SU428217A1 - DIGITAL DEVICE FOR MEASURING THE SPEED AND FLOW OF THE LIQUID • ^^ '• ki ft: L "f: -R :::' vrfSfg '^' ^.!! HER tiU ^ iii ^; b & iu - Google Patents

Description

one

The invention relates to magnetohydrodynamic meters (MHD meters) of the flow rate of a liquid and to electromagnetic flowmeters.

In the known digital MHD-meters, the flow velocities use an AC-current compensator containing code-analogue converters, exemplary voltages to which are supplied from a section of the winding of an autotransformer connected to the power supply circuit of the measuring MHD converter. The voltage of several converters "code-analog is evaluated and, in accordance with their significance, is summed up. The total compensating voltage is compared with an analog MHD converter signal proportional to the flow rate and in phase with the converter supply current. The voltage difference (the error signal) is amplified and fed to a control device that changes the numerical code before the voltage at which the error signal is zero. The resulting numeric code is fed to the indicator, calibrated in units of flow rate.

In order to create a symmetrical input value of the autocompensator, a comparison of the compensating voltage and the signal of the MHD converter is carried out on the compensating transformer voltage.

A disadvantage of such devices is the presence of a large number of transformers, which introduce significant phase shifts. To match the phases of the compass and

measured voltages, it is necessary to use phase shifting / C-circuits, the instability of parameters of which reduces accuracy. The purpose of the invention is to improve the measurement accuracy. This is achieved by the fact that, in the proposed digital device, the digital autocompensator is equipped with a compensating current autotransformer, the primary winding of which is connected in series to the power supply circuit of the converter loaded on

The shunts of the spgnal secondary windings are included in the signal compensation circuit of the converter, and the secondary sections of the adjusting winding are connected to the shunt and switches of the switching device.

In addition, in order to provide a predetermined zero level, the digital autocompensator is equipped with a bias current transformer, the primary winding of which is connected in series with the primary winding of the compensating transformer, and the secondary windings are connected in series with the secondary signal windings of the compensating transformer.

The drawing shows a block diagram of a proposed device consisting of a conductive MHD i-converter / flow rate (speed), a power supply 2 and a digital autocompletion device 3. A digital autocomponent 3 contains transformers connected to the MHD i-converter / current compensating circuit 4 current, a comparison device 6 with a balanced input, a control device 7, a switching device 8 and an indicator 9. The compensating current transformer 4 has three secondary windings - an adjusting 10 l alarm U / n 12, expeirmen- schunty respectively at 13, 14 and 15. The winding 10 iodklyuchena to the shunt 13 through the switches 16 of the switching device 5. The secondary windings 17 and 18 of the biasing current transformer 5 loaded on the variable resistors 19 and 20. The apparatus operates as follows. The voltage difference between the converter 1 and the compensating misses taken from the shunts 14, 15, 19 and 20 is fed to the comparison device. The control device 7 through the switch (its device 8 changes the number of turns of the winding 10, thereby changing the voltage taken from the shunts 14 and 15, until the input voltage of the comparison device 6 is zero. Switched keys 16 the switching device 8 organizes a flow or speed code, which is indicated in the indicator 9. The bias current transformer 5 sets the zero of the autocompensator 3. The inclusion of equal compensating aprons in the measuring circuits that connect each electrode The gateway with the comparison device 6 allows you to create a symmetrical input circuit of the autocompensator and avoid the influence of leakage currents on the meter readings. Subject and search 1. The digital device for measuring the velocity and flow rate of the fluid containing the tipper , an indicator, a magnetohydrodynamic converter of the flow rate (velocity) of a fluid flow, a digital auto-capacitor including series-connected comparing, controlling and switching devices, characterized in that, in order to improve the accuracy rhenium, digital avtokomiensator provided komiensiruYuSch .IM current autotransformer whose primary is connected in series in tsei iitani transducer schunty signal loaded on the secondary windings included in the transducer signal compensation circuit and an adjusting section of the secondary winding connected to the shunt switching device and keys. 2. The device according to claim 1, characterized in that, in order to provide a predetermined zero level, the digital autocompensator is equipped with a bias current transformer, the winding of which is connected in series with the primary winding of the compensating transformer, and the secondary windings are connected in series with the secondary signal windings of the locator transformer.