SU1335895A1 - Electric properties meter for rocks and ores - Google Patents

Abstract

The invention relates to a control and measuring technique and can be used in conducting geophysical surveys by the method of electrical exploration. The purpose of the invention, the improvement of measurement accuracy, is achieved by eliminating the influence of parasitic impedance connected in parallel to the sample to be measured. This resistance consists of a parallel connection of the sensor's own capacitance and connecting wires, the output resistance of the current generator, as well as the input resistances and the capacitance of the differential amplifier. The device contains a master oscillator 1, a phase splitter 2, a compensation unit 3, a differential amplifier 4, a stable current generator 5, channels 6 and 7 for measuring the active and reactive components, respectively, switch 8, two-electrode sensor 9 with the sample to be measured and reference impedance 10. The unit 3 includes an attenuator 11, a compensating resistor 12 and a capacitor 13. The transfer coefficient of the attenuator 11 is fixed, set during tuning and does not change during operation. The values of the reference resistors and capacitor are selected near the high-resistance measurement limit. 1 hp f-ly, 1 ill. "(L with sd sd 00 s sd

Description

The invention relates to instrumentation technology and can be used in conducting geophysical surveys using electrical survey methods.

The purpose of the invention is to improve the measurement accuracy by eliminating the influence of parasitic impedance connected in parallel with the sample to be measured. This parasitic resistance consists of the parallel connection of the sensor's own capacitance and the connecting wires of the output resistance of the current generator, the input resistances and the capacitance of the differential amplifier.

The drawing shows a structural diagram of an electrical property meter.

Measuring electrical properties of rocks and ores contains a series-connected master oscillator 1, phase splitter 2, compensation unit 3, differential amplifier 4, the inverting and non-inverting inputs of which are connected respectively to the first and second outputs of the compensation unit 3 and the stable current generator 5, the output of which is connected to the inverting input of the differential amplifier 4, the measurement channels of the active 6 and reactive 7 components, with their inputs, are connected to the output of the differential amplifier 4, and with the outputs of the phase splitter 2, the switch 8, the two-electrode sensor 9 with the sample to be measured and the reference impedance 10 formed by the parallel connection of a resistor and a capacitor, the input of the switch 8 connected to the output of the current generator 5, and its outputs to the electrodes of the two-electrode sensor 9 and output reference impedance 10.

Compensation unit 3 comprises an attenuator 11, whose input is the input of compensation unit 3 and connected to the output of phase splitter 2, and the output is the first output of compensation unit 3 and connected to the non-inverting input of differential amplifier 4, and parallel-connected variable compensating resistor 12 and capacitor 13 The first terminals of which are connected to the output of the phase splitter 2, and the latter are the second output of the compensation unit 3 and are connected to the inverting input of the differential amplifier 4.

The device works as follows.

The master oscillator 1 generates on

a set frequency that is applied to the input of the phase splitter 2, which produces quadrature voltages shifted in phase by 90 °. These voltages are applied to the reference inputs of the measurement channels of active 6 and reactive 7 components of complex conductivity. In addition, one of them, whose phase shift is taken as 0 °, is fed to the input of block 3

five

0

five

compensation, and from its outputs to the non-inverting and inverting inputs of the differential amplifier 4. The output voltage of the differential amplifier 4 is fed to the input of the voltage-controlled current generator 5, and the output current of the latter through the switch 8 to the two-electrode sensor 9 with the mountain sample under study breeds. The current flowing through the sample being measured creates a drop

0 the voltage that goes to the inverting input of the differential amplifier 4, closes the negative feedback circuit of this amplifier. The output voltage of the differential amplifier 4 is fed to the signal inputs of the measurement channels of the active 6 and reactive 7 components, where the active and reactive components of the complex conductivity of the sample being measured are recorded and recorded.

The input signal of the compensation unit 3 is fed to the non-inverting input of the differential amplifier 4 through an attenuator 11, and to the inverting input of the same amplifier 4 through parallel-connected compensating resistor 12 and a capacitor 13.

The system of two equations, where the first describes the balance of currents at the inverting input of the differential amplifier, and the second relates the input output voltages of this amplifier, we have:

five

0

five

five

0

where e is the output voltage of the phase splitter 2;

S is the steepness of the current generator 5 at the input voltage; Uo - voltage on inverting input

amplifier 4;

UBUX voltage at the output of the differential amplifier 4; Ki is the attenuation coefficient of the attenuator 11;

K is the gain factor of the differential amplifier 4;

Zx is the resistance of the sample to be measured; Zk is a compensating resistance equal to the parallel resistance of resistor 12 and capacitor 13; Zn is the parasitic resistance connected in parallel to the measured one and equal to the parallel connection of the input capacitance and the resistance of the differential amplifier 4 via the inverting input, the output resistance of the current generator 5, the own capacitance of the sensor 9 and connect the / (s) wires.

Finding the value of the output voltage of the differential amplifier 4, we have

e

K, / z, + (Sl +, .- 1

ZnZ (

s H-T (T-T-T-to Zx z "ZK

When choosing

7 - LZ - n with

K; Zfl Ujb The last expression is converted to the form EK.1

and

6S

S zx

1 +

one

S K z

If the interpretation of the results is done by simplifying the formula

and-., J

b z

the systematic error will not exceed

b

S-K- Z,

Taking into account that the transmission coefficient of the measuring converter is

„And exit”

Cd

еS Zx

and is usually chosen within 0 ,, then for the magnitude of the errors can be written

b -.

K-KI

Thus, at / К / 200-300, which is easily achieved using modern operational amplifiers as a differential amplifier 4, the measurement error does not exceed

b 1%.

The attenuator transfer ratio 11 is fixed, fixed when the instrument is tuned, and does not change during operation. For the selection of the values of the compensating W.ORR resistor 12 and the capacitor 13 to the output of the current generator 5, the switch 8 connects the reference resistance 10 and the adjustment of the resistor 12 and the capacitor 13

Achieve the required readings in the active b and reactive 7 component channels. The values of the reference resistor and capacitor are selected near the high impedance measurement limit.

Claims (2)

1.Meter of electrical properties of rocks and ores, containing successively connected master oscillator and phase splitter, measuring channels of active and reactive components, the reference inputs of which are connected to the outputs of the phase splitter, two-electrode, sensor with measured sample, current generator and differential an amplifier, the inverting input of which is connected to the output of the current generator, and the output to the signal inputs of the measurement channels of the active and reactive components, characterized in 0, in order to improve the measurement accuracy by eliminating the influence of the parasitic complex resistance connected in parallel to the sample being measured, a complex reference resistance, a switch and a compensation unit, whose input is connected to one of the outputs of the phase splitter, are additionally introduced. the second outputs, respectively, to the non-inverting and inverting inputs of the differential amplifier, while one of the terminals of the complex reference resistance is grounded, the input of the power switch li ne to the output of the current generator, and the outputs of the switch - to the conclusion integrated reference electrode resistance and to snip date, the differential amplifier output is connected to the input of the current generator. 2. The meter according to claim 1, characterized by the fact that the compensation unit contains an attenuator whose input is the input of the compensation unit and its output is the first output of the compensation unit, and the parallel connected variable compensating resistors and capacitor, the first high 45 the waters of which are connected to the input of the attenuator, and the latter are the second output of the compensation unit.