WO2022257745A1

WO2022257745A1 - Online measuring device for electrolyte density of automatic liquid suction type lead-acid storage battery

Info

Publication number: WO2022257745A1
Application number: PCT/CN2022/094502
Authority: WO
Inventors: 陈明
Original assignee: 陈明
Priority date: 2021-06-10
Filing date: 2022-05-23
Publication date: 2022-12-15
Also published as: CN113314774A

Abstract

An online measuring device for the electrolyte density of an automatic liquid suction type lead-acid storage battery, comprising: a floating type density sensor (6); a cavity (1), the cavity (1) being mounted on a lead-acid storage battery to be tested; and a pump, which pumps electrolyte of the lead-acid storage battery into the cavity (1) or discharges the electrolyte from the cavity (1) into the lead-acid storage battery. A data acquisition device (2) that acquires data of the floating type density sensor (6) floating in the cavity (1) is provided on the top of the cavity (1). Density measurement is carried out by employing an electrolyte sampling means, and the insufficiency of errors caused by liquid level height change of electrolyte in a storage battery due to temperature change is overcome.

Description

An on-line measuring device for the electrolyte density of an automatic liquid-absorbing lead-acid battery

related application

This application claims the priority of the Chinese patent application submitted to the China Patent Office on June 10, 2021 with the application number 202110645401.2 and the application title "An on-line measuring device for the electrolyte density of an automatic liquid-absorbing lead-acid battery".

technical field

The application relates to the field of measuring the electrolyte density of lead-acid batteries, in particular to an on-line measuring device for the electrolyte density of an automatic liquid-absorbing lead-acid battery.

Background technique

During the use of lead-acid batteries (especially open batteries), the density of the electrolyte is an important basis for analyzing the actual capacity of the battery. The density of the electrolyte increases with the increase of the charge level of the battery and decreases with the increase of the discharge level. Because the battery is charged, the lead sulfate on the plate is decomposed, the content of sulfuric acid in the electrolyte increases, and the density increases. When the battery is discharged, lead sulfate is generated on the two pole plates, the content of sulfuric acid in the electrolyte decreases, and the density decreases. In addition, during the charging process of the battery, the gassing will also cause the battery to lack water (especially the open battery), which will affect the density of the battery electrolyte.

Therefore, when the lead-acid battery is detected online, it is often necessary to detect the density of the electrolyte of the lead-acid battery. The Chinese invention patent authorization announcement number CN105958141B discloses a lead-acid battery intelligent detection device. In this intelligent detection device, Equipped with a liquid level detection rod and a density sensor. The liquid level detection rod of the lead-acid battery intelligent detection device is set in the acid battery to detect the liquid level, and the density sensor is a floating density sensor floating in the electrolyte in the acid battery. Indicates the density of the electrolyte, the more the part that floats out of the water, the greater the density, and the less the part that floats out of the water, the lower the density of the electrolyte.

The structure of the floating liquid density sensor is relatively simple. It generally includes a sphere with a counterweight and a cylinder connected to the sphere. The diameter of the cylinder is smaller than that of the sphere. When measuring, because the sphere has a counterweight, one end of the sphere The liquid sinks inwards, and part of the cylinder part will float on the liquid surface. Generally, the cylinder part will be perpendicular to the horizontal plane. By adjusting the counterweight, the entire sphere can sink under the water during measurement, and the cylinder part will protrude. On the water surface, the specific gravity of the liquid can be measured by measuring the height of the cylinder part.

Using a floating density sensor to float on the liquid surface of the lead-acid battery, the density of the electrolyte can be determined by measuring the volume of the floating liquid surface in real time. At present, in order to facilitate the measurement, the height of the column part of the floating density sensor is generally used to correspond to the corresponding density. However, when measuring the electrolyte of the lead-acid battery in real time, the liquid level will also change continuously due to the constant temperature change. , resulting in the height of the column part of the floating density sensor will also change accordingly, resulting in errors in measurement.

The above content is only used to assist the understanding of the solution of the present application, and does not mean to admit that the above content is the prior art.

technical problem

This application aims at the shortcomings of the current floating density sensor when detecting the electrolyte density of lead-acid batteries, and provides an on-line measuring device for the electrolyte density of lead-acid batteries with automatic liquid absorption. In this device, a certain amount is automatically sampled when measurement is required. The electrolyte solution, the density detection of the sampled electrolyte solution is carried out.

technical solution

The technical solution of this application to achieve its technical purpose is: an on-line measuring device for the electrolyte density of an automatic liquid-absorbing lead-acid battery, including a floating density sensor and a cavity; the cavity is installed on the lead-acid battery to be tested ; The electrolyte of the lead-acid battery to be tested is pumped into the cavity or discharged from the cavity into the pump to be tested in the lead-acid battery; a collection floating density sensor is arranged on the top of the cavity to float in the cavity data acquisition device.

In one embodiment, in the above-mentioned online measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: the cavity is a cylindrical cavity, and the bottom is provided with a plug partially immersed in the electrolyte in the lead-acid battery ; The top of the cavity is provided with a piston and a motor that drives the piston to slide up and down in the cavity.

In one embodiment, in the above-mentioned online measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: the cavity is a cylindrical cavity, and the bottom is provided with a plug partially immersed in the electrolyte in the lead-acid battery The pump is arranged on the upper side wall of the cylindrical cavity, including a cylinder communicated with the cylindrical cavity, a piston set in the cylinder, and a motor that drives the piston to reciprocate in the cylinder.

In one embodiment, in the above-mentioned on-line measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: the cavity and the cylinder form a three-way structure.

In one embodiment, in the above-mentioned on-line measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: the diameter of the spherical part of the floating density sensor is smaller than the diameter of the cylindrical cavity, and a positioning ring is also included. The positioning ring is tightly fixed in the middle of the column part of the floating density sensor.

In one embodiment, the above-mentioned on-line measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: also includes a buoy floating on the surface of the electrolyte to indicate the liquid level of the electrolyte, and the buoy is arranged at a position The lower side of the ring is sleeved on the cylinder part of the floating density sensor.

In one embodiment, the above-mentioned on-line measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: it also includes a plug arranged at the bottom of the cavity to prevent the floating density sensor from falling out of the cavity, and the plug has The tip inserted into the electrolyte also has a channel for the electrolyte to enter the cavity in the middle of the plug.

In one embodiment, in the above-mentioned online measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: the data acquisition device is a capacitive data acquisition device, including a capacitor assembly tightly fixed on the top of the cavity and arranged on the The electrode on the top outside of the floating density sensor cylinder part; the capacitor assembly includes a first semi-circular electrode and a second semi-circular electrode arranged oppositely, under the buoyancy of the electrolyte, the floating density sensor cylinder Part of the electrodes on the outside of the top extend into the middle of the first semi-circular electrode and the second semi-circular electrode, and a detection circuit for detecting the capacitance between the first semi-circular electrode and the second semi-circular electrode is also included.

In one embodiment, in the above-mentioned on-line measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: the data acquisition device is a photoelectric data acquisition device, including a The shading plate and at least two groups of optoelectronic components composed of photoelectric transceivers arranged on both sides of the shading plate, the light shading plate has light-transmitting long holes of different heights, and each group of photoelectric components is opposite to a light-transmitting long hole.

In one embodiment, in the above-mentioned on-line measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery: the data acquisition device is a grating type data acquisition device, including a fixed grating fixed on the top of the cavity, oppositely arranged A pair of sending and receiving optoelectronic devices on both sides of the fixed grating, set on the movable grating on the top of the floating density sensor cylinder, the movable grating is parallel to the fixed grating, and the movable grating moves up and down relative to the fixed grating to generate Moiré fringes; a detection circuit for detecting the moiré fringes is also included.

Beneficial effect

The present application adopts the method of sampling the electrolyte to measure the density, so as to overcome the deficiency of the error caused by the change of the liquid level of the electrolyte in the storage battery due to the temperature change.

The application will be described in more detail below with reference to the drawings and embodiments.

Description of drawings

Accompanying drawing 1 is the structure diagram of the on-line measurement device of the electrolyte density of the self-absorbing type lead-acid storage battery of embodiment 1 of the present application.

Accompanying drawing 2 is the structure diagram of the plug used in the embodiment 1 of the present application.

Accompanying drawing 3 is the structure diagram of the positioning ring used in the embodiment 1 of the present application.

Accompanying drawing 4 is the structural diagram (1) of the capacitive data acquisition device in the embodiment 1 of the present application.

Accompanying drawing 5 is the structural diagram (2) of the capacitive data collector in the embodiment 1 of the present application.

Accompanying drawing 6 is the structural diagram (1) of the photoelectric data acquisition device in the embodiment 2 of the present application.

Accompanying drawing 7 is the structural schematic diagram (2) of the photoelectric data acquisition device in the embodiment 2 of the present application.

Accompanying drawing 8 is the structural diagram of the shading plate in the embodiment 2 of the present application.

Accompanying drawing 9 is the structural diagram (1) of the photoelectric data acquisition device in the embodiment 3 of the present application.

Accompanying drawing 10 is the structural schematic diagram (2) of the photoelectric data acquisition device in the embodiment 3 of the present application.

Accompanying drawing 11 is the structure schematic diagram of the on-line measurement device of the electrolyte density of the self-absorbing type lead-acid storage battery of embodiment 4 of the present application.

Embodiments of the present invention

Embodiment 1, this embodiment is an online measuring device for the electrolyte density of an automatic liquid-absorbing lead-acid battery that detects the electrolyte density of a lead-acid battery in real time, and it is an automatic liquid-absorbing type lead-acid battery electrolyte density sensor. As shown in Figure 1, the density sensor is installed on the lead-acid battery and connected with the battery management system of the lead-acid battery.

In the present embodiment, what is used to measure the liquid density in the on-line measuring device of the electrolyte density of the automatic liquid-absorbing type lead-acid battery is a floating density sensor 6; it is a conventional density sensor for measuring liquid density at present, as shown in Fig. 1 and Fig. As shown in 5, the floating density sensor 6 is mainly composed of two parts, a sphere part 6-1 with a counterweight and a cylinder part 6-2 connected with the sphere part 6-1. Since the sphere part 6-1 has a counterweight, Therefore, when it is suspended on the liquid surface, the spherical part 6-1 is down, and the column part 6-2 is up, and the weight of the discharged liquid is the total weight of the floating density sensor 6 itself. The total weight is constant, therefore, the more the volume of the spherical part 6-1 combined with the cylindrical part 6-2 surfaced, the smaller the volume of the discharged liquid, and therefore, the denser the liquid, and vice versa . Therefore, in this embodiment, the measurement of the density of the electrolyte is attributed to the height of the top surface of the measurement column part 6-2, the higher the height, the greater the density of the electrolyte.

In this embodiment, the density measurement is carried out after sampling the electrolyte in the lead-acid battery. Therefore, there is a chamber 1 for measuring the electrolyte as shown in Figure 1. In this embodiment, the chamber 1 is as shown in FIG. The test tube body is general, and the floating density sensor 6 is arranged in the cavity 1. In this embodiment, the lower end of the cavity 1 is blocked by a plug 7 to prevent the floating density sensor 6 from falling from the lower end of the cavity 1. When the on-line measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid battery of this embodiment is installed, the plug 7 will be submerged in the electrolyte of the lead-acid battery. When there is some air in the receptor, the electrolyte in the lead-acid battery will be sucked into the cavity 1. In this embodiment, the plunger pump is used to extract the air in the cavity to absorb the liquid. As shown in Figure 1, the liquid suction device Including a cylinder 11 communicating with the cavity 1, a piston 10 is arranged in the cylinder 11, and a motor 12 (screw motor is used in this embodiment) is used to drive the piston 10 to reciprocate rapidly in the cylinder 11. A one-way switch is arranged on the cylinder body 11, and the air in the chamber body 1 can be pumped out once every time it goes back and forth. After several times of pumping out, the electrolyte solution can be sucked into the chamber. For the mouth suction device, there can also be many forms, such as an air extractor, which takes away part of the air from the cavity 1 upper end. As shown in Figure 2, the plug 7 has a hole in the middle, which is the passage 7-1 through which the electrolyte enters the cavity 1, and can absorb the electrolyte in the lead-acid battery.

As shown in Figure 1, in this embodiment, in order to prevent lodging in the floating density sensor 6, a positioning ring 3 is also provided in the cavity 1, and the positioning ring 3 is tightly fixed in the middle of the cavity 1 as shown in Figure 3, and its function It is to make the floating density sensor 6 move up and down along the axis without deviation, and there is a through hole 3-1 in the middle through which the cylindrical part 6-2 of the floating density sensor 6 passes. In addition, there is also a float 5, the float 5 is a light material, and can also be an annular shape like a fixed ring, which has enough space with the cavity 1 and the floating density sensor 6, can float on the electrolyte surface, and is used for indication Electrolyte liquid level height, in the present embodiment, cavity body 1 is a section glass tube, can utilize position sensor 4 to judge the height of liquid level in cavity body 1 outside glass tube, like this, can control motor 12 by this position sensor 4 To work, it is enough to make the electrolyte pumped into the cavity 1 reach the measurement standard. In this way, the detection device arranged at the upper end of the cavity 1, that is, the data acquisition device 2, can be used for measurement preparation.

In this embodiment, both the cavity 1 and the cylinder 11 can be made of glass or other transparent PVC materials. In practice, the cavity 1 and the cylinder 11 form a three-way structure, as shown in FIG. 1 .

In this embodiment, the data acquisition device 2 is a capacitive data acquisition device, as shown in Figure 4 and Figure 5, including a capacitor assembly tightly fixed on the top of the cavity 1 and arranged on the outside of the top of the floating density sensor 6 cylinder part 6-2 The electrode 2-3; the capacitor assembly includes the first semi-circular electrode 2-1 and the second semi-circular electrode 2-2 oppositely arranged, under the buoyancy of the electrolyte, the floating density sensor 6 cylinder part 6 -2 The electrode 2-3 on the outside of the top extends into the middle of the first semi-circular electrode 2-2 and the second semi-circular electrode 2-3, and the electrode 2- on the outside of the floating density sensor 6 cylinder part 6-2 top 3 Change the capacitance between the first semi-circular electrode 2-1 and the second semi-circular electrode 2-2 when moving up and down, and also include detecting the first semi-circular electrode 2-1 and the second semi-circular electrode The detection circuit of capacitance between 2-2.

When using this embodiment to measure, the screw motor is controlled, and the electrolyte is sucked into the chamber 1 by the plug 7 channel 7-1 until the float 5 rises to the designated position (positioned by the position sensor 4, the purpose of this step is to make the electrolysis liquid height is a fixed value), measure the capacitance between the first semi-circular ring electrode 2-2 and the second semi-circular ring electrode 2-3, and convert the corresponding electrolyte specific gravity value. After the measurement is over, the screw motor is controlled to discharge the electrolyte from the plug 7 channel 7-1 into the lead-acid battery.

The on-line measuring device for the electrolyte density of the automatic liquid-absorbing type lead-acid storage battery of the present embodiment has the following characteristics:

(1) On-line automatic measurement of electrolyte specific gravity can be realized.

(2) Make it possible to automatically manage and control the uninterrupted power supply of the battery pack.

(3) Reduce labor costs.

(4) Accurately measure battery performance.

(5) Make big data analysis and management of lead-acid batteries possible.

(6) The electrolyte is sucked into the sensor cavity only during the measurement, eliminating the influence of the change of the electrolyte level on the measurement accuracy.

Embodiment 2, as shown in Figures 6 and 7, the difference between this embodiment and Embodiment 1 is that the data acquisition device 2 used in this embodiment is a photoelectric data acquisition device, including 6 columns of floating density sensors The shading plate 2-6 on the top of the part 6-2 and the four groups of photoelectric components 2-4 composed of photoelectric transceivers arranged on both sides of the shading plate 2-6, the shading plate 2-6 has light transmission lengths of different heights. The hole 2-6-1 is shown in Figure 8, and each group of photoelectric components 2-4 is opposite to a long light-transmitting hole 2-6-1. In the present embodiment, light-shielding plate 2-6 structure as shown in Figure 8, light-shielding plate 2-6 is pure black, has 4 slits of different lengths above (translucent long hole 2-6-1 ), when the transmitting tube in the photoelectric module 2-4 is in the slit position, the receiving device outputs a digital value of 1; otherwise, the receiving device outputs a digital value of 0. In this embodiment, the photoelectric components 2-4 can use a pair of infrared receiving diodes and infrared emitting diodes, the shortest slit corresponds to the photoelectric switch 1, the longest slit corresponds to the photoelectric switch 4, and so on. When the hydrometer moves from the bottom (at this time the specific gravity of the electrolyte is the smallest) to the top (at this time the specific gravity of the electrolyte is the largest), it is relatively equal to four groups of photoelectric switches moving from top to bottom at the same time, through different photoelectric switch output combinations, you can Get the electrolyte density range. During measurement, control screw motor, electrolytic solution is sucked cavity 1 by plug 7 passages 7-1, rises to designated position until float 5, and at this moment, float 5 rises to designated position (by position sensor 4 Positioning, the purpose of this step is to make the height of the electrolyte a fixed value), through different output combinations of photoelectric modules 2-4, the density range of the electrolyte is obtained (see Table 1). After the measurement is over, the screw motor is controlled to discharge the electrolyte out of the sensor cavity through the opening of the plug.

Table I

(3) Reduce labor costs.

(4) Accurately measure battery performance.

(5) Make big data analysis and management of lead-acid batteries possible.

Embodiment 3. The difference between embodiment 3 and the previous two embodiments is that the data acquisition device 2 is a raster type data acquisition device, as shown in FIG. 9 and FIG. 10 . The grating type data acquisition device includes a fixed grating 2-8 fixed on the top of the cavity 1, a pair of sending and receiving optoelectronic devices 2-7 arranged on both sides of the fixed grating 2-8, and arranged on the floating density sensor 6 cylinder The movable grating 2-9 on the top of the part 6-2 is parallel to the fixed grating 2-8, and the movable grating 2-9 moves up and down relative to the fixed grating 2-9 to generate moiré fringes; it also includes detection The moiré fringe detection circuit.

In this embodiment, there is a movable grating 2-9 on the top of the column part 6-2 of the floating density sensor 6, and the movable grating 2-9 will be relatively fixed according to the depth of the floating density sensor 6 sinking into the electrolyte. The grating 2-8 moves up and down to generate moiré fringes, and a pulse signal proportional to the relative displacement can be generated through the detection circuit. The change of the measured pulse signal can calculate the change of the height of the hydrometer, and then calculate the change of the specific gravity of the electrolyte.

During the measurement, the screw motor is controlled, and the electrolyte is sucked into the chamber 1 from the plug 7 channel 7-1 until the float 5 rises to the designated position, until the float rises to the designated position (positioned by the position sensor, the purpose of this step The height of the electrolyte is a fixed value), at this time, the float 5 rises to the designated position, and the change of the grating pulse signal is measured at the same time to calculate the height change of the hydrometer, and then calculate the change of the specific gravity of the electrolyte. After the measurement is over, the screw motor is controlled to discharge the electrolyte out of the sensor cavity through the opening of the plug.

(1) The key point of this application is the sensor combination structure of hydrometer + grating sensor.

(2) The method of measuring the specific gravity of the electrolyte with a hydrometer + a grating-type combined sensor.

(3) Grating component structure.

(4) The structure and usage of the positioning ring.

(5) Float structure and usage method.

(6) Structure and usage of moving grating.

(7) The structure and usage of screw motor + piston.

Embodiment 4 As shown in Figure 11, the main difference between this embodiment and previous embodiments 1, 2, 3, and 4 is that it is an online measuring device for the electrolyte density of the automatic liquid-absorbing lead-acid storage battery in embodiment 4 of the present application Among them, the structure of the plunger pump used is different. In this embodiment, the pump is installed on the top of the cylindrical cavity 1, including a piston 10 with the inner wall of the cylindrical cavity 1 as the cylinder body, and drives the piston 10 along the cylinder. The motor 12 that slides up and down on the inner wall of the cylindrical cavity 1 is like a suction cylinder formed by the piston 10 and the cylindrical cavity 1. When the piston 10 slides upwards under the drive of the motor 12, the air pressure in the cylindrical cavity 1 decrease, then immerse in the channel 7-1 in the middle of the plug 7 in the electrolyte of the lead-acid battery, and the electrolyte enters the cylindrical cavity 1 from the channel 7-1, pay attention to observe the height of the float 5, When it reaches the set height, stop the motor and conduct electrolyte density test.

Claims

An on-line measuring device for electrolyte density of an automatic liquid-absorbing lead-acid battery, comprising:

Floating density sensor (6);

A cavity (1), the cavity (1) is installed on the lead-acid battery to be tested;

A pump that pumps the electrolyte solution of the lead-acid battery to be tested into the cavity (1) or discharges it from the cavity (1) into the lead-acid battery to be tested;

The data acquisition device (2) is arranged on the top of the cavity (1) and is used for collecting a floating density sensor (6) floating in the cavity (1).
The on-line measuring device according to claim 1, wherein: the cavity (1) is a cylindrical cavity, and the bottom is provided with a plug (7) partially immersed in the electrolyte in the lead-acid battery; in the cavity ( 1) is provided with a piston (10) and a motor (12) that drives the piston (10) to slide up and down in the cavity (1).
The on-line measurement device according to claim 1, wherein: the cavity (1) is a cylindrical cavity, and the bottom is provided with a plug (7) partially immersed in the electrolyte in the lead-acid battery; On the upper side wall of the cylindrical cavity (1), including the cylinder (10) communicated with the cylindrical cavity (1), the piston (11) arranged in the cylinder (10) drives the piston (11) ) a motor (12) that reciprocates back and forth in the cylinder body (10).
The online measuring device according to claim 3, wherein: the cavity (1) and the cylinder (10) form a three-way structure.
The online measuring device according to claim 3, wherein: the diameter of the spherical part (6-1) of the floating density sensor (6) is smaller than the diameter of the cylindrical cavity (1), and the online measuring device also Including a positioning ring (3), the positioning ring (3) is tightly fixed on the inner wall of the middle part of the cavity (1), and is connected with the cylinder part (6-2) of the floating density sensor (6) There are gaps in between.
The online measuring device according to claim 5, wherein: it also includes a buoy (5) floating on the surface of the electrolyte for indicating the liquid level of the electrolyte, and the buoy (5) is arranged under the positioning ring (3) side, set on the column part (6-2) of the floating density sensor (6).
The online measuring device according to claim 5, wherein: it also includes a plug (7) arranged at the bottom of the cavity (1) to prevent the floating density sensor (6) from falling out of the cavity (1), said plug (7) has a tip that intervenes in the electrolyte, and also has a channel (7-1) for the electrolyte to enter the cavity (1) in the middle of the plug (7).
The online measuring device according to any one of claims 1 to 7, wherein:

The data acquisition device (2) is a capacitive data acquisition device, including a capacitor assembly tightly fixed on the top of the cavity (1) and a capacitor assembly arranged outside the top of the floating density sensor (6) cylinder part (6-2). Electrodes (2-3); the capacitor assembly includes a first semi-circular electrode (2-1) and a second semi-circular electrode (2-2) oppositely arranged, under the buoyancy of the electrolyte, the floating The electrode (2-3) outside the top of the cylinder part (6-2) of the type density sensor (6) stretches into the middle of the first semi-circular ring electrode (2-2) and the second semi-circular ring electrode (2-3) , also includes a detection circuit for detecting the capacitance between the first semi-circular electrode (2-1) and the second semi-circular electrode (2-2).
The online measuring device according to any one of claims 1 to 7, wherein:

Described data acquisition device (2) is the photoelectric data acquisition device, comprises the light shield (2-6) that is arranged on the top of the floating density sensor (6) cylinder part (6-2) and is arranged on the light shield ( 2-6) At least two groups of optoelectronic components (2-4) composed of optoelectronic transceivers on both sides, the light shielding plate (2-6) has light-transmitting long holes (2-6-1) of different heights , each group of photoelectric components (2-4) is opposite to a long light-transmitting hole (2-6-1).
The online measuring device according to any one of claims 1 to 7, wherein:

The data acquisition device (2) is a grating type data acquisition device, comprising a fixed grating (2-8) fixed on the top of the cavity (1), and a pair of Transmitting and receiving optoelectronic devices (2-7), the movable grating (2-9) that is arranged on the top of the floating density sensor (6) cylinder part (6-2), the movable grating (2-9) and The fixed grating (2-8) is parallel, and the movable grating (2-9) moves up and down relative to the fixed grating (2-9) to generate moiré fringes; the on-line measurement device also includes a detection circuit for detecting the moiré fringes.