SU817533A1 - Device for measuring liquid surface tension - Google Patents

Description

The invention relates to the control. measuring equipment, in particular to measuring devices of physicochemical parameters of solutions of surface-active substances (surfactants), and can be used to automatically measure the dynamic surface tension of the same liquid (FLF) of liquids, the concentration of surfactants in solutions in laboratory conditions. A device for measuring the surface tension (PN) of a liquid bone based on a bubbling method of measurement, consisting of a vessel filled with a test fluid of two tubes of different diameters, immersed in a liquid at different depths and connected to a gas source and measuring circuit, is known. . The difference in the tube loading depths is 2/3 of the difference between their radii. 4 To one tube, gas is supplied directly from the gas source, and to the other through a solenoid valve so that when the valve is closed, the gas goes only through one tube, and when the valve is open only through a friend. Accordingly, alternately, the pressure sensor generates signals of a higher THAT, then a Lower voltage and is connected via an amplitude voltmeter to an electric circuit to obtain a difference of signals, which is a function of the MO recorded by the recorder. m The accuracy of measuring the surface tension of pure one-component liquids by a known device is 0.1% t15. A disadvantage of this device when used to measure DPN of liquid solutions is the large error in the results. The closest to the present invention is a device for measuring the PN of liquids, containing pneumatic and electrical measurement circuits, a pneumoelectric transducer, a setter for the existence of the interface, phase shapers of large and small pneumatic substructures and a bubble mode synchronizer, in which the capillary and the bubbling tube are mounted on the same level in the liquid under study 2. Despite the fact that the output of the synchronizer of the mode of formation of bubbles enters simultaneously Both on the measuring capillary and the bubbling tube, the moments of reaching

The greatest pressures in them are always displaced among themselves in time. This is due to the fact that the time constant of the capillary and the bubbling tube is different due to their different design patterns (internal diameters) and the lengths of the pneumatic supply lines. In addition, if it is possible to achieve the simultaneous formation of gas bubbles from the capillary and the bubbling tube by manually adjusting the throttles for one value of the time of existence of the measured interface and the specific value of its surface tension, for other values of these parameters the process of formation of gas bubbles from the capillaries Pa and bubbling tube will not happen again simultaneously. But. This leads to the fact that the differential transducer does not register the difference between the highest pressures during the formation of gas bubbles from the capillary and the bubbling tube, and, consequently, to the measurement error of the DPN. This error reaches 2.5% and in many cases does not satisfy the requirements

.scientific research laboratories. The purpose of the invention is to improve the accuracy of measuring the DPN of liquids and surfactant solutions by creating equal temporal conditions for the formation of gas bubbles from two calibrated capillaries.

The goal is achieved by the fact that a device for measuring the surface tension of liquids by the method of maximum pressure in a gas bubble, containing a source of pitakitsy gas, two calibrated capillaries of various flow areas, two formers of pneumatic backwaters, a setter for the existence of a phase interface, a pneumoelectric converter, a differential amplifier and recording device, additionally contains a solenoid valve with two separately switched circuits

Switching on, an electronic relay unit with two outputs of control and phase-shifted relay signals of the same-regulated duty cycle, a measuring circuit and amplitude amplification of pulses, two input and one output electronic switches and two memory elements, while the pneumoelectric converter through the measuring circuit and expansion of the amplitude of the pulses, two input electronic keys, two memory guns, a differential amplifier and an output electronic key connected to a recording device, the input of the electronic relay unit oedinen setpoint yield the lifetime of the interface outputs separately coupled to the control inputs of input kitsimi ekt- e.

Solenoid keys and solenoid valve power supply windings, the pneumatic inputs of which are connected to the source of supply gas, and the outlets are connected to the calibrated capillaries and the pneumatic subformers.

FIG. 1 is a block diagram of a device for measuring surface tension of liquids; in fig. 2 is a schematic diagram of a solenoid valve.

A device for measuring the surface tension of liquids consisting of a source of supply gas, a solenoid, valve 2 with two separate switching circuits and switching circuits, measuring capillaries 3 and 4 of different internal diameters, dipped into the test liquid in such a way that the lower end of the capillary with a large radius the outlet is above the bottom of the capillary with a smaller radius of the outlet rf by the value of Ah 2 () / 3. The measurement of the maximum pressure during the formation of gas bubbles from the capillaries is carried out using a differential pneumatic converter 5, a generator of bi-shaped electrical oscillations and an electrical measuring circuit 7 with a standard output signal. In addition, the device contains a circuit 8 for measuring and expanding the amplitude of pulses, a generator 9 for the time of existence of an interface, an electronic relay unit 10. with two outputs for controlling and shifting along the phase of relay signals. Alternately adjustable duty cycle, a differential amplifier 11 registering 12, electronic keys 13–15, constant and adjustable chokes 16–19.

The solenoid valve (FIG. 2) consists of a body 20, six connecting nipples 21, two cores 22 with sealing gaskets on the ends, two coils 23 and two springs 24. In the absence of power supply of the coils, the two cores are sealed together by the springs internal cavities of the left, middle and. right side of the valve.

The unit for the time of existence of the interface of the phases is made in the form of an electronic time relay assembled from radio elements of domestic production and allows to obtain single short-term relay pulses at the output with an interval from 0, 5 to 600 s with possible deviations of ± 0.05-0.5 s .

Claims (2)

The electronic relay unit makes it possible to obtain, at two control outputs, phase-shifted relay signals of the same adjustable duty cycle. The duration of the relay output signals is adjustable in the range from 0.5 to 5 s and must be longer than the time required to form a single gas bubble from any capillary. Electro-relay unit assembled from radio elements of domestic-made electronic-magnetic relays. The pulse amplitude measurement and expansion scheme makes it possible to measure (the first stage), and then expand over time (the second stage of the circuit) there is no period of control relay signals of the electronic relay unit, the maximum amplitude of the input signal proportional to the measured greatest pressure alternately forming gas bubbles from the capillary device. The measurement of the surface tension of liquids by the device is carried out as follows. The device is electrically and pneumatically powered and the measuring capillaries 3 and 4 are immersed in the liquid under investigation so that the lower end of the capillary with a large inner radius Tg is above the lower end of the capillary with a smaller internal radius g by the value of DN 2 (r2- d) / 3. With the help of the setting device 9, the required time of existence of the investigated interface is established (Fig. 1). in the periods between pulses of the electronic relay unit, which is triggered by a short pulse of the setter of the time of existence of the interface, a part of the supply gas. through adjustable throttles 18 and 19 with the help of which the menisci of the test liquid in the capillaries are installed in their lower part, released into the atmosphere. This contributes to the process of absorption of surfactant molecules on the surface under study. In addition, during these periods, the electronic switches 1315 are locked, the elements, as well as the storage capacitor of the measuring circuit and the amplitude expansion of the signals are connected to the device body, and a zero signal is fed to the input of the recording device 12. At the moments when, at the output of the setting device 9 of the time for the existence of the interface, the first short-term pulse appears, relay pulses of a given duration appear on the I and III of the electronic relay unit. From output 1 of the electronically-reagent unit, the signal will go to the opening of the key 13 and the left winding of the solenoid valve 2. As a result of moving the left heart of the solenoid valve 2 to the left, the output of the supplying gas to the atmosphere through the choke 18 and the internal cavity of the capillary 3 will be blocked from the bottom the cavity of the differential transducer 5. At the same time, the pressure in the inner cavity of the capillary 3 will sharply increase to the maximum value necessary for the formation of a gas bubble from the outlet. The voltage proportional to the pressure in the formation of a gas bubble is measured by measuring circuit 7. The highest value of this voltage is measured and expanded by measuring 8 and expanding the amplitude of the pulses, since: the presence of pulses at the output of II G electronically - the relay unit 10, the capacitor of the pulse measurement and expansion circuit is disconnected from the housing. The output voltage of the measuring circuit and the amplitude amplitude of the pulses is supplied through the open electronic key 13 to the memory element and is stored by it. The electronic key 13 in the presence of pulses at the output of the electronic relay unit 10 is open, and the electronic keys 14 and 15 are closed; After the pulses at the outputs I and I of the electronic relay unit 10 are precreated, the left core returns to its original state, the internal cavity of the capillary 3 is again connected — through the choke 18 with the atmosphere, the electronic switch 13 is closed, the storage capacitor of the measurement and expansion circuit 8 the amplitudes of the pulses are again closed on the device case. The condenser remains charged until a voltage is proportional to the maximum pressure in the gas bubble formed from the capillary 3. ka 9 the time of existence of the interface of the phases of the second short-term pulse relay pulse of a predetermined duration on II and again on the 111 outputs of the electronic relay unit. This will cause the right core of the solenoid valve to move to the right position, thereby overlapping the message of the internal cavity of the capillary 4 through the throttle valve 19 to the atmosphere and establish itself with the lower cavity of the differential converter 5. The capacitor of the measurement and expansion pulse circuit 8 will register the greatest voltage, corresponding to the maximum pressure in the gas bubble, formed by demus I-capillary 4. It is the voltage from the output of the circuit through the open input electronic key 14 by means of a nonlinear pulse output II of block 10 will enter capacitor C. and charge it to a voltage proportional to the maximum pressure in the gas bubble formed from the capillary 4. The differential voltage amplified by the differential amplifier 11 on the memory capacitors C-) and Ca through the open capacitor the time of the output electronic key 15 is fed to the input of the registering device 12. After the termination of the existence of pulses at the outputs III and 11 of the electronic relay unit 10, the electronic measuring circuit of the device returns to its original state. The process of measuring the PN of the test liquid at the appearance of the two is as follows-. Short pulse at the output of the unit time of the existence of the surface-phase separation is similar. By changing the time setting of the interface elements using the setting device 9, it becomes possible to measure the DPN of the liquid or surfactant solution in the time range from 0.5 to 600 s. The value of П is calculated using the formula fi DR 2 (1 / g - l / r) where rp is the difference between the maximum pressures during the formation of a gas bubble from the capillaries. The use of new elements in order to alternately form gas bubbles from two calibrated capillaries of different internal diameters and installed at different depths in the liquid under study, as well as their interconnection in the device, makes it possible to increase the accuracy of measurement of dynamic surface tension to 0.5%, those. It makes it possible to more accurately analyze the passage of surface phenomena in surfactant solutions over time, as well as to more accurately study the process of achieving an equilibrium state in solutions and the effect of certain conditions and properties of the components on its course under laboratory conditions. Apparatus of the Invention A device for measuring the surface tension of liquids by the method of maximum pressure in a gas bubble, containing a gas supply source, two calibrated capillaries of different flow sections, two pneumatic overhead formers, a time limit for the existence of an interface, pneumatic electric converter, a differential amplifier, and a recording Apparatus characterized in that, in order to improve the accuracy of measurement of dynamic surface tension, and the same temporal conditions for the formation of gas bubbles from two calibrated capillaries, it additionally contains a solenoid valve with two separately switched switching circuits, an electronic relay unit with two outputs of control and phase-shifted relay signals of the same J and cyclic porosity, measurement circuit and expansion of the amplitude of the pulses, two input and one output electronic key- and two memory elements, while the pneumatic transducer through a circuit measuring and expanding the amplitude of them pulses, two input electronic keys, two memory elements, a differential amplifier and an output electronic key are connected to the registering device, the input of the electronic relay unit is connected to the output of the set time limit for the interface, the outputs are separately connected to the control of the electronic input keys and windings power supply of the solenoid valve, the pneumatic inputs of which are connected to the source of its gas, and the outlets - to the calibrated capillaries and the formers of the pneumatic supports ov Sources of information taken into account in the examination 1. US patent I 3426584, CL- 73-64.4. 2. The author's certificate 603879, cl. G 01 M 13/02, 1975 (prototype). chg.1 23 hch