SU1216716A1 - Electromagnetic method of measuring specific electric conductance of non-ferromagnetic conducting articles - Google Patents

Abstract

The invention relates to instrumentation engineering and can be used to measure the specific electrical conductivity of non-ferromagnetic conductive products. The invention is an improvement in the accuracy of measuring the specific electrical conductivity by reducing the influence of fluctuations in the gap between the transducer and the product. The method consists in exciting with the aid of a transformer converter eddy currents in the product, moving the converter to a fixed gap, changing the frequency of the current of excitation until the output voltage of the converter installed on the product with and without a gap is equal, measuring this change in frequency and determining the specific electrical conductivity of the product. 3 il. i (L to 55

Description

The invention relates to instrumentation technology and can be used to measure the electrical conductivity of non-ferromagnetic conductive products.

The purpose of the invention is to increase the accuracy of measurement of specific electrical conductivity.

FIG. 1 shows a block diagram of a device implementing the method; FIG. 2 shows a calibration curve explaining the principle of operation of the device according to the proposed method; FIG. 3 shows the hodographs of the relative applied voltage of the surface transformer eddy current transducer from the generalized parameters oC / and /, where h is the gap between the eddy current transducer and product.

The device contains a generator 1, an overhead transformer vortex converter 2, a compensator 3 of the input voltage of a vortex converter 2, a differential amplifier 4, a phase detector 5, an indicator 6, a frequency generator 7, a digital frequency meter 8,

The method is carried out as follows.

Before measurement on the reference sample set the zero value of the device in a known manner. The converter 2 is excited by the current of the generator 1 of a constant frequency, which is chosen from the conditions for providing a generalized parameter

  Rj

, d

 3, where (j,

- miI

The minimum possible value of electrical conductivity. The value of the signal frequency is recorded at the digital frequency meter 8 with respect to the frequency of the reference voltage coming from the generator 7,

The signal from converter 2 is amplified by differential amplifier 4, detected by detector 5, the reference voltage of which is supplied from compensator 3 and reflected by indicator 6, Compensator 3 changes the amplitude and phase of the compensating voltage to achieve equal to the input voltage of the eddy current converter and the sum of the voltage them in the amplifier 4. At the same time, the resulting eddy current output voltage

five

0

five

0

five

0

five

0

five

the converter on the selected reference sample on indicator 6 is zero. After that, measurements of the specific electrical conductivity of the monitored product are made.

The measurement of electrical conductivity is carried out as follows.

A pre-configured converter is installed on the product and, according to the indication of indicator 6, the voltage value of the converter is fixed. In this case, the component of the eddy current transducer output is orthogonal to the excitation current, which depends on both cj and the gap between the transducer and the product.

Next, the eddy current transducer is installed above the controller. my product with a fixed increment of the gap, for example, the corresponding U about 0.1. As can be seen from the hodograph (Fig. 3), this leads to a change in the components of the resulting output voltage of the eddy current transducer, t, e, changing the gap is equivalent to changing b or the frequency of the exciting current by a certain amount that will be different for different values of electrical conductivity. By varying the frequency of the excitation current of the generator 1, an equalization is made on the indicator 6 orthogonal to the excitation current components of the resulting output voltage of the eddy current transducer with a fixed increment of the gap and without it. According to the measured increment of the frequency of the exciting current, recorded by the frequency meter 8 and previously constructed in the process of the device’s gradation, the specific electrical conductivity of the monitored product is determined by the curve (FIG. 2)

The method allows to increase the accuracy of measurements with a significant fluctuation of the gap between the transducer and the product. Indeed, as can be seen from the hodograph (Fig, 3), a change in the gap by a fixed amount (L (V, 0.1, Ddx: 0.2, etc., d) results in equivalent increments

ft, independent of the initial gap value. Therefore, variations in the frequency of the excitation current will not depend on the initial value of the gap between the eddy current transducer and the product being monitored. Therefore, to implement the method, it is sufficient to construct only one calibration curve (FIG. 2) for wide ranges of variation of electrical conductivity and gap. The curve (Fig. 2) is obtained from the hodograph family (Fig. 3) for values 3-10, "i 0.1-0.5, L 06 0.1, which at the initial frequency of the exciting current f 10 kHz corresponds to the range of variation of the specific electrical conductivity of products from 5 to 60 cm / m.

four-

16716

Claims (1)

Formula of gain Electromagnetic method of measuring the specific electrical conductivity of non-ferromagnetic conductive products, consisting in the excitation of eddy currents by a transformer converter and measuring the output voltage of the converter, which causes the frequency of the converter to be shifted to a fixed gap. excitement until the moment of equality output 15, the voltage of the converter installed on the product with or without a gap is measured by this frequency change, and the specific electrical conductivity is determined from a known calibration dependence. fpU2.f & f A / l-L U 25 Ad-oj d 0, .5 J3 0 10 20 30 40 SO AU Ugfi Srig.G. fig.Z Editor S.Lyzhova Compiled by V.Fnliyov Tehred O.Vashchishina 997/55 Circulation 778 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Filial PPP Patent, g, Uzhgorod, st. Project, 4 Proofreader G. Reshetnik