SU1627919A1 - Rotational viscometer - Google Patents

Abstract

The invention relates to a measurement technique, namely, instruments for measuring viscosity and studying the rheological characteristics of liquids. The purpose of the invention is to improve the measurement accuracy. A known device containing electric drive 1, external cylinder 2 with liquid under test 2, internal "receiving cylinder 4, asynchronous electric motor 5 with excitation winding 6 and control winding 7, angular displacement sensor 8, amplifier 9 and recorder 17, amplitude detectors are introduced 10 and II, comparator 12, reversible counter 13, gene; pulse 14 and digital-to-analog converters 15 and 16, which will increase the measurement accuracy by increasing the accuracy of determining the static torque of an asynchronous motor and the moment of viscous friction, regardless of the voltage variation of the power source, reducing the ambient temperature and warming up the induction motor 5 by introducing a feedback circuit consisting of a digital-to-analog converter 15 and a comparator 12, eliminating the need for voltage stabilization in the circuit field windings, I Il. (L with & s with

Description

 The invention relates to a measurement technique, namely, instruments for measuring viscosity and radiation of the rheological characteristics of liquids.

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

The drawing shows the functional diagram of the rotational viscometer.

The device contains an electric drive 1, an outer cylinder 2 in which the test fluid 3 is located, an inner sensing cylinder 4, an induction motor 5 with excitation winding 6 and control winding 7, an angular displacement sensor 8, amplifier 9, amplitude detectors 10 and 11, comparator 12, a reversible counter 13, a pulse generator 14, a digital-to-analog converter (CDL) 15 with a constant reference voltage, a DAC 16 with a variable reference voltage, a recorder 17, and an alternating voltage source 18.

The actuator 1 is mechanically connected to an external cylinder 2 filled with the test liquid 3, inside which an internal sensing cylinder 4 is coaxially fixed at one end of the axis of the asynchronous motor 5. At the other end of the axis of the asynchronous motor 5 an angular displacement sensor 8 is fixed, the output of which is connected through the amplifier 9 to one output of the control winding 7 of the induction motor 5, the other output of which is connected through an amplitude detector JO to one input of the comparator 12 and through one p A resistor (not labeled) to a common bus (not shown). The excitation winding 6 of the asynchronous electric motor 5 is connected by a single output through a capacitor (not labeled) to the alternating voltage source 18 and another output through an amplitude detector 11 - and a DAC reference input 16, the output of which is connected to the recorder input 17, and through a different resistor (not labeled ) - to the common bus. The comparator 12 is connected by another input to the output of the DAC 15 and the output to one input of the reversing counter 13 connected by another input to the output of the pulse generator and the outputs to the informational inputs of the DAC 15 and 16.

0

five

Q 0 5 Q

five

Rotational viscometer works as follows.

When the external cylinder 2 rotates at an angular velocity (O due to the presence of viscosity of the test liquid 3 placed inside it, the internal sensing cylinder 4 also begins to rotate, and the rotor of the sensor 8 is angularly displaced. The signal from the output of the sensor 8 is angularly displaced to the input of the amplifier

9, which in the control winding 7 generates the voltage required to stop in the internal sensing cylinder 4 fixed to the rotor axis of the induction motor 5. The excitation winding 6 is connected to an alternating voltage source through a phase-shifting circuit. In this case, the current in the circuit of the control winding 7 is measured by an amplitude detector

10, from which the output voltage is constant, proportional to the amplitude of the measured current, is fed to one input of the comparator 12, which enters

The digital voltmeter is formed by a reversible counter 13 connected to the comparator output, a generator of 14 pulses and a DAC 15, while in the established mode the output of the DAC 15 contains a voltage equal to the output voltage of the digital-analog converter the amplitude detector 10, the binary code corresponding to this voltage arises at the outputs of the reversible counter 13 connected to the information inputs of the DAC 16, which multiplies the analog signal and the code, DAC 16 output voltage is generated, equal to the product of binary values, proportional to the current in the control winding 7 and the voltage at the output of the amplitude detector 11, proportional to the current in the excitation winding 6.

Thus, the expression for the static moment M appearing on the axis of the asynchronous motor 5 and corresponding to the viscosity of the liquid under study 3 has the form

 yiB,

where K is a constant coefficient j

In current in the control winding 7; &Apos; is the current in the excitation winding 6.

4-Ю2

K-97irU7K7B rpatS n (lMV

where (O, is the synchronous angular velocity of rotation of the magnetic field in the windings of the asynchronous electric motor 5;

- - coefficient of cast Ig; phase difference between currents

 AT

AND

 U.

Mr. - the reduced resistance of the rotor synchronous

electric motor 5.

In this expression, K is a constant coefficient, since the effect of the change in rpu from temperature on Mgt is insignificant, and it can be ignored.

Claims (1)

Using the invention, it improves the accuracy of measurements from 3–4 to 0.1–0.2% due to an increase in the dosobothRHOcfn determination of the static torque of an asynchronous motor and the moment of viscous friction, regardless of the voltage variation of the power source, and the decrease in the influence of ambient temperature. environment and warm-up asynchronous electric motor. This eliminates the need to use voltage stabilization in the field of the excitation winding, which simplifies the design, reduces power losses, reduces weight and dimensions. The limitation on the power of the asynchronous motor is removed, which allows expanding the viscosity measurement range of the test substances by about 2 times. Invention Formula Rotational viscometer containing electric drive, outer cylinder, ten 20 25 15 thirty 35 40 an internal sensing cylinder, an angular displacement sensor, a recorder, a capacitor, an asynchronous electric motor with excitation and control windings, filled with an investigated liquid, in which the internal sensing cylinder is placed coaxially with the external cylinder; on the one side of the axis there is an internal reproducible cylinder fixed on the one hand and AC source, common bus and amplifier, connected by an input to the output of an angular displacement sensor - and output - to one terminal of a control winding, one output The excitation winding is connected through a capacitor to a source of alternating voltage, which is connected with the fact that, in order to improve the measurement accuracy, two amplitude detectors, a pulse generator, two digital analogue converters, a reversible counter and a comparator connected by one input to the output of the first amplitude detector, another input to the output of the first digital-analogue converter and an output to one input of a reversible counter connected by another input to the output of the pulse generator and output With the data to the information inputs of both digital-to-analog converters, the first amplitude detector is connected to the other output of the control winding, the second amplitude detector is connected to the other output of the second excitation winding and output to the reference input of the second digital-analog converter, the output of which is connected to the recorder's input.