CN215373842U - Staggered relay catheter type longitudinal TDR sensor - Google Patents
Staggered relay catheter type longitudinal TDR sensor Download PDFInfo
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- CN215373842U CN215373842U CN202121882272.0U CN202121882272U CN215373842U CN 215373842 U CN215373842 U CN 215373842U CN 202121882272 U CN202121882272 U CN 202121882272U CN 215373842 U CN215373842 U CN 215373842U
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Abstract
The utility model discloses a staggered relay conduit type longitudinal TDR sensor, which comprises a conduit and more than two groups of probes, wherein the probes are sequentially and uniformly distributed in a staggered manner along the longitudinal direction of the conduit, two adjacent probes are symmetrically arranged by taking the axis of the conduit as the center, and the probes are connected with a BNC connector through a coaxial cable. The probe consists of an impedance converter, a transverse straight needle body and a longitudinal straight needle body. The impedance converter is arranged in the conduit, a transverse straight needle body is arranged in the impedance converter along the axial direction of the impedance converter, and one end of the coaxial cable is connected with the transverse straight needle body. The longitudinal straight needle body comprises a central longitudinal straight needle body and a lateral longitudinal straight needle body which are attached to the outer side wall of the catheter. The longitudinal TDR sensor is inserted into the bottom of the sludge, the position of a medium boundary layer is determined in a multi-section probe inspection mode, and finally the depth or the thickness of the medium boundary layer is measured. The method is mainly applied to measuring the silt siltation depth in the river channel, and has the advantages of accurate measurement result, high sensitivity and strong stability.
Description
Technical Field
The utility model relates to the technical field of depth measuring instruments, in particular to a staggered relay conduit type longitudinal TDR sensor.
Background
The Time Domain Reflectometry (TDR) was generated in the thirty years of the last century and was originally used to detect and locate damaged locations of communication cables. When an electromagnetic pulse excitation signal is transmitted along a transmission line, the impedance of the transmission line is changed due to the interruption, damage or discontinuity of surrounding substances, the transmitted signal is reflected at the discontinuous point due to the impedance change, and the position of the discontinuous point can be accurately judged by precisely measuring the travel time difference of an incident wave and a reflected wave of an electromagnetic wave. With the discovery that the TDR technology can measure the volume water content of soil in the seventies of the last century, the technology is widely applied to the field of agriculture. Since the eighties, the technology is also applied to the field of geotechnical engineering, is applied to the aspects of measuring the water content and the dry density of soil bodies, monitoring the stability of landslides, measuring the underground water level and the electric conductivity, monitoring the pollution of the soil bodies, controlling the quality of chemically reinforced soil and the like, and is widely concerned with the characteristics of convenience, safety, economy, digitization, easy remote control communication and the like.
Dispersive electromagnetic properties of a substance are determined by its relative dielectric constant
To be quantitatively described as being equal to the dielectric constant ε in the medium*And dielectric constant in vacuum ∈0＝8.854×10-12Ratio (farad/m):
this is a dimensionless parameter in complex form:
the real part epsilon 'reflects the polarization degree and energy storage of the dielectric material under the external applied magnetic field, and the imaginary part epsilon' reflects the energy loss of the dielectric material under the external applied magnetic field. The transmission of electromagnetic waves in a dielectric medium satisfies the following formula:
where v is the propagation velocity of the electromagnetic wave in the medium, c is the speed of light, and tan δ { [ ε "+ (σ) } isDC/ωε0) Designated as loss factor, the canadian scholars g.c. topp states that the soil is essentially a homeotropic linear homogeneous medium which satisfies: ε '< ε' and σ when the frequency of the electromagnetic wave is high enoughDC/ωε0ε′＜＜1。
Thus, at this time: ε' ≈ (c/v)2 (1.2)
In the field of TDR soil measurement, Ka≈(c/v)2Is said to characterize the dielectric constant, easy to see, Ka＝ε′。
From the equation (1.2), we can see that the real part of the relative dielectric constant of the medium can be obtained by measuring the propagation velocity of the electromagnetic wave in the medium.
A TDR system for measuring soil moisture is shown in figure 7 of the specification when a high bandwidth step signal is applied along the coaxial cable at time t0Reaching the initial part of the probe, a reflection is generated due to the change of impedance, while the rest of the signal continues to advance along the probe, at time t1When the electromagnetic wave reaches the bottom of the probe, a second reflection is generated, and the electromagnetic wave is easy to see by considering the travel of the electromagnetic wave along the probe with the length of L:
substitution into (1.1) gives:
therefore, the real part of the relative dielectric constant of the medium can be directly obtained for measuring the transmission time delta t of the electromagnetic wave along the probe.
On the other hand, the probe used in the time domain reflection technology is an application based on the electromagnetic wave transmission line theory, and generally has two-needle or three-needle structure, and the three-needle structure can reduce the attenuation of energy in the electromagnetic wave transmission process more than the two-needle structure, thereby increasing the measurement range. Therefore, in the TDR technique, a three-pin probe structure is more adopted.
The three-needle probe is connected with a TDR signal generator, the middle needle body is connected with the anode, the two outer needle bodies are connected with the cathode to form a three-parallel transmission line structure, and electromagnetic waves are transmitted along the three-needle probe in a TEM wave form. The impedance formed by the transmission line is given by the following equation:
where D and D are the width of the middle needle and the distance between the two outer needles, respectively, and ε' is the real part of the dielectric constant of the medium in which the probe is inserted.
As can be seen from equation (1.5), a change in the medium around the probe causes a change in the impedance of the probe, and thus causes reflection of the electromagnetic wave. Because the real part of the dielectric constant of water is large and relatively stable, the real part can be directly measured by inserting the probe into water, and the dielectric constant of soil is small (the dielectric constant of soil particles is 2-4), the probe can be inserted into the bottom of sludge, and the position of the sludge and the water where the sludge is connected is determined through a formula (1.4), so that the depth of the sludge is determined.
The time domain reflection technology is used for measuring by means of reflection of transmitted electromagnetic wave signals, and the high-frequency electromagnetic waves are transmitted along the probe, so that the signal attenuation speed is high, the length of the probe is limited to a certain extent, and meanwhile, the length of the probe is required to be lengthened as much as possible in consideration of the range requirement of practical application. In order to measure the depth of the sludge in the river channel, the length of the probe needs to be set to be quite long to meet the actual requirement, and experiments show that the accuracy and the sensitivity of the measurement result are greatly reduced by adopting the probe with the length of 40 cm. After the probe exceeds 40cm, the longer the probe, the lower the measurement accuracy and sensitivity. In summary, due to the limitation of the length of the probe, the current sensor (probe) is difficult to meet the requirement of actual sludge monitoring.
SUMMERY OF THE UTILITY MODEL
The utility model aims to provide a staggered relay conduit type longitudinal TDR sensor which can be used for measuring the depth or thickness of a medium boundary layer, such as the depth of silt siltation in a river channel, and has accurate measurement result and high sensitivity.
In order to achieve the purpose, the utility model adopts the following technical scheme:
the staggered relay catheter type longitudinal TDR sensor comprises a catheter and more than two groups of probes, wherein the probes are sequentially and uniformly distributed in a staggered manner along the longitudinal direction of the catheter, two adjacent probes are symmetrically arranged by taking the longitudinal plane of the catheter as the center, and the probes are connected with a BNC connector through coaxial cables;
the probe consists of an impedance converter, a transverse straight needle body and a longitudinal straight needle body;
the impedance converter is tubular and is arranged in the conduit, a transverse straight needle body is arranged in the impedance converter along the axial direction of the impedance converter, and one end of the coaxial cable is connected with the transverse straight needle body;
the longitudinal straight needle body comprises a central longitudinal straight needle body and lateral longitudinal straight needle bodies which are positioned at two sides of the central longitudinal straight needle body and are parallel to the central longitudinal straight needle body, the lateral longitudinal straight needle bodies are attached to the outer side wall of the catheter, and the upper end of the central longitudinal straight needle body is connected with the transverse straight needle body; the upper end of each side longitudinal straight needle body is provided with an annular right-angle bend, and the annular part of the annular right-angle bend is vertical to the longitudinal straight needle body;
the side wall of the conduit is provided with a through hole, the impedance converter is inserted into the through hole, and the impedance converter is fixedly connected with the straight line part bent at the right angle in the annular shape.
Further setting the following steps: the longitudinal straight probe bodies of two adjacent probes are provided with overlapping parts on a longitudinal plane, and the overlapping distance of the overlapping parts is 30-80 mm.
Further setting the following steps: the impedance converter is a T-shaped tubular member consisting of a pipe cap and a sleeve, the pipe cap is fixedly connected with the sleeve in an inserting mode, and a transverse straight needle body is inserted into the sleeve along the axial direction of the sleeve.
Further setting the following steps: the front end of the transverse straight needle body is provided with an insertion hole, and one end of the coaxial cable penetrates through the pipe cap to be inserted into the insertion hole and connected with the transverse straight needle body.
Further setting the following steps: still be equipped with the current-conducting tube in the cover, the one end of current-conducting tube is connected with the pipe cap, and the other end is connected with the straight line portion of cyclic annular right angle bend, be provided with the separate layer between current-conducting tube and the horizontal straight needle body.
Further setting the following steps: the lateral wall of pipe is provided with the recess, and vertical straight needle body crouches and adorns in the recess.
Further setting the following steps: the length of the central longitudinal straight needle body and the lateral longitudinal straight needle bodies is set to be 200mm-300mm, the width is set to be 2mm-4mm, the thickness is set to be 0.8mm-1.2mm, and the distance between the needle bodies of the two lateral longitudinal straight needle bodies is set to be 40mm-50 mm.
Further setting the following steps: the outer diameter of the conduit is set to be 80-150mm, and the wall thickness of the conduit is set to be 20-30 mm.
Further setting the following steps: the conduit, the sleeve and the separating layer are all made of high-molecular low-dielectric-constant materials.
Further setting the following steps: the transverse straight needle body, the longitudinal straight needle body, the tube cap and the conductive tube are all made of metal materials.
In conclusion, the beneficial technical effects of the utility model are as follows:
(1) the longitudinal TDR sensor is inserted into the bottom of the sludge, the position of a medium boundary layer is determined in a multi-section probe inspection mode, and finally the depth or the thickness of the medium boundary layer is measured. The method can be used for judging the positions of medium boundary layers such as water-oil boundary layers, water-soil boundary layers and the like, determining the depth or thickness of the medium boundary layers, is mainly applied to determining the silt siltation depth in a river channel in soil measurement, and can ensure accurate measurement result, high sensitivity and strong stability.
(2) The staggered relay type probe arrangement mode can avoid the dead zone of measurement, thereby improving the detection precision.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic view of the structure and connection between the longitudinal straight needle body and the transverse straight needle body in the present invention;
FIG. 3 is a schematic structural diagram of an impedance converter and a coaxial cable according to the present invention and a connection relationship diagram thereof;
FIG. 4 is a front view of a straight longitudinal needle body in accordance with the present invention;
FIG. 5 is a side view of a catheter of the present invention;
FIG. 6 is a schematic diagram showing the measurement of sludge fouling thickness in a river in the example;
FIG. 7 is a schematic diagram of TDR measurement of soil moisture in the background art.
Reference numerals: 1. a conduit; 2. an impedance converter; 21. a pipe cap; 22. a sleeve; 23. a conductive tube; 24. a separation layer; 3. a transverse straight needle body; 31. a jack; 4. a longitudinal straight needle body; 41. a central longitudinal straight needle body; 42. a lateral longitudinal straight needle body; 43. bending the annular right angle; 5. a coaxial cable; 6. a BNC connector; 7. and a through hole.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings, and it should be understood that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
Examples
Referring to fig. 1, the staggered relay catheter type longitudinal TDR sensor disclosed by the utility model comprises a catheter 1 and more than two groups of probes, wherein the probes are sequentially and uniformly distributed in a staggered manner along the longitudinal direction of the catheter 1, and two adjacent probes are symmetrically arranged by taking the longitudinal plane of the catheter 1 as the center. The catheter 1 is made of a high-molecular low-dielectric-constant material, preferably polytetrafluoroethylene. The outer diameter of the catheter 1 is 80-150mm, preferably 120mm, and the wall thickness of the catheter 1 is 20-30mm, preferably 25 mm.
Referring to fig. 2, the probe is composed of an impedance converter 2, a transverse straight needle body 3 and a longitudinal straight needle body 4, and the probe passes throughThe coaxial cable 5 is connected with a BNC connector 6, wherein, the transverse straight needle body 3 and the longitudinal straight needle body 4 are made of metal materials, preferably stainless steel. The impedance converter 2 is tubular and is arranged in the catheter 1, a transverse straight needle body 3 is arranged in the impedance converter 2 along the axial direction of the impedance converter, and one end of a coaxial cable 5 is connected with the transverse straight needle body 3. The impedance converter 2 is a T-shaped tubular member consisting of a pipe cap 21 and a sleeve 22, the pipe cap 21 and the sleeve 22 are fixedly inserted, and the transverse straight needle body 3 is inserted in the sleeve 22 along the axial direction of the sleeve. Wherein the outer diameter of the sleeve 22 is D0Inner diameter of d0Length of L0. The length of the columnar horizontal straight needle body 3 made of stainless steel is L0Diameter d2The front end of the transverse straight needle body 3 is provided with an insertion hole 31, one end of the coaxial cable 5 penetrates into the pipe cap 21, the inner conductor of the coaxial cable 5 is inserted into the insertion hole 31, and the inner conductor of the coaxial cable 5 and the transverse straight needle body 3 are fixedly connected in a cold pressing mode. The outer insulating layer of the coaxial cable 5 inside the cap 21 is stripped off to tightly connect the outer conductor of the coaxial cable 5 with the cap 21.
A plurality of through holes 7 corresponding to the probes one by one are formed in the side wall of the guide pipe 1, the sleeve 22 is made of polytetrafluoroethylene materials, the sleeve 22 is tightly inserted into the through holes 7, the periphery of the sleeve is sealed by resin adhesive, and moisture is prevented from permeating along the gaps of the through holes 7.
Referring to fig. 3, the outer sidewall of the catheter 1 is tightly attached to the three-pin longitudinal straight needle body 4 from top to bottom, in order to avoid air infiltration between the outer sidewall of the catheter 1, a groove may be disposed on the outer sidewall of the catheter 1, and the longitudinal straight needle body 4 is horizontally disposed in the groove, but this is not limited. The longitudinal straight needle body 4 comprises a central longitudinal straight needle body 41 and side longitudinal straight needle bodies 42 which are positioned at two sides of the central longitudinal straight needle body 41 and are parallel to the central longitudinal straight needle body 41, and the upper end of the central longitudinal straight needle body 41 is welded and fixed with the transverse straight needle body 3. The upper end of each side longitudinal straight needle body 42 is provided with an annular right-angle bend 43, and the annular part of the annular right-angle bend 43 is perpendicular to the longitudinal straight needle body 4. Also inserted into the casing 22 is a length L0Outer diameter of d0Inner diameter of d1Wherein d is1＞d2The conductive tube 23 has one end connected to the cap 21 and the other end connected to the straight part of the annular right-angle bend 43The wire portions are connected. In order to avoid the short circuit caused by the contact between the central longitudinal straight needle body 41 and the lateral longitudinal straight needle body 42, a separation layer 24 is arranged between the conductive tube 23 and the lateral straight needle body 3, and the separation layer 24 is made of polytetrafluoroethylene with high polymer and low dielectric constant.
Referring to fig. 4 and 5, the length L of the central longitudinal straight needle body 41 and the lateral longitudinal straight needle bodies 42 is set to 200mm to 300mm, preferably 250mm, the width D is set to 2mm to 4mm, preferably 3mm, the thickness is set to 0.8mm to 1.2mm, preferably 1mm, and the needle body interval D of the two lateral longitudinal straight needle bodies 42 is set to 40mm to 50 mm. The longitudinal straight needle bodies 4 of two adjacent probes are provided with overlapping parts in the longitudinal plane, and the overlapping distance L' of the overlapping parts is 30mm-80mm, preferably 50 mm. The detection precision of the head end and the tail end of the probe is not high, the detection ranges of the two probes can be verified by setting the overlapping distance of the two probes, and the measurement blind area can be avoided by staggering the relay type probe arrangement mode, so that the detection precision is improved.
The working principle and the beneficial effects of the utility model are as follows:
as the trace of the single probe is only provided with two reflection points of a starting point and an end point as long as the single probe is positioned in a single medium no matter the whole probe is positioned in water/oil/soil layer, and the section of the probe positioned at the junction of different media has three reflection peaks, the position of a medium boundary layer can be determined in a multi-section probe inspection mode, and finally the depth or the thickness of the medium boundary layer can be measured. The distance L from the medium boundary layer to the root of the straight needle body at the longitudinal center of the section of the probe is deduced from the formula (1.4)1The calculation formula is as follows:
where, t is1-t0，t0Time corresponding to reflection peak formed for starting point of probe, t1Time, K, corresponding to a reflection peak formed for a change in probe impedance at the media boundary layerwCharacterization of dielectric constant for a Medium located above a Medium interface layer measured by an InstrumentAnd (4) counting.
The method can be used for judging the positions of medium boundary layers such as water-oil boundary layers, water-soil boundary layers and the like, determining the depth or thickness of the medium boundary layers, and is mainly applied to determining the depth of silt siltation in a river channel in soil measurement. And the staggered relay type probe arrangement mode can avoid the dead zone of measurement, thereby improving the detection precision.
Referring to fig. 6, taking the example of measuring the depth of sludge deposition in the river channel, the method comprises the following steps:
(1) drilling holes at corresponding monitoring points of the river channel, wherein the diameter of each hole is slightly smaller than the outer diameter of the guide pipe 1;
(2) inserting the longitudinal TDR sensor into the drill hole until the bottom of the longitudinal TDR sensor reaches the bottom of the sludge, fixing the longitudinal TDR sensor, and settling for about 1 month to enable the sludge to be tightly attached to the probe on the outer side wall of the guide pipe 1;
(3) measuring the distance h from the reference surface to the river bottom by taking the horizontal surface of the river channel as the reference surface0And the distance h between the reference plane and the root of the central longitudinal straight needle body 41 of the first probe1；
(4) The BNC connector 6 of the coaxial cable 5 is connected with the TDR host machine for measurement to obtain a trace diagram of each probe;
(5) finding out a trace diagram with three main reflection peaks, determining that the corresponding nth section of probe is positioned in the water-soil boundary layer, and calculating the distance L from the water-soil boundary layer to the root of the central longitudinal straight needle body 41 of the section of probe by the following formula1：
(6) Calculating to obtain the depth H of the sludge:
H＝h0-L1-L2-h1
wherein L is2＝nL-(n-1)L′。
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; while the utility model has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. Crisscross relay pipe formula vertical TDR sensor, its characterized in that: the device comprises a catheter (1) and more than two groups of probes, wherein the probes are sequentially and uniformly distributed in a staggered manner along the longitudinal direction of the catheter (1), two adjacent probes are symmetrically arranged by taking the longitudinal plane of the catheter (1) as the center, and the probes are connected with a BNC connector (6) through a coaxial cable (5);
the probe consists of an impedance converter (2), a transverse straight needle body (3) and a longitudinal straight needle body (4);
the impedance converter (2) is tubular and is arranged in the catheter (1), a transverse straight needle body (3) is arranged in the impedance converter (2) along the axial direction of the impedance converter, and one end of a coaxial cable (5) is connected with the transverse straight needle body (3);
the longitudinal straight needle body (4) comprises a central longitudinal straight needle body (41) and lateral longitudinal straight needle bodies (42) which are positioned on two sides of the central longitudinal straight needle body (41) and arranged in parallel with the central longitudinal straight needle body (41), the lateral longitudinal straight needle bodies are attached to the outer side wall of the catheter (1), and the upper end of the central longitudinal straight needle body (41) is connected with the transverse straight needle body (3); the upper end of each side longitudinal straight needle body (42) is provided with an annular right-angle bend (43), and the annular part of the annular right-angle bend (43) is vertical to the longitudinal straight needle body (4);
the side wall of the conduit (1) is provided with a through hole (7), the impedance converter (2) is inserted into the through hole (7), and the impedance converter (2) is fixedly connected with the linear part of the annular right-angle bend (43).
2. The staggered relay catheter-based longitudinal TDR sensor of claim 1, wherein: the longitudinal straight needle bodies (4) of two adjacent probes are provided with overlapping parts on the longitudinal plane, and the overlapping distance of the overlapping parts is 30-80 mm.
3. The staggered relay catheter-based longitudinal TDR sensor of claim 1, wherein: the impedance converter (2) is a T-shaped tubular component consisting of a pipe cap (21) and a sleeve (22), the pipe cap (21) and the sleeve (22) are fixedly inserted, and a transverse straight needle body (3) is inserted in the sleeve (22) along the axial direction of the sleeve.
4. The staggered relay catheter longitudinal TDR sensor of claim 3, wherein: the front end of the transverse straight needle body (3) is provided with an insertion hole (31), and one end of the coaxial cable (5) penetrates through the pipe cap (21) to be inserted into the insertion hole (31) and connected with the transverse straight needle body (3).
5. The staggered relay catheter-based longitudinal TDR sensor of claim 4, wherein: a conductive tube (23) is further arranged in the sleeve (22), one end of the conductive tube (23) is connected with the tube cap (21), the other end of the conductive tube is connected with the linear part of the annular right-angle bend (43), and a separation layer (24) is arranged between the conductive tube (23) and the transverse straight needle body (3).
6. The staggered relay catheter-based longitudinal TDR sensor of claim 1, wherein: the outer side wall of the catheter (1) is provided with a groove, and the longitudinal straight needle body (4) is horizontally arranged in the groove.
7. The staggered relay catheter-based longitudinal TDR sensor of claim 1, wherein: the length of the central longitudinal straight needle body (41) and the lateral longitudinal straight needle bodies (42) is set to be 200mm-300mm, the width is set to be 2mm-4mm, the thickness is set to be 0.8mm-1.2mm, and the distance between the needle bodies of the two lateral longitudinal straight needle bodies (42) is set to be 40mm-50 mm.
8. The staggered relay catheter-based longitudinal TDR sensor of claim 1, wherein: the outer diameter of the catheter (1) is set to be 80-150mm, and the wall thickness of the catheter (1) is set to be 20-30 mm.
9. The staggered relay catheter type longitudinal TDR sensor according to any one of claims 5 to 8, wherein: the conduit (1), the sleeve (22) and the separating layer (24) are all made of high-molecular low-dielectric-constant materials.
10. The staggered relay catheter type longitudinal TDR sensor according to any one of claims 5 to 8, wherein: the transverse straight needle body (3), the longitudinal straight needle body (4), the tube cap (21) and the conductive tube (23) are all made of metal materials.
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