CN203337506U - Liquid surface tension coefficient measuring instrument based on droplet method - Google Patents

Abstract

A liquid surface tension coefficient measuring instrument based on a droplet method is composed an iron frame table (1), a glass vessel (2), a pipette (3), a photoelectric door (4), a timing and counting instrument (5) and the like, and is characterized in that the photoelectric door (4) is fixed to a support (7) through a fixing screw (6), the support (7) is fixedly connected with the iron frame table (1), the photoelectric door (4) is connected with the timing and counting instrument (5) through a cable, the pipette (3) used for sucking tested liquid is fixed beside the support (7) through a Fischer clamp (8), and the glass vessel (2) used for containing the tested liquid is arranged on the iron frame table (1). The tested droplets generate the effect of shielding infrared through the center of the photoelectric door (4), pulse signals converted through a detection circuit are input into a single-chip microcomputer system to be processed, and the total number of the droplets is displayed on a nixie tube. According to the liquid surface tension coefficient measuring instrument based on the droplet method, the photoelectric door is additionally arranged under the pipette, the timing and counting instrument is used for recording the total number of the dropped droplets, manual counting through naked eyes is changed into automatic electronic measurement, the method is convenient, reliable, simple and easy to implement, experiment errors are reduced, and experiment efficiency is improved.

Description

Measurement of liquid surface tension coefficient instrument based on sessile drop method

Technical field

The utility model relates to a kind of college physical experiment teaching instrument, specifically a kind of Measurement of liquid surface tension coefficient instrument based on sessile drop method.

Background technology

Liquid surface tension coefficient is an important parameter of performance liquid property, and the method for measuring liquid surface tension coefficient is a lot, and what at home and abroad usually adopt in laboratory at present is capillary tube technique, pull the method for method and number fluid drips number etc.Teaching practice for many years shows, the experiment effect of first two method is not bery desirable.Be mainly manifested in capillary tube technique and will could determine reference level with more liquid, liquid level is difficult for accurately determining to the distance of the minimum point of capillary meniscus, and in order to measure accurately, need to increase some equipment, operate more complicatedly, can not observe directly again the impact on liquid surface tension coefficient of surface tension of liquid effect and impurity simultaneously; The vibrations of the method that pulls in operating process are larger on the spring impact, and are difficult to get hold of the yardstick of membrane, and instrument is many, is difficult to operation, and error is larger.Number drop rules are to utilize the liquid gravitate from the Capillary of vertically the laying formation drop that lands downwards, when drop reaches maximal value and has just fallen, gravity and surface tension equate, as long as measure average weight and the radius capillaceous that several dropping liquids drip, just can obtain liquid surface tension coefficient.Compare the first two method, sessile drop method has simple to operate, to be measured less, the advantage such as expense is low.But traditional several sessile drop methods need with the naked eye observational record drop to drip number, inefficiency and easily makeing mistakes, greatly limited promoting the use of of the method.

The utility model content

For the above-mentioned deficiency of prior art, the technical problems to be solved in the utility model is a kind of Measurement of liquid surface tension coefficient instrument based on sessile drop method of design.

Solving this technical problem adopted technical scheme is: a kind of Measurement of liquid surface tension coefficient instrument based on sessile drop method, by iron stand, glass dish, transfer pipet, photoelectricity door, timing calculating instrument etc., formed, its photoelectricity door is fixed on support by fixed screw, and support and iron stand are fixed; The photoelectricity door is connected with the timing calculating instrument by cable; Clamping by support by Fei Shi for the transfer pipet of drawing fluid to be measured, for the glass dish that holds fluid to be measured, be placed on the iron stand base.

Said photoelectricity door is grooved infrared light electric switch, and infrared transmitter and infrared remote receiver are arranged on respectively the both sides of groove.

Be furnished with signal deteching circuit, data processing memory circuit on said timing calculating instrument internal circuit board, digital pipe display circuit, power switch and function button are arranged on panel.

The beneficial effects of the utility model are: by increase the photoelectricity door below transfer pipet, utilize the fallen drop of timing calculating instrument survey record to drip number, artificial naked eyes counting is become to autoelectrinic and measure, convenient and reliable, simple, both reduced experimental error, improved again conventional efficient.

The accompanying drawing explanation

Fig. 1 is the utility model structural representation.

Fig. 2 is the utility model signal circuit block diagram.

Fig. 3 is the utility model circuit theory diagrams.

Embodiment

The utility model is described in further detail below in conjunction with embodiment and with reference to accompanying drawing: first introduce by the number sessile drop method and measure the principle of liquid surface tension coefficient and relevant calculating:

The testing liquid that is M by the pipette, extract quality, then gently ooze it from the transfer pipet lower end, because of gravitate, at the mouth of pipe of transfer pipet, form bag-shaped drop, and the superficial layer of this bag-shaped drop has a thin narrow neck.When the weight of drop increases to neck top liquid level the surface tension of below liquid level is not enough to support its gravity, drop is just by the fracture of neck place and fall.The diameter d of fracture trace can be measured with reading microscope.

Fracture trace top liquid level to the surface tension f of below liquid level is:

f＝απd (1)

In formula, α is liquid surface tension coefficient, and d is fracture trace circle diameter.

If total drop number when in transfer pipet, liquid all drips to the greatest extent is N, the suffered gravity of each drop of liquid

For: $G=\frac{\mathrm{Mg}}{N}---\left(2\right)$

Drop falls the moment surface tension and equates with gravity, that is: f=G

By (1) and (2) two formulas, can be obtained $\mathrm{\α}=\frac{\mathrm{Mg}}{\mathrm{N\πd}}---\left(3\right)$

Record M, d, each amount of N, can try to achieve given liquid at the surface tension coefficient α measured under environment by formula (3).Wherein M can accurately record by electronic scales, and d can repeatedly measure to average by reading microscope and obtain, and N can record automatically by photoelectricity door and timing calculating instrument.

Referring to Fig. 1, this Measurement of liquid surface tension coefficient instrument based on sessile drop method, be comprised of iron stand 1, glass dish 2, transfer pipet 3, photoelectricity door 4, timing calculating instrument 5 etc., and photoelectricity door 4 is fixed on support 7 by fixed screw 6, and support 7 is fixing with iron stand 1; Photoelectricity door 4 is connected with timing calculating instrument 5 by cable; Press from both sides 8 for the transfer pipet 3 of drawing fluid to be measured by Fei Shi and be fixed in support 7 sides, be placed on iron stand 1 for the glass dish 2 that holds fluid to be measured.

Said photoelectricity door 4 is grooved infrared light electric switch, and infrared transmitter and infrared remote receiver are arranged on respectively the both sides of groove.

Be furnished with signal deteching circuit 9, data processing memory circuit 10 etc. on said timing calculating instrument 5 internal circuit boards, digital pipe display circuit 11, power switch and function button are arranged on panel.

Referring to Fig. 2, tested drop evenly falls through photoelectricity door 4, during each drop process photoelectricity door 4 center, infrared ray is blocked, all the other section infrared ray normally receives, so circulation, photoelectricity door 4 is converted into output of pulse signal by this signal, inputs to Single Chip Microcomputer (SCM) system after the circuit conditioning after testing and count and finally demonstrate total drop number on charactron.Function button can be controlled count enable and stop zero clearing etc.

Referring to Fig. 3, the signal deteching circuit 9 of this Measurement of liquid surface tension coefficient instrument based on sessile drop method is by photoelectricity door 4 and voltage comparator U ₁complete, voltage comparator adopts operational amplifier LM324.When circuit works, when dripless is blocked, infrared remote receiver has infrared radiation, and at this moment, the resistance of infrared remote receiver is very little, and most of voltage all is added in R ₂upper, this is voltage comparator U just ₁the forward input voltage, and the negative sense input voltage is by R ₃and R ₄dividing potential drop obtains, and R ₂the voltage of getting is greater than this reference voltage value, therefore voltage comparator U at this moment ₁the output high level; When between the infrared emission receiving tube, the obstacle of drop being arranged, infrared remote receiver is without infrared radiation, and at this moment the resistance of infrared remote receiver is very large, and most of voltage all is added on infrared remote receiver, and this is also voltage comparator U ₁the forward input voltage, and the negative sense input voltage is also by R ₃and R ₄dividing potential drop obtains, the same with original voltage, at this moment, and R ₂the voltage of getting is less than this reference voltage value, therefore voltage comparator U at this moment ₁output low level.

Referring to Fig. 3, the core that the data of this Measurement of liquid surface tension coefficient instrument based on sessile drop method are processed memory circuit 10 is U ₂chip, this chip is enhancement mode 51 single chip computer AT 89S52.This single-chip microcomputer has 4K byte FLASH flash memory, 128 byte inner RAM, 32 I/O mouth lines, two 16 bit timings/counters, 5 vectorial two-stages interruptions, a full duplex serial communication port, but the work such as settling signal reception & disposal storage.C ₁and R ₅form reset circuit of SCM, when powering on to Program reset, C ₁available 10 μ F/25V electrochemical capacitors, R ₅use the 1K precision resistance.C ₂, C ₃and CR ₁form the single-chip microcomputer oscillatory circuit, provide time reference, C ₂and C ₃available 22pF ceramic disc capacitor, CR ₁available 12MHz crystal oscillator.The pulse of INT0 pin collection signal, often come a negative edge pulse-break service routine to carry out counting once.P1.5 is connected respectively TB with the P1.7 pin ₁and TB ₂button, realize counting control and zero clearing.TB ₁press key for the first time, counter starts counting and shows in real time count value; TB ₁stop counting by key counter for the second time, the data that displayed value keeps stopping before counting are constant; Press TB ₂key, counter O reset restPoses, and shows that data are zero.Single-chip microcomputer P2 mouth connects U ₃four seven sections LED common anode charactrons, adopt the dynamic scan mode real time output data to show count value.

Referring to Fig. 3, the digital pipe display circuit 11 of this Measurement of liquid surface tension coefficient instrument based on sessile drop method is by four seven sections LED common anode charactron U ₃with four positive-negative-positives, 9012 triodes, form.Take turns scan flow group of four figures pipe by control triode break-make and realize that dynamic scan shows.Font code information, by the output of single-chip microcomputer P2 mouth, can realize that counting shows.

Below by using method, further set forth dynamic structure relation of the present utility model: before experiment starts, regulate the position of photoelectricity door 4, when making drop fallen, can, through the center of photoelectricity door 4, effectively block infrared ray.When experiment starts, opening power, press TB ₁key starts counting, and the data that on timing calculating instrument 5 panels, charactron shows after drop drips off are total drop number N.The speed that the drop of controlling well in transfer pipet 3 upper ends drips down, as far as possible slow, when treating that drop is soon fallen, regulate the distance of the lens barrel of reading microscope to drop neck breaking part, make to see the picture of drop neck breaking part clearly from eyepiece, utilize reading microscope to measure the diameter d of drop neck breaking part.Before experiment starts, with electronic scales, measure the glass dish 2 quality m1 that empty Sheng falls liquid, after drop is all fallen, then measure the gross mass m2 of liquid and glass dish 2, mass M=the m2-m1 of liquid used.By the M recorded, d, the aforementioned correlation formula of N data substitution, can calculate surface tension of liquid and surface tension coefficient.

Claims (3)

1. the Measurement of liquid surface tension coefficient instrument based on sessile drop method, by iron stand (1), glass dish (2), transfer pipet (3), photoelectricity door (4), timing calculating instrument (5) etc., formed, it is characterized in that photoelectricity door (4) is fixed in support (7) by fixed screw (6) upper, support (7) is fixing with iron stand (1); Photoelectricity door (4) is connected with timing calculating instrument (5) by cable; Press from both sides (8) for the transfer pipet (3) of drawing fluid to be measured by Fei Shi and be fixed in support (7) side, be placed on iron stand (1) for the glass dish (2) that holds fluid to be measured.

2. the Measurement of liquid surface tension coefficient instrument based on sessile drop method as claimed in claim 1, is characterized in that said photoelectricity door (4) is grooved infrared light electric switch, and infrared transmitter and infrared remote receiver are arranged on respectively the both sides of groove.

3. the Measurement of liquid surface tension coefficient instrument based on sessile drop method as claimed in claim 1, it is characterized in that on said timing calculating instrument (5) internal circuit board being furnished with signal deteching circuit (9), data processing memory circuits (10) etc., digital pipe display circuit (11), power switch and function button are arranged on panel.

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