CN113108733B - Two-wire vibration wire sensor with temperature detection function and detection method thereof - Google Patents
Two-wire vibration wire sensor with temperature detection function and detection method thereof Download PDFInfo
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- CN113108733B CN113108733B CN202110459640.9A CN202110459640A CN113108733B CN 113108733 B CN113108733 B CN 113108733B CN 202110459640 A CN202110459640 A CN 202110459640A CN 113108733 B CN113108733 B CN 113108733B
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Abstract
The invention discloses a two-Wire vibration Wire sensor with a temperature detection function and a detection method thereof, wherein the sensor comprises a steel Wire with two ends fixed on a diaphragm, a coil arranged right below the steel Wire, and a reader for identifying output data of the coil, the coil is connected in parallel with a composite tag for monitoring the environmental temperature of the steel Wire, and the parallel connection end of the coil and the composite tag is connected with the reader through a 1Wire signal Wire; the composite tag consists of a temperature sensor and a 1Wire chip which are connected in parallel, two pins of the temperature sensor and the 1Wire chip which are connected in parallel are respectively connected with two ends of a coil in parallel to form two 1Wire ports respectively, and a reader performs bidirectional data transmission with the coil, the temperature sensor and the 1Wire chip through a 1Wire signal Wire; the invention can synchronously realize real-time acquisition of temperature and sensor parameter information, and can detect the resonant frequency of the steel string and acquire the temperature-corrected steel string stress state change.
Description
Technical Field
The invention relates to the technical field of vibrating wire sensors, in particular to a two-wire vibration wire sensor with a temperature detection function and a detection method thereof.
Background
The vibrating wire type sensor is also called as a steel wire type sensor, and is a non-electric quantity electric measuring sensor which is widely valued and widely applied at home and abroad at present. The steel string type sensor has the advantages of simple structure, firmness, durability, strong anti-interference capability (close range), reliable measured value, high precision and resolution, good stability and the like; the output of the device is a frequency signal (generally mV-level sine wave), and the device is widely applied to the engineering test of rock and soil, concrete and steel structures.
The steel wire and the material for manufacturing the vibrating wire sensor are both expanded and contracted under the influence of temperature change, so that the temperature change can influence the frequency of the steel wire, the vibration frequency of the steel wire can be influenced by the ambient temperature, shielding and elimination are needed, otherwise, the measuring precision of the sensor can be seriously reduced, and when the tension of the steel wire is calculated, the current frequency of the sensor needs to be measured, and parameters such as the factory frequency, the length of the steel wire, the material density and the like are used for jointly completing the calculation of physical quantity.
However, the existing vibrating wire sensor has the following defects:
(1) The real-time temperature is monitored by using the thermistor, most of data outgoing lines of the thermistor and the vibrating wire sensor are in a three-wire system or a four-wire system, the cable length of each sensor is generally tens of meters or even hundreds of meters in the application process of the vibrating wire sensor, the cable always accounts for 30% -70% of the cost of the whole sensor, technicians always only measure the vibration frequency of the steel wire in order to pursue efficiency and reduce working strength, and a mode for measuring the temperature by using the thermistor is not practical.
(2) Parameters such as factory frequency, length of the steel wire, material density and the like are marked on the vibrating wire type sensor in a metal label mode, so that the method is inconvenient to use, and the difficulty in calculating the tension applied to the steel wire is increased.
Disclosure of Invention
The invention aims to provide a two-wire vibration wire sensor with a temperature detection function and a detection method thereof, which are used for solving the technical problems that the cable is long, the cost is high, parameters such as factory frequency, the length of a steel wire, material density and the like are marked by utilizing a metal label mode, the use is inconvenient, and the difficulty in calculating the tension applied to the steel wire is increased in the prior art.
In order to solve the technical problems, the invention specifically provides the following technical scheme:
the two-Wire vibration Wire sensor with the temperature detection function comprises a steel Wire with two ends fixed on a diaphragm and a coil arranged right below the steel Wire, wherein the coil is connected with a composite tag used for monitoring the environment temperature of the steel Wire in parallel, and the parallel connection end of the coil and the composite tag is connected with a reader through a 1Wire signal Wire;
the composite tag is composed of a temperature sensor and a 1Wire chip in parallel connection, two pins of the temperature sensor and the 1Wire chip after being connected in parallel are respectively connected with two ends of the coil in parallel to form two 1Wire ports, the two 1Wire ports are respectively connected with a reader through a 1Wire signal Wire, and the reader is in bidirectional data transmission with the coil, the temperature sensor and the 1Wire chip through the 1Wire signal Wire.
As a preferable scheme of the invention, the reader has a data reading function and a data sending function through the 1Wire signal Wire, the reader sends an excitation signal to the coil to monitor the stress change of the steel Wire, and the reader is used for reading the signal sent by the coil and reading the data information of the temperature sensor and the 1Wire chip.
As a preferable scheme of the invention, the temperature sensor is used for monitoring the environmental temperature of the steel string in real time, and the 1Wire chip is used for storing the parameter information of the temperature sensor and the steel string.
As a preferred embodiment of the present invention, the reader includes a microprocessor unit, a line switch connected to the microprocessor unit, and a frequency measurement circuit and a temperature measurement circuit connected to the microprocessor unit, the frequency measurement circuit and the temperature measurement circuit being connected to the 1Wire signal line through the line switch;
the temperature measuring circuit is used for identifying output data of the temperature sensor and reading parameter information about the temperature sensor and the steel Wire, which is stored by the 1Wire chip;
the frequency measurement circuit is used for identifying output data of the coil.
As a preferable scheme of the invention, the circuit of the coil is connected with a diode D1 in series, the circuit of the composite tag is connected with a diode D2 and a resistor R1 in series, two ends of the composite tag are connected with a zener diode D3 in parallel, and the connection directions of the diode D1 and the diode D2 are opposite.
As a preferable scheme of the invention, a power pin of the 1Wire chip is short-circuited to a grounding pin of the temperature sensor, the short-circuited grounding pin is used as a label negative electrode of the whole composite label, and a data pin of the temperature sensor is used as a label data pin of the whole composite label;
the tag negative electrode and the tag data pin are respectively connected with two ends of the coil in parallel and respectively form two 1Wire ports.
In order to solve the above problems, the present invention further provides a detection method of a two-wire vibration wire sensor with a temperature detection function, comprising the following steps:
step 100, manufacturing a two-wire vibration wire sensor, wherein a composite tag is built in the vibration wire sensor, the vibration wire sensor composite tag isolates two paths of polarities by using two diodes D1 and D2, and a bipolar parallel circuit is formed by using a connecting test wire A, B;
step 200, accessing a reader, and calibrating frequency-physical quantity parameters and temperature-physical quantity parameters in a memory chip of the composite tag by using the reader;
and 300, regularly reading frequency data monitored by the vibrating wire sensor and temperature data monitored by the composite tag, and calculating stress changes of the vibrating wire sensor after temperature correction.
In a preferred embodiment of the present invention, in step 200, the temperature-physical parameter is specifically a thermal expansion coefficient of the steel string, and the frequency-physical parameter is specifically an elastic modulus of the steel string, a sectional area of the steel string, a length of the steel string, and a material density.
As a preferred embodiment of the present invention, in step 300, the specific implementation steps for calculating the stress variation after the temperature correction of the vibrating wire sensor are as follows:
step 301, starting four line switches controlled by a micro-processing unit MCU to realize the functions of measuring line selection and anode-cathode switching;
step 302, a micro-processing unit MCU controls a line switcher to switch a connection test line A, B to a temperature measurement circuit, and the micro-processing unit MCU controls the temperature measurement circuit to detect a connected composite label and reads the temperature value of the composite label and the basic information of a sensor stored in the composite label;
step 303, the micro-processing unit MCU controls the line switcher to switch the connection test line A, B to the frequency measurement circuit, and the micro-processing unit MCU controls the frequency measurement circuit to detect the connected vibrating wire sensor coil, sends an excitation signal to the coil and reads a return signal of the coil to obtain a frequency value;
and 304, substituting the obtained temperature value of the composite tag, the internally stored sensor basic information and the frequency value into a strain formula of the steel string, and calculating a steel string strain value which excludes the influence of the environmental temperature on the frequency.
As a preferable scheme of the invention, the strain formula of the steel string excluding the influence of the ambient temperature on the frequency is as follows:
wherein the method comprises the steps of
ρ is the string density, L is the string length; e is the elastic modulus of the steel string; a is the section area of a steel string;
f 0 the initial frequency value is the initial frequency value when the sensor is not stressed, and f is the frequency value after being stressed;
Δt is the temperature change amount, and α is the thermal expansion coefficient.
Compared with the prior art, the invention has the following beneficial effects:
the invention replaces the thermistor in the prior art with the composite tag to monitor the temperature change, thereby synchronously realizing the real-time acquisition of the temperature and the parameter information of the sensor, simultaneously detecting the resonance frequency of the steel string, and synchronously acquiring the temperature-corrected steel string stress state change by combining the resonance frequency and the temperature parameter through a calculation formula.
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. It will be apparent to those of ordinary skill in the art that the drawings in the following description are exemplary only and that other implementations can be obtained from the extensions of the drawings provided without inventive effort.
FIG. 1 is a schematic diagram of a two-wire vibration wire sensor according to an embodiment of the present invention;
fig. 2 is a schematic flow chart of a detection method of a two-wire vibration wire sensor according to an embodiment of the present invention.
Reference numerals in the drawings are respectively as follows:
1-steel string; a 2-coil; 3-reading instrument; 4-composite tag; 5-1Wire signal lines;
31-a microprocessor unit; a 32-line switcher; 33-a frequency measurement circuit; 34-a temperature measurement circuit;
41-a temperature sensor; 42-1Wire chip.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in FIG. 1, the two-wire vibration wire sensor with the temperature detection function is provided, the real-time acquisition of temperature, the calculation of parameter information and temperature correction parameters by the sensor can be realized, the physical quantity subjected to temperature correction can be obtained at the same time of frequency measurement, and the measurement accuracy of the vibration wire sensor is improved.
The two-wire vibration wire sensor provided in this embodiment includes a steel wire 1 having both ends fixed to a diaphragm, and a coil 2 provided directly under the steel wire 1.
The general working principle of the steel string type sensor is as follows: the steel wire 1 is placed in a magnetic field generated by the coil 2, after a power supply is turned on and the steel wire 1 is excited, the steel wire 1 vibrates, and the vibrating steel wire 1 moves in the magnetic field to cut magnetic lines of force, so that potential can be induced in the coil 2, the induced potential steel wire cuts the magnetic lines of force, and the frequency of generating weak electric signals in the coil is the resonance frequency of the steel wire 1. According to the mechanical principle, the resonance frequency of the steel string and the tension or pulling force born by the string are in a linear relation, so that the tension stress of the tightening degree of the steel string to be measured can be obtained by measuring the resonance frequency of the steel string.
As a preferred mode of the embodiment, the coil 2 comprises an exciting coil and a receiving coil which are connected in parallel, the exciting coil is used for receiving an exciting signal sent by the reader 3, the receiving coil is powered on to excite the steel string 1 to vibrate under the action of vibration of the steel string 1 when in operation, the exciting coil is electrified to excite the steel string 1 to vibrate, the steel string 1 cuts magnetic lines of force of a magnetic field generated by the receiving coil and generates induced potential, the generated induced potential is sent into an amplifier by the receiving coil to be amplified and output, and meanwhile, part of an output signal is fed back to the exciting coil to keep vibration of the steel string, thus the feedback cycle is continuously carried out, and amplitude stabilizing measures of a circuit are added to enable the steel string to reach constant amplitude and continuous vibration kept by the circuit, and then frequency signals related to tension of the steel string are output.
In the present embodiment, the basic structure of the string sensor is the same as that in the prior art, and the present embodiment is advantageous in that a temperature measurement function is integrated so that a stress variation of the string is corrected by temperature compensation.
The coil 2 is connected in parallel with a composite tag 4 for monitoring the ambient temperature of the steel string 1, and the parallel connection end of the coil 2 and the composite tag 4 is connected with a reader 3 through a 1Wire signal line 5.
It should be noted that the 1-wire single bus uses a single signal line, which transmits both clock and data and the data transmission is bidirectional. The device has the advantages of saving I/O port line resources, along with simple structure, low cost, convenient bus expansion and maintenance, and the like.
The composite tag 4 is formed by connecting a temperature sensor 41 and a 1Wire chip 42 in parallel, and two pins of the temperature sensor 41 and the 1Wire chip 42 which are connected in parallel are respectively connected with two ends of the coil 2 in parallel to form two 1Wire ports.
Namely, the power supply pin of the 1Wire chip 42 is short-circuited to the grounding pin of the temperature sensor 41, and the short-circuited grounding pin is used as the tag negative electrode of the whole composite tag 4, the data pin of the temperature sensor 41 is used as the tag data pin of the whole composite tag 4, and the tag negative electrode and the tag data pin are respectively connected with two ends of the coil 2 in parallel and respectively form two 1Wire ports.
Further, the parallel connection mode of the coil 2 and the composite tag is as follows: the circuit at the coil 2 is connected with a diode D1 in series, the circuit at the composite tag is connected with a diode D2 and a resistor R1 in series, two ends of the composite tag are connected with a zener diode D3 in parallel, and the connection directions of the diode D1 and the diode D2 are opposite.
According to the embodiment, the composite tag is manufactured through a physical structure of parallelly connecting the temperature sensor DS18B20 and the EEPROM chip DS2431 based on the 1Wire interface protocol, and automatic reading of unique tag code identification, sensor manufacturer information, cable length, calculation parameters, real-time temperature and the like and calculation of physical quantity are realized through a reading end remote communication circuit and method, so that personnel intervention in the whole reading process is completely avoided, the working efficiency is improved, and the labor cost is saved.
The two 1Wire ports are respectively connected with the reader 3 through a 1Wire signal Wire 5, and the reader 3 carries out bidirectional data transmission with the coil 2, the temperature sensor 41 and the 1Wire chip 42 through the 1Wire signal Wire 5.
In the present embodiment, the temperature sensor 41 is used for monitoring the environmental temperature of the steel string 1 in real time, and the 1Wire chip 42 provides parameter information of the temperature sensor 41 and the steel string 1.
The reader 3 has a data reading function and a data sending function, the reader 3 recognizes output data of the temperature sensor 41 and the coil 2 and reads parameter information of the temperature sensor 41 and the steel Wire 1 carried by the 1Wire chip 42, and the reader 3 sends an excitation signal to the coil 2 to monitor stress change of the steel Wire 1.
Preferably, the reader 3 includes a microprocessor unit 31, a line switch 32 connected to the microprocessor unit 31, and a frequency measurement circuit 33 and a temperature measurement circuit 34 connected to the microprocessor unit 31, the frequency measurement circuit 33 and the temperature measurement circuit 34 being connected to the 1Wire signal line 5 through the line switch 32.
The temperature measurement circuit 34 is used for recognizing output data of the temperature sensor 41 and reading parameter information about the temperature sensor 41 and the steel string 1 stored in the 1Wire chip 42.
The frequency measurement circuit 33 is used to identify the output data of the coil 2.
The specific implementation method comprises the following steps: in order to prevent the coil 2 and the temperature sensor 41 in parallel connection from interfering with each other, the sensor is internally provided with a unique bipolar parallel circuit formed by isolating two paths of polarities by using two diodes D1 and D2, wherein the line a is positive, the line B is negative, the diode D1 is conducted and the diode D2 is cut off when the frequency is measured, the line a is negative, the line B is positive, the diode D2 is conducted and the diode D1 is cut off when the temperature is measured, and further, in order to prevent the voltage applied at two ends of the temperature sensor from exceeding the limit, a voltage stabilizing diode is connected in parallel for protection.
The whole reader is controlled by a Microprocessor Unit (MUC) to control a line switcher to switch to a certain physical measurement channel, and then to control a certain measurement circuit to perform measurement. Particularly, under the control of the MCU, the polarity of the AB can be automatically judged, and the line switcher is controlled to automatically switch to finish the measurement of a certain physical quantity, so that a user does not need to distinguish the A line from the B line, and the implementation method is as follows:
the MCU controls the line switcher to connect the AB line with the temperature measuring circuit, the A is assumed to be the positive electrode B and the negative electrode is assumed to be the negative electrode, the temperature measurement is carried out, if the temperature sensor cannot normally communicate with the line switcher, the instruction is sent to switch the AB polarity and the temperature sensor can not communicate with the DS18B20 again, if the temperature sensor cannot correctly communicate with the DS18B20, the external temperature sensor is determined to be absent, and the frequency measurement is carried out instead.
When the frequency is measured, firstly, assuming that A is the positive electrode B is the negative electrode, sending an excitation signal and reading a return frequency signal, if the expected frequency signal is obtained, continuing to calculate the frequency, otherwise, sending an instruction to switch the AB polarity to the line switcher, and carrying out the frequency measurement flow again, and if the effective frequency signal output by the sensor cannot be obtained, determining that no external vibrating wire sensor coil exists.
The existing vibrating wire sensor with temperature detection often utilizes a thermistor to detect the environmental temperature of the steel wire 1, the thermistor is a resistor with the resistance value changing along with the temperature, the temperature value can be calculated by measuring the resistance value of the sensor through an electronic circuit, the temperature is also not discussed in detail, the temperature is monitored by utilizing the thermistor, so that the vibrating wire sensor is integrally provided with four or three outgoing lines, in the application process of the vibrating wire sensor, the cable length of each sensor is generally tens of meters or hundreds of meters, the cable usually accounts for 30% -70% of the cost of the whole sensor, the steel wire frequency and the temperature need to be measured separately, and in the engineering application of the vibrating wire sensor, technicians responsible for monitoring and reading are usually used for measuring the vibration frequency of the steel wire only for pursuing efficiency and reducing working strength.
In order to solve the above-described problems, the present embodiment integrates a temperature sensor inside the vibrating Wire sensor, and stores basic parameter information of the temperature sensor 41 and basic parameter information of the steel Wire 1, such as manufacturer information of the temperature sensor 41, equipment number, cable length of the 1Wire signal line 5, factory initial parameters and temperature correction parameters, and manufacturer information of the steel Wire 1, correspondence between stress variation and vibration amplitude, and the like, with the 1Wire chip 42.
Therefore, the composite tag replaces a thermistor in the prior art to monitor temperature change, temperature real-time acquisition and sensor parameter information can be synchronously realized, meanwhile, the resonance frequency of the steel string can be detected, and the temperature-corrected steel string stress state change can be synchronously acquired by combining a calculation formula with the resonance frequency and the temperature parameter.
In order to further explain the working principle of the two-wire vibration wire sensor with the temperature detection function, as shown in fig. 2, the present embodiment further provides a detection method of the two-wire vibration wire sensor with the temperature detection function, which specifically includes the following steps:
and 100, manufacturing a two-wire vibration wire sensor, wherein a composite tag is built in the vibration wire sensor, the vibration wire sensor composite tag isolates two paths of polarities by using two diodes D1 and D2, and a bipolar parallel circuit is formed by using a connecting test line A, B.
Step 200, accessing a reader, and calibrating the frequency-physical quantity parameters and the temperature-physical quantity parameters in a memory chip of the composite tag by using the reader.
The temperature-physical quantity parameter is specifically the thermal expansion coefficient of the steel string, and the frequency-physical quantity parameter is specifically the elastic modulus of the steel string, the sectional area of the steel string, the length of the steel string and the material density.
Step 300, the frequency data monitored by the vibrating wire sensor and the temperature data monitored by the composite tag are read at fixed time, and the stress change of the vibrating wire sensor after temperature correction is calculated.
In the step, the specific implementation steps for calculating the stress change after the temperature correction of the vibrating wire sensor are as follows:
step 301, starting four line switches controlled by a micro-processing unit MCU to realize the functions of measuring line selection and anode-cathode switching;
in step 302, the micro-processing unit MCU controls the line switcher to switch the connection line A, B to the temperature measurement circuit, assuming that a is positive and B is negative, the micro-processing unit MCU controls the temperature measurement circuit to detect the connected composite tag, if the composite tag cannot normally communicate with the temperature sensor, the micro-processing unit MCU sends an instruction to switch the polarity AB to the line switcher, that is, the current a is negative and the current B is positive, and the micro-processing unit MCU communicates with the temperature sensor again, if the current a cannot correctly communicate with the temperature sensor, it is determined that no external temperature sensor exists, and frequency measurement is performed instead.
If the frequency-physical quantity parameter is communicated with the temperature sensor, the temperature value of the composite tag and the internal stored sensor basic information, namely the thermal expansion coefficient of the steel string, are read, and the frequency-physical quantity parameter is specifically the elastic modulus of the steel string, the sectional area of the steel string, the length of the steel string and the material density.
And 303, the micro-processing unit MCU controls the line switcher to switch the connection test line A, B to the frequency measuring circuit, and the micro-processing unit MCU controls the frequency measuring circuit to detect the connected vibrating wire sensor coil, sends an excitation signal to the coil and reads a return signal of the coil to obtain a frequency value.
During frequency measurement, only the AB polarity during temperature measurement is required to be reversely adjusted, an excitation signal is sent, a return frequency signal is read, the expected frequency signal can be obtained, the frequency is calculated continuously, and if the effective frequency signal output by the sensor cannot be obtained, no external vibrating wire sensor coil is considered.
And 304, substituting the obtained temperature value of the composite tag, the internally stored sensor basic information and the frequency value into a strain formula of the steel string, and calculating a steel string strain value which excludes the influence of the environmental temperature on the frequency.
The strain formula of the steel string for eliminating the influence of the ambient temperature on the frequency is as follows:
wherein the method comprises the steps of
ρ is the string density, L is the string length; e is the elastic modulus of the steel string; a is the section area of a steel string;
f 0 the initial frequency value is the initial frequency value when the sensor is not stressed, and f is the frequency value after being stressed;
Δt is the temperature change amount, and α is the thermal expansion coefficient.
It should be noted that, after the steel wire is placed in the magnetic field and excited in a certain way, the steel wire will vibrate, and the vibrating steel wire moves in the magnetic field to cut magnetic lines, so that electric potential can be induced in the vibration pickup coil, and the frequency of the induced electric potential (the steel wire cuts the magnetic lines and generates weak electric signals in the coil) is the resonance frequency of the vibrating wire. According to the mechanical principle, the resonance frequency of the steel string and the tension or pulling force born by the string are in a linear relation, so that the tightening degree (tensioning stress) of the steel string to be measured can be obtained by measuring the resonance frequency of the steel string, various sensors such as pressure, displacement and the like are manufactured by utilizing the characteristic, the sensor structure is deformed due to the change of the pressure or the displacement and then the tightening degree of the steel string is influenced, the resonance frequency is correspondingly changed, and the physical quantity changes such as the pressure or the displacement born by the sensor can be calculated by measuring the frequency value of the sensor.
The derivation process of the strain formula of the steel string is as follows:
the degree of the tension of the steel string is the stress state of the steel string, and the stress and the resonance frequency of the steel string meet the formula
In the above formula:
f: frequency value of steel string
L: length of steel string
T: tension to which the steel string is subjected
ρ: density of steel string material
Can be deduced
T＝4×ρ×L 2 ×f 2 (2)
For the finished steel string sensor, the length L and the material density rho of the steel string are known constants and are generally expressed by k, so that the tensile stress of the steel string has a one-to-one correspondence with the resonance frequency of the steel string, and the tensile force is in direct proportion to the square of the steel string. The tensile stress is changed by the influence (such as pressure) of the external environment of the sensor, so that the value of the external environment can be calculated through the frequency value.
Let k=4×ρ×l 2 Then the string tension t=4×ρ×l 2 ×f 2 ＝k×f 2 (3)；
For any vibration wire sensor manufactured, the k value is a fixed constant, a specific value can be obtained by the calibration process, and when the sensor is deformed by external force, the change amount of the tension of the steel wire can be calculated by the following formula
ΔT＝k×(f 2 -f 0 2 ) (4)
In the above, f 0 The initial frequency value is the frequency value after the sensor is stressed when the sensor is not stressed.
However, it should be noted that both the steel wire and the material from which the vibrating wire sensor is made are subject to temperature changes that affect the frequency of the steel wire. The strain gauge vibrating wire sensor is described below as an example.
From the strain formula
Can be obtained
In the above formula, epsilon represents strain, E represents elastic modulus of the steel string, and A represents sectional area of the steel string. Since the elastic modulus and the sectional area are constant, the method can
Reduced to k c Then
When the environment temperature of the steel wire changes or the length of the steel wire changes due to external force, the frequency value changes, and in order to enable the vibrating wire sensor to truly reflect the strain quantity, the influence of the environment temperature on the frequency needs to be removed, so the method has the following formula:
wherein Δt is the temperature change amount, and α is the thermal expansion coefficient
By influencing the test on the temperature change of a vibrating wire strain sensor of a certain model, the calculated result deviation is 4 multiplied by 10 when the temperature is changed by 1 DEG C -6 Left and right strain. The measuring range of the conventional strain sensor is generally +/-1000 micro-strain, 40 micro-strain changes of the strain amount are generated when the ambient temperature changes by 10 ℃, the strain amount is equivalent to 2% of the full measuring range of the sensor, and if the temperature influence is not removed, the measuring error of the sensor is 2%, and the measuring error is far lower than the measuring precision of 0.1% generally required by engineering.
Therefore, the two-wire vibration wire sensor of the embodiment simultaneously completes the work of the sensor end for measuring the frequency of the steel wire and acquiring the internal temperature. The two-Wire vibration Wire sensor steel Wire frequency measurement, temperature measurement, automatic sensor code identification, dynamic parameter information acquisition and automatic physical quantity calculation are realized through the 1Wire signal Wire communication and remote measuring and reading method, so that the sensor cost is greatly reduced, the data acquisition and calculation efficiency is improved, the labor intensity of technicians is reduced, and the sensor measurement accuracy is improved.
The above embodiments are only exemplary embodiments of the present application and are not intended to limit the present application, the scope of which is defined by the claims. Various modifications and equivalent arrangements may be made to the present application by those skilled in the art, which modifications and equivalents are also considered to be within the scope of the present application.
Claims (4)
1. Two-wire vibration wire sensor with temperature detection function, including both ends are fixed steel string (1) on the diaphragm and set up coil (2) under steel string (1), its characterized in that: the coil (2) is connected in parallel with a composite tag (4) for monitoring the ambient temperature of the steel string (1), and a reader (3) is connected to the parallel connection end of the coil (2) and the composite tag (4) through a 1Wire signal line (5);
the composite tag (4) is formed by connecting a temperature sensor (41) and a 1Wire chip (42) in parallel, two pins of the temperature sensor (41) and the 1Wire chip (42) which are connected in parallel are respectively connected with two ends of the coil (2) in parallel to form two 1Wire ports, the two 1Wire ports are respectively connected with the reader (3) through a 1Wire signal Wire (5), and the reader (3) carries out bidirectional data transmission with the coil (2), the temperature sensor (41) and the 1Wire chip (42) through the 1Wire signal Wire (5);
the circuit of the coil (2) is connected with a diode D1 in series, the circuit of the composite tag is connected with a diode D2 and a resistor R1 in series, two ends of the composite tag are connected with a zener diode D3 in parallel, and the connection directions of the diode D1 and the diode D2 are opposite;
the reader (3) comprises a microprocessor unit (31), a line switcher (32) connected with the microprocessor unit (31), and a frequency measurement circuit (33) and a temperature measurement circuit (34) connected with the microprocessor unit (31), wherein the frequency measurement circuit (33) and the temperature measurement circuit (34) are connected with the 1Wire signal line (5) through the line switcher (32);
the temperature measuring circuit (34) is used for identifying output data of the temperature sensor (41) and reading parameter information about the temperature sensor (41) and the steel Wire (1) stored in the 1Wire chip (42);
-the frequency measurement circuit (33) is adapted to identify output data of the coil (2);
the detection method of the two-wire vibration wire sensor comprises the following steps:
step 100, manufacturing a two-wire vibration wire sensor, wherein a composite tag is built in the vibration wire sensor, the vibration wire sensor composite tag isolates two paths of polarities by using two diodes D1 and D2, and a bipolar parallel circuit is formed by using a connecting test wire A, B;
step 200, accessing a reader, and calibrating frequency-physical quantity parameters and temperature-physical quantity parameters in a memory chip of the composite tag by using the reader, wherein the temperature-physical quantity parameters are specifically thermal expansion coefficients of the steel strings, and the frequency-physical quantity parameters are specifically elastic modulus of the steel strings, sectional area of the steel strings, length of the steel strings and material density;
step 300, periodically reading frequency data monitored by the vibrating wire sensor and temperature data monitored by the composite tag, and calculating stress change of the vibrating wire sensor after temperature correction, wherein the step comprises the following steps:
starting four line switches controlled by the MCU to realize the functions of measuring line selection and anode-cathode switching;
the micro-processing unit MCU controls the line switcher to switch the connection line A, B to the temperature measuring circuit, and the micro-processing unit MCU controls the temperature measuring circuit to detect the connected composite tag and read the temperature value of the composite tag and the basic information of the sensor stored in the interior;
the micro-processing unit MCU controls the line switcher to switch the connection test line A, B to the frequency measuring circuit, and the micro-processing unit MCU controls the frequency measuring circuit to detect the connected vibrating wire sensor coil, sends an excitation signal to the coil and reads a return signal of the coil to obtain a frequency value;
substituting the obtained temperature value of the composite tag, the internally stored sensor basic information and the frequency value into a strain formula of the steel string, and calculating the steel string strain value which excludes the influence of the environmental temperature on the frequency;
the strain formula of the steel string for eliminating the influence of the ambient temperature on the frequency is as follows:
wherein the method comprises the steps of
ρ is the string density, L is the string length; e is the elastic modulus of the steel string; a is the section area of a steel string;
f 0 the initial frequency value is the initial frequency value when the sensor is not stressed, and f is the frequency value after being stressed;
Δt is the temperature change amount, and α is the thermal expansion coefficient.
2. The two-wire vibration wire sensor with temperature detection function according to claim 1, wherein: the reader (3) has a data reading function and a data sending function through the 1Wire signal Wire (5), the reader (3) sends an excitation signal to the coil (2) to monitor the stress change of the steel string (1), and the reader (3) is used for reading the signal sent by the coil (2) and reading the data information of the temperature sensor (41) and the 1Wire chip (42).
3. A two-wire vibration wire sensor with temperature detection function as claimed in claim 2, wherein: the temperature sensor (41) is used for monitoring the environment temperature of the steel string (1) in real time, and the 1Wire chip (42) is used for storing parameter information of the temperature sensor (41) and the steel string (1).
4. The two-wire vibration wire sensor with temperature detection function according to claim 1, wherein: the power supply pin of the 1Wire chip (42) is short-circuited to the grounding pin of the temperature sensor (41), the short-circuited grounding pin is used as a label negative electrode of the whole composite label (4), and the data pin of the temperature sensor (41) is used as a label data pin of the whole composite label (4);
the tag negative electrode and the tag data pin are respectively connected with two ends of the coil (2) in parallel and respectively form two 1Wire ports.
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| CA1231851A (en) * | 1985-03-06 | 1988-01-26 | Stuart M. Mcglade | Strain sensor |
| CN204086219U (en) * | 2014-09-22 | 2015-01-07 | 东北大学 | A kind of bridge health monitoring system |
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| USRE31416E (en) * | 1976-10-13 | 1983-10-18 | The Foxboro Company | Electric signal transmitter for vibrating-wire sensor |
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| CN206488790U (en) * | 2017-03-03 | 2017-09-12 | 杨毅 | Storage type vibrating wire sensor in demarcation |
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| CN111462469A (en) * | 2020-04-02 | 2020-07-28 | 中国电建集团昆明勘测设计研究院有限公司 | Multi-channel acquisition terminal |
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| CA1231851A (en) * | 1985-03-06 | 1988-01-26 | Stuart M. Mcglade | Strain sensor |
| CN204086219U (en) * | 2014-09-22 | 2015-01-07 | 东北大学 | A kind of bridge health monitoring system |
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