SU1767337A1 - Device for remote voltage and current registration - Google Patents

Abstract

The device relates to an electrical measurement technique. The purpose is remote sensing of voltage or current in a wide frequency spectrum using a radio frequency cable. The device is recommended for cases of large remoteness of the recording device of the transmitter, as well as the use of cables of small cross section, when their ohmic resistance is commensurate with the wave, that is, when the measurement error caused by this, using traditional schemes is unacceptably large. The aim of the invention is to improve the accuracy of registration. The device includes a sensor of the recorded signal (ohmic or capacitive) cable with a matching input resistor and a matching output resistor, or an output matching RC-circuit. A series of two types of RLC chains are included in series with the output resistor or the output matching RC circuit, the first of which is the parallel connection of the RLC elements, the second the parallel connection of R and the LC chain. The matching output resistor, or the matching RC circuit and the second type of RLC chains, are also included to form a chain to which the recording device is connected (for example, an oscilloscope). 2 Il.

Description

This invention relates to the field of electrical measurements. The purpose is remote sensing of voltage or current in a wide frequency spectrum using a radio frequency cable.

The device is recommended for cases of large remoteness of the recording device from the sensor, as well as the use of thin section cables, when their ohmic resistance is comparable with the wave resistance, i.e. when the error when using traditional measurement circuits is unacceptably high.

In the traditional measurement scheme, which includes a sensor, a recording device and a cable connecting them, matched on both sides, with respect to

ohmic cable resistance to wave R cab

You can see it --- 1 in the case of recording signals of the same amplitude, but of different frequencies, for example, tens of hertz and tens of kilohertz amplitude of signals on the instrument RKa6

re divided by 9%. and at

- 2 -

H

V | to

WITH

VI

accordingly, by 26.4%, i.e. completely unacceptable figures are obtained.

From remote measurement devices that exclude this factor, devices with a light guide instead of a cable are known. Their disadvantage is high cost, the need to have a power source, which is susceptible in relation to the mechanical effects on the fiber.

Of the devices that eliminate the effects of the ohmic resistance of the cable, inductive coils that are included in the cable cut through a certain distance are well known, however, the full compensation of the influence of the ohmic resistance by this method is practically unattainable, in addition, the transmitted signal power is reduced, and the cable itself The multiple included coils become unusable for reuse.

A tailored cable with an increased inductance only partially eliminates signal distortion and is expensive.

The aim of the invention is to improve the accuracy of signal registration (tenfold) due to more effective reduction of the error by simpler and cheaper means. This is achieved by those. that error compensation is provided by a specially calculated resistance value of the input terminating resistor and the use of RLC chains at the cable output.

FIG. 1 shows the scheme of the proposed device for an ohmic sensor; in fig. 2 is a circuit for a capacitive sensor.

The sensor, made with the help of resistors 1.2 or capacitors 19, 20, is connected to measuring cable 3 via an input terminating resistor 5. A series of symmetrically identical identical groups of elements is connected to the end of the cable:

- in parallel interconnected resistors 6 (10), capacitors 11 (17) and inductors 12 (18);

- parallel connected resistors 7 (9) and a chain of series-connected capacitors 14 (16) and inductors 13 (15), as well as a resistor 8 or a chain of resistor 8 and a capacitor

21 for the case of a capacitive sensor.

The recording device is connected between the inner ends of the inductance 12,18 parallel to the rest of the series circuit,

The device is based on the traditional scheme with an ohmic or capacitive sensor and a cable matched on both sides.

The ratio of the parameters of the circuit section of the cable connected to the output is such that the input impedance of this section at any signal frequency is equal to the cable impedance - this is in line with the traditional scheme and setting, but unlike the traditional setting, the matching resistance

resistor 5 is taken smaller than the full resistance and is defined as a function of the cable's ohmic resistance, its length and specific electrical parameters. The need for this is caused by transients in the cable — reflections and refractions of electromagnetic waves at each point of the cable due to ohmic resistance, leading to frequency errors.

The proposed setting of the input resistor reduces the error at the cable output 5 times. In addition, the remaining uncompensated error has such a dependence on the signal frequency, at which its value periodically decreases with increasing frequency and increases (the signal at the cable output increases) - each time at a lower level.

The action of the RLC chains is based on compensating these sections for increasing the error due to resonance at the corresponding frequencies. In doing so, each pair of RLC chains with the same RLC resonates in one of the frequency bands at which the output signal increases. At resonance, a chain with a parallel connection of RLC increases the impedance, and with a mixed one decreases the impedance, and since the latter is included in the circuit that shunts the device, the voltage on it decreases, compensating for the increase in voltage at the cable output.

A pair of chains 6, 11. 12 and 7, 13, 14 compensates for the first maximum error, and a pair of 9, 15, 16 and 10, 17, 18 - the second (at high frequencies). Compensation for subsequent increases in error is almost not required because of their smallness.

When the ratio of the ohmic and the wave R cab Z

Claims (1)

Signal registration will be 1% vs 36% in the traditional scheme. Claims An apparatus for remotely registering voltage and current, comprising a sensor, an input terminating resistor, an output terminating resistor or an RC circuit, registering a device and connecting it to the sensor via an input terminating resistor, an RF cable, characterized in that increase the accuracy of registration, the first and second chains of the same number are entered in it, each of which contains a resistor, a capacitor, a coil and a resistor connected in parallel, connected in parallel parallel cable resistance  2.5 series-connected coil and capacitor, with the parameters of resistance, inductance and capacitance of each first chain equal to the corresponding parameters of each adjacent second chain, the second chain connected in series with the output matching resistor or RC chain between the corresponding first chains and parallel to the recording device which is connected by a radio frequency cable with a sensor through the corresponding first chains. five 0 ki, and the resistance value of the input terminating resistor is z (eRK / 2z R51-eRK / a / K where RB is the resistance value of the input matching resistor; t is the wave resistance of the radio frequency cable; RK is the resistance of the RF cable; Ra is the internal resistance of the sensor.  ABOUT s I Vb. 19 L 5 ± 20 #V $ /. / B FIG. 2