SU1262393A1 - Device for measuring electrical resistance of liquid and components of polarizing impedance - Google Patents

Description

The presence of a transformer bridge arm consisting of the conductometric transducer 3 and the adjustable resistor 4 connected in series to a smaller chamber allows the range of resistance measurement of the liquid to be significantly extended towards smaller values. 1 il.

The invention relates to studies of the electrophysical properties of a liquid and can be used to measure the electrical resistance of a liquid and the equivalent components of the polarization impedance of a double layer at the surface of the electrodes. The purpose of the invention is to improve the accuracy and extend the measurement range by fully balancing bridge circuits and eliminating an unregulated resistor. The drawing shows a block diagram of the proposed device. 15 The device contains a generator 1 connected to the primary winding trans; Former 2, the secondary windings of which are 1: 1 turns and form the inductive shoulders of the transformer bridge, the latter also includes a three-electrode conductometric converter 3, divided by the middle electrode into two unequal chambers along the length with the end of one inductive arm, and the extreme electrode of the smaller chamber is connected through the right adjustable resistor 4 with the end of the other inductive arm. The first adjustable capacitor 5 and the first balance indicator 6, with the appropriate position of the pairs of windows of the switch 7, are connected to a transformer bridge to compensate for earth leakage currents and to indicate the balance, respectively. In addition, the device contains a voltage divider 8, for example, in the form of a variable resistor, a second adjustable capacitor 9 and a second balance indicator 10, which together with a three-electrode conductometric converter 3 and an adjustable resistor 4 with the position of the contacts of the switch shown in the drawing In the case of B in Par 15 RGD 7, a four-arm bridge with an electronically connected conductometric converter 3 is formed. The device works as follows. The measurements are carried out in two stages. Initially, the transformer bridge is balanced by changing the knowledge of the adjustable resistor 4 and the capacitor 5 with the corresponding position of the switch contact pairs (the position of the contact pairs is opposite to that shown in the drawing). the moment of balance of the bridge is true vene LE ... ±. S + + R + X ", + R.C - c + x kg - x" e R, 5, and -equivalent components of the polarization impedance of the double layer at the outermost electrode more and less. cameras conductometric converter 3, respectively; “The resistance of the fluid in the larger and smaller chambers of the three-electrode conductometric transducer 3; R.cH x, are equivalent components of the polarization impedance of a double layer at the middle electrode from the side of the larger and smaller chambers of the three-electrode conductive transducer 3, which must be taken into account on the basis that the power lines of the current passing between the extreme electrodes, cross the double layer at the middle electrode of the shaft; equivalent resistance to leakage current on the case from the larger electrical circuit of the three electrode conductor transducer 3; resistance of adjustable resistor A; total equivalent resistance to leakage currents to the case from a smaller chamber of a conductometric converter 3, an adjustable resistor 4 and a capacitor 5. (2Rn + 2X "+ 2R 2K" + 2X "2R, n ne equivalent of where R,, X" are polarizing double impedance layer at one of the extreme electrodes of the conductivity transducer; equivalent resistance to leakage current to ground from the conductive-transducer; total equivalent resistance to leakage currents to the body from adjustable resistors 4 and cond Ator 9; p - voltage divider 8 indication. Due to the fact that the resistance of a three-electrode conductometric converter in a two-electrode connection is complex, 1 934 Electrodes in a three-electroscopic capacitor converter are measured under the same conditions and, if they are made the same , then the equality RnS X „8 R, -b X„ „, (2) holds true and with the full balance of the bridge X, j8 X ,,, (3) Equality (1) with regard to expressions (2) and (3) implies that 4 i.e. the value of adjustable resistor 4 with the balance of the transformer bridge corresponds to the resistance of the fluid in the three-electrode conductometric converter. At the second stage, the bridge is balanced with a two-electrode switching on a three-electrode conductometric converter by measuring the division factor of division 8 and the second adjustable capacitor 9. The position of the contact pairs of the inserted switch 7 corresponds to that shown in the drawing. In oment balance of the bridge. It requires the inclusion of an adjustable capacitor to compensate for the reactive component, and it is impossible to strictly distinguish between the equivalent leakage current to ground X,., And the equivalent reactive components of polarization impedance X and X, compensated for by the adjustable capacitor. , then when processing the results of this measurement, it is necessary to allow a methodological error. It is assumed that where X is the equivalent resistance to earth leakage currents from the adjustable resistor A. Equality (5) with regard to equality (6) HdvHo bring to the form R, 5 Х „- п (2Rn-t- 2Rn + + n (2Х „+ 2Х„,),

1262393 (

- equivalent} 5 tons - 4

the values of the shoulder formed by the adjustable resistor 4 and the capacitor 9 with the set value of the capacitance C9 of the capacitor 9 at the frequency of the alternating current and.

R4

  with I Ae + A

+ R

2 „h. -

Not

-P

 Hd9

X „+ X

ps The measured values of the equivalent active and reactive components of the polarization impedance of the double layer at the electrodes include only the non-excluded methodical error determined by the adopted equality (6). Thus, the introduction of the switch in the proposed device allows increasing the measurement accuracy due to achieving a complete equilibration of bridge circuits by changing the switching on of the balance indicators and adjustable capacitors with the help of a switch depending on the measurement being carried out. Replacing the shoulder of a transformer bridge, consisting of a smaller connected camera of a conductometric transducer and an unregulated and adjustable resistors, with a stand of a serially connected smaller camera of a conductometric transducer and adjustable resistor, significantly extends the range of resistance measurements. TYPE of liquid in the direction of small values. Improving the accuracy of measuring the electrical resistance of the fluid and the components of the polarization impedance of the double layer at the electrodes improves the quality of the calibration of conductometers and increases the efficiency of studies of the electrophysical parameters of the fluid, especially with regard to studying the properties of a dual electric layer, knowledge of which is necessary, for example, when developing conductometric devices.

Permanent bolTytes i smaller kam (; p three-year 1 control 1 of conductometric converter 3, respectively, Ac and L

then using

a constant three-electrode conductometric converter and the resistance of the liquid in it through the specific electrical conductivity liquid, from equality (7) taking into account equality (A), you can get

(eight)

Claims (1)

(9) Claims of the Invention A device for measuring the electrical resistance of a liquid and the components of a polarization impedance, comprising a generator whose output is connected to the primary winding of a voltage transformer, the two secondary windings of which form the inductive shoulders of a transformer bridge, the first terminal of the first secondary winding of a voltage transformer connected to the first terminals of the adjustable resistor and the first adjustable capacitor, a three-electrode conductometric converter, divided the middle electrode is divided into two cameras of different lengths and connected to two measuring bridges, of which one is connected to the bridge by three electrodes, and to the other bridge by two extreme electrodes, a voltage divider, a second adjustable capacitor, two balance indicators, different to that that, in order to increase the accuracy and expand the measurement limits, a switch was introduced into it, the first input of the first pair of switched inputs of which is connected to the first output of the first secondary winding of a voltage transformer, the second output The first output of the second secondary winding is connected to the second input of the first pair of switching inputs of the switch, the input of the second pair of switching inputs of which is connected to the second output of the first adjustable capacitor, the input of the third pair of switching inputs of the switch connected to the first output of the second adjustable capacitor, the second output of which 71 connected to the second output of the adjustable resistor, with a smaller electrode, the chamber of the three-electrode conductometric converter and the fourth input a pair of switching inputs of the switch, the second output of the second secondary winding of the voltage transformer is connected to an electrode longer in the chamber of the three-electrode conductometric converter and to the first output voltage divider, the second output of which is connected to the first output of the adjustable resistor, the third output of the voltage divider is connected to the input of the house of the fifth pair of switching inputs of the switch, the middle electrode of the three-electrode conductometric converter is connected to the input of the sixth pair of switching x switch inputs; the first input of the first balance indicator, the first and third outputs of the switch are connected to the common bus, the second and sixth outputs of the switch are connected to the second input of the first balance indicator, and the fourth and fifth outputs of the switch are connected to the first and second inputs, respectively second balance indicator.