SU496499A1 - Electrical measuring instrument - Google Patents

Description

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The invention relates to electrical measuring equipment, in particular, to the creation of electrical measuring devices without moving mechanical parts based on the use of electro-optical effects in liquid crystals.

Electrical measuring instruments are known that contain a liquid crystal placed between two electrodes, one of which is solid and connected to a source of measured voltage, and the other is made up of isolated discrete elements, and an auxiliary source of alternating voltage.

However, such devices have a relatively narrow measurement range due to the high threshold voltage of all electro-optic indices and insufficient input resistance due to the presence of a resistive voltage divider in the measuring circuit.

The purpose of the invention is to expand the measurement range and increase the input resistance

This is achieved by the fact that the device is equipped with a voltage transformer, secondary

the winding of which is made sectional with the number of sections equal to the number of discrete elements and connected to each discriminatory element by the output from the corresponding section, and the primary winding is connected to the auxiliary voltage source, while the source of the measured voltage is connected to the beginning of the secondary winding transformer.

The drawing is a diagram of the proposed device (one example of implementation).

The electrical instrument contains a liquid crystal placed between two electrodes, one of which is made solid 1, and the other is composed of isolated discrete elements from 2-1 to 2-fl.

The device is equipped with a transformer for example 3 with a partitioned secondary winding containing from 4-1 to 4-tl (sections where the number of sections PJ is equal to the number of discrete elements from 2-1 to 2.-I ... Each discrete element is connected to the corresponding section from 4-1 to 4-fl secondary transformer ibmot. The primary winding of the transformer 3 is connected to an auxiliary source of high-frequency voltage 5. To ground one of the windings of the transformer 3 at high frequency used shunt capacitor 6, After connecting the source you The device is ready for measurement. The sectioned winding of the transformer is a high-frequency voltage divider. At the same time, a high-frequency voltage is applied to each discrete electrode (j21 L iV, k-K. p Lt (J is the high-frequency voltage applied to transformer 3 primary winding; - transformer 3 transformation ratio; - transformer secondary inductance; inductance of a secondary winding part, composed of inductances from 4-1 to 4-L; pulling the voltage of the liquid crystal depends on the amplitude of the high-frequency voltage U || -. In accordance with different values and on discrete elements from 2-1 to 2 - n for rare liquid crystal indices, set a different value of the threshold voltage (y and ... ... and). by,) The measured constant or low-frequency alternating voltage p .. is supplied directly to each discrete element through the resistance of the secondary section of the transformer 3. The secondary resistance of the transformer 3 is several orders of magnitude lower than the intrinsic resistance of the liquid crystal. Therefore, with a sufficient degree of accuracy, we can assume that all discrete elements are supplied with the same measured voltage and equal to U. Since the value of (j is set then different for different indices, the electro-optical effect will be observed only on those indices where U exceeds U Xpor The boundary between excited and unexcited indices is a reference mark. When the measured value changes, the voltage number of excited indices changes accordingly to the implementation of an analog sample in the form of a change in the length of the white column against a dark background .. In the proposed device, the measurement range is greatly expanded due to the decrease in the threshold on the index indices located at the beginning of the scale, while in a known device to ensure a given accuracy, the threshold voltage of the threshold voltage is set high (30-40 in) over the entire length of the scale. The input resistance of the device is significantly increased due to the absence of a resistive divider in the measuring circuit. Thus, the flowing current is determined only by the intrinsic conductivity of the liquid crystal, which usually ranges from to 10. Claims of the invention: An electrical measuring instrument containing a liquid crystal placed between two electrodes, one of which is solid and connected to a source of measured voltage, and the other is made up of isolated discrete elements, and an auxiliary source of alternating current voltage characterized by that, in order to expand the measuring range and increase the input resistance, it is equipped with a voltage transformer, the secondary winding of which is sectional with the number of sections equal to the number of disk elements, and connected to each discrete element by the output from the corresponding section, and the primary winding is connected to the auxiliary voltage source, while the source of the measured voltage is connected by another output to the beginning of the secondary winding of the transformer.

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