SU699399A1 - Ultrasonic viscosimeter - Google Patents

Description

one

The invention relates to a measurement technique, in particular, to devices for measuring the rheological characteristics of liquid media.

 Ultrasonic devices for measuring internal friction: in metals and liquids, containing a pathogen connected in series, a measuring transducer, a linear amplifier, a detector comparing device, a trigger measuring device 1.

Due to the influence of temperature, these devices have a low measurement accuracy.

The closest to the invention in its technical essence is an ultrasonic viscometer that contains a pulse generator, a power amplifier, the output of which is connected to a measuring transducer and a preamplifier input, connected in series with a terminal amplifier, detector-filter, comparison device, trigger, measuring device 12.

However, the accuracy of measurements of a known viscometer is reduced due to the additional heating of the measured liquid, due to the conversion of the energy of mechanical oscillations of the converter into heat. When trying to limit the amount of heat by reducing the amplitude of the oscillations of the converter, the measurement accuracy starts to deteriorate due to the influence of the amplifier noise. This aggravates the measurement | that the initial vibration of the converter depends on the measured viscosity (it decreases with increasing viscosity). ).

These phenomena limit the accuracy of measurements and narrow the dynamic,

5, the range of measured values, which is especially manifested with an increase in the oscillation frequency of the converter, since the heat release is directly proportional to the cube of the frequency.

0

The aim of the invention is to expand the measurement range and increase their accuracy.

This is achieved by the fact that the device is additionally introduced

Claims (2)

5 modulator and cascade with adjustable frequency bandwidth, the control inputs of which are connected to the measuring device, the second input and output of the modulator are connected respectively with the output of the pulse generator and the input of the power amplifier, and the second input and output of the cascade with adjustable band respectively preamplifier output and termination amplifier input. The drawing shows a diagram of the ultrasonic viscometer. The proposed viscometer contains a pulse generator 1, a modulator 2, a power amplifier 3, a measuring transducer 4, a preamplifier 5, a cascade with an adjustable band b, a terminal usi |; 1 7, a detector-filter 8, a comparison device 9 characterized by two levels of comparison, trigger 10 with separate inputs, measuring device 11, the viscometer can be used as a measuring device for magnetostrictive sensors and torsional oscillations representing oscillatory systems Quality factor which depends on the magnitude of the measured viscosity, Co Venn QO Q factor of said sensors is equal, priblizitelno500, When immersed in liquid sensed by sensor quality factor Q j; and varies with the quality factor Q) ". where Qsf Itf / oL, is the natural frequency of oscillation of the sensor, ci. - attenuation of free oscillations of the sensor in a liquid. For the sensor by author. No. 204379 G5 L where R and RJJ- are, respectively, external and internal radii of the sensor resonator; P is the density of the resonator material. 26 is the length of the resonator; p is the density and viscosity of the liquid being measured. For a nickel resonator with dimensions. I 3 cM, .R 0.5 cm., RO 0.4 cm, the oscillation frequency f 25000 HZ, Qo 500, In this case, in the case of water measurement ("0.01 poises, P 1 g / cm) QA 6750 Q 466 and in the case of the mineral madla (J 1.77 poise, p 0.905; G / cm5) G | 169, 126. The considered viscometer works with pulsed excitation sensors. The generator 1 generates triggering voltage pulses. The modulator 2 amplifies this signal depending on the magnitude of the feedback voltage coming from the output of the measuring device 11. I then amplified by the amplifier 3, the pulses go to the measuring transducer (sensor) 4 and to the input of the amplifier 5. The attenuating voltage removed by the sensor is amplified in preamplifier 5, passes through a cascade with adjustable band 6 and terminal amplifier 7. The band of frequencies transmitted by cascade 6 is controlled by a feedback circuit with an output Measuring device 1i Envelope of amplified voltage, depending on the attenuation ωL-rcf / Qj ,, is detected by the detector-filter 8 and is fed to a comparison device & 9 with two levels of comparison E, (H, and ECJ Pulses corresponding to The levels Ej. and Ej; 2 are fed to the inputs of trigger 10, the duration of the impulse ut which, in the first approximation, does not depend on the measurements of the initial amplitude of the attenuating signal of the sensor x: M V where E is EC. The measuring device 11 calculates the measured value L P; K based on the known (measured in advance) its values QQ, f, If Ri f RO P-1 ci / Ec2 "device measured value bt, feedback voltage, taken from device 11, proportional to Q. With increasing Q, the bandwidth of the band passed by cascade 5 narrows, and the gain of the amplifier containing the stages 5,6 and 7 does not change. In this case, the effective noise value decreases with decreasing measured viscosity amplifier that contributes to the preservation the accuracy of the device with a decrease in viscosity and, therefore, allows to expand the range of measured values in the direction of their reduction while maintaining the specified accuracy. The homogeneity of the introduction to the circuit of the modulator 2 is due to the following. At a time, the amplitude of oscillations of the sensor resonator at a constant amplitude of excitation depends on the magnitude of the measured viscosity. This is due to the fact that when the sensor is immersed in a liquid, the resonator becomes asymmetrical, as a result of which part of the oscillation energy is dissipated in the mounting system of the resonator. In the measurement range under consideration, v (Q 126 - 466), the amplitude of oscillations p e30HaTOjC a differs by a factor of 2-3 at the extreme points of the range (as the viscosity increases, the amplitude decreases). The minimum amplitude allowed at high viscosities should be chosen , based on the permissible overheating of the fluid, arising due to the conversion of the energy of mechanical vibrations into heat. The magnitude of this overheating should be significantly less than the accuracy of temperature stabilization in the thermostat, i.e. significantly less than 0.02 - 0.1 ° C for laboratory thermostats. It was found out by experiments that in the case of the ultrasonic frequency of oscillations it is relatively difficult to achieve a small overheating, because even with a small amplitude of oscillations as 0.5-10 cm a noticeable heat release is observed, which is also confirmed by theoretical calculations. An increase in the amplitude of oscillations in liquids with low viscosity leads to a deterioration in measurement accuracy due to an increase in overheating, which can be eliminated by the introduction of modulator 2, ensuring that the sensor excitation decreases with increasing Qj. It also contributes to the expansion of the range of measured values and the measurement accuracy. The use of the proposed viscometer makes it possible to extend the range of measured values by at least 15 times, to reduce the temperature instability of the measured liquid by two orders of magnitude and. bring them to hundredths of a degree, which allows technological control of the viscosity of slow-moving (non-mixed) liquids, in which heat exchange is hampered. Ultrasonic viscometer comprising a pulse generator, a power amplifier, the output of which is connected to a measuring transducer and a preamplifier input, connected in series with a terminating amplifier, a detector-filter, a comparison device, a trigger, a measuring device, characterized in that in order to extend the measurement range and increase their accuracy, it additionally introduced a modulator and a cascade with adjustable frequency bandwidth, control inputs (and which are connected The second input and output of the modulator are connected respectively to the output of the pulse generator and the input of the power amplifier, and the second input and output of the cascade with an adjustable band, respectively, the output of the preamplifier and the input of the terminal amplifier ./ Sources of information taken into account during the examination 1.FUSfield HJ, Apparatus for Instrur Menti 1950, V 21, 7, p, 612. 2.Smirnov Yu.K ,, Tolokonnikov S.V. Ultrasonic viscometer, sat. Ultrasonic technology, 1966, issue 1, (prototype).