SU1599711A1 - Viscosity vibration pickup - Google Patents

Abstract

The invention relates to the investigation of various properties of materials, in particular, to the design of a vibration viscosity sensor. Vibration viscosity sensor allows to expand the range of studied liquids, to increase the reproducibility of measurement results. The vibration viscosity sensor contains a two-leg tuning fork, at the base of which piezoelectric transducers are installed, and a hollow spring with an inlet and an outlet for the input and output of the test fluid, installed between the tuning-fork legs and rigidly connected perpendicular to them. 2 Il.

Description

The invention relates to a technique for measuring viscosity, in particular to the device of highly sensitive flow-through vibration sensors for use in research laboratories, in medicine, for monitoring technological processes.

The aim of the invention is to expand the scope and increase accuracy by stabilizing the form factor.

FIG. 1 depicts the proposed sensor; in fig. 2 - interdependence dependence (IT p - and p J and YTT.

The proposed sensor consists of a tuning fork 1,. Piezoelectric elements 2, a spring 3. The tuning fork is mounted on the support 4.

D -. measuring sensor is included in the feedback circuit

generator, providing work at the resonance frequency. With this, one of the piezoelectric elements is energized by a voltage Ir, from the other piezoelectric element the voltage IV is removed, which is proportional to the amplitude, and VB1IH mechanical oscillations arise.

When moving the tuning fork legs, the spring walls are displaced relative to the fluid enclosed in it. The friction between the spring and the fluid (and in the fluid itself) causes an additional (compared to the losses in the tuning fork and in the spring) energy dissipation. The quality factor of the vibrator is one. To achieve the same amplitude of oscillations, more Up will be needed or at the same exciting voltage there will be less amplitude and, accordingly, P,

ate

: o: oh

31599711

I For Newtonian fluids, friction between oscillations is rapMOHH4ecKONry. the law of the body and fluid is described by the formula

Z .. G

 Al

AT

Ilf

Ui

 cYpa

de z

resistance

mechanical fluid;

force causing movement; oscillation amplitude; amplitude of the oscillation speed;

sludge fluid; fluid viscosity;

- coefficients of proportionality.

In addition to fluid resistance, resistance is also present.

AT

iV. V

conditional by internal friction of the measuring system (suspension) and

Vf

Z B

UFO UI

G de z

IT

  +

7: 6

P

at

Pg

at

and

I

mechanical resistance;

excitation voltage in the absence of fluid spring;

voltage proportional to the displacement when there is no VII liquid in the spring.

With stabilized we have. K (Up- Pr).

The measurements are carried out in the following way.

The value of U p is found when there is no liquid in the spring (filled with air). Find U.j: when filling the spring of the calibration fluid. Determine the coefficient K by the formula

TO

- viscosity

density kk 1k of cleaning fluid.

Further, at a constant value of Id, P is determined — the test liquid

Find the desired value of LHO by the formula

and)

  Kdi.p

ten

15

five

thirty

35

40

45

50

five

or according to the calibration dependence, which can be constructed after determining U, - a series of liquids with known Ypt values. When measuring, there is no operation of immersing the test body in a liquid, i.e. the dependence of U on the immersion depth is excluded. The spring always has the same volume and internal surface. Thus, the filling automatically ensures the same flatness of the contact of the test body with the liquid, which ensures an increase in the accuracy and reproducibility of the measurement results.

Example. Brass tuning fork 1 with a resonance frequency f. with; 400 Hz is fixed in support 4. Piezo elements 2 are glued near the base of the legs. A stainless steel rod of tubular shape (wall thickness, 1 mm) 12 mm in diameter (slightly larger than the distance between the legs — 10 mm) is tightly inserted between the tuning fork legs.

When the sensor was tested, piezoelectric elements were included in the feedback circuit of the autogenerator. The value of 11 s was kept constant (2.5 V). Measured with a digital voltmeter U p 1 V, the spring was filled with hoses, connected to its ends. The values of Up 11,, are obtained on the absolute axis (fig, 2). when filling the tube with air (T-, O) J with heptane (t. 1) with benzene (t. 2), water (t. T).

Scheduled sensitivity of the sensor is K 0.7 v / i (kg Pa-m.

The use of the proposed sensor ensures high sensitivity in the area of low viscosity; increasing the reproducibility of the obtained results; ease of manufacture of the sensor,

Claims (1)

Invention Formula A vibration viscosity sensor containing a two-leg tuning fork, at the base of which piezoelectric transducers are installed, is due to the fact that, in order to improve measurement accuracy by stabilizing the shape factor, it is provided with a hollow spring with an input and output for input and removal of the test medium installed between the tuning-fork blades and rigidly connected perpendicular to them. Rig. one 0 0.2 9ig.2 i Compiler L. Ulnov ; Editor T. Parfenova Tehred A. Kravchka Proofreader M, Kucher va : Order 3136 Circulation 487 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology CCJICP 113035, Moscow, Zh-35., Raushsk nab., D, 4/5. Subscription