CN213715149U

CN213715149U - Novel automatic acid-base titrator

Info

Publication number: CN213715149U
Application number: CN202022610030.8U
Authority: CN
Inventors: 余健毅; 张静; 赵训雄
Original assignee: Hunan Haosen Pharmaceutical Co ltd
Current assignee: Hunan Haosen Pharmaceutical Co ltd
Priority date: 2020-11-12
Filing date: 2020-11-12
Publication date: 2021-07-16
Anticipated expiration: 2030-11-12

Abstract

A novel automatic acid-base titrator comprises a titrating device, a color measuring device and a control device; the titration device comprises a peristaltic pump, a reagent tube, a photoelectric switch, a titration tube and an electromagnetic stirrer; the reagent tube, the peristaltic pump and the burette are connected through a hose; the electromagnetic stirrer is arranged in the burette; the peristaltic pump is used for driving a titrant in the reagent tube, and when the titrant drips, the photoelectric switch responds and sends a pulse signal to a port of the single chip microcomputer; the color measuring device is a color measuring instrument and is used for measuring the color of a sample in the burette, and the color measuring instrument realizes color measurement by measuring the spectral power distribution reflected by an object; the control device comprises a singlechip and a display printing module, and the singlechip sends a pump driving signal to realize the motion of the peristaltic pump; the color signal of the sample in the burette collected by the color measuring instrument is input to the input port of the singlechip after being subjected to A/D conversion; the display printing module displays the detection result of the detected sample in a display screen and prints the detection result.

Description

Novel automatic acid-base titrator

Technical Field

The utility model relates to a titrator especially relates to a novel automatic acid-base titrator belongs to chemical analysis test equipment field.

Background

Acid-base titration analysis is widely applied no matter chemistry, chemical engineering, environmental science, food sanitation or life science, and the traditional acid-base titration method is that an acid-base or alkali-base burette is used, liquid filling is complicated and is not accurate enough, and the prior art discloses an intelligent electronic acid-base titrator as a Chinese patent application (application number: CN2015109706908, publication number: CN 106885872A), which is characterized by comprising a standard liquid storage bottle (1), a liquid guide micro-diameter pipe (2), a stepping motor (3), a pump head (4), a titration reaction pipe (5), a non-contact electric conduction electrode (6), an energy source and communication line (7), a central chip (8) and a touch panel (9); under the instruction of the central control and calculation center, the whole process of titrant sample introduction, high-frequency signal input, conductance response signal acquisition and amplification, titration curve recording, result display and recording is automatically completed. Chinese patent (application number: CN2013207032682, publication number: CN 203616257U) discloses a full-automatic acid-base titrator, which comprises an experimental box, a burette, a light source emitter and a light source receiving processor, wherein a round base for placing a beaker is arranged in the bottom of the experimental box, a stirrer is arranged in the experimental box, the burette is provided with a peristaltic pump and a flow sensor, the lower part of the experimental box is provided with an automatic lifting instrument, and the upper part of the experimental box is provided with a round groove. The round base is fixedly connected with the top end of the automatic lifting instrument. Chinese patent (application date: CN2015202197974, publication number: CN 204514887U) discloses an automatic acid-base titrator, which comprises a liquid storage bottle for storing acid/alkali liquor, a burette, a liquid storage vessel for storing liquid to be titrated, a shell with a box-type structure and an intelligent controller; the liquid storage bottle is fixed at the top of the inner cavity of the shell through a fixed seat; a vibration device is arranged in the inner cavity of the shell; the liquid storage vessel is locked and fixed on the vibrating device through a fixing clamp; the top end of the burette is connected to the liquid outlet of the liquid storage bottle, the bottom end of the burette extends into the liquid storage dish, and a sharp-nose dropper is connected to the orifice at the bottom end of the burette; a micro metering pump and an automatic valve are sequentially arranged on the burette from top to bottom; and a pH value sensor is arranged at the bottom of the inner cavity of the liquid storage vessel. For another example, chinese patent (application No. CN2015209820792, publication No. CN 205139108U) discloses an acid-base titrator, which includes a plurality of burettes and a plurality of titration containers, wherein the plurality of burettes are mounted on a titration turntable, the top of the titration turntable is connected to a slide rail through a rotating member, the plurality of titration containers are fixed on a chassis, the bottom center of the chassis is connected to a motor through a driving device, and the plurality of titration containers correspond to the plurality of burettes in the vertical position.

However, the acid-base titrator is found in engineering use, and due to the structure or relative simplicity, the acid-base titration accuracy of the acid-base titrator is often in error, or due to the complex structure of the acid-base titrator, the acid-base titration accuracy is not favorable for daily maintenance.

SUMMERY OF THE UTILITY MODEL

The utility model aims at realizing automatic monitoring titration terminal point, avoiding the artificial factor of terminal point observation, greatly reducing the terminal point judgment error.

The utility model adopts the technical scheme as follows:

a novel automatic acid-base titrator comprises a titrating device, a color measuring device and a control device; it is characterized in that: the titration device comprises a peristaltic pump, a reagent tube, a photoelectric switch, a titration tube and an electromagnetic stirrer, wherein the reagent tube, the peristaltic pump and the titration tube are connected through a hose, and the electromagnetic stirrer is arranged in the titration tube; the peristaltic pump is used for driving a titrant in the reagent tube, and when the titrant drips, the photoelectric switch responds and sends a pulse signal to a port of the single chip microcomputer; the color measuring device is a color measuring instrument and is used for measuring the color of a sample in the burette, and the color measuring instrument realizes color measurement by measuring the spectral power distribution reflected by an object; the control device comprises a single chip microcomputer and a display printing module, and the single chip microcomputer sends a pump driving signal to realize the movement of the peristaltic pump; the color signal of the sample in the burette collected by the color measuring instrument is input to the input port of the singlechip after being subjected to A/D conversion; and the display printing module displays the tristimulus values and chromaticity coordinates of the detected samples in a display screen and prints the detection results.

Preferably: the peristaltic pump comprises a pump head, a hose and a transmission device; the conveying of the titrant by the peristaltic pump is realized by the extrusion process of a hose; the transmission device transmits power to the pump shaft to drive the pump head to rotate at a certain speed.

Preferably: the peristaltic pump adopts a stepping motor as a transmission device.

Preferably: when the single chip sends out a starting instruction of the peristaltic pump, the output starting pulse is input into the pulse distributor and passes through the power amplifier and then is fed to the winding of the stepping motor to drive the stepping motor to move according to the instruction, so that the pump head is driven to rotate.

Preferably: the color measuring instrument comprises an integrating sphere, an illumination light source, a coupling lens, an optical fiber, a CCD photoelectric conversion array, a linear array CCD image sensor, a concave grating, a main channel and a reference channel signal processor; the illumination light source is corrected by a D65 filter, mixed by an integrating sphere and irradiated on a sample to be measured; a tested sample is placed on a sample clamp tangent to the wall of the integrating sphere; the coupling lens and the optical fiber enable spectral information reflected by a tested sample to reach the concave grating through the incident slit, so that a visible spectrum is sequentially imaged on a receiving surface of the linear array CCD detector and is transmitted to the single chip microcomputer input interface through the photoelectric signal processing circuit on the main channel; the reference channel is used for following, monitoring and compensating adverse effects on a measurement result caused by instability of a light source in the main channel, and light source signals are transmitted to the input interface of the single chip microcomputer through the optical fiber through the photoelectric signal processing circuit.

Preferably: the photoelectric switch comprises a light emitting diode, a phototriode, a high input impedance I/V conversion amplifier and a pulse shaping circuit; when the titrant enters the action range of the light receiver, the electric signal passes through the high input impedance I/V conversion amplifier and then the 1K resistor to light the light emitting diode, the phototriode receives an optical pulse and modulates the optical pulse into an electric pulse signal, and the electric pulse signal is input into a C/T0 port of the singlechip through the pulse shaping circuit; the port C/T0 is set to counter mode.

Preferably: the singlechip is an 8051 type singlechip.

Preferably: and the display printing module displays the tristimulus values and chromaticity coordinates of the detected samples in a display screen and prints the detection results.

The utility model discloses beneficial effect:

the titration end point is automatically monitored by adopting a color measuring instrument, so that the artificial factor of end point observation is avoided, and the end point judgment error is greatly reduced. In addition, the peristaltic pump is adopted to drive the carrier liquid, and the titration quantity of each titrant is relatively accurate; the instrument is also provided with a singlechip to realize flow control, display and printing, so that the whole machine can realize automatic operation.

Drawings

Fig. 1 is a schematic view of the working principle of the acid-base titrator of the utility model.

Fig. 2 is a schematic structural view of the peristaltic pump of the present invention.

Fig. 3(a) is a schematic diagram of the driving circuit of the present invention.

Fig. 3(b) a schematic diagram of control pulses in a peristaltic pump drive circuit according to the present invention.

Fig. 4 is a schematic view of the drip counting operation principle of the present invention.

Fig. 5 (a) and (b) are schematic diagrams of the differential mode structure and the signal output characteristics thereof according to the present invention.

Fig. 6 is a schematic view of the overall structure of the color meter of the present invention.

Wherein: 1. the device comprises a reagent tube, 2 a peristaltic pump, 3 a photoelectric switch, 4 a burette, 5 an electromagnetic stirrer, 6 a pump shell, 7 a hose, 8 a pump head, 9 a pump shaft, 10 a roller, 11 an integrating sphere, 12 an optical trap, 13 a concave grating, 14 a D65 filter, 15 a pulse xenon lamp, 16 an incident slit, 17 a measured object, 18 an optical fiber and 19 a coupling lens.

Detailed Description

The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments described below are by way of example only, and other obvious variations will occur to those skilled in the art.

Acid-base titration is a titration analysis based on an acid-base reaction, which reacts according to a certain stoichiometry: x (component to be measured) + R (reagent) = P (reaction product), that is, a reagent (R) solution of known concentration is added dropwise to the solution to be measured until the added reagent reacts with the component to be measured stoichiometrically, and then the content of the component to be measured is calculated from the concentration and volume of the reagent solution used. Among them, strong acids (HCl, HClO4, etc.) or strong bases (NaOH, KOH, etc.) are generally used as reagents. In chemical analysis, the metering point is determined by the color change of the indicator. Titration is stopped when the indicator happens to be at the color change point of the color transition, referred to as the end point of titration.

As shown in fig. 1. The novel automatic acid-base titrator comprises a titrating device, a color measuring device and a control device; the titration device comprises a peristaltic pump, a reagent tube, a photoelectric switch, a titration tube and an electromagnetic stirrer, wherein the reagent tube, the peristaltic pump and the titration tube are connected through a hose, and the electromagnetic stirrer is arranged in the titration tube; the peristaltic pump is used for driving a titrant in the reagent tube, and when the titrant drips, the photoelectric switch responds and sends a pulse signal to a port of the single chip microcomputer; the color measuring device is a color measuring instrument and is used for measuring the color of a sample in the burette, and the color measuring instrument realizes color measurement by measuring the spectral power distribution reflected by an object; the control device comprises a single chip microcomputer and a display printing module, and the single chip microcomputer sends a pump driving signal to realize the movement of the peristaltic pump; the color signal of the sample in the burette collected by the color measuring instrument is input to the input port of the singlechip after being subjected to A/D conversion; and the display printing module displays the tristimulus values and chromaticity coordinates of the detected samples in a display screen and prints the detection results.

During measurement, a proper amount of a sample to be measured and an indicator are added into a burette, and a titrant is filled in a reagent tube and is connected with a peristaltic pump through a hose; and (5) switching on a power supply, and starting the peristaltic pump, the electromagnetic stirrer and the color measuring device. The peristaltic pump is used for driving the titrant, when the titrant drips and passes through the photoelectric switch, the photoelectric switch responds and sends electric pulses to a C/T port of the computer, and the drop number metering is realized. The electromagnetic stirrer was used to stir the sample to allow for full reaction. Along with the proceeding of the acid-base reaction, the concentrations of the reactant and the product are changed, so that the color of the indicator is changed. When the color of the solution in the sample tube reaches a preset value, the reaction is judged to be at the end point, and the titration and stirring work is stopped. And obtaining the volume of the titrant according to the dripping result, thereby calculating the content of the component to be measured.

The peristaltic pump 2 is composed of four parts, namely a pump shell, a pump head, a hose and a transmission device, and is shown in figure 2. It is a micro-precise pump, accurate in quantification and stable in flow. The flow stability precision and the reproducibility precision are both less than 1%. The peristaltic pump conveys the liquid by virtue of the squeezing process of the hose. The transmission device transmits power to the pump shaft to drive the pump head to rotate at a certain speed. When the roller on the pump head presses the peristaltic pump hose, the carrier liquid in the hose is squeezed to the output direction. The pump head continues to rotate and automatically relieves the pressure on the hose. The compressed hose is restored by the elasticity of the hose, and vacuum is generated in the hose to suck liquid into the tube cavity. The liquid in the tube cavity is output out of the pump body under the action of next extrusion.

The peristaltic pump uses a stepping motor as a transmission device, and a driving circuit thereof is shown in fig. 3 (a). After the single chip gives out starting instruction, the pulse is fed through pulse distribution circuit and power amplifier and fed into the winding of step motor to drive the step motor to step according to the instruction so as to drive pump head to rotate, and the rotating speed of the pump head depends on the frequency of pulse signal.

The stepping motor is a pure digital control motor, and is an open-loop control element for converting electric pulse into angular displacement or linear displacement, the pulse amplitude is determined by the level of a digital element, and TTL is 0-5V; the CMOS is 0-10V. The on and off times can be controlled in a time-delayed manner to ensure stepping into position, the control pulses being illustrated schematically in fig. 3 (b). The single chip microcomputer directly converts the parallel binary code into a serial pulse sequence and realizes direction control, each pulse can enable the stepping motor to rotate by a fixed stepping angle, and the final position of the stepping motor can be known as long as the initial position is known according to the size of the stepping angle and the actual number of steps. The control of the extrusion direction of the carrier liquid in the hose is realized by controlling the stepping motor, the rotation direction of the stepping motor is related to the electrifying sequence of the internal winding, the electrifying sequence is changed to change the rotation direction of the stepping motor, and the electrifying sequence of the three-phase six-beat working mode comprises forward rotation A-AB-B-BC-C-CA and reverse rotation A-AC-C-CB-B-BA.

The implementation of the pulse allocation of the present invention is realized by hardware. The pulse distribution chip adopts a PMM8713 type chip, the chip belongs to unipolar control, and a three-phase six-beat working mode can be selected for controlling the stepping motor. The pulse distribution selects single clock input, a Schmitt shaping circuit is arranged in the input end of the pulse distribution selecting single clock input, the anti-interference capability is improved, a 4-18V direct-current power supply is used, and the output current is 20 mA. When a single clock input mode is selected, the 3 rd pin of the PMM8713 chip is a stepping pulse input end, the 4 th pin is a steering control end, and the input of the two pins is provided and controlled by the singlechip. Because the pulse distributor PMM8713 is adopted, the singlechip only needs to provide stepping pulse to carry out speed control, and the work of pulse distribution is finished by the pulse distributor, thereby reducing the work load of the singlechip.

The titration speed of the titration device is realized by controlling the rotating speed of the peristaltic pump through the stepping pulse frequency sent by the singlechip, namely: controlling the frequency of the stepping pulse to realize speed regulation by a hard pulse distribution mode, carrying out pulse output operation by an interrupt service submodule in a built-in timer of the singlechip, and adjusting a timing constant of the timer to realize speed regulation; in order to generate step pulse, a timing constant is calculated according to a given pulse frequency and the machine period of the single chip microcomputer, the timer determines timing time, the timer generates interruption when overflowing, a square wave output with a given frequency is obtained in an interruption submodule through the operation of changing the level state of a pin P1.0 of the single chip microcomputer, and the frequency of the square wave can be changed by changing the timing constant.

The pulse signal generated by the pulse distributor is input into the stepping motor driver, and the output power driving signal drives the winding of the stepping motor to drive the stepping motor to step according to the instruction, so that the pump head is driven to rotate, and the speed of the peristaltic pump is adjusted.

As shown in fig. 4. The photoelectric switch part consists of a light-emitting diode, a phototriode, a high input impedance I/V conversion amplifier and a pulse shaping circuit. When the titrant enters the action range of the light receiver, the phototriode receives a light pulse and modulates the light pulse into an electric pulse signal, and the electric pulse signal is amplified and shaped and then input into a C/T0 port of the 8051 singlechip. The port C/T0 is set in counter mode, and executes the counting interrupt service instruction to realize the drop counting when receiving the pulse signal. Since the amount of drops per drop is small, to increase sensitivity, dual-photosensitive transistors are used, which are operated in differential mode, as shown in fig. 5. When titrant drips, the output voltage signal VD1 of the detector D1 is reduced, and the output voltage signal VD2 of the detector D2 is increased. The output voltage Vout = VD 1-VD 2 (1); the differential mode circuit is adopted to process signals, so that the signal to noise ratio of measurement is improved, and the drop number measurement is more accurate and reliable.

In the titration analysis, the endpoint of the titration is judged by the color change of the sample solution. Because of human subjective factors, there is a difference in identifying color difference, so a large error is caused when the color change is judged by naked eyes. In this case, a colorimeter is introduced, and the change of the solution color is monitored in real time by adopting a photoelectric detection technology. The color measuring instrument mainly comprises an integrating sphere, an illumination light source, a linear array CCD image sensor, a concave grating, a main channel and reference channel signal processor and a microcomputer control system, and is shown in figure 6. The colorimeter achieves color measurement by measuring the spectral power distribution reflected by an object. The holographic concave flat field grating is adopted, and the collimation, the convergence and the dispersion are integrated, so that the volume of the light splitting system is reduced, and the loss of light energy is reduced. The CCD photoelectric conversion array is used as a receiver, so that the measuring process and the time for transmitting and reading information are extremely short, and the real-time measurement of spectral information can be realized. The color measuring instrument adopts d/8 degree illumination and meets the measurement geometrical condition. An optical trap is provided on the integrating sphere to eliminate the regular reflection portion on the sample to be measured. The illumination source is modified with a D65 color filter. The sample to be measured is placed on a sample holder tangent to the wall of the integrating sphere. The illumination light is mixed by the integrating sphere and then irradiated on the sample to be measured. The coupling lens and the optical fiber enable the spectral information reflected by the sample to reach the holographic concave flat field grating through the entrance slit, and the visible spectrum is sequentially imaged on the receiving surface of the linear array CCD detector through the dispersion effect of the grating. The main measurement channel is used for obtaining spectral information of a reflection sample, and the spectral information is received by the linear array CCD and then read by a computer after passing through the photoelectric information processing circuit, the data acquisition and interface adaptation circuit. The purpose of the reference channel is to effectively follow, monitor and compensate for the adverse effect on the measurement result caused by the instability of the light source in the main channel. And after the signal data of the main channel and the reference channel are obtained by the computer, calculating the tristimulus values and chromaticity coordinates of the sample.

The utility model discloses a color meter is from the automatic monitoring titration terminal point, and the color measurement precision is less than or equal to 0.003, has avoided the human factor that the terminal point was observed, has greatly reduced the terminal point and has judged the error. In addition, the peristaltic pump is adopted to drive the carrier liquid, each drop of titrant is less than or equal to 4.5 mu L, and the precision can reach 0.1 mu L. The utility model discloses still be equipped with singlechip microcomputer and provide calculation, control, demonstration and printing, make the complete machine realize automatic function. The acid-base titrator can be used for measuring acid, alkali and substances capable of directly generating proton transfer with the acid and the alkali, and has high analysis precision.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It should be understood by those skilled in the art that the present invention is not limited by the above embodiments, and the above embodiments and what is described in the specification are the principles of the present invention, and that various changes and modifications may be made without departing from the spirit and scope of the present invention, and these changes and modifications fall within the scope of the present invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A novel automatic acid-base titrator comprises a titrating device, a color measuring device and a control device; it is characterized in that: the titration device comprises a peristaltic pump, a reagent tube, a photoelectric switch, a titration tube and an electromagnetic stirrer, wherein the reagent tube, the peristaltic pump and the titration tube are connected through a hose, and the electromagnetic stirrer is arranged in the titration tube; the peristaltic pump is used for driving a titrant in the reagent tube, and when the titrant drips, the photoelectric switch responds and sends a pulse signal to a port of the single chip microcomputer; the color measuring device is a color measuring instrument and is used for measuring the color of a sample in the burette, and the color measuring instrument realizes color measurement by measuring the spectral power distribution reflected by an object; the control device comprises a single chip microcomputer and a display printing module, and the single chip microcomputer sends a pump driving signal to realize the movement of the peristaltic pump; the color signal of the sample in the burette collected by the color measuring instrument is input to the input port of the singlechip after being subjected to A/D conversion; and the display printing module displays the detection result of the detected sample in a display screen and prints the detection result.

2. The novel automatic acid-base titrator as claimed in claim 1, wherein: the peristaltic pump comprises a pump head, a hose and a transmission device; the conveying of the titrant by the peristaltic pump is realized by the extrusion process of a hose; the transmission device transmits power to the pump shaft to drive the pump head to rotate at a certain speed.

3. The novel automatic acid-base titrator as claimed in claim 2, wherein: the peristaltic pump adopts a stepping motor as a transmission device.

4. The novel automatic acid-base titrator as claimed in claim 3, wherein: when the single chip sends out a starting instruction of the peristaltic pump, the output starting pulse is input into the pulse distributor and passes through the power amplifier and then is fed to the winding of the stepping motor to drive the stepping motor to move according to the instruction, so that the pump head is driven to rotate.

5. The novel automatic acid-base titrator as claimed in claim 3, wherein: the color measuring instrument comprises an integrating sphere, an illumination light source, a coupling lens, an optical fiber, a CCD photoelectric conversion array, a linear array CCD image sensor, a concave grating, a main channel and a reference channel signal processor;

the illumination light source is corrected by a D65 filter, mixed by an integrating sphere and irradiated on a sample to be measured; a tested sample is placed on a sample clamp tangent to the wall of the integrating sphere;

the coupling lens and the optical fiber enable spectral information reflected by a tested sample to reach the concave grating through the incident slit, so that a visible spectrum is sequentially imaged on a receiving surface of the linear array CCD detector and is transmitted to the single chip microcomputer input interface through the photoelectric signal processing circuit on the main channel;

the reference channel is used for following, monitoring and compensating adverse effects on a measurement result caused by instability of a light source in the main channel, and light source signals are transmitted to the input interface of the single chip microcomputer through the optical fiber through the photoelectric signal processing circuit.

6. The novel automatic acid-base titrator as claimed in claim 1, wherein: the photoelectric switch comprises a light emitting diode, a phototriode, a high input impedance I/V conversion amplifier and a pulse shaping circuit; when the titrant enters the action range of the light receiver, the electric signal passes through the high input impedance I/V conversion amplifier and then the 1K resistor to light the light emitting diode, the phototriode receives an optical pulse and modulates the optical pulse into an electric pulse signal, and the electric pulse signal is input into a C/T0 port of the singlechip through the pulse shaping circuit; the port C/T0 is set to counter mode.

7. The novel automatic acid-base titrator as claimed in claim 1, wherein: the singlechip is an 8051 type singlechip.

8. The novel automatic acid-base titrator as claimed in claim 1, wherein: and the display printing module displays the tristimulus values and chromaticity coordinates of the detected samples in a display screen and prints the detection results.