CN115792393A

CN115792393A - Detection device

Info

Publication number: CN115792393A
Application number: CN202210866873.5A
Authority: CN
Inventors: 吴泳智; 彭倜
Original assignee: Shenzhen Liushu Technology Co ltd
Current assignee: Shenzhen Liushu Technology Co ltd
Priority date: 2021-07-22
Filing date: 2022-07-22
Publication date: 2023-03-14
Also published as: CN218068146U; CN113589047A

Abstract

The invention relates to a detection device integrating EIS liquid impedance measurement and a refractometer, which comprises an optical measurement system, an impedance measurement system and a processing system, wherein the optical measurement system comprises a light source, a light source controller and a light source controller; the optical measurement system comprises a light source system, a reflecting prism and an optical receiver system; the impedance measurement system comprises an electrode system and a circuit system; the processing system is connected with the optical receiver system and the circuit system; the testing device comprises a reflecting prism, a ring-shaped piece, an electrode system and a liquid storage tank, wherein the reflecting prism is arranged on one surface of the reflecting prism, a hollow-out part in the middle of the ring-shaped piece is matched with one surface of the reflecting prism to form the liquid storage tank for containing liquid to be tested, an electrode of the electrode system extends into the liquid storage tank to be contacted with the liquid to be tested, and the liquid to be tested in the liquid storage tank forms an interface between the surface of the prism and the liquid level on the reflecting prism so as to realize simultaneous testing of refraction and liquid impedance.

Description

Detection device

Technical Field

The invention relates to the field of liquid measurement, in particular to a detection device integrating EIS liquid impedance measurement and a refractometer.

Background

Measurement using Electrochemical Impedance Spectroscopy (EIS) is a common method for liquid measurement. Electrochemical impedance spectroscopy, i.e., measuring the variation of impedance with the frequency of a sine wave, is very effective for detecting liquids involving ionic conduction, especially multi-ionic mixed liquids, and a considerable part of information in mixed ionic solutions can be easily obtained by using an EIS system. The refractive index of the liquid is increased after the solid soluble substances are dissolved, and the measurement of the content of the solid soluble substances can be achieved through the refractive index measurement, so that the refractometer can be used for measuring the content of the solid soluble substances in the liquid.

However, the refractometer only reflects the concentration of soluble solids in the liquid in the measurement process, and such a measurement mode has disadvantages in measuring many liquids, for example, when measuring a liquid with a low ion concentration, the refractometer cannot be very accurately evaluated, and then is a mixed solution mixed with ions, active substances, cells and the like, and the refractometer only reflects the properties of soluble parts in the liquid, but cannot reflect the properties of insoluble proteins, cells and the like. For example, when the sucrose aqueous solution is prepared by ultrapure water, the sucrose does not have other ionized ions except sucrose molecules inside the sucrose aqueous solution, and the sucrose exists in a molecular crystal state and does not have an ionized state, so that information displayed by the sucrose aqueous solution during electrical impedance measurement does not greatly differ from water, and the concentration of the sucrose aqueous solution cannot be judged by simply measuring the electrical impedance.

Therefore, both the refractometer and the EIS system have problems of being unable to measure or inaccurate in measurement, and although the accuracy can be increased by separate measurement of the refractometer and the EIS system, new problems arise, such as the risk of contamination of the sample during the transfer process, and particularly, the problem of insufficient sample amount in the case of a small sample amount in separate measurement.

Further, the electrodes used in the conventional EIS measuring instrument are generally cylindrical, and as shown in fig. 1, fig. 1 is a schematic structural view of the conventional EIS measuring instrument. When the EIS measuring instrument is used, an additional fixing structure is needed to fix the plurality of electrodes in the figure 1 in a liquid to be measured, the using operation is complicated, and the size of the EIS measuring instrument is large.

Disclosure of Invention

The invention aims to provide a detection device integrating EIS liquid impedance measurement and a refractometer.

The specific scheme is as follows:

a detection device comprises a liquid storage tank, an electrode module, a processing module, a light source module, a reflection module containing a detection area and a photosensitive module,

the detection area is positioned at the bottom of the liquid storage tank, and the liquid storage tank is used for containing liquid to be detected;

the light source module is used for emitting light beams to the detection area of the reflection module, the photosensitive module is used for forming a photosensitive image on at least part of the light beams totally reflected by the reflection module, and the processing module is used for determining the refractive index of the liquid to be detected according to the photosensitive image;

the electrode module comprises at least two electrodes which are arranged in the liquid storage tank and positioned around the detection area, and is used for contacting with the liquid to be detected in the liquid storage tank; the processing module is used for applying an electric signal to at least one electrode in the electrode module, acquiring the electric signal of the at least one electrode in the electrode module, and determining the electrochemical impedance spectroscopy EIS of the liquid to be detected according to the applied electric signal and the acquired electric signal.

Optionally, the at least two electrodes are in a shape of a sheet, and are laid at the bottom of the reservoir and surround the detection area.

Optionally, the at least two electrodes are laid on the surface of the detection region, or the at least two electrodes are laid on the surface of the inner side wall of the reservoir.

Optionally, the at least two electrodes include a counter electrode, a working electrode and a reference electrode, wherein at least one of the size, the position and the shape of the counter electrode and the working electrode are symmetrically arranged, and the distance between the reference electrode and the working electrode is smaller than the distance between the reference electrode and the counter electrode.

Optionally, the at least two electrodes are disposed on a circuit board, and a temperature sensor is disposed on the circuit board.

Optionally, the reservoir is conical, and a water level prompt line is carved in the reservoir.

Optionally, the photosensitive module includes a photosensitive area array, and at least one converging lens is disposed between the reflective module and the photosensitive module, and is configured to converge the light beam totally reflected by the reflective module onto the photosensitive area array.

Optionally, the processing module includes a main control chip and a peripheral circuit built outside the main control chip, where the main control chip is configured to output an ac signal through a DAC provided therein, and the peripheral circuit is configured to shape the ac signal.

Optionally, the peripheral circuit includes a low-pass filter circuit for performing low-pass filtering on the ac signal output by the main control chip, and a circuit for eliminating dc bias voltage from the output of the low-pass filter circuit.

Optionally, the processing module is further configured to collect an alternating current signal from the electrode module;

the peripheral module further comprises a circuit for respectively carrying out zero-crossing detection on the alternating current signal output by the main control chip and the alternating current signal collected from the electrode module, and a phase comparison circuit for carrying out phase comparison on the two paths of alternating current signals subjected to zero detection to obtain a phase difference pulse signal.

Optionally, the processing module further includes an analog-to-digital conversion circuit, configured to obtain a duty ratio of the phase difference pulse signal when the frequency of the phase difference pulse signal is greater than 1 kHz; the processing module further comprises a timer for acquiring the duty ratio of the phase difference pulse signal when the frequency of the phase difference pulse signal is not more than 1 kHz.

The detection device provided by the invention can be used for measuring soluble solids and insoluble solids in a liquid system by simultaneously realizing refraction measurement and electrochemical impedance measurement on liquid, so that the measurement robustness is improved, and the refraction measurement and the impedance measurement are finished by using the same liquid to be measured and simultaneously measuring, so that the liquid to be measured does not need to be transferred, the possibility of sample pollution is avoided, the measurement accuracy is greatly improved, and the measurement time is shortened.

Drawings

Fig. 1 shows a structural diagram of an electrode used in a conventional EIS measuring instrument.

FIG. 2 shows a schematic view of an embodiment of the detection apparatus of the present application.

Fig. 3 is a schematic diagram showing a positional relationship among the light source module, the reflection module and the light sensing module in the detection apparatus.

Fig. 4 and 5 are schematic structural views of two embodiments of the planar electrode, respectively.

FIG. 6 is a schematic diagram of a portion of the internal structure of one embodiment of the detection device.

FIG. 7A is a diagram of the logical architecture of one embodiment of a processing module in the detection apparatus of the present application.

Fig. 7B is a logic architecture diagram of one embodiment of a low pass filter circuit in the detection apparatus of the present application.

Fig. 8 is a schematic diagram of a circuit structure of the detection apparatus for amplifying the filtered ac signal output by the main control chip and eliminating the dc bias voltage.

Fig. 9 shows a schematic configuration of a half-wave trimming circuit and an amplifying circuit in the detection apparatus.

Fig. 10 shows a schematic diagram of a zero-cross detection circuit and a phase comparison circuit in the detection apparatus.

Fig. 11 shows input and output schematic diagrams of the phase comparison circuit.

Fig. 12 shows an impedance plot of an aqueous sucrose solution.

FIG. 13 shows the refractive index of water and a 40% aqueous solution of sucrose.

Fig. 14 shows a liquid system for milk.

Detailed Description

To further illustrate the various embodiments, the invention provides the accompanying drawings. The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the embodiments. Those skilled in the art will appreciate still other possible embodiments and advantages of the present invention with reference to these figures. The components in the drawings are not necessarily to scale, and similar reference numerals are generally used to identify similar components.

The invention will now be further described with reference to the drawings and the detailed description.

As shown in fig. 2, the present embodiment provides a detection apparatus 20 that can measure EIS of a liquid. The detection device comprises a reservoir (not shown) for containing a liquid to be detected, an electrode module 22 and a processing module 21. Wherein the electrode module 22 comprises at least two electrodes disposed within the reservoir. The processing module is used for applying an alternating signal (such as a sine wave signal) to at least one electrode in the electrode module and for collecting an electrical signal on at least one electrode in the electrode module. The processing module 21 is further configured to detect an electrochemical impedance spectroscopy EIS of the liquid to be detected according to the acquired electrical signal.

In one example, the detection device is not only used to detect the EIS of the liquid to be measured, but also to detect the refractive index of the liquid to be measured. Specifically, the detection device further includes a light source module 23, a reflection module 24, and a light sensing module 25. As shown in fig. 3, fig. 3 is a schematic diagram of a positional relationship among the light source module, the reflection module and the light sensing module in the detection apparatus. The reflection module 24 comprises a prism, one surface of which is arranged at the bottom of the reservoir. For convenience of description, the area of the prism surface corresponding to the bottom of the liquid storage tank is referred to as a detection region 241 hereinafter. The light source module 23 is used for emitting a light beam to the detection area 241 of the prism. When the liquid to be measured is filled in the liquid storage tank, and the total reflection condition is satisfied between the liquid to be measured and the prism, a light beam (i.e., a light beam with an incident angle greater than or equal to the total reflection angle) which satisfies the total reflection condition in the light beams emitted from the light source module to the detection area of the prism is totally reflected to the light sensing module 25 by the detection area, and a light beam (i.e., an incident angle less than the total reflection angle) which does not satisfy the total reflection condition is transmitted out from the detection area.

Alternatively, the wavelength of the green portion may be used in the light source module, since the light sensing module 25 is sensitive to the green channel light acceptance. The light emitting device in the light source module can be realized by adopting an LED linear array light source method, and the LED linear array light source can be realized by sticking a plurality of LED chips on a PCB. Because there is the clearance between the inside LED chip unit of LED linear array light source, this can influence the homogeneity of the light of final formation of image, consequently can increase even light piece in the light-emitting side of LED chip and realize the effect of even light, even light piece can adopt even light piece such as light diffuser plate, various materials make to realize the even of light, finally make the formation of image also more even, can reach better measuring effect.

In addition, because the exiting light of the existing LED chip has a certain spread angle, some non-parallel light rays may affect the measurement accuracy, and some non-parallel light rays may cause an artifact or some factors interfering with the measurement of the light rays collected by the optical receiver. Generally, the collimating system can collimate the light by other means such as a cylindrical lens, a convex lens, a slit, and the like.

Optionally, the detection device further includes a module for decoupling the exit position and the exit angle of the light source, so that the light beams incident to the detection area at the same angle can be incident to the same position of the light sensing module when being reflected to the light sensing module. Therefore, a sudden brightness change boundary is formed on the photosensitive image detected by the photosensitive module. It can be understood that when the refractive indexes of the liquids to be measured are different, the total reflection angle of the light beam totally reflected on the prism is different, and therefore, the position of the brightness abrupt change boundary formed on the photosensitive module is also different. Therefore, the processing module is also used for calculating the refractive index of the liquid to be measured by detecting the position of the boundary of the brightness picture on the photosensitive image.

The module for decoupling the exit position and the exit angle of the light source in the detection device may be implemented by a slit or a small hole located at the light emitting surface of the light source module, and the slit or the small hole may also be implemented by a collimation system at the exit end of the light source module at the same time. Alternatively, as shown in fig. 3, it may be implemented by a condensing lens 26 between the prism 24 and the photosensitive module 25. The light beam totally reflected by the prism 24 enters the converging lens 26, and is converged on the photosensitive surface of the photosensitive module 25 by the converging lens 26. Compared with the light source module, the small holes are formed in the light emitting surface of the light source module to achieve decoupling of the angle and the position of an incident light beam of the photosensitive linear array in one dimension (namely the direction parallel to the photosensitive linear array), the convergence module is arranged between the prism and the photosensitive module to achieve decoupling in two dimensions, the photosensitive module of the photosensitive surface array is adopted in a matched mode to detect the light beam, more information can be obtained, the accuracy of the refractive index of liquid to be detected is improved, and even more information of the liquid to be detected can be obtained.

Optionally, the photosensitive module 25 includes an optical filter and an optical receiver. Since the optical devices in the optical receiver have different sensitivity degrees to different wavelengths, the optical filter functions to preferentially select the light source within the wavelength range from the light beam emitted by the light source module. Secondly, in order to filter out other wavelengths of stray light entering the optical receiver in the environment, the stray light may be due to other light sources, such as other wavelengths of light entering the optical system from the sunlight, and the like.

The optical receiver mainly comprises a CMOS, a CCD or other optical receiving components, which can effectively receive the light emitted by the light source and reflected by the prism system, so as to obtain effective light information for the subsequent measurement system to perform the relevant measurement. The optical receiver can adopt an area array CMOS to detect the image sensor, so that the cost is lower, the accuracy is higher, the installation requirement is reduced, and the things which can not be realized by a plurality of one-dimensional sensors can be realized, such as improving the accuracy, enhancing the anti-interference capability, adding other measurement functions and the like; moreover, even if air bubbles exist at the detection area of the prism or the liquid to be detected does not completely cover the total reflection interface, the abrupt change boundary of the brightness can still be clearly distinguished.

In one example, the electrode module 22 includes at least two electrodes affixed to the interior surface of the reservoir and arranged around the detection region 241. Because the voltage and the current need to be measured respectively by the double electrodes, and the voltage fluctuates to some extent when the current flows, the measurement result is not accurate enough, and the measurement accuracy can be improved by adopting the structure of the three electrodes. The electrode module can determine a system of measuring electrodes according to a system of measuring liquid during impedance measurement, and generally comprises three electrode systems, namely a two-electrode system, a three-electrode system and a four-electrode system. When impedance measurement is carried out, if the electrode potential of the auxiliary electrode is determined to be unchanged or change can be ignored in the test process, a reference electrode is not needed, and the measurement can be carried out by adopting a two-electrode system.

In order to reduce the influence of the electrode potentials of the working electrode and the auxiliary electrode (counter electrode) changing during the test, a three-electrode system is used, which has a working electrode (research electrode), a reference electrode and an auxiliary electrode (counter electrode) for measuring and monitoring the potential difference between the reference electrode and the working electrode with high input impedance, almost no current passes through the reference electrode, and current passes between the working electrode and the auxiliary electrode.

In order to overcome the influence of electrode polarization and environmental fluctuation, a four-electrode test system can be adopted, which utilizes a pair of external electrodes to introduce exciting current into liquid and measures the voltage on a pair of internal electrodes, and mainly adopts an alternating current impedance method to test resistance.

Optionally, each electrode is in a planar sheet shape and is laid at the bottom of the liquid storage tank. Compare prior art's spatial structure's electrode, each electrode in this application adopts planar structure to set up in the bottom of liquid groove, can simplify the design and the processing degree of difficulty of the waterproof construction to the electrode module, and the electric field that distributes in the liquid is more even in the bottom distribution moreover, more is favorable to the collection of electrode pair signal.

The material of the electrode can be a platinum electrode, a titanium electrode, a carbon electrode and other metal compound electrodes. There are various implementations of the electrodes. In order to achieve a small integration of the planar electrodes, the electrodes may optionally be integrated on a circuit board. The circuit board can be a flexible circuit board of FPC technology, or a PCB circuit board, or an aluminum-based circuit board. The PCB can be made of FR4 resin and is subjected to metallization edge covering treatment. Wherein, the thickness of the flexible circuit board of the FPC technology can be 0.09mm or even thinner.

Methods of making planar electrodes are various. For example, a metal sheet is fixed on the surface of the circuit board by means of adhesive or the like as an electrode, and contacts on the circuit board are welded to the metal sheet to conduct the electrodes, or the metal sheet is adhered to the circuit board by means of conductive adhesive to make the metal sheet and the contacts on the circuit board contact and conduct. For another example, the bare copper sheet of the circuit board is used for gold deposition process, and a layer of nickel-gold is plated to form the electrode, the nickel-gold has the advantages of corrosion resistance and long service life, and the scheme can control the thickness of the electrode to be very thin. The FPC copper skin has mature process, the thickness can be controlled within 0.15mm, and the PI material of the FPC covering film is non-toxic, so that the FPC copper skin can be used for manufacturing tableware and medical appliances, and a detection device is convenient to use in some catering or medical fields. Also for example, each electrode may be implemented using copper plating. When the circuit board is a flexible circuit board of an FPC (flexible printed circuit) process, the circuit board can be reinforced by sticking a plurality of stainless steel sheets on the circuit board, and exposed copper is arranged on the steel sheets to form contacts so as to form a plurality of planar electrodes. The electrodes can be made of the same or different materials, and the problem of reducing the accuracy of the measurement result caused by different corrosion degrees of different materials during measurement can be solved by adopting the same materials.

As shown in fig. 4 and 5, fig. 4 and 5 are schematic structural views of two embodiments of the planar electrode, respectively. In the two schematic diagrams, the circuit board 40 is provided with a through hole 41, and the through hole 41 is located at the bottom of the liquid storage tank and is used for corresponding to the detection area of the prism when the circuit board 40 is fixed on the surface of the prism.

Around the through hole 41 are attached three

metal sheets

42, 43 and 44 for realizing three electrodes, respectively, and between any two metal sheets is attached a plastic spacer sheet 45. The shapes of the foils may be different when the two illustrations are different. The edge of the foil may be aligned with the edge of the circuit board in fig. 4 and the foil is looped around the through hole 41 in fig. 5, the edge being inside the edge of the circuit board. Optionally, as shown in fig. 4 and 5, a temperature sensor 46 is further disposed on the circuit board, and the heat is conducted to the lower side of the temperature sensor through the large area of copper under the planar electrode, so that the temperature sensor can directly measure the temperature conducted by the planar electrode. Since the refractive index of the liquid drifts with a change in temperature, a deviation occurs in determining the solid soluble content of the liquid based on the refractive index of the liquid. The temperature of the liquid to be measured by the temperature sensor arranged in the detection device can be convenient for the processing module to correct the measurement result according to the temperature when calculating the refractive index of the liquid to be measured, so that the accuracy of refractive index measurement is improved; the electrode plays a role of a heat conducting medium, so that the electrode has good thermal conductivity, the temperature sensor can measure the temperature of the liquid to be measured more accurately, and the accuracy of the temperature sensor in measuring the temperature of the liquid to be measured is improved.

Where the electrode module has a three-electrode structure, the CE counter electrode 43, the SE working electrode 42, and the RE reference electrode 44 are provided. Optionally, at least one of the size, position and shape of the CE counter electrode 43 and the SE working electrode 42 is symmetrically arranged, and the distance between the RE reference electrode 44 and the SE working electrode 42 is smaller than the distance between the RE reference electrode 44 and the CE counter electrode 43, so as to improve the performance of the electrode module. When the electrode module is a dual-electrode structure, optionally, the two electrodes are symmetrically arranged. When the electrode module is of a four-electrode structure, optionally, the four electrodes may be symmetrically arranged in pairs, and the symmetrical arrangement may be a symmetrical arrangement of at least one of size, position and shape.

As shown in fig. 6, fig. 6 is a partial internal structure diagram of an embodiment of the detection device. Optionally, the reservoir 61 is tapered to improve ease of cleaning the reservoir. Optionally, a scribing line is further arranged in the liquid storage tank, and is used for reminding a user that the scribing line is exceeded when the liquid to be detected is placed in the liquid storage tank, so that the liquid amount required by the detection device when the refractive index and the EIS of the liquid to be detected are measured is ensured. Optionally, a light-transmitting waterproof layer covering the electrode module and the detection region is further disposed at the bottom of the liquid storage tank.

Each electrode in the electrode module 62 extends into the liquid storage tank, the liquid to be measured can form a prism and liquid surface interface on the prism 63, and light is filtered by the optical filter and received by the optical receiver by means of total reflection of the prism and liquid surface interface. The electrodes can be embedded in the surface of the prism and extend into the liquid storage tank, or laid on the detection area of the prism, or laid on the inner peripheral wall of the liquid storage tank in a surrounding manner, or penetrated into the liquid storage tank from the peripheral wall of the liquid storage tank, and the like.

When the liquid to be measured is filled in the liquid storage tank, the counter electrode and the reference electrode are main nodes for measuring potential and impedance, so that potential or current with certain frequency and amplitude is required to be applied to the working electrode. The signal excited on the electrode can be a static direct current signal, which can measure measurement information such as conductivity, static potential and the like; or an alternating current signal excited according to a certain frequency and amplitude, wherein the frequency range can be 0.0001Hz-10MHz, and the amplitude can be-10V-10V, so that the response parameters of the potential and the impedance of the liquid under different frequencies can be measured.

The processing module excites a sinusoidal signal with a certain frequency width and amplitude to the liquid to be measured through at least one electrode in the electrode module, multi-dimensional information is formed through detecting the impedance, potential and phase of the liquid between the electrodes and through the relationship between the electrodes and the frequency, the obtained multi-dimensional information and the signal measured by the optical receiver can describe the property of the liquid together, and the property of the liquid to be measured can be more accurately judged.

There are many implementations of the signal stimulus. For example, the ac signal may be directly output from a Digital to Analog Converter (DAC) chip controlled by a main control chip, or may be directly output from a modulation resonant circuit. The DAC chip can generate sine wave signals with high frequency, such as sine waves of 1Mhz, but the cost is high, the model selection is difficult, the problem is easy to occur at the end of a supply chain in production, the modulation resonant circuit can realize the frequency adjustment of output alternating current signals, but the realization difficulty is high, and the cost is difficult to control and realize miniaturization due to the complex and large circuit structure.

In one example, as shown in FIG. 7, FIG. 7 is a diagram of the logical architecture of one embodiment of a processing module in the detection apparatus of the present application. Optionally, in the application, the processing module includes a single chip, and the DAC provided in the single chip is used as a signal excitation source to output an alternating current signal, so that the cost can be greatly reduced and the miniaturization can be realized. In one example, the single chip microcomputer comprises a main control chip ESP32S2. However, the waveform of the ac signal output from the DAC of the main control chip ESP32S2 is likely to be distorted after the frequency exceeds 100 kHz. Optionally, the processing module further includes a low-pass filter circuit for processing the ac signal output by the DAC in the main control chip to make the waveform reach the standard. Alternatively, the low-pass filter circuit may be a butterworth low-pass filter, as shown in fig. 7B, and fig. 7B is a schematic structural diagram of an example of the low-pass filter circuit, and the ac signal output from the DAC is input to the circuit from the port ESP _ SIN _ DAC in fig. 7B for low-pass filtering. In some examples, the ac signal processed by the low pass filter may have a dc bias voltage, and optionally, the processing module further includes a cancellation bias circuit for canceling the dc bias voltage from the ac signal processed by the low pass filter. Optionally, the processing module may further include an amplifier, configured to amplify the ac signal output by the main control chip and output the amplified ac signal to the electrode module, for example, to an electrode CE in the electrode module. As shown in fig. 8, fig. 8 is a schematic diagram of a circuit structure of the detection apparatus for amplifying the filtered ac signal output by the main control chip and eliminating the dc bias voltage. After being filtered, the ac signal output from the main control chip is input from CE _ SIN _ BY _ OFFSET to the OFFSET operational amplifier circuit 81 and the power amplifier 82, and then output to the electrode RE and the electrode CE. Through the DAC output alternating current signal who utilizes in the singlechip from the area in this application, and set up a plurality of peripheral circuits outside the singlechip and handle the alternating current signal of main control chip output, can export high-frequency alternating current signal, compare and directly adopt the DAC chip can greatly reduced cost, and compare modulation resonant circuit and can reduce the volume, realize the miniaturization.

The processing module is also used for collecting signals generated by the electrodes. For example, in a three-electrode configuration, the processing module is connected to the electrode WE for collecting electrical signals on the electrode WE. Because the collected electric signals are mostly Analog quantity signals, optionally, the processing module further includes an Analog-to-digital converter (ADC) circuit for converting the Analog quantity signals into digital signals and inputting the digital signals into the processing module. The ADC may be a self-contained ADC within a single chip. And the processing module calculates the impedance according to the maximum value acquired by the ADC, and further measures the change of the impedance along with the frequency of the alternating current signal. Optionally, the operational amplifier resistor in the ADC circuit is an adjustable resistor, so that the range of the ADC can be changed, and the maximum value obtained by the ADC circuit can be adjusted.

Optionally, the processing module further includes an amplifying circuit on the signal link of the collecting electrode module, and is configured to amplify the ac signal collected by the electrode module before the ADC circuit, and then half-wave rectify the amplified ac signal and input the rectified ac signal to the ADC in the single chip microcomputer. As shown in fig. 9, fig. 9 is a schematic diagram of a half-wave collating circuit and an amplifying circuit in the detection apparatus. The electrode WE is sequentially connected with the trans-group amplifying circuit 91 and the amplifying circuit 92, and an electric signal on the electrode WE is amplified by the trans-group amplifying circuit 91 and the amplifying circuit 92, then input to the half-wave rectifying circuit 93 for half-wave rectification, and then input to the ADC through the WE _ SIN _ POS.

The processing module is further used for acquiring the phase change of the alternating current signal generated by the DAC and the alternating current signal collected by the ADC. Optionally, the ADC circuit may be implemented by a high-precision ADC chip, so that the ADC chip may acquire a complete waveform for the ac signal, but the sampling capability of the ADC chip is very high, which results in high cost. Optionally, in this embodiment, the processing module is further configured to perform zero-crossing detection on the alternating current signal generated by the DAC and the alternating current signal acquired by the electrode module, and perform logical and on the two signals after the zero-crossing detection to obtain a phase difference pulse signal, where a duty ratio of the phase difference pulse signal represents a phase difference of the two signals.

As shown IN fig. 10 and 11, the ac signal generated by the DAC and the ac signal collected by the electrode module are respectively input to the zero-cross detection circuit 101 and the zero-cross detection circuit 102 from two ports SIN _ IN1 and SIN _ IN2, and the two positive voltage partial pulses obtained are input to the phase detection circuit 103 for phase comparison, for example, logical and operation (as shown IN fig. 11) to obtain a phase difference pulse. Alternatively, the signal input from the SIN _ IN1 port may be a signal output from the CE _ SIN port IN the circuit diagram shown IN fig. 8, and the signal input from the SIN _ IN2 port may be a signal output from the WE _ SIN port IN the circuit diagram shown IN fig. 9.

The processing module is also used for carrying out positive and negative phase detection and PWM duty ratio measurement on the phase difference pulse signals. Because the duty ratio and the phase of the phase difference pulse are in a linear relation, when the frequency of the phase difference pulse signal is more than 1Khz, the phase difference pulse signal can be subjected to RC low-pass filtering, and the phase difference pulse is converted into a direct current signal for detection. The PWM duty cycle of the pulse signal is then calculated based on the filtered voltage value and a preset scaling function. The relationship between the voltage values and the PWM duty cycles at different frequencies may be non-linear, and the functional relationship between the filtered voltage values and the PWM duty cycles of the pulse signals may be pre-calculated and stored in the processing module. When the frequency of the phase difference pulse signal is less than 1Khz, the PWM duty ratio of the phase difference pulse signal can be measured by GPIO edge capture or PCNT pulse capture, or can be detected by a timer of a singlechip. Therefore, the phase measurement precision can be improved, and the phase measurement precision can reach +/-0.1 degrees. Compared with an ADC chip with high precision, the method has the advantages that the circuit cost can be greatly reduced by acquiring the duty ratio after zero-crossing detection and logic and calculation of two paths of signals.

The following illustrates the advantages of the detection apparatus provided by this embodiment over existing refractometers and EIS impedance measurements.

Example 1

In a non-conductive liquid system, since liquid is not ionized, such as a sucrose aqueous solution, in the case of preparing a sucrose aqueous solution with ultrapure water, since there is no ionized ion except for sucrose molecules inside the sucrose aqueous solution, sucrose exists in a state of molecular crystal, and there is no ionized state, therefore, information displayed by the sucrose aqueous solution during electrical impedance measurement is not greatly different from water (see fig. 12 for an impedance graph of the sucrose aqueous solution), and thus the concentration of sucrose aqueous solution cannot be simply determined by electrical impedance measurement.

However, the concentration of the sucrose aqueous solution causes a change in the refractive index of the liquid, and thus a very large difference is exhibited in the measurement results of the refractometer (the refractive index of water and a 40% sucrose aqueous solution is shown in fig. 13, and the left part is water and the right part is a 40% sucrose aqueous solution in fig. 12).

It can therefore be seen that the refractometer can detect the optical properties of the liquid to achieve detection of the liquid under wakefulness which is not electrochemically measurable.

Therefore, by simultaneously carrying out electrochemical property measurement and refraction measurement on the solution to be measured, the robustness of the measurement result can be greatly improved. For another example, honey in the market is classified more, but the honey is not very different in concentration, for example, honey of different flowers such as sophora flower honey is about 75% sugar degree. When the honey is measured, the measurement result of the refractometer cannot directly reflect the specific variety of the honey, but the conditions of other components except sugar in the honey can be directly reflected by an electrochemical impedance measurement method, and the quality and variety of the honey can be more quickly discriminated by the measurement mode.

Example 2

There are also numerous soluble ionic systems (calcium, potassium, phosphorus, etc.) and insoluble adipocytes, proteins, etc. in milk, these insoluble substances also being very important nutrient elements in milk. Soluble solids contained in milk can only be measured by refractometry, but the parameters of most interest to milk are protein content and fat content. The milk can be regarded as a liquid system as in fig. 14, where the grey parts in fig. 14 represent fat cells which are liquid and the circled parts. When an impedance meter is used to excite electrical signals of different frequencies (0.01 Hz-100000 Hz), (i) is often the path for low frequency currents, and (ii) is the path for high frequency currents. Therefore, two peaks of corresponding impedance at different frequencies can be detected, and therefore the amount of fat in the milk can be judged. Even specific electrodes can be manufactured to detect specific elements in the milk, such as CPE electrodes can specifically react with serum in the milk and be reflected on an electrochemical impedance spectrum.

The detection device fusing EIS liquid impedance measurement and the refractometer provided by the specific embodiment has the following advantages:

1. the measurement of soluble solids and insoluble solids in a liquid system is carried out on the liquid by simultaneously realizing refraction measurement and electrochemical impedance measurement, so that the measurement robustness is improved; especially for concentration measurements and for species measurements of liquids.

2. And when the optical properties cannot be distinguished, the electrochemical properties are distinguished, so that complementary measurement is realized.

3. When the liquid is capable of being measured for both measurement modes, the advantages of a certain measurement scheme can be utilized to achieve a more accurate measurement.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A detection device, characterized by: comprises a liquid storage tank, an electrode module, a processing module, a light source module, a reflecting module containing a detection area and a photosensitive module,

the electrode module comprises at least two electrodes which are arranged in the liquid storage tank and positioned around the detection area, and is used for contacting with the liquid to be detected in the liquid storage tank; the processing module is used for applying an electric signal to at least one electrode in the electrode module, collecting the electric signal of the at least one electrode in the electrode module, and determining the Electrochemical Impedance Spectroscopy (EIS) of the liquid to be detected according to the applied electric signal and the collected electric signal.

2. The detection device according to claim 1, wherein the at least two electrodes are in the form of a sheet, and are disposed on the bottom of the reservoir and around the detection region.

3. The detection device of claim 2, wherein the at least two electrodes are laid flat on the surface of the detection zone or the at least two electrodes are laid on the surface of the inner side wall of the reservoir.

4. The detection device of claim 1, wherein the at least two electrodes comprise a counter electrode, a working electrode, and a reference electrode, wherein at least one of the size, position, and shape of the counter electrode and the working electrode are symmetrically arranged, and the distance between the reference electrode and the working electrode is less than the distance between the reference electrode and the counter electrode.

5. The sensing device of claim 1, wherein the at least two electrodes are disposed on a circuit board, and wherein a temperature sensor is disposed on the circuit board.

6. The testing device of claim 1, wherein said reservoir is tapered and a water level indicating line is drawn in said reservoir.

7. The detecting device according to claim 1, wherein the photosensitive module includes a photosensitive area array, and at least one converging lens is disposed between the reflective module and the photosensitive module for converging the light beams totally reflected by the reflective module onto the photosensitive area array.

8. The detection device according to claim 1, wherein the processing module includes a main control chip and a peripheral circuit built outside the main control chip, wherein the main control chip is configured to output an ac signal through a DAC thereof, and the peripheral circuit is configured to shape the ac signal.

9. The detection device as claimed in claim 7, wherein the peripheral circuit comprises a low pass filter circuit for low pass filtering the ac signal output from the main control chip, and a circuit for removing the dc bias voltage from the output of the low pass filter circuit.

10. The detection device of claim 7, wherein the processing module is further configured to collect an alternating current signal from the electrode module;

11. The detection apparatus according to claim 9, wherein the processing module further comprises an analog-to-digital conversion circuit for acquiring a duty cycle of the phase difference pulse signal when the frequency of the phase difference pulse signal is greater than 1 kHz;

the processing module further comprises a timer for acquiring the duty ratio of the phase difference pulse signal when the frequency of the phase difference pulse signal is not more than 1 kHz.