CN113108733A - Two-wire vibrating wire sensor with temperature detection function and detection method thereof - Google Patents
Two-wire vibrating wire sensor with temperature detection function and detection method thereof Download PDFInfo
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Abstract
The invention discloses a two-Wire vibrating Wire sensor with a temperature detection function and a detection method thereof, wherein the two-Wire vibrating Wire sensor comprises a steel Wire, a coil and a reading instrument, wherein the two ends of the steel Wire are fixed on a diaphragm; the composite tag is formed by connecting a temperature sensor and a 1Wire chip 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, and the reading instrument performs bidirectional data transmission with the coil, the temperature sensor and the 1Wire chip through a 1Wire signal Wire; the invention can synchronously realize the real-time temperature acquisition and sensor parameter information, can detect the resonance frequency of the steel string, and can acquire the stress state change of the steel string after temperature correction.
Description
Technical Field
The invention relates to the technical field of vibrating wire sensors, in particular to a two-wire vibrating wire sensor with a temperature detection function and a detection method thereof.
Background
The vibrating wire sensor is also called steel wire sensor, and is one kind of non-electric quantity and electric measuring sensor widely used in China and other countries. The steel string type sensor has the advantages of simple structure, firmness, durability, strong anti-interference capability (close distance), reliable measured value, high precision and resolution, good stability and the like; the output of the device is a frequency signal (generally a mV-level sine wave), and the device is widely applied to geotechnical, concrete and steel structure engineering tests.
The steel wire and the material for manufacturing the vibrating wire sensor are both affected by temperature change to generate expansion and contraction, so the temperature change affects the frequency of the steel wire, the vibration frequency of the steel wire is affected by the environmental temperature and needs to be shielded and eliminated, otherwise the measurement accuracy of the sensor is seriously reduced, and when the tension on the steel wire is calculated, the current frequency of the sensor needs to be measured, and the parameters of factory frequency, the length of the steel wire, the material density and the like are used for jointly completing the calculation of the physical quantity.
However, the existing vibrating wire sensor has the following defects:
(1) the thermistor is used for monitoring real-time temperature, data outgoing lines of the thermistor and the vibrating wire sensor are mostly of a three-wire system or a four-wire system, the length of a cable of each sensor is dozens of meters or even hundreds of meters generally in the application process of the vibrating wire sensor, the cable usually accounts for 30% -70% of the cost of the whole sensor, technicians usually measure the vibration frequency of a steel wire only for pursuing efficiency and reducing working strength, and the mode of measuring the temperature by the thermistor is not practical.
(2) Most vibrating wire sensors are marked with parameters such as delivery frequency, length of steel strings, material density and the like by using a metal label, so that the use is inconvenient, and the difficulty in calculating the tension of the steel strings is improved.
Disclosure of Invention
The invention aims to provide a two-wire vibrating wire sensor with a temperature detection function and a detection method thereof, and aims to solve the technical problems that in the prior art, a cable is long and high in consumption, parameters such as delivery frequency, length of a steel wire and material density are marked in a metal label mode, so that the use is inconvenient, and the difficulty in calculating the tension of the steel wire is increased.
In order to solve the technical problems, the invention specifically provides the following technical scheme:
a two-Wire vibrating Wire sensor with a temperature detection function comprises a steel Wire and a coil, wherein two ends of the steel Wire are fixed on a diaphragm, the coil is arranged right below the steel Wire, the coil is connected with a composite label in parallel for monitoring the environmental temperature of the steel Wire, and the parallel connection end of the coil and the composite label is connected with a reading instrument through a 1Wire signal Wire;
the composite tag is formed by connecting a temperature sensor and a 1Wire chip in parallel, two pins of the temperature sensor and the 1Wire chip which are 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 the reading instrument through 1Wire signal lines, and the reading instrument performs bidirectional data transmission with the coil, the temperature sensor and the 1Wire chip through the 1Wire signal lines.
As a preferable scheme of the present invention, the reading device has a data reading function and a data transmitting function through the 1Wire signal line, the reading device sends an excitation signal to the coil to monitor a stress change of the steel string, and the reading device is configured to read a signal transmitted by the coil and read data information of the temperature sensor and the 1Wire chip.
As a preferable scheme of the present invention, the temperature sensor is configured to monitor an ambient temperature of the steel string in real time, and the 1Wire chip is configured to store parameter information of the temperature sensor and the steel string.
As a preferable scheme of the present invention, the reading device includes a microprocessor unit, a line switch connected to the microprocessor unit, and a frequency measuring circuit and a temperature measuring circuit connected to the microprocessor unit, and the frequency measuring circuit and the temperature measuring circuit are connected to the 1Wire signal line through the line switch;
the temperature measuring circuit is used for identifying the output data of the temperature sensor and reading the parameter information about the temperature sensor and the steel string stored in the 1Wire chip;
the frequency measurement circuit is used for identifying the output data of the coil.
In a preferred embodiment of the present invention, a diode D1 is connected in series to the circuit of the coil, a diode D2 and a resistor R1 are connected in series to the circuit of the composite tag, a zener diode D3 is connected in parallel to both ends of the composite tag, and the connection directions of the diode D1 and the diode D2 are opposite.
As a preferred scheme of the present invention, a power pin of the 1Wire chip is short-circuited to a ground pin of the temperature sensor, the ground pin is used as a label cathode of the whole composite label after short-circuited, and a data pin of the temperature sensor is used as a label data pin of the whole composite label;
the tag cathode 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 vibrating wire sensor with a temperature detection function, comprising the following steps:
step 100, manufacturing a two-wire vibrating wire sensor, arranging a composite tag in the vibrating wire sensor, isolating two polarities of the vibrating wire sensor composite tag by using two diodes D1 and D2, and forming a bipolar parallel circuit by using a connecting measuring wire A, B;
step 200, accessing a reading instrument, and calibrating a frequency-physical quantity parameter and a temperature-physical quantity parameter in a storage chip of the composite tag by using the reading instrument;
and 300, regularly reading frequency data monitored by the vibrating wire sensor and temperature data monitored by the composite tag, and calculating the stress change of the vibrating wire sensor after temperature correction.
In a preferred embodiment of the present invention, in step 200, the temperature-physical quantity parameter is a thermal expansion coefficient of the steel string, and the frequency-physical quantity parameter is a modulus of elasticity, a cross-sectional area, a length and a material density of the steel string.
As a preferred embodiment of the present invention, in step 300, the specific implementation steps of calculating the stress variation after the temperature correction of the vibrating wire sensor are as follows:
step 301, starting four line switchers controlled by a microprocessing unit (MCU) to realize functions of measuring line selection and switching positive and negative electrodes;
step 302, the micro-processing unit MCU controls the circuit switcher to switch the connection measuring line A, B to the temperature measuring circuit, controls the temperature measuring circuit to detect the connected composite label, and reads the temperature value of the composite label and the sensor basic information stored in the interior;
303, the micro-processing unit MCU controls the circuit switcher to switch the connection measuring line A, B to the frequency measuring circuit, 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;
and 304, substituting the obtained temperature value of the composite label, the internally stored sensor basic information and the frequency value into a strain formula of the steel string, and calculating the strain value of the steel string for eliminating the influence of the environmental temperature on the frequency.
As a preferred 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
Rho is the chord density and L is the chord length; e is the string elastic modulus; a is the section area of the steel string;
f0the initial frequency value when the sensor is not stressed is obtained, and f is the frequency value after stress;
Δ t is the temperature change and α is the thermal expansion coefficient.
Compared with the prior art, the invention has the following beneficial effects:
the composite label is used for monitoring temperature change instead of a thermistor in the prior art, so that not only can real-time temperature acquisition and sensor parameter information be synchronously realized, but also the resonance frequency of the steel string can be detected, and the stress state change of the steel string subjected to temperature correction can be synchronously acquired 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 should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.
FIG. 1 is a schematic structural diagram of a two-wire vibrating 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 vibrating wire sensor according to an embodiment of the present invention.
The reference numerals in the drawings denote the following, respectively:
1-steel string; 2-a coil; 3-a reading instrument; 4-a composite label; 5-1Wire signal line;
31-a microprocessor unit; 32-line switcher; 33-a frequency measurement circuit; 34-a temperature measuring circuit;
41-temperature sensor; 42-1Wire chip.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. 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.
As shown in fig. 1, the present invention provides a two-wire vibrating wire sensor with a temperature detection function, which can achieve real-time temperature acquisition, sensor calculation parameter information, and temperature correction parameters, and can obtain temperature-corrected physical quantities at the same time of frequency measurement, thereby improving the measurement accuracy of the vibrating wire sensor.
The two-wire vibrating wire sensor provided by the present embodiment includes a steel wire 1 having both ends fixed to a diaphragm, and a coil 2 disposed directly below the steel wire 1.
The general working principle of the steel string type sensor is as follows: the steel string 1 is placed in the magnetic field generated by the coil 2, after the power supply is turned on and the steel string 1 is excited, the steel string 1 will vibrate, and the vibrating steel string 1 cuts magnetic lines of force in the magnetic field, so that electric potential can be induced in the coil 2, the steel string cuts the magnetic lines of force, and the frequency of weak electric signals generated in the coil is the resonance frequency of the steel string 1. According to the mechanics principle, the resonance frequency of the steel string is in a linear relation with the tension or pulling force borne by the string, so that the tension stress of the steel string to be measured can be obtained by measuring the resonance frequency of the rigid string.
Preferably, 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 reading instrument 3, the receiving coil is subjected to potential change under the vibration action of the steel string 1, a power supply is switched on during operation, the exciting coil is electrified to excite the steel string 1 to vibrate, the steel string 1 cuts magnetic lines of a magnetic field generated by the receiving coil after vibrating and generates induced potential, the generated induced potential is sent to an amplifier by the receiving coil to be amplified and output, meanwhile, a part of an output signal is fed back to the exciting coil to maintain the vibration of the steel string, so that continuous feedback circulation is realized, and amplitude stabilizing measures of a circuit are added to enable the steel string to achieve constant-amplitude continuous vibration maintained by the circuit and then to output a frequency signal related to the tension of the steel string.
In the present embodiment, the basic structure of the string type sensor is the same as that in the related art, and the present embodiment has an advantage in that a temperature measurement function is integrated, thereby correcting stress variation of the string by temperature compensation.
The coil 2 is connected in parallel with a composite tag 4 for monitoring the environmental temperature of the steel string 1, and the parallel connection end of the coil 2 and the composite tag 4 is connected with a reading instrument 3 through a 1Wire signal Wire 5.
It should be added that the 1-wire single bus uses a single signal line, which transmits both clock and data transmission is bidirectional. The bus interface has the advantages of saving I/O interface line resources, simple structure, low cost, convenience for 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 pin of the 1Wire chip 42 is short-circuited to the ground pin of the temperature sensor 41, the ground pin is used as the label cathode of the whole composite label 4 after being short-circuited, the data pin of the temperature sensor 41 is used as the label data pin of the whole composite label 4, and the label cathode and the label data pin are respectively connected in parallel with two ends of the coil 2 and respectively form two 1Wire ports.
Further, the parallel connection mode of the coil 2 and the composite tag is as follows: the circuit where the coil 2 is located is connected with a diode D1 in series, the circuit where the composite tag is located is connected with a diode D2 and a resistor R1 in series, two ends of the composite tag are connected with a voltage stabilizing diode D3 in parallel, and the connection directions of the diode D1 and the diode D2 are opposite.
In the embodiment, the composite label is manufactured by a physical structure of the temperature sensor DS18B20 and the EEPROM chip DS2431 which are based on the 1Wire interface protocol and connected in parallel, and the identification of the unique code of the label, the automatic reading of the information of the manufacturer of the sensor, the length of a cable, the calculation parameters, the real-time temperature and the like and the calculation of the physical quantity are realized by the reading end remote communication circuit and the method, so that the interference of personnel in the whole measuring and 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 reading instrument 3 through the 1Wire signal Wire 5, and the reading instrument 3 performs 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 ambient temperature of the steel string 1 in real time, and the 1Wire chip 42 provides the parameter information of the temperature sensor 41 and the steel string 1.
The reading instrument 3 has a data reading function and a data sending function, the reading instrument 3 identifies the output data of the temperature sensor 41 and the coil 2, reads the parameter information of the temperature sensor 41 and the steel string 1 carried by the 1Wire chip 42, and the reading instrument 3 sends an excitation signal to the coil 2 to monitor the stress change of the steel string 1.
Preferably, the reader 3 includes a microprocessor unit 31, a line switch 32 connected to the microprocessor unit 31, and a frequency measuring circuit 33 and a temperature measuring circuit 34 connected to the microprocessor unit 31, the frequency measuring circuit 33 and the temperature measuring circuit 34 being connected to the 1Wire signal line 5 through the line switch 32.
The temperature measuring circuit 34 is used for identifying the output data of the temperature sensor 41 and reading the parameter information about the temperature sensor 41 and the steel string 1 stored by the 1Wire chip 42.
The frequency measuring 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 relation from interfering with each other, two diodes D1 and D2 are used inside the sensor to isolate two polarities to form a unique bipolar parallel circuit, wherein a line a is positive and a line B is negative when measuring frequency, a diode D1 is turned on and a diode D2 is turned off, and a line a is negative and a line B is positive when measuring temperature, a diode D2 is turned on and a diode D1 is turned off, 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 reading instrument is controlled by a Microprocessor Unit (MUC) to control a line switcher to switch to a certain physical quantity measuring channel and then control a certain measuring circuit to measure. Particularly, under the control of the MCU, the polarity of the AB can be automatically determined, and the line switcher is controlled to automatically switch to complete the measurement of a certain physical quantity, so that the user does not need to distinguish the line a from the line B, and the implementation method is as follows:
and the MCU controls the circuit switcher to connect the AB line with the temperature measuring circuit, assumes that A is the positive pole and B is the negative pole, carries out temperature measurement, sends an instruction to the circuit switcher to switch the AB polarity if normal communication with the temperature sensor is unavailable, and communicates with the DS18B20 again, and if the communication is still not accurate, determines that no external temperature sensor is available and carries out frequency measurement.
And during frequency measurement, firstly, assuming that A is a positive electrode and B is a negative electrode, sending an excitation signal and reading a return frequency signal, continuously calculating the frequency if an expected frequency signal is obtained, otherwise, sending an instruction to a line switcher to switch AB polarity, and carrying out a frequency measurement process again, and if an 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 usually uses a thermistor to detect the ambient temperature of the steel wire 1, the thermistor is a resistor with resistance value changing with the temperature, the resistance value of the sensor can be measured through an electronic circuit to calculate the temperature value, the temperature value is not discussed in detail herein, the thermistor is used to monitor the ambient temperature, so that the vibrating wire sensor integrally has four or three outgoing lines, in the application process of the vibrating wire sensor, the cable length of each sensor is usually dozens of meters or even hundreds of meters, the cable usually accounts for 30% -70% of the cost of the whole sensor, and the steel wire frequency and the temperature need to be measured separately.
In order to solve the above problem, the present embodiment integrates the temperature sensor inside the vibrating Wire sensor, and uses the 1Wire chip 42 to store the basic parameter information of the temperature sensor 41, and the basic parameter information of the steel Wire 1, such as the manufacturer information of the temperature sensor 41, the device number, the cable length of the 1Wire signal line 5, the factory initial parameter and the temperature correction parameter, and the manufacturer information of the steel Wire 1, the correspondence between the stress variation and the vibration amplitude, and the like.
Therefore, the composite tag is used for monitoring temperature change instead of a thermistor in the prior art, so that not only can real-time temperature acquisition and sensor parameter information be synchronously realized, but also the resonance frequency of the steel string can be detected, and the stress state change of the steel string subjected to temperature correction can be synchronously acquired by combining the resonance frequency and the temperature parameter through a calculation formula.
In order to further explain the working principle of the two-wire vibrating wire sensor with temperature detection function, as shown in fig. 2, the present embodiment further provides a detection method of the two-wire vibrating wire sensor with temperature detection function, which specifically includes the following steps:
step 100, manufacturing a two-wire vibrating wire sensor, arranging a composite tag in the vibrating wire sensor, isolating two polarities of the vibrating wire sensor composite tag by using two diodes D1 and D2, and forming a bipolar parallel circuit by using a connecting measuring wire A, B.
And 200, accessing a reading instrument, and calibrating the frequency-physical quantity parameter and the temperature-physical quantity parameter in the storage chip of the composite tag by using the reading instrument.
The temperature-physical quantity parameters are the thermal expansion coefficient of the steel string, and the frequency-physical quantity parameters are the elastic modulus, the sectional area, the length and the material density of the steel string.
And step 300, regularly reading the frequency data monitored by the vibrating wire sensor and the temperature data monitored by the composite tag, and calculating the stress change of the vibrating wire sensor after temperature correction.
In this step, the concrete implementation steps of calculating the stress change after the temperature correction of the vibrating wire sensor are as follows:
step 301, starting four line switchers controlled by a microprocessing unit (MCU) to realize functions of measuring line selection and switching positive and negative electrodes;
step 302, the micro processing unit MCU controls the line switcher to switch the connection measuring line A, B to the temperature measuring circuit, assuming that a is a positive electrode and B is a negative electrode, the micro processing unit MCU controls the temperature measuring circuit to detect the connected composite label, if the circuit switcher cannot normally communicate with the temperature sensor, the circuit switcher is instructed to switch the polarity of AB, that is, a is a negative electrode and B is a positive electrode at the moment, and communicates with the temperature sensor again, if the circuit switcher cannot correctly communicate, the circuit switcher is determined to have no external temperature sensor, and then the frequency measurement is performed.
And if the temperature sensor is communicated with the temperature sensor, reading the temperature value of the composite tag and the sensor basic information stored in the composite tag, namely the thermal expansion coefficient of the steel string, and the frequency-physical quantity parameters are 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 step 303, the microprocessing unit MCU controls the circuit switcher to switch the connection measuring line A, B to the frequency measuring circuit, 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.
When the frequency is measured, the AB polarity during temperature measurement is adjusted in a reverse direction, an excitation signal is sent, a return frequency signal is read, the expected frequency signal can be obtained, the frequency is continuously calculated, and if the effective frequency signal output by the sensor cannot be obtained, the coil of the vibrating wire sensor is determined to be not externally connected.
And 304, substituting the obtained temperature value of the composite label, the internally stored sensor basic information and the frequency value into a strain formula of the steel string, and calculating the strain value of the steel string for eliminating the influence of the environmental temperature on the frequency.
The strain formula of the steel string excluding the influence of the environmental temperature on the frequency is as follows:
wherein
Rho is the chord density and L is the chord length; e is the string elastic modulus; a is the section area of the steel string;
f0the initial frequency value when the sensor is not stressed is obtained, and f is the frequency value after stress;
Δ t is the temperature change and α is the thermal expansion coefficient.
It should be added that, after the steel string is placed in the magnetic field and excited in a certain way, the steel string will vibrate, and the vibrating steel string will make magnetic line cutting motion in the magnetic field, so that an electric potential can be induced in the vibration pickup coil, and the frequency of the induced electric potential (the steel string cuts the magnetic line, and generates a weak electric signal in the coil) is the resonant frequency of the vibrating string. According to the mechanical principle, the resonance frequency of the steel string is in a linear relation with the tension or the pulling force borne by the string, so that the tension degree (tension 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 change of the pressure or the displacement causes the deformation of the sensor structure to influence the tension degree of the steel string, the resonance frequency is correspondingly changed, and the frequency value of the measuring sensor can calculate the change of physical quantities such as the pressure or the displacement and the like borne by the sensor.
The derivation of the string strain formula is therefore:
the degree of 'tension' of the steel string is the stress state of the steel string, and the stress of the steel string and the resonance frequency thereof satisfy the formula
In the above formula:
f: frequency value of string
L: length of steel string
T: tension to which the string is subjected
ρ: density of steel string material
Can deduce
T＝4×ρ×L2×f2 (2)
For the manufactured steel string sensor, the length L and the material density rho of the steel string are known constants and are generally represented by k, so that the tensile stress borne by the steel string has a one-to-one correspondence relation 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 equal 4 × ρ × L2And the string tension T is 4 Xrho multiplied by L2×f2＝k×f2 (3)；
For any manufactured vibrating wire sensor, the k value is a fixed constant and can obtain a specific numerical value through a calibration process, and when the sensor deforms under the action of external force, the tension change quantity of the steel wire can be calculated according to the following formula
ΔT＝k×(f2-f0 2) (4)
In the above formula, f0Is the initial frequency value when the sensor is not stressed, and f is the frequency value after stress.
It should be noted that both the steel wire and the material from which the vibrating wire sensor is made expand and contract under the influence of temperature changes, which affect the frequency of the steel wire. The following description will take a strain gauge wire sensor as an example.
From the formula of strain
Can obtain
In the above formula,. epsilon.represents strain, E represents string elastic modulus, and A represents string cross-sectional area. Since the elastic modulus and the sectional area are constant, the elastic modulus and the sectional area can be constant
Simplified as kcThen, then
When the environmental temperature of the steel wire changes or the length of the steel wire changes due to external force, the change of the frequency value is caused, and in order to enable the vibrating wire sensor to truly reflect the strain, the influence of the environmental temperature on the frequency needs to be eliminated, so the following formula is provided:
in the above formula, Δ t is the temperature change amount, and α is the thermal expansion coefficient
Through testing the influence of temperature change of a vibrating wire strain sensor of a certain model, when the temperature changes by 1 ℃, the deviation of the calculation result is 4 multiplied by 10-6Left and right strain. The measuring range of the conventional strain sensor is generally +/-1000 micro-strain, if the ambient temperature changes by 10 ℃, the change of 40 micro-strains of the strain amount is generated, which is equivalent to 2% of the full measuring range of the sensor, and if the influence of the temperature is not eliminated, the sensor can generate 2% of measuring error which is far lower than the measuring precision of 0.1% generally required by engineering.
Therefore, the two-wire vibrating wire sensor of the embodiment simultaneously completes the sensor end work of steel wire frequency measurement and internal temperature acquisition. The two-Wire vibrating Wire sensor realizes the frequency measurement of the steel Wire of the two-Wire vibrating Wire sensor, the temperature measurement, the automatic identification of the sensor code, the dynamic acquisition of the parameter information and the automatic calculation of the physical quantity by the 1Wire signal Wire communication and remote measurement and reading method, greatly reduces the cost of the sensor, improves the data acquisition and calculation efficiency, reduces the labor intensity of technicians and improves the measurement precision of the sensor.
The above embodiments are only exemplary embodiments of the present application, and are not intended to limit the present application, and the protection scope of the present application is defined by the claims. Various modifications and equivalents may be made by those skilled in the art within the spirit and scope of the present application and such modifications and equivalents should also be considered to be within the scope of the present application.
Claims (10)
1. The utility model provides a two-wire system vibrating wire sensor with temperature detects function, includes that 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 with a composite tag (4) used for monitoring the environmental temperature of the steel string (1) in parallel, and the parallel connection end of the coil (2) and the composite tag (4) is connected with a reading instrument (3) through a 1Wire signal Wire (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 reading instrument (3) through a 1Wire signal Wire (5), and the reading instrument (3) performs bidirectional data transmission with the coil (2), the temperature sensor (41) and the 1Wire chip (42) through the 1Wire signal Wire (5).
2. The two-wire vibrating wire sensor with temperature detection function according to claim 1, wherein: the reading instrument (3) has a data reading function and a data sending function through the 1Wire signal Wire (5), the reading instrument (3) sends an excitation signal to the coil (2) to monitor the stress change of the steel string (1), and the reading instrument (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. The two-wire vibrating wire sensor with temperature detection function according to claim 2, wherein: the temperature sensor (41) is used for monitoring the ambient temperature of the steel string (1) in real time, and the 1Wire chip (42) is used for storing the temperature sensor (41) and the parameter information of the steel string (1).
4. The two-wire vibrating wire sensor with temperature detection function according to claim 2, wherein: the reading instrument (3) comprises a microprocessor unit (31), a line switcher (32) connected with the microprocessor unit (31), and a frequency measuring circuit (33) and a temperature measuring circuit (34) connected with the microprocessor unit (31), wherein the frequency measuring circuit (33) and the temperature measuring circuit (34) are connected with the 1Wire signal line (5) through the line switcher (32);
the temperature measuring circuit (34) is used for identifying the output data of the temperature sensor (41) and reading the parameter information which is stored by the 1Wire chip (42) and is about the temperature sensor (41) and the steel string (1);
the frequency measuring circuit (33) is used for identifying the output data of the coil (2).
5. The two-wire vibrating wire sensor with temperature detection function according to claim 1, wherein: the circuit where the coil (2) is located is connected with a diode D1 in series, the circuit where the composite label is located is connected with a diode D2 and a resistor R1 in series, two ends of the composite label are connected with a voltage stabilizing diode D3 in parallel, and the connection directions of the diode D1 and the diode D2 are opposite.
6. The two-wire vibrating wire sensor with temperature detection function according to claim 1, wherein: a power supply pin of the 1Wire chip (42) is in short circuit with a grounding pin of the temperature sensor (41), the grounding pin is used as a label cathode of the whole composite label (4) after being in short circuit, and a data pin of the temperature sensor (41) is used as a label data pin of the whole composite label (4);
the tag cathode and the tag data pin are respectively connected with two ends of the coil (2) in parallel and respectively form two 1Wire ports.
7. A detection method based on the two-wire vibrating wire sensor with temperature detection function according to any one of claims 1 to 6, characterized by comprising the steps of:
step 100, manufacturing a two-wire vibrating wire sensor, arranging a composite tag in the vibrating wire sensor, isolating two polarities of the vibrating wire sensor composite tag by using two diodes D1 and D2, and forming a bipolar parallel circuit by using a connecting measuring wire A, B;
step 200, accessing a reading instrument, and calibrating a frequency-physical quantity parameter and a temperature-physical quantity parameter in a storage chip of the composite tag by using the reading instrument;
and 300, regularly reading frequency data monitored by the vibrating wire sensor and temperature data monitored by the composite tag, and calculating the stress change of the vibrating wire sensor after temperature correction.
8. The method for detecting a two-wire vibrating wire sensor with temperature detection function according to claim 7, wherein in step 200, the temperature-physical quantity parameters are thermal expansion coefficient of steel wire, and the frequency-physical quantity parameters are elastic modulus, sectional area, length and material density of steel wire.
9. The method for detecting a two-wire vibrating wire sensor with a temperature detection function according to claim 7, wherein in step 300, the concrete implementation steps for calculating the stress variation after the temperature correction of the vibrating wire sensor are as follows:
step 301, starting four line switchers controlled by a microprocessing unit (MCU) to realize functions of measuring line selection and switching positive and negative electrodes;
step 302, the micro-processing unit MCU controls the circuit switcher to switch the connection measuring line A, B to the temperature measuring circuit, controls the temperature measuring circuit to detect the connected composite label, and reads the temperature value of the composite label and the sensor basic information stored in the interior;
303, the micro-processing unit MCU controls the circuit switcher to switch the connection measuring line A, B to the frequency measuring circuit, 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;
and 304, substituting the obtained temperature value of the composite label, the internally stored sensor basic information and the frequency value into a strain formula of the steel string, and calculating the strain value of the steel string for eliminating the influence of the environmental temperature on the frequency.
10. The method for detecting a two-wire vibrating wire sensor with temperature detection function according to claim 8, wherein the strain formula of the steel wire excluding the influence of the ambient temperature on the frequency is:
wherein
Rho is the chord density and L is the chord length; e is the string elastic modulus; a is the section area of the steel string;
f0the initial frequency value when the sensor is not stressed is obtained, and f is the frequency value after stress;
Δ t is the temperature change and α is the thermal expansion coefficient.
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