SU1432417A1 - High-frequency meter of electrochemical system impedance - Google Patents

Abstract

The invention relates to electrical measuring equipment and can be used to study the properties of electrochemical systems. The purpose of the invention is to improve the measurement accuracy and expand the operating frequency range by introducing a first intermediate frequency signal generator and an electronically controlled attenuator, voltage follower, exemplary passive two-pole, second current transformer, current-to-voltage measuring transducer. The meter consists of generators 1 and 27, an electronically controlled attenuator 2, cable 3, an electrochemical cell 4 with electrodes 5, 6, a transformer 7, a potentiostat 9, a measuring transducer 12 current to voltage, and an intermediate frequency driver 13, 19 , a block 17 of phase-sensitive detectors, a measuring transducer 20 into voltage, a transformer 21, an exemplary passive two-terminal 22, a repeater 23 voltage. 1 il. ((L

Description

four

Sde

to

four

The invention relates to an electronic measuring technique and can be used to study the properties of electrochemical systems.

The purpose of the invention is to improve the measurement accuracy and the widening of the working frequency range.

The drawing shows the functional electrical circuit of the meter.

The meter contains a series-connected harmonic oscillator 1 and an electronically controlled attenuator 2, to the output of which an electrochemical cell 4 is connected to an auxiliary 5 and 6 working electrodes through a connecting cable 3, and the working electrode is passed through the toroidal core of the current transformer 7.

To the section of the cell between the polarizing electrode 8 and the common wire is connected the output of a potentiostat 9, the potential input of which is connected to the reference electrode 10. The porous diaphragm 11 prevents the passage of reaction products formed on the polarization electrode 8 when a constant component current flows in the main cell volume. The secondary winding of the current transformer 7 through the current-to-voltage measuring converter 12, the first intermediate frequency signal generator 13, consisting of a series-connected mixer 14, a low-pass filter 15 and an intermediate frequency amplifier 16, is connected to the reference input of the 17-phase detector unit and the input an automatic control circuit 18 connected by an output with control of the attenuator 2 input. The signal input of block 17 via the second intermediate frequency driver 19, a measuring signal eobrazovatel 20 in the voltage and current transformer 21, and an exemplary passive two-terminal network 22 and the voltage follower 23 is connected to the bunks auxiliary electrode.

Shaper 19 contains a mixer 24, a low pass filter 25 and an intermediate frequency amplifier 26.

Heterodyne inputs of the mixers 14 and 24 of the formers 13 and 19 are connected to the output of the second harmonic oscillator 27.

Izieritel1 works as follows.

 generator 1 through attenuator 2 and cable 3 is applied to cell area 4 of the chalk by electrodes 5 and 6, the Current Tp flowing through electrode 6j is sensed by the secondary winding of transformer 7 and converted by converter 12 into a voltage that goes to the signal input of the mixer 14 The heterodyne input of the mixer 14 receives the voltage of the generator 27. The operating frequency of the generator 27 f is shifted relative to the frequency of the generator 1 f by the value of f p const, while f |, p; The intermediate frequency voltage is extracted by the filter 15, amplified by the amplifier 16 and fed to the reference input of the block 17 and the input of the circuit 18. This circuit compares the output voltage of the shaper 13, equal to its reference voltage E g and their inequalities are formed by an amplified difference signal, which, acting on attenuator 2, sets such a voltage at its output that, neglecting the statistical error of the automatic control loop for the measuring circuit, the relation

and

(3

 Rmy

(one)

where and ,, ipK, K ,, K, K, k, jK, ipK,

40

.

(2)

where k, j. KT

K,, K, K c are the transfer coefficients of the corresponding nodes of the meter -t — the introduced parasitic phase shift of the voltage shaping channel and 13.

From (2) it follows that for | K, | const, llpi Е || j IK, I is a constant value.

The current IP, the flow through the cell area of melut auxiliary 5 and working 6 electrodes with an impedance L creates a voltage drop across it

and

 I

p and

(3)

The voltage U, through the repeater 23, the two-port 22, the transformer 21, the converter 20 and the driver 19 is fed to the signal input of the block 17. The voltage

and 13 th „| K„ le J, (4)

de K | j-k, - transfer coefficients of the corresponding meter nodes}

If is the introduced parasitic phase shift of the channel of formation of voltage.

and 9Converting the inflation (4) with the teaching (2) and (3), have

-j.

20

Uig Ul3 1 - LHle

(five)

Q 25 30

where cr arctg (X / R),

X and R - imaginary and valid

impedance components L c. Since the voltage U - | w sat; is fed to the reference inputs of the block 17, i.e. the direction of the vector Utj is ACCEPTED for the origin of the phase angles of the meter signals, then the output signals of this block are respectively

UR | K || LJcos (IfJ, and y | kl | LHlsin (i -I- 1 /),

40

de K} (, iKle is the conversion factor, K is the transfer coefficient of block 17 when the common-mode signals are fed to its inputs.

When the equality Lf + is fulfilled (f. - (About hyphenation (6) are transformed.

Q 25 30

(6)

35

Ug | K (| bn (co8 4-1KIR, and | K || Kk (81pc | n - IKIX

From expressions (7), it follows that with C) O when the ratio K | K1 const is fulfilled, the output signals of block 17 are directly proportional to

-

20

40

 .

the required component is the R and X impedance L, between the auxiliary 5 and the working 6 electrodes of the electrochemical cell.

Claims (1)

Invention Formula A high-frequency impedance meter for electrochemical systems, containing a first harmonic oscillator and an automatic control unit, connected respectively to the signal and control inputs of an electronically controlled attenuator, the output of which is connected to the first terminal for connecting an electrochemical system, the first measuring current converter in eg connected via a first current transformer to a second terminal for connecting an electrochemical system, a potentiostat whose output connected to the third terminal 25 for connecting the electrochemical system, the input to the fourth terminal, and a phase-sensitive detector unit, the reference input of which is connected to the input of the automatic control unit 30, in order to increase the measurement accuracy and increase the working frequency range , a second harmonic oscillator, a current transformer and a current-to-voltage measuring converter, an exemplary passive bipolar array and two frequency converters, with the transducer outputs introduced into it. the leu frequencies are connected to the inputs of the phase-sensitive detector unit, the signal inputs to the outputs current transducers into voltage, and heterodyne inputs connected to the output of the second generator; ra harmonic input the second measuring transducer current to voltage through the second a current transformer, an exemplary passive two-pole, and a voltage follower, which are connected in series, are connected to the fifth terminal for connecting an electrochemical system. 35