Numerical measurement system and method based on LVDT sensor
阅读说明:本技术 一种基于lvdt传感器的数值测量系统及方法 (Numerical measurement system and method based on LVDT sensor ) 是由 *** 应继伟 焦迪 殷建国 汪邦运 于 2019-09-16 设计创作,主要内容包括:本发明揭示了一种基于LVDT传感器的数值测量系统及方法,系统包括恒频恒幅信号发生单元、通道选通及LVDT驱动单元、真有效值快速采样单元和微处理器单元,所述恒频恒幅信号发生单元的输出端与所述通道选通及LVDT驱动单元的输入端连接,所述通道选通及LVDT驱动单元的输出端与所述真有效值快速采样单元的输入端连接,所述真有效值快速采样单元的输出端与所述微处理器单元的输入端连接,所述微处理器单元的输出端与所述通道选通及LVDT驱动单元的输入端连接。(The invention discloses a numerical value measuring system and method based on an LVDT sensor, wherein the system comprises a constant-frequency constant-amplitude signal generating unit, a channel gating and LVDT driving unit, a true effective value rapid sampling unit and a microprocessor unit, wherein the output end of the constant-frequency constant-amplitude signal generating unit is connected with the input end of the channel gating and LVDT driving unit, the output end of the channel gating and LVDT driving unit is connected with the input end of the true effective value rapid sampling unit, the output end of the true effective value rapid sampling unit is connected with the input end of the microprocessor unit, and the output end of the microprocessor unit is connected with the input end of the channel gating and LVDT driving unit.)
1. A numerical value measuring system based on an LVDT sensor is characterized by comprising a constant-frequency constant-amplitude signal generating unit, a channel gating and LVDT driving unit, a real effective value rapid sampling unit and a microprocessor unit, wherein the output end of the constant-frequency constant-amplitude signal generating unit is connected with the input end of the channel gating and LVDT driving unit, the output end of the channel gating and LVDT driving unit is connected with the input end of the real effective value rapid sampling unit, the output end of the real effective value rapid sampling unit is connected with the input end of the microprocessor unit, and the output end of the microprocessor unit is connected with the input end of the channel gating and LVDT driving unit.
2. The LVDT sensor-based numerical measurement system according to claim 1, wherein the constant frequency and constant amplitude signal generating unit comprises a first integrated analog switch and a zero-shift operational amplifier, wherein the square wave signal outputted from the microprocessor unit controls on/off of the first integrated analog switch, so that the signal outputted from the first integrated analog switch is a constant frequency and constant amplitude square wave signal, and the zero-shift operational amplifier is connected to the first integrated analog switch for converting the constant frequency and constant amplitude square wave signal into a constant frequency and constant amplitude bipolar sine wave signal.
3. The LVDT sensor-based numerical measurement system according to claim 2, wherein the channel gating and LVDT driving unit includes a second integrated analog switch and an integrated funnel-type instrumentation amplifier, the microprocessor unit controlling the second integrated analog switch to access the LVDT sensor and connecting a constant frequency constant amplitude bipolar sine wave signal to an input of the integrated funnel-type instrumentation amplifier to enable the microprocessor unit to obtain a response coefficient of the accessed LVDT sensor.
4. The LVDT sensor-based numerical measurement system according to claim 3, further comprising an access gate low noise pre-amplifying unit, an input terminal of the access gate low noise pre-amplifying unit being connected to an output terminal of the channel gate and LVDT driving unit, an output terminal of the access gate low noise pre-amplifying unit being connected to an input terminal of the true valid value fast sampling unit.
5. The LVDT sensor-based numerical measurement system of claim 4, further comprising a programmable gain unit, an input of which is connected to an output of the microprocessor unit, and an output of which is connected to an input of the access gate low noise pre-amplification unit.
6. The LVDT sensor-based numerical measurement system of claim 5 wherein the access-gated low noise preamplifier unit includes a zero drift instrumentation amplifier and a resistor, the microprocessor unit adjusting the response coefficient of the LVDT sensor by selecting a gain-matched resistor for the zero drift instrumentation amplifier via the programmable gain unit based on the stored sensitivity value.
7. The LVDT sensor-based numerical measurement system of claim 4, wherein the true effective value fast sampling unit comprises an integrated true effective value chip for fast converting the output sine wave signal of the access gate low noise pre-amplification unit into a high precision direct current signal.
8. The LVDT sensor-based numerical measurement system of claim 1, further comprising a display and communication unit coupled to the microprocessor unit.
9. A numerical measurement method based on an LVDT sensor is characterized by comprising the following steps:
acquiring an hour hand signal;
acquiring an output signal of the sensor after correcting the sensitivity based on the clock signal;
obtaining a measurement value of the sensor based on the output signal;
wherein the sensor is an LVDT sensor.
10. The LVDT sensor-based numerical measurement method of claim 9, wherein the obtaining a measured value of the sensor based on the output signal comprises:
amplifying the output signal to obtain a measurement signal;
purifying the measurement signal;
the measurement signal is converted into a direct current signal.
Technical Field
The invention belongs to the field of manufacturing of detection instruments, and relates to a numerical measurement system and a numerical measurement method based on an LVDT sensor.
Background
At present, a vibrating string type strain sensor is widely applied in the fields of engineering buildings, bridges, reservoir dams and the like. The vibrating wire type strain sensor is generally applied to the field of geotechnical engineering particularly due to the advantages of simple structure and strong anti-interference capability.
However, vibrating wire strain sensors have also been the subject of extensive debate in the industry due to their apparent technical shortcomings. The vibrating wire strain sensor with the tensioned metal string as the sensitive element has the advantages that after the length of the string is determined, the change of the natural vibration frequency can show the magnitude of the tension borne by the string, and a certain relation between the frequency and the stress can be obtained through certain conversion. With the continuous and intensive research and analysis of the vibrating wire type strain sensor, and the combination of the practical failure cases applied in engineering, the inherent physical defects of the vibrating wire type strain sensor are gradually revealed: 1. the vibrating wire strain sensor is not suitable for long-term monitoring. It is well known that any object will deform when subjected to an external force; meanwhile, any object can generate the expansion and contraction phenomenon under the condition that the temperature difference changes, and the vibrating wire type strain sensor is not affected by the factors. The vibrating wire of the vibrating wire type strain sensor is tensioned and fixed on the elastic diaphragms at the two ends, so that the two ends of the vibrating wire are influenced by superposition of certain tension and gravity; the vibrating wire will inevitably deform. The relative positions of the internal molecules or ions of the tensioned vibrating wire are changed in a peristalsis mode, and meanwhile additional internal forces between atoms and molecules are generated to counteract the external force and try to restore to the state before deformation. When the balance is reached, the additional internal force is equal to the external force and opposite to the external force. Theoretically, the internal stress of a desired single crystal metal material does not yield permanently within the elastic limit under load conditions. However, since the metal material actually used is of a polycrystalline structure, there are a large number of internal crystal defects; in the situation that the temperature difference is not changed greatly, due to the crystal phase difference and the short-range diffusion of atoms, the material is subjected to micro plastic deformation; when the temperature difference is increased, the phenomena of atom long-range diffusion and lattice dislocation slip tending to be severe occur in the material, and the continuous accumulation of the microscopic plastic deformation evolves into the macroscopic plastic deformation along with the time. The metal can generate micro plastic deformation in the elastic stress range, and the mechanism of dislocation short-range slip, solute atom directional dissolution, directional vacancy flow, crystal sliding and the like in the crystal can be successfully explained. The physical mechanism that occurs on the wire also occurs on the vibrating wire that is tensioned at both ends in the vibrating wire strain sensor. 2. The vibrating wire strain sensor has serious temperature effect. Since the linear thermal expansion coefficient of the vibrating wire strain sensor is related to the material, machining precision, shape and the like, before the sensor is used, the vibrating wire strain sensor needs to be calibrated and compensated in a single body. 3. The vibrating wire type strain sensor is not suitable for being used in the measurement occasion of complex deformation. According to the theory that the steel body deforms under the action of external force and the volume of the steel body does not change under the action of material mechanics and elasticity mechanics, if the steel body is compressed and deformed axially under pressure, the radial direction inevitably expands and deforms along the principle of volume invariance, and the effect of radial expansion is related to the shape and the material of the steel body, so that the change of radial expansion is a distribution function along the axial direction. If the distribution function of the axial change is not uniform, the vibrating wire in the vibrating wire type strain sensor arranged on the steel body is twisted, and the twisting phenomenon can be converted into axial additional external force, so that the measurement of the vibrating wire type strain sensor is inaccurate. Therefore, it is not surprising that a failure is often detected in the detection of a construction stress or the like using a vibrating wire strain sensor.
The strain and stress monitoring in various building projects is an important measurement index, the true condition of a building member under a stress condition is objectively reflected by accurately measuring the strain or stress of various materials used in the building projects and various supports used in foundation pit enclosures under the stress condition, and reliable and accurate data are provided for the engineering construction and the use and operation processes, so that a multichannel self-adaptive self-fixed elevation precision LVDT data acquisition system which has high precision, is irrelevant to radial change, has small temperature coefficient, high automation degree (no need of manual interference) and is convenient for data interaction and a measurement method thereof are necessary to research and develop.
Disclosure of Invention
An ideal engineered microstrain monitoring system would be: 1. the method has the advantages that the measured data are accurate and reliable, 2, a convenient information interaction mode is provided for users, 3, the energy supply of a monitoring system does not need manual intervention in principle, and 4, the monitoring frequency is set flexibly.
The invention aims to provide a multichannel self-adaptive fixed elevation precision LVDT data acquisition and measurement system and method for a human-computer interaction interface, which have solar energy and power supply adapter energy supplement, extremely accurate axial detection precision, insensitivity to radial deformation, a self-calibration function for range-gain of various LVDT sensors, a self-adaptive function for processing system gain, an extremely small temperature coefficient, wireless remote GPRS data interaction, a short-range wireless or wired networking function and convenience.
In order to fully illustrate and understand the principles of the present invention and the technical approaches adopted, it is necessary to understand the manner in which microstrain stress monitoring is currently performed in engineering construction.
Take the excavation of steel structure support in deep foundation pit as an example. In the excavation process of the deep foundation pit, in order to prevent the collapse of the edge of the foundation pit, a reinforced concrete continuous wall needs to be constructed around the excavated foundation pit, and because the pressure of a soil body is huge, the constructed continuous wall needs to be appropriately supported, and a supporting beam is generally formed by two modes: reinforced concrete supporting beam and steel structural support beam. The steel structure supporting beam is a construction mode widely adopted internationally, and is also a trend of a supporting method in deep foundation pit excavation and maintenance engineering in China. The stress condition (deformation condition) of the steel support beam of the steel support structure is accurately measured, so that the safety of the whole engineering construction is related, and by means of accurately measuring the stress (deformation) of the steel support beam, the aims of reversely verifying the correctness of design calculation and reducing the construction cost can be fulfilled. The stress and micro-strain of the steel structure supporting beam are monitored by adopting high-precision and high-sensitivity LVDT micro-strain sensors, and the LVDT micro-strain sensors are arranged at key stress positions of the supporting beam (the arrangement position is required to accord with the Saint-Venn principle). And the measurement data of the sensors at the monitoring points are transmitted to a monitoring management station in a cable connection mode.
The invention relates to a multichannel self-adaptive self-fixed high-precision LVDT data acquisition and measurement system and a method.
The multichannel self-adaptive self-fixed high-precision LVDT data acquisition and measurement system is used for realizing that: the method comprises the steps of realizing constant-frequency amplitude-stabilized excitation on an LVDT sensor with 32 channels (in an embodiment, the number of the channels can be expanded as required) in a time division multiplexing mode, conditioning output response signals of the LVDT sensor (including system gain self-adaption, automatic calibration of the LVDT sensor, extraction of final conditioning signals of the LVDT of each channel by adopting quick true effective value processing, judgment of the motion direction of the sensor, 16-bit A/D sampling and calculation), realizing wireless networking among monitoring points in a short-range wireless mode, providing data interaction in a Bluetooth wireless mode, providing remote GPRS wireless data interaction, providing a solar energy and power adapter charging function, and providing a high-stability low-noise power supply for related units. The LVDT sensor group is composed of a plurality of LVDT sensors and corresponding machinery.
When the multichannel adaptive self-determination high-precision LVDT data acquisition and measurement system is powered on, a microprocessor in the system waits for receiving a setting instruction of a working mode of the system, wherein the setting instruction comprises the number and the independent number of the LVDT sensors to be sampled, the sampling frequency, and the upper limit and lower limit alarm information of the measurement data of each single sensor. The operating mode setting parameters may be received in three ways: 1. the method comprises the following steps of carrying out field programming on a microprocessor of the system through an external serial port, 2, providing man-machine interaction between a liquid crystal touch display screen configured by the system and the microprocessor, and 3, interacting between the system and a GPRS remote wireless data interaction network. After receiving the working parameters, the multichannel adaptive self-fixed high-precision LVDT data acquisition and measurement system firstly acquires the power supply condition information of the system, and if the power supply of a lithium battery pack configured by the system is normal, the initialization process of each accessed LVDT sensor is started; otherwise, the information that the system needs to supplement the electric energy is sent to the different places through the remote wireless GPRS network. Since each type of LVDT sensor has different output responses (different sensitivities) under the same input excitation, the initialization process includes: 1. the sensitivity of each accessed LVDT sensor is automatically measured and stored in a nonvolatile memory of the system so as to realize the automatic calibration function; 2. and automatically adjusting the gain of the sensor in the data conditioning process according to the measured value of the sensitivity of each LVDT sensor, thereby realizing the self-adaptive function of data conditioning.
After initialization and the set measuring time is up, the invention carries out measurement on each accessed LVDT sensor in a time-sharing mode through a gating integrated analog switch under the control of a configured microprocessor: the microprocessor gives the coded address to the relevant integrated analog switch and the LVDT sensor of the corresponding channel is accessed to the system. The microprocessor obtains an n KHZ digital pulse signal with extremely stable repetition frequency after frequency division by a configured crystal oscillator clock source, the digital pulse signal obtains a bipolar sine-form fundamental wave after passing through a multi-feedback band-pass filter, and the fundamental wave excites a primary winding of a related selected LVDT sensor after being amplified and driven by a funnel-type instrument amplifier; double-end response signals sent by the selected LVDT sensors are read into the zero-drift instrument amplifier after being gated by the corresponding integrated analog switches; at this point, the gain of the zero drift instrumentation amplifier is automatically configured by the microprocessor based on the sensitivity parameters stored in the non-volatile memory at initialization of the selected LVDT sensor.
The signal is amplified and converted by a zero drift instrument amplifier to be converted into a single-ended measurement signal, and then is further purified by a multiplex feedback band-pass filter. 1. The signal is converted into a direct current signal by a fast sampling high-precision true effective value processing circuit, and finally a high-precision measurement value is obtained after 16-bit AD conversion; and 2, judging the motion direction of the double-end signal output by the LVDT sensor by a direction judging circuit respectively according to the voltage of each end relative to the reference ground (circuit ground) of the circuit. The invention realizes the direction discrimination of the measurement signal by the following modes: the LVDT sensor outputs a response double-ended signal, the voltages UA and UB to earth at each end of the LVDT sensor are respectively buffered (in order not to influence the differential measurement value), and proportional subtraction processing is carried out, so that even if the difference between the UOA and the UOB is small, a considerable difference UC can still be obtained after the proportional differential subtraction processing, the UC obtains a '0' or '1' signal after an integrated comparator, and the '0' or '1' signal represents two relative movement directions of the armature of the LVDT sensor.
And repeating the operation process until all the accessed LVDT sensors are sampled, sending the sampling data of each sensor and the corresponding environment temperature data through various configured communication circuits, finishing the measurement, and enabling the system to enter a sleep state until the next measurement time is up to be automatically awakened. The communication circuit sends measurement information according to a selected communication mode after receiving measurement data sent by the multichannel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system, wherein remote wireless GPRS communication is default and can not be changed; and short-range wireless communication bluetooth and WIFI are optional. In order to ensure the measurement accuracy of the multichannel self-adaptive self-fixed high-accuracy LVDT data acquisition and measurement system, the system adopts an ARM M7 microprocessor (STM32H750) with 16-bit AD sampling, so that the requirements on the stability of system power supply and a reference source are higher, and the system adopts an ultrahigh-accuracy reference source (ADR4530) with the temperature drift coefficient less than or equal to 2 ppm/DEG C.
In order to adapt to a long-term unattended monitoring environment, the multichannel self-adaptive fixed-elevation precision LVDT data acquisition and measurement system adopts a 37 ampere-hour and 4.2V high-capacity parallel lithium battery pack for power supply, and is assisted by a solar charging circuit and provided with a power adapter charging interface. In order to safely and properly charge the parallel lithium battery pack, a solar energy and alternating current hybrid charging management system special for the high-capacity parallel lithium battery pack is developed, the maximum charging current of the solar energy and alternating current hybrid charging management system for realizing charging is 1.5 amperes, namely the parallel lithium battery pack is charged by C/18.5 of the capacity of the distributed battery pack, and the energy can be supplemented in principle on 2 sunny days. The matched 37 ampere-hour parallel lithium battery pack can maintain enough working power supply for more than 1.5 months under the condition of
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method is characterized in that: and converting a double-end signal output by the LVDT sensor into a single-end signal by adopting a zero-drift instrument amplifier, and performing linear compensation on the gain of the zero-drift instrument amplifier and the ambient temperature in order to further inhibit the temperature drift of converting the double-end signal into the single-end signal.
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method is characterized in that: a fast sampling true effective value processing mode is adopted to obtain and convert the output signal of the LVDT sensor, and the traditional mode of processing the signal of the LVDT sensor by adopting phase-sensitive detection is abandoned.
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method is characterized in that: the solar energy charging, the high-capacity lithium battery energy storage and the power supply mode of providing an energy interface by a power adapter are adopted, and the long-term normal operation of the system can be realized without human intervention in principle.
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method, for LVDT sensor processing flow is: a constant-frequency constant-amplitude standard signal source (6.0P-P V, 2.5KHz sine wave) is used as an input signal of a funnel type amplifier with two gain coefficients. After the LVDT sensor is driven by the funnel amplifier, the output response of the LVDT sensor is conditioned by links such as a program control gain zero drift instrument amplifier, a noise suppression band-pass filter, a quick sampling true effective value and the like, and then is sampled by a 16-bit A/D of a microprocessor.
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method is characterized in that: during initialization, a funnel type amplifier with two gain coefficients (0.8 and 0.4) is adopted to drive the LVDT sensors so as to obtain the output response coefficient of each connected LVDT sensor.
A multichannel self-adaptive self-fixed high-precision LVDT data acquisition and measurement system and method are characterized in that an output response coefficient SS and sensitivity KS of a universal LVDT sensor are determined as reference (taking Shenzhen Shang as a product with the SDVG20-VA measuring range of 2.5 mm of science and technology development Limited company as an example):
setting a programmable gain zero drift instrument amplifier at a certain fixed gain A (in the embodiment, A is 2), connecting a constant-frequency 2.5KHz and constant-amplitude 3.0VRMS (volt) standard signal source into an input end (VIN0.8) of a gain coefficient of a funnel type amplifier 0.8 to drive an LVDT sensor, and obtaining V0.8S after an AD sampling value of output response of the LVDT sensor; a constant-frequency constant-amplitude standard signal source is connected to an input end (VINS0.4) of a funnel type amplifier driving LVDT sensor with a gain coefficient of 0.4, and output response of the constant-frequency constant-amplitude standard signal source is V0.4S after an AD sampling value; so output response delta: VS ═ D0.8S-D0.4S, input signal increment: v ═ VIN0.8-VIN0.4 ═ 3 × 0.8) - (3 × 0.4), KS ═ VS/. v, and KS is the output response coefficient of the universal LVDT sensor. And storing the obtained KS into a nonvolatile memory of the microprocessor.
The micrometer stage with 0.2 micrometer accuracy is used, the amplifier of the programmable gain zero drift instrument is set at a certain fixed gain A (in the embodiment, A is 2), and a constant-frequency constant-amplitude standard signal source is connected to the input end of a funnel type amplifier driving LVDT sensor with 0.8 gain coefficient. The universal LVDT sensor was locked to the micrometer stage and the output response VCWS1 was obtained. Adjusting the micrometer stage to change by 0.2 micrometer to obtain
When the invention is put into operation, the initialization process is firstly carried out (the initialization operation is started by the system when the sensor is used later or is powered off or damaged sensors are replaced). The accessed LVDT sensors are sequentially selected through the high-performance integrated analog switch, and the V (VIN) is equal to VIN0.8-VIN0.4 and V (V) is repeated to the accessed LVDT sensors automatically and sequentially under the condition of gain A of the program control amplifier
VOUTN ═ VOUTN0.8-VOUTN0.4, KN ═ VOUTN/. VIN operation, thereby obtaining KN for each access sensor; the KN is also automatically stored in non-volatile memory in the microprocessor (these values do not change unless an LVDT sensor failure is replaced or cancelled). During measurement, the invention automatically compares the measured value of the LVDT of the selected channel N (corresponding to a specific LVDT sensor) with the standard K value according to the corresponding KN, and the compared coefficient is used as the basis for the microprocessor to select the gain of the amplifier of the program control gain zero-drift instrument, so that the LVDT sensors with different sensitivities can obtain proper gain AN for amplification (no saturation occurs). Note that: during normal measurement, the funnel type amplifier is always in a 0.8 gain coefficient input state.
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method is characterized in that: the KN of each LVDT sensor obtained by the above measures is also used to achieve automatic calibration. The specific process is as follows: determining the gain AN of the microprocessor for automatically selecting the amplifier of the program-controlled gain zero-drift instrument according to the KN value obtained by each accessed LVDT sensor to obtain AN AD conversion value DATN, and calculating DZHN ═ DATN multiplied by A/AN, namely: DZHN is the value of gain a used to convert the measured value DATN to a generic LVDT; and finally, calculating LN (DZHN multiplied by KS/KN) multiplied by 0.2 micrometer to obtain the displacement measurement value of the Nth access LVDT sensor, thereby realizing automatic calibration.
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method is characterized in that: the method comprises the steps that a crystal oscillator frequency division mode is adopted to generate a square wave signal with extremely accurate frequency, the square wave signal is fed to a control input end of an integrated analog switch, a data input end of the integrated analog switch is connected with a reference source, and the integrated analog switch outputs a chopping signal with constant frequency and constant amplitude under the control of the square wave signal. And extracting fundamental waves of the chopped wave signals by adopting a multi-feedback band-pass filtering mode, wherein the constant-frequency constant-amplitude fundamental waves are used as input excitation signals of a driver of the LVDT sensor.
A multichannel adaptive self-fixed high precision LVDT data acquisition and measurement system and method is characterized in that: the Bluetooth mode is adopted to provide information interaction for a user using a mobile phone, the LORA wireless communication mode is adopted to realize local networking among monitoring points, and the remote wireless GPRS mode is adopted to provide information interaction for a remote monitoring station.
The multichannel self-adaptive high-precision LVDT data acquisition and measurement system comprises a constant-frequency constant-amplitude signal generating unit, a channel gating and LVDT driving unit, an access gating low-noise preamplification unit, a program control gain unit, a true effective value rapid sampling unit, a motion direction judging unit and a microprocessor unit, wherein the output end of the constant-frequency constant-amplitude signal generating unit is connected with the input end of the channel gating and LVDT driving unit, the output end of the channel gating and LVDT driving unit is connected with the input end of the access gating low-noise preamplification unit, the output end of the access gating low-noise preamplification unit is respectively connected with the input end of the true effective value rapid sampling unit and the input end of the motion direction judging unit, the output end of the true effective value rapid sampling unit and the output end of the motion direction judging unit are respectively connected with the input end of the microprocessor unit, the output end of the microprocessor unit is respectively connected with the input end of the channel gating and LVDT driving unit and the input end of the program control gain unit, and the output end of the program control gain unit is connected with the input end of the access gating low-noise preamplification unit.
Further, the constant-frequency and constant-amplitude signal generating unit comprises an integrated analog switch and a zero-drift operational amplifier, the square wave signal output by the microprocessor unit controls the on-off of the integrated analog switch, so that the signal output by the integrated analog switch is a constant-frequency and constant-amplitude square wave signal, and the zero-drift operational amplifier is connected with the integrated analog switch and is used for converting the constant-frequency and constant-amplitude square wave signal into a constant-frequency and constant-amplitude bipolar sine wave signal.
Further, the channel gating and LVDT driving unit includes an integrated analog switch and an integrated funnel-type instrumentation amplifier, and the microprocessor unit controls the integrated analog switch to connect a bipolar sine wave signal of constant frequency and constant amplitude to an input terminal of the integrated funnel-type instrumentation amplifier, so that the microprocessor unit obtains a response coefficient of an accessed LVDT sensor.
Further, the access gating low-noise preamplifier unit comprises a zero-drift low-noise variable-gain instrument amplifier and a resistor, and the microprocessor unit selects a resistor with matched gain for the zero-drift low-noise variable-gain instrument amplifier according to the stored sensitivity value to adjust the response coefficient of the LVDT sensor.
Furthermore, the real effective value rapid sampling unit comprises an integrated real effective value chip and is used for rapidly converting the sine wave signal output by the access gating low-noise preamplification unit into a high-precision direct current signal.
Furthermore, the motion direction judging unit comprises three integrated operational amplifiers and an integrated comparator, two signals output and responded by the two ends of the LVDT sensor are respectively amplified through the integrated operational amplifiers, the two amplified signals are subjected to proportional difference through the other integrated operational amplifier, and the output signal of the integrated operational amplifier is used as the input signal of the quasi-zero-crossing comparator formed by the integrated comparator.
Further, the device also comprises a display and communication unit which is connected with the microprocessor unit.
The multichannel adaptive high-precision LVDT data acquisition and measurement method comprises the following steps:
acquiring a clock signal;
acquiring an output signal of the sensor after correcting the sensitivity based on the clock signal;
obtaining detection information of the sensor based on the output signal, wherein the detection information comprises a measurement value and a movement direction;
wherein the sensor is an LVDT sensor.
Further, the acquiring the clock signal includes:
setting working parameters;
based on the operating parameters, a clock signal is derived.
Further, the setting of the operating parameter includes one of the following modes:
setting working parameters by a JTAG interface;
setting working parameters through human-computer interaction;
and the GPRS remote wireless data interaction sets working parameters.
Further, the operating parameters include one or more of the following combinations:
sensor number, collection frequency, collection time, and alarm information of upper and lower limits of measurement values.
Further, the clock signal is a frequency stabilization signal obtained by frequency division of the crystal oscillator.
Further, the acquiring, based on the clock signal, the output signal of the sensor after the sensitivity correction includes:
an excitation signal of the sensor is acquired.
Further, the acquiring an excitation signal of the sensor comprises:
chopping a reference source to obtain a digital signal;
extracting a fundamental wave of the digital signal;
and amplifying the fundamental wave to obtain an excitation signal of the sensor.
Further, the obtaining a measurement value of the sensor based on the output signal includes:
amplifying the output signal to obtain a measurement signal;
purifying the measurement signal;
the measurement signal is converted into a direct current signal.
Further, the deriving a direction of motion of the sensor based on the output signal comprises:
and obtaining the motion direction information of the sensor based on the comparison of the double-end output response signals of the sensor.
Further, the comparing of the double-ended output response signals of the sensors comprises:
the difference of the two-ended output response signal comparisons is amplified.
Further, the correcting the sensitivity of the sensor includes:
the sensitivity of the sensor is adjusted to be equal to a standard value, wherein the standard value is set.
Further, the adjusting the sensitivity of the sensor to be equal to a standard value includes:
and adjusting the amplification factor corresponding to the sensitivity of the sensor.
Further, the adjusting the amplification factor corresponding to the sensitivity of the sensor includes:
and switching the selection resistor to adjust the amplification factor.
A numerical measurement system based on an LVDT sensor comprises a constant-frequency constant-amplitude signal generating unit, a channel gating and LVDT driving unit, a true effective value rapid sampling unit and a microprocessor unit, wherein the output end of the constant-frequency constant-amplitude signal generating unit is connected with the input end of the channel gating and LVDT driving unit, the output end of the channel gating and LVDT driving unit is connected with the input end of the true effective value rapid sampling unit, the output end of the true effective value rapid sampling unit is connected with the input end of the microprocessor unit, and the output end of the microprocessor unit is connected with the input end of the channel gating and LVDT driving unit.
Further, the constant-frequency and constant-amplitude signal generating unit comprises a first integrated analog switch and a zero-drift operational amplifier, the square wave signal output by the microprocessor unit controls the on-off of the first integrated analog switch, so that the signal output by the first integrated analog switch is a constant-frequency and constant-amplitude square wave signal, and the zero-drift operational amplifier is connected with the first integrated analog switch and is used for converting the constant-frequency and constant-amplitude square wave signal into a constant-frequency and constant-amplitude bipolar sine wave signal.
Further, the channel gating and LVDT driving unit includes a second integrated analog switch and an integrated funnel-type instrumentation amplifier, and the microprocessor unit controls the second integrated analog switch to access the LVDT sensor and connects a constant-frequency constant-amplitude bipolar sine wave signal to an input end of the integrated funnel-type instrumentation amplifier, so that the microprocessor unit obtains a response coefficient of the accessed LVDT sensor.
The system further comprises an access gating low-noise preamplification unit, wherein the input end of the access gating low-noise preamplification unit is connected with the output end of the channel gating and LVDT driving unit, and the output end of the access gating low-noise preamplification unit is connected with the input end of the true effective value rapid sampling unit.
The input end of the program control gain unit is connected with the output end of the microprocessor unit, and the output end of the program control gain unit is connected with the input end of the access gating low-noise preamplifier unit.
Further, the access gating low-noise preamplifier unit comprises a zero drift instrument amplifier and a resistor, and the microprocessor unit selects a resistor with matched gain for the zero drift instrument amplifier to adjust the response coefficient of the LVDT sensor through the program control gain unit according to the stored sensitivity value.
Furthermore, the real effective value rapid sampling unit comprises an integrated real effective value chip and is used for rapidly converting the sine wave signal output by the access gating low-noise preamplification unit into a high-precision direct current signal.
Further, the device also comprises a display and communication unit which is connected with the microprocessor unit.
And further, the system also comprises a hybrid charging and power supply conversion power supply which is used for providing electric energy for the system to work.
A numerical measurement method based on an LVDT sensor comprises the following steps:
acquiring an hour hand signal;
acquiring an output signal of the sensor after correcting the sensitivity based on the clock signal;
obtaining a measurement value of the sensor based on the output signal;
wherein the sensor is an LVDT sensor.
Further, the obtaining a measurement value of the sensor based on the output signal includes:
amplifying the output signal to obtain a measurement signal;
purifying the measurement signal;
the measurement signal is converted into a direct current signal.
Due to the adoption of the technical processing and measuring method, the effect of the invention is obvious:
1. and a zero drift instrument amplifier and linear compensation are adopted to obtain more accurate measurement data.
2. And a fast true effective value processing mode is adopted to acquire and convert the output signal of the LVDT sensor.
3. The gain of the data conditioning circuit has the self-adaptive function to the LVDT sensor which is connected with the data conditioning circuit and has various input-output responses (sensitivity).
4. The LVDT sensor has a self-calibration function for various input-output response (sensitivity) of the connected LVDT.
5. The solar energy and power grid hybrid power supply mode is adopted to charge the configured large-capacity lithium battery pack, and the long-term operation of the manual dry-preheating system is not required in principle.
6. The LVDT sensor is provided with an original excitation signal with extremely accurate frequency by adopting a crystal oscillator frequency division mode, the amplitude of the original excitation signal is stabilized by adopting an integrated analog switch to a reference source chopping mode, and the accurate input excitation signal is provided for the LVDT sensor by adopting a mode of extracting fundamental waves in the original excitation signal and double reference sources by adopting a multi-feedback band-pass filtering mode.
7. Providing communication service for users in a Bluetooth, LORA and GPRS wireless mode; and a network port and RS485 mode is adopted to provide wired communication service for users.
8. The invention provides human-computer interaction for users by adopting the liquid crystal touch screen and a remote wireless GPRS mode.
For a better understanding of the nature and features of the present invention, reference should be made to the following examples and accompanying drawings.
Drawings
FIG. 1 is a block diagram of the multi-channel adaptive high-precision LVDT data acquisition and measurement system according to the present invention;
FIG. 2 is a circuit diagram of the connection between the constant frequency and amplitude signal generating unit and the channel gating and LVDT driving unit according to the present invention;
FIG. 3 is a circuit diagram of an integrated analog switch IC20 according to the present invention;
FIG. 4 is a circuit diagram of an integrated analog switch IC21 according to the present invention;
FIG. 5 is a circuit diagram of an integrated analog switch IC22 according to the present invention;
FIG. 6 is a circuit diagram of an integrated analog switch IC23 according to the present invention;
FIG. 7 is a circuit diagram of an integrated analog switch IC24 according to the present invention;
FIG. 8 is a circuit diagram of an integrated analog switch IC25 according to the present invention;
FIG. 9 is a circuit diagram of an integrated analog switch IC26 according to the present invention;
FIG. 10 is a circuit diagram of the gated low noise pre-amp cell and true valid value fast sampling cell connections of the present invention;
FIG. 11 is a circuit diagram of the microprocessor IC12 of the present invention;
FIG. 12 is a circuit diagram of a motion direction discriminating unit according to the present invention;
FIG. 13 is a circuit diagram of the microprocessor IC14 of the present invention;
FIG. 14 is a circuit diagram of a high precision integrated reference source IC13 in accordance with the present invention;
FIG. 15 is a circuit diagram of an integrated boost converter chip IC4 according to the present invention;
fig. 16 is a circuit diagram of the connection of the integrated boost converter IC5, the integrated low dropout IC6 and the integrated low dropout IC7 according to the present invention;
FIG. 17 is a circuit diagram of an integrated buck chip IC8 in accordance with the present invention;
FIG. 18 is a circuit diagram of the integrated polarity reversing chip IC9 and the negative supply low dropout chip IC10 in accordance with the present invention;
FIG. 19 is a solar charging circuit diagram according to the present invention;
fig. 20 is a diagram of an ac-dc converter circuit according to the present invention.
Detailed Description
The main technical parameters of the embodiment of the invention are as follows: a. 32LVDT sample channels. b. An LVDT sensor with a free movable end is adopted, and two ends of the LVDT sensor are fixed on a measured object, and the length of two ends (fixed ends) of the LVDT sensor is 150 mm. c. And GPRS long-distance wireless data interaction and Bluetooth short-range data interaction modes are adopted. d. The axial movement direction of the measured object is consistent with the movement direction of the LVDT sensor inclined iron. e. The measurement environment temperature range is-10 ℃ to 65 ℃. f. The time interval between two adjacent sampling is 1 hour.
Please refer to fig. 2 to fig. 20. A multichannel self-adaptive self-fixed elevation precision LVDT data acquisition and measurement system is composed of a constant frequency and constant amplitude
Please continue to refer to fig. 2 to fig. 20. The constant-frequency constant-amplitude
The channel gating and
The access gating low-
The input of the motion
The true effective value
The display and
The hybrid charging and power
Please continue to refer to fig. 2 to fig. 20. The composition and principle of each circuit unit of the present invention are further described in detail below.
As shown in fig. 2, the constant frequency and constant amplitude
The following description will be incorporated to describe the channel gate and
As shown in fig. 2 to 4, the channel gating and
As shown in fig. 5 to 10, the access-gated low
The description is divided into three initialization phases:
initialization phase one
Assume that the values of KS, VDCW for the universal LVDT sensor have been obtained in the manner described above and permanently stored in the microprocessor memory.
The initial access of each sensor to the system must execute an initialization process, and when the system is restarted after power failure, the invention can prompt interactive information of 'whether initialization is needed' through a configured touch display screen. The purpose of initialization is to acquire the output response coefficient of each access LVDT sensor, compare the output response coefficient with the sensitivity (based on the SDVG20-VA product with the range of 2.5 mm, which is believed to be the science and technology development Limited company in Shenzhen) of the general LVDT sensor stored in the
When the initialization stage one is executed, the
Then, the
Initialization phase two
In the first initialization phase, the
Then, the
Initialization phase three
During the initialization phase three, the microprocessor IC12(STM32H750) in the
When a certain LVDT sensor is connected to the system, the output response coefficient KX is obtained after initialization. The gain calculation formula G of the zero drift instrumentation amplifier IC27(INA188) in the access gated low
As shown in fig. 10, the true effective value
As shown in fig. 12, the motion
As shown in fig. 13 and 14, the
As shown in fig. 11, the display and
As shown in fig. 15 to fig. 18, the
The
As shown in fig. 19, the solar charging portion of the
As shown in fig. 20, the ac-dc conversion portion is composed of a monolithic ac-dc conversion chip IC2(TOP266), a three-terminal regulator (TL431),
The method provided by the invention realizes the monitoring of micro strain, micro-scale change, mechanical quantity and the like of high-precision engineering using various LVDT sensors and provides a convenient calibration means for the occasions using a large number of LVDT heavy checkpoints, thereby greatly reducing the fussy high-precision calibration work for a large number of LVDT sensors and providing a quick and high-precision self-adaptive measurement method for the automatic monitoring and detecting occasions. The invention is especially suitable for the occasions with severe environment and high-precision and rapid measurement requirements, such as engineering monitoring, nuclear facilities (equipment), aviation equipment, engines and the like.
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