SU1688195A1 - Device for conductometric measurements - Google Patents

Abstract

The avoidance relates to conductometry and can be used in the physicochemical studies of conductive liquids and the design of conductometers. The purpose of the invention is to simplify the device. The co-l device holds two operational amplifiers 1,., An alternating voltage generator 3, a current meter C, a conductometric cell 5 with a current of 6, / and two 8.9 potential electrodes, thanks to the fact that one of the poles of the reference voltage generator connected to a common bus opamp, i.e. with the point of connection of the sources of dual supply of these amplifiers, the level of interference induced from external and internal sources of emf is reduced, the possibilities of using the device are expanded. 1 il. (L with

Description

The invention relates to conductometry and can be used in the physicochemical studies of conductive liquids, in particular electrolytes, and the design of conductometers.

The purpose of the invention is to simplify the device.

The drawing shows a diagram of the device.

The device contains the first 1 and second 2 operational amplifiers, an alternating voltage generator 3 (U0), a current meter k, a conductometric cell 5 with two current 6.7 and two potential 8.9 electrodes.

The current electrode 6 through the current meter k is connected to the output of the first operational amplifier 1, and the current electrode 7 is connected to the output of the operational amplifier 2, the potential electrode 8 is connected to the inverting input of the operational amplifier 1, and the potential electrode 9 to the inverting output of the operational amplifier 2, one from the generator poles (3 of the reference voltage is connected to the non-inverting input of the second operational amplifier 2, the non-inverting input of the operational amplifier 1 and the second pole of the generator 3 of the reference voltage with connected to a common bus.

The device works as follows.

Under the action of the reference voltage of the generator 3, a voltage appears at the output of the amplifier 2, which through the liquid filling the cell 5 and through the electrode 8 is fed to the inverted axis oo

with

SL

31

The operational input of the operational amplifier 1. The circuit formed by the series connection of the cell 5 and the current meter k is under the voltage equal to the difference of the output voltages (relative to the common bus) of the amplifiers 1 and 2. At the same time a current flows through the current electrodes 6 and 7 which practically does not branch through the potential electrodes 8 and 9 into the external circuit due to the large input resistance of the operational amplifiers. But through these potential electrodes the feedback of both amplifiers is negatively coupled. Therefore, due to the very large gain of the amplifiers, the voltage between the non-inverting and inverting inputs of both amplifiers is all close to zero, and the difference between this gain and zero is the smaller, the larger the gain of the amplifiers. This means that the voltage on the electrode 9 (relative to the common bus is almost equal to the reference voltage of the generator 3, and the voltage on the electrode 8 is almost zero.

As a result, the voltage between potential electrodes 9 and 8 practically coincides with the reference voltage P0, regardless of the conductivity of the liquid (solution). That is, when switching from a fluid with one electrical conductivity (b) to a fluid with another electrical conductivity, the effect of negative feedback of both amplifiers causes the current through cell 5 to change so that the voltage between the potential electrodes retains its value.

Voltage between potential electrodes

“-, s

(one)

- 5 o 5

five

about Q

five

where I is the current flowing through the cells; AP is a constant depending on

cell designs. In this device, the voltage between the potential electrodes coincides with the reference I0, then

1 - I b,

An

those. the current detected by the meter t is proportional to (e. The meter b can be connected between the output of amplifier 2 and the current electrode 7. Connecting generator 3 to a common bus of operational amplifiers reduces the effect of interference.

F o r mula inventions

A conductometric measurement device comprising a first amplifier, an alternating reference voltage generator, a current meter, a conductometric cell with two current and two potential electrodes, one of whose current electrodes is connected to an amplifier output through a current meter, simplification, a second amplifier is introduced into it, the output of which is connected to the second current electrode, the inverting input of the first amplifier is connected to the first potential electrode, and the second amplifier is connected to the second potential electrode, one of the poles of the alternating reference voltage generator is connected to the non-inverting input of the second amplifier, and the other pole and the non-inverting input of the first amplifier are connected to a common bus, both of which are operational.

Claims (1)

The formula of the invention. A device for conductometric measurements, comprising a first amplifier, an alternating reference voltage generator, a current meter, a conductometric cell with two current and two potential electrodes, one of the current electrodes of which is connected to the amplifier output through a current meter, characterized in that, for the sake of simplification, a second amplifier is introduced to it, the output of which is connected to the second current electrode, the inverting input of the first amplifier is connected to the first potential electrode, and the second amplifier to the second With a potential electrode, one of the poles of the alternating reference voltage generator is connected to the non-inverting input of the second amplifier, and the other pole and non-inverting input of the first amplifier are connected to a common bus, both amplifiers are operational.