).