SU1499198A1 - Measuring transducer of electric conductance of liquids - Google Patents

Abstract

The invention makes it possible to increase the accuracy of measurements of the electrical conductivity of a liquid by compensating for the quadrature error. When the primary converter 1 is immersed in the liquid under study, in the turn of the connection 5 a current flows proportional to the instantaneous value of the electrical conductivity of the liquid. If there is no quadrature disturbance, the voltage at the input of the integrator 16 is zero, and the voltage at the output of the modulator 17 and the quadrature disturbance compensation current in the winding 9 are also zero. When a quadrature disturbance occurs, the phase at the output of the phase shifter 11 changes, which causes the voltage at the output of the integrator 16 to become different from zero and an additional current appears in the winding 9 to compensate for the quadrature disturbance. 2 Il.

Description

3149

The invention relates to a technique for measuring the electrophysical parameters of liquids and can be used in oceanography for the study of specific electric conductivity fields.

The purpose of the invention is to improve the measurement accuracy.

Figure 1 shows the principle of an electrical block diagram of a measuring transducer for electrical conduction of liquids; FIG. 2 is a block diagram of a current modulator manufactured according to the following digital-to-analog converter circuit.

The measuring transducer contains a primary transducer 1, an intermediate transducer 2, a quadrature interference compensation unit 3 and a harmonic voltage generator A.

The primary converter 1 with a liquid coil 5 consists of a voltage transformer 6 and a transformer comparator 7 currents with an output winding 8 and a compensation winding 9.

Intermediate transducer 2 consists of a serially connected matching unit (a 10, first phase shifter 11, first synchronous detector 12, first integrator 13, and current modulator 14.

The quadrature interference compensation unit 3 consists of the second synchronous detector 15, the second integrator 16 and the voltage modulator 17 and the second phase shifter 18, the output of which is connected to the reference input of the synchronous detector 15, connected in series.

a torus 24 pulses; a key 25; a reversible counter 26; and a controlled voltage divider 27.

The Converter operates as follows.

When the transducer 1 is immersed in the liquid under study in the turn of the connection, a current flows proportional to the instantaneous value of the conductivity of the liquid. The input of unit 10 receives a voltage proportional to the difference in magnetic fluxes generated by the currents in the liquid coil 5 and the winding 9. This voltage, amplified by unit 10, through the phase shifter 11 is fed to the inputs of the detectors 12 and 15. The active (useful) component of the output voltage Phase 11 is rectified by detector 12 and fed through integrator 13 to the input of modulator 14, namely, to the inputs of threshold elements 20 and 21. If the absolute value of the output voltage of the integrator 13 is less than the voltages of the threshold elements 20 and 21, then their outputs are in the state O, the output of the element OR is also in the state O, the key is closed, and the pulses from the output of the generator 24 are not fed to the input of the reversible counter 26.

This means that the primary measuring transducer 1, which is a transformer bridge, is balanced, the output code N of the device and the compensation current of the useful signal supplied to the winding 9 from the analog output of the current modulator 14 correspond to the steady-state value of the liquid-i conductivity

KOCTrf.

The communication element 19, which in practical implementation of the converter is implemented as a resistor or capacitor, serves to convert the output voltage of the modulator 17 into a quadrature interference compensation current supplied to the winding 9 when using a resistor and creates a 90-degree shift to compensate for quadrature interference with a capacitor.

The current modulator 14, made according to the following digital-to-analog converter (DAC) circuit, consists of threshold elements 20 and 21, element OR 22, trigger 23 characters, if the value of the fluid's electrical conductivity increases, then, at the output of the detector 12 and at the output of the integrator 13 is a positive voltage, jco, topoe, when a positive voltage is exceeded, trigger a voltage

threshold element 20 translates it into state 1, which ensures that trigger 23 is set to state 1 and issue a command to add pulses to the reversing counter 26. At the same time, element OR 22 is in state 1, key 25 is open, and clock pulses are output generator 24 is fed to the counting input of the reversible counter 26 until 51

Horn element 20 will not go to state O. This will happen when the increased values of the N code and the compensation current of the main signal are consistent with the new increased value of the fluid's electrical conductivity.

Similarly, the signal is compensated at the input of unit 10 with a decrease in the conductivity value of the liquid.

If there is no quadrature disturbance, the voltage at the input of the integrator 16 is zero, and the voltage at the output of the modulator 17 and the quadrature disturbance compensation current in the winding 9 are also zero. When a quadrature disturbance occurs, the phase at the output of the phase shifter 11 changes. This leads to the fact that the voltage at the output of the integrator 16 becomes different from zero and an additional current appears in the winding 9 to compensate for the quadrature interference. Thus, at the output of the phase shifter 11, the quadrature interference voltage is continuously | close to zero, as a result of which the subsequent stages of intermediate converter 2 receive a signal depending only on the electrical conductivity of the fluid, which increases the sensitivity and accuracy of the converter.

Claims (1)

Invention Formula Measuring converter of electrical conductivity of liquids 986 transformer primary transformer, the output winding of which is connected to the input of the matching unit, the first synchronous detector, the first integrator and the current modulator connected in series, the analog output of which is connected to the compensation winding of the primary converter, and the reference inputs of the first synchronous detector and the current modulator are interconnected connected in series to the input of the first synchronous detector a second synchronous detector, a second integrator and a voltage modulator, trans phase shifter, the second phase shifter, the output of which is connected to the reference inputs of the second synchronous detector and voltage modulator, harmonic voltage generator connected to the supply winding of the primary converter and to the input of the second phase shifter, characterized in that, in order to improve measurement accuracy, the reference inputs of the first synchronous detector and the current modulator are connected to the harmonic voltage generator; the inputs of the synchronous detectors are connected to the output of the first phase shifter, whose input is li ne to the output of the matching block and vpsod modulator voltage is connected through a coupler to an analog output modulation current vym torus.