SU1385092A1 - Variable conductivity standard - Google Patents

Abstract

The invention relates to the technique of electrical measurements and can be used as an element of balancing and counting the active conductivity in high-precision capacitive bridges. The variable measure of active conductivity contains isolated friends.

Description

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from one another stators 1-3, filled in the form of hollow coaxial electrodes, separation screens 4, 5 placed between them, rotors 6, 7 in the form of packages of cylindrical electrodes, resistor 8, housing 9 with cylinder 17, displacement mechanisms having rods

11, 12 and reference drums 13, 14, electrically isolated from the rods, with dielectric inserts 15, 16. The variable measure has a wide range of reproducible values and high accuracy at high frequencies. 3 pe. .

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The invention relates to electrical measuring equipment and can be used as an element of balancing and counting on the active conductivity (G) in high-frequency capacitive bridges.

A feature of high frequencies (HF), covering the range of 0.1-100 MHz, is the difficulty of measuring the active component of the complex wire; dimness (or complex resistance) of the object being measured. Resistance stores are not applied at all to HF, since their frequency tolerance and its changes when switching resistors is significantly greater than that of conductivity stores. The error in conduction stores at RF is 1-10%. The purpose of the invention is to expand the range of reproducible values and improve accuracy at high frequencies.

Fig. 1 shows the proposed conductance} in Fig. 2, an electrical circuit for replacing the measure; FIG. 3 is a circuit for incorporating a measure into a transformer capacitive bridge.

The variable measure of active conductivity (Fig. 1) contains the first 1, the second 2 and the third 3 stators located between them, which are hollow coaxial electrodes, and there are separation screens 4 and 5 placed between the stators 1-3, the first 6 and a second rotor 7 that covers it, made in the entrance of packages of cylindrical electrodes, a removable resistor 8 installed between the housing 9 and the end wall of the stator 3. Stators 1 and 2 are connected to the connecting terminals

measures made in the form of an output connector 10, and the rotors 6 and 7 are mechanically connected to the rods 11 and 12 of the displacement mechanisms, provided with counting drums 13 and 14, are electrically isolated from the rods by the dielectric inserts 15 and 16 and are shielded sections formed by the housing 9 and the cylinder 17 mounted thereon. The stators 1 and 3 together with the rotor 6 and the stators 2 and

3 together with the rotor 7 form two series-connected variable capacitors with a contactless piston with a capacity of C and C, creating together with a resistor R a T-shaped circuit (Fig. 2). The active conductivity through passage of this circuit has a negative value (and provided that oR (C, + 2) 1 is determined by the formula

 G - (o2RC, C2.

The capacity parallel to it is a very small amount, not exceeding hundredths of a picofarad.

The proposed measure of active conductivity works as follows.

Using the connector 10, the measure is inserted into the measuring arm of the bridge (FIG. 3) and the drums 13 and 14 are set to zero. In this case, the rotors 6 and 7 are in the withdrawn position, the capacitance between the stators 1 and 3 and the capacitance between the stators 2 and 3 are cut by dividing screens

4 and 5, the active conductivity of the measure is zero. The bridge is balanced by the elements of the initial balance. Parallel to the measure, a measurement object is connected, for example, a capacitor, by rotating the drum 14, the rotor 7 is inserted into the space between the ground rotors of stators 2 and 3 by means of rods 12 and dielectric inserts 16, creating capacitance C, which, together with resistance. Then, using a drum 13, a rod M and a dielectric, the insert 15, the rotor 6 is introduced into the space between the electrodes of the stators 1 and 3 until the bridge is in equilibrium with respect to active conductivity. The capacitance C created in this case, as can be seen from the formula, is directly proportional to the active conductivity, which in turn is equal to the active conductivity of the object being measured. The achievement of direct proportionality (i.e. linearity of the scale of the measure) is promoted by the cylinder 17, which acts as an additional screen, eliminating parasitic capacitive coupling between the rotors 6 and 7. Balancing the bridge in capacity introduced by the object being measured is . At the same time, a slight change in the output capacitance of a measure of hundredths of picofarad is compensated.

Compared with the prototype, the proposed measure has a range of reproducible values of active conductivity extended 100-1000 times and covers up to 5 orders of magnitude. This is provided by the ability to control the dividing price over a wide range by using a replaceable resistor and variable capacitors with a large overlap ratio. The reproduction accuracy at high frequencies is no less than an order of magnitude and is determined mainly by the error in calculating the capacitance of capacitors with a contactless piston, which is 0.1%. One-sided arrangement of electrodes associated with

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connecting leads, and a resistor allows you to provide the measure with a coaxial connector without extending the current-carrying conductors, which also improves the accuracy of the measure.

For example, for a layout at a frequency of 1 MHz, a C / Cr of 0.5–50 pF, R 30–200 Ω, is adopted. Then G 340 - 210 cm (i.e., the measure covers 5 orders of active conductivity). For a measured object with a capacity of 10 pF, this corresponds to tgS -0.3, i.e. Covers the entire real range of loss of capacitive objects.

Claims (1)

Invention Formula A variable measure of active conductivity, comprising a housing, outputs, a resistor and a capacitor consisting of a rotor with a rod of a displacement mechanism, first and electrically connected to one of the terminals of the second stator, in order to extend the range of reproducible values and increase accuracy at high frequencies, it is equipped with a third stator, a second rotor and separation screens, the third stator is placed coaxially between the first and second stators, the second rotor covers the first rotor, and separate nye screens placed between the stators, the rotors are in a package vvde tsnpin--cylindrical electrodes and electrically insulated from the rod mechanism pe-. displacement, the first stator is electrically connected to the other output, and the resistor is mounted between the housing and the third. FIG. 2 H) OCi CiCf ifCi P Cf Fig.Z