WO2021051850A1 - Multi-channel, adaptive, high-accuracy lvdt data acquisition and measurement system and method - Google Patents

Abstract

A multi-channel, adaptive and high-accuracy LVDT data acquisition and measurement system and method, the system comprising a constant-frequency, constant amplitude signal generation unit (1), a channel gating and LVDT drive unit (2), a receiving gated low-noise preamplification unit (3), a programmable gain unit (4), a true RMS value rapid sampling unit (5), a motion direction determining unit (6) and a microprocessor unit (7); the constant frequency, constant amplitude signal generation unit (1) is connected to the channel gating and LVDT drive unit (2), the channel gating and LVDT drive unit (2) is connected to the receiving gated low-noise preamplification unit (3), the receiving gated low-noise preamplification unit (3) is connected to each of the true RMS value rapid sampling unit (5) and the motion direction determining unit (6), the true RMS value rapid sampling unit (5) and the motion direction determination unit (6) are each connected to the microprocessor unit (7), the microprocessor unit (7) is connected to each of the channel gating and LVDT drive unit (2) and the programmable gain unit (4), and the programmable gain unit (4) is connected to the receiving gated low-noise preamplification unit (3).

Description

Multi-channel adaptive high-precision LVDT data acquisition and measurement system and method Technical field

The invention belongs to the field of detecting instrument manufacturing, and relates to a multi-channel adaptive LVDT data acquisition and measurement system and method suitable for engineering micro-strain monitoring.

Background technique

At present, a strain sensor called vibrating wire is widely used in engineering construction, bridges, reservoirs and dams. The vibrating wire strain sensor is widely used in the field of geotechnical engineering due to its simple structure and strong anti-interference ability.

However, the vibrating wire strain sensor has also become a subject of widespread debate in the industry due to its obvious technical defects. A vibrating wire strain sensor that uses a tensioned metal string as a sensitive element. When the length of the string is determined, the amount of change in its natural vibration frequency can indicate the magnitude of the tension on the string. The frequency and the receiving force can be obtained through a certain conversion. A certain relationship between forces. With the continuous in-depth research and analysis of vibrating wire strain sensors, combined with actual failure cases applied in engineering, the inherent physical defects of vibrating wire strain sensors have gradually been revealed: 1. Vibrating wire strain sensors are not suitable for use in Long-term monitoring. As we all know, any object will deform when subjected to an external force; at the same time, any object will expand and contract when the temperature difference changes, and the vibrating wire strain sensor is also affected by the above factors without exception. The vibrating wire of the vibrating wire strain sensor is tensioned and fixed on the elastic diaphragms at both ends. Therefore, both ends of the vibrating wire are affected by the superposition of a certain tension and gravity; the vibrating wire will inevitably undergo deformation. The tensioned vibrating wire will have a creeping change in the relative position between the internal molecules or between the ions, and at the same time, additional internal forces between the atoms and between the molecules will be generated to offset the external force, and try to return to the state before the deformation. When the balance is reached, the additional internal force will be equal to the external force received, but in the opposite direction. In theory, under load conditions, the internal stress of an ideal single crystal metal material will not undergo permanent plastic deformation within the elastic limit. However, since the metal materials actually used have a polycrystalline structure, there are a large number of internal crystal defects; when the temperature difference is not large, the material will undergo microscopic plastic deformation due to the difference in crystal phase and the close diffusion of atoms; When it increases, the long-range diffusion of atoms and the tendency of lattice dislocation slip to become violent will appear in the material. As time goes by, the continuous accumulation of micro plastic deformation will evolve into macro plastic deformation. Metals will produce microscopic plastic deformation within the range of elastic stress, which can be successfully explained by mechanisms such as short-range slippage of dislocations in crystals, directional dissolution of solute atoms, directional vacancy flow, and crystal sliding. The physical mechanism that occurs on the wire also occurs on the vibrating wire that is tightened at both ends of the vibrating wire strain sensor. 2. The temperature effect of vibrating wire strain sensor is serious. Since the linear thermal expansion coefficient of the vibrating wire strain sensor is related to the material, machining accuracy, shape, etc., it is necessary to individually calibrate and compensate the vibrating wire strain sensor before use. 3. Vibrating wire strain sensor is not suitable for use in complex deformation measurement occasions. According to the theory of material mechanics and elasticity that steel body deforms when subjected to external force but does not change in volume, if the steel body undergoes compression deformation in the axial direction when subjected to pressure, but in accordance with the principle of constant volume, expansion and deformation will inevitably occur in the radial direction. The effect of radial expansion is related to the shape and material of the steel body. Therefore, the radial expansion change 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 strain sensor mounted on the steel body will be twisted, which can be converted into an additional external force in the axial direction, resulting in the measurement of the vibrating wire strain sensor. accurate. Therefore, it is not surprising that there are frequent failures in the use of vibrating wire strain sensors for engineering stress detection.

The monitoring of strain and stress in various construction projects is a very important measurement index. Through the strain or stress of various materials used in construction projects and various supports used in foundation pit enclosures under stress conditions Accurate measurement can objectively reflect the true conditions of building components under stress conditions, and provide reliable and accurate data for the construction and operation of the project. Therefore, the research and development of a high-precision, independent of radial changes, small temperature coefficient, A multi-channel self-adaptive self-calibrating high-precision LVDT data acquisition system and its measurement method with high degree of automation (without manual intervention) and convenient data interaction are very necessary.

Summary of the invention

The ideal engineering micro-strain monitoring system should be: 1. Accurate and reliable measurement data; 2. Provide convenient information interaction methods for users; 3. In principle, there is no need for human intervention to monitor the energy supply of the system; 4. Flexible monitoring frequency settings.

The invention aims to provide an engineering detection with solar energy and power adapter supplementary energy, extremely accurate axial detection accuracy, insensitive to radial deformation, self-calibration function for the range-gain of various LVDT sensors, and processing System gain has self-adaptive function, extremely small temperature coefficient, wireless remote GPRS data interaction, short-range wireless or wired networking function, convenient human-computer interaction interface, multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method .

In order to fully explain and understand the principles of the present invention and the technical methods adopted, it is necessary to understand the current methods of micro-strain stress monitoring in engineering construction.

Take the steel structure support for deep foundation pit excavation as an example. In the process of deep foundation pit excavation, in order to prevent the edge of the foundation pit from collapsing, a reinforced concrete continuous wall needs to be built around the excavated foundation pit. Due to the huge soil pressure, it is necessary to properly support the constructed continuous wall. There are usually two Support beams are formed in several ways: reinforced concrete support beams and steel structure support beams. Steel structure supporting beam is a widely used construction method in the world, and it is also the trend of supporting methods in deep foundation pit excavation and maintenance projects in my country. Accurately measuring the force status (deformation status) of the steel support beam of the steel support structure is related to the safety of the entire project construction. With the help of the accurate determination of the force (deformation) of the steel support beam, the correctness of the design calculation can be verified in reverse. The purpose of reducing engineering cost. The high-precision, highly sensitive LVDT micro-strain sensor is used to monitor the stress and micro-strain of the steel structure support beam. These LVDT micro-strain sensors are placed on the key force-bearing parts of the support beam (the placement location must comply with the Saint-Venant principle). The measurement data of each monitoring point sensor is transmitted to the monitoring management station through cable connection.

The invention relates to a multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method.

The multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system is used to realize: realize constant frequency and stable amplitude excitation and LVDT for 32-channel (in the embodiment, the number of channels can be expanded as needed) LVDT sensor in a time-division multiplexing manner. Sensor output response signal conditioning (including system gain adaptation, LVDT sensor automatic calibration, fast true effective value processing to extract the final conditioning signal of each channel LVDT, sensor movement direction identification, 16-bit A/D sampling and calculation), short-range wireless The method realizes wireless networking between monitoring points, provides Bluetooth wireless data interaction, provides remote GPRS wireless data interaction, provides solar energy and power adapter charging functions, and provides high stability and low noise power supply for related units. The LVDT sensor group is composed of several LVDT sensors and corresponding mechanical structures.

When the multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system is powered on, the microprocessor in the system waits to receive the setting command of the system working mode. The setting command includes the number of LVDT sensors that need to be sampled and Alarm information of independent number, sampling frequency, upper and lower limit of each single sensor measurement data. The working mode setting parameters can be received in three ways: 1. Perform on-site programming of the system's microprocessor via an external serial port; 2. Through the human-computer interaction provided by the LCD touch screen configured in the system and the microprocessor, 3. The interaction between the GPRS remote wireless data interaction network and the system. After the multi-channel adaptive self-calibration high-precision LVDT data acquisition and measurement system receives the working parameters, it first collects the power supply status information of the system. If the power supply of the lithium battery pack configured in the system is normal, it will enter the Initialization process; otherwise, the information that the system needs to supplement power will be sent to the remote place through the remote wireless GPRS network. Since various LVDT sensors have different output responses (different sensitivity) under the same input excitation, the initialization process includes: 1. Automatically determine the sensitivity of each connected LVDT sensor and store it in the system's non-volatile memory to achieve automatic Calibration function; 2. According to the measured value of the sensitivity of each LVDT sensor, the gain of the sensor during data conditioning is automatically adjusted to realize the adaptive function of data conditioning.

After initialization and when the set measurement time is reached, the present invention performs measurement on each connected LVDT sensor in a time-sharing manner through the gated integrated analog switch under the control of the configured microprocessor: The integrated analog switch gives the coded address, and the LVDT sensor of the corresponding channel is connected to the system. The microprocessor obtains a digital pulse signal of n KHZ with extremely stable repetition frequency through the configured crystal oscillator clock source. The digital pulse signal is passed through multiple feedback band-pass filters to obtain a bipolar sinusoidal fundamental wave. The wave is amplified and driven by the funnel-type instrument amplifier to excite the primary winding of the selected LVDT sensor; the double-ended response signal sent by the selected LVDT sensor is also gated by the corresponding integrated analog switch, and then read into the zero-drift instrument amplifier; At this time, the gain of the zero-drift instrument amplifier is automatically configured by the microprocessor according to the sensitivity parameters stored in the non-volatile memory when the selected LVDT sensor is initialized.

After being amplified and converted by a zero-drift instrument amplifier, it becomes a single-ended measurement signal, which is further purified by multiple feedback band-pass filters. 1. The signal is converted into a DC 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; 2. The double-ended signal output by the LVDT sensor, each end is relative to the circuit reference ground ( The voltage of the circuit ground is determined by the direction determination circuit respectively. The present invention realizes the direction discrimination of the measurement signal in the following way: the LVDT sensor outputs the response double-ended signal, and the ground voltages UA and UB at each end are buffered separately (in order not to affect the differential measurement value), and then proportional Subtraction processing. Therefore, even if the difference between UOA and UOB is small, a considerable difference UC can be obtained after the proportional difference subtraction processing. The UC obtains a "0" or "1" signal after an integrated comparator. This "0" Or "1" signal represents the two relative movement directions of the armature of the LVDT sensor.

Repeat the above operation process until all connected LVDT sensors are sampled. After the sampling data of each sensor and the corresponding environmental temperature data are sent through various communication circuits configured, the measurement is over and the system enters a sleep state until Automatically wake up when the next measurement time arrives. After the communication circuit receives the measurement data sent by the multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system, it sends the measurement information according to the selected communication mode, wherein the remote wireless GPRS communication is the default and cannot be changed ; And short-range wireless communication Bluetooth and WIFI are optional. In order to ensure the measurement accuracy of the multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system, this system uses the ARM M7 microprocessor (STM32H750) with 16-bit AD sampling, so the stability and benchmark of the system power supply Source requirements are relatively high, and the present invention uses an ultra-high precision reference source (ADR4530) with a temperature drift coefficient of less than or equal to 2 ppm/°C.

In order to adapt to the long-term unattended monitoring environment, this multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system uses a 37Ah, 4.2V large-capacity parallel lithium battery pack for power supply, supplemented by a solar charging circuit and equipped with a power adapter Charging interface. In order to safely and appropriately charge parallel lithium battery packs, a high-capacity parallel lithium battery pack solar and AC hybrid charging management system dedicated to the present invention has been developed. The maximum charging current of the solar and AC hybrid charging management system that realizes charging according to the present invention is 1.5A, that is, charge the parallel lithium battery pack with C/18.5 of the battery pack capacity. In principle, the energy supplement can be completed in 2 clear days. The equipped 37Ah parallel lithium battery pack can maintain sufficient working power of the present invention for more than 1.5 months under the condition of full load monitoring 24 times a day; during this period, only two sunny days are required.

The battery pack can recover full energy. Therefore, the multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system does not need manual intervention to restore energy supplement in principle. Taking into account the unpredictability of weather factors, the present invention is also equipped with a power adapter charging port.

A multi-channel adaptive self-calibration high-precision LVDT data acquisition and measurement system and method, which is characterized by: adopting a zero-drift instrument amplifier to convert the double-ended signal output by the LVDT sensor into a single-ended signal, in order to further suppress the conversion of the double-ended signal to The temperature drift of the single-ended signal is linearly compensated for the gain of the zero-drift instrument amplifier and the ambient temperature.

A multi-channel adaptive self-calibration high-precision LVDT data acquisition and measurement system and method, which is characterized by: adopts a fast sampling true effective value processing method to obtain and convert the output signal of the LVDT sensor, and abandons the use of phase-sensitive detection. The traditional way of processing LVDT sensor signals.

A multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method, which is characterized by: adopts solar charging, high-capacity lithium battery energy storage, and a power adapter to provide energy interface power supply. In principle, no human intervention is required The long-term normal operation of the system can be realized.

A multi-channel adaptive self-calibration high-precision LVDT data acquisition and measurement system and method. The processing flow for the LVDT sensor is: using a constant frequency and constant amplitude standard signal source (6.0PPV, 2.5KHz sine wave) as a gain coefficient The input signal of the funnel amplifier. After the LVDT sensor is driven by the funnel amplifier, its output response is adjusted by the programmable gain zero-drift instrument amplifier, noise suppression bandpass filter, fast sampling true effective value and other links, and then it is sampled by the microprocessor's 16-bit A/D.

A multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method, which is characterized in that a funnel amplifier with two gain coefficients (0.8, 0.4) is used to drive the LVDT sensor during initialization to obtain each connected LVDT sensor The output response coefficient.

A multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method, which is characterized by determining the output response coefficient SS and sensitivity KS of a general-purpose LVDT sensor as a benchmark (based on SDVG20- from Shenzhen Xinwei Technology Development Co., Ltd. Take a product with a VA measuring range of 2.5 mm as an example):

Set the programmable gain zero-drift instrument amplifier to a fixed gain A (A=2 in the example), a constant frequency 2.5KHz, constant amplitude 3.0VRMS (volt) standard signal source is connected to the input end of the funnel amplifier with a gain coefficient of 0.8 (VIN0.8) drives the LVDT sensor, and its output response is V0.8S after the AD sampling value; the constant frequency and constant amplitude standard signal source is connected to the funnel amplifier to drive the input end of the LVDT sensor with a gain coefficient of 0.4 (VINS0.4). The output response is V0.4S after the AD sampling value; so the output response increment:

Input signal increment:

KS is the output response coefficient of a general-purpose LVDT sensor. Store the KS obtained above into the non-volatile memory of the microprocessor.

Use the 0.2 micron precision micrometer bench, the programmable gain zero drift instrument amplifier is set to a fixed gain A (A = 2 in the example), and the constant frequency and constant amplitude standard signal source is connected to the funnel amplifier to drive the LVDT sensor with 0.8 gain The input terminal of the coefficient. Lock the universal LVDT sensor on the micrometer stand, and get the output response VCWS1 at this time. Adjust the micrometer stage to change 0.2 microns to obtain the output response VCWS2; calculation

get

VDCW is the output voltage amplitude (voltage value after A/D conversion) corresponding to a 0.2 micron change in a general LVDT sensor. Store the KS and VDCW obtained above into the non-volatile memory of the microprocessor. Once the first and second initialization steps are completed, the subsequent production acquisition system only needs to directly store the KS and VDCW values into the memory and quote them.

When the present invention is put into operation, it will first go through the initialization process (in future use, or power failure, or replacement of the damaged sensor, the system will start the initialization operation). Through the high-performance integrated analog switch, the connected LVDT sensors are selected in sequence, and under the condition of the programmable amplifier gain A, the connected L VDT sensors are automatically repeated in sequence

as well as

Operate to obtain the KN of each connected sensor; the KN is also automatically stored in the non-volatile memory in the microprocessor (unless a certain LVDT sensor failure is replaced or cancelled, these values will not change). During measurement, the present invention automatically compares the LVDT measurement value of the selected channel N (corresponding to a specific LVDT sensor) with the standard K value according to its corresponding KN, and the compared coefficient is used as the microprocessor to select the programmable gain zero-drift instrument amplifier The basis of gain, so that LVDT sensors with different sensitivities can be amplified by the appropriate gain AN (not to be saturated). Note: During normal measurement, the funnel amplifier is always in the 0.8 gain factor input state.

A multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method is characterized in that the KN of each LVDT sensor obtained by the above-mentioned measures has also been automatically calibrated. The specific process is as follows: According to the KN value obtained by each connected LVDT sensor, the microprocessor automatically selects the gain AN of the programmable gain zero-drift instrument amplifier to obtain the AD conversion value DATN, and the operation DZHN=DATN×A/AN, that is: DZHN is Convert the measured value DATN into the value of gain A used by general LVDT; then calculate LN=(DZHN×KS/KN)×0.2 micron, which is the Nth measured value of displacement connected to the LVDT sensor, thus realizing automatic setting Mark.

A multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method, which is characterized in that a square wave signal with extremely accurate frequency is generated by means of crystal oscillator frequency division, and the square wave signal is fed to the control input of an integrated analog switch , The data input terminal of the integrated analog switch is connected to the reference source, and under the control of the square wave signal, the integrated analog switch outputs a constant frequency and constant amplitude chopping signal. The multiple feedback band-pass filtering method is used to extract the fundamental wave of the chopping signal, and the constant frequency and constant amplitude fundamental wave is used as the input excitation signal of the driver of the LVDT sensor.

A multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system and method, which is characterized by: using Bluetooth to provide information interaction for mobile phone users, using LORA wireless communication to achieve local networking between monitoring points, using The remote wireless GPRS method provides information interaction for remote monitoring stations.

Multi-channel adaptive high-precision LVDT data acquisition and measurement system, including constant frequency and constant amplitude signal generation unit, channel gating and LVDT drive unit, access gating low noise preamplifier unit, programmable gain unit, true effective value fast sampling unit , A motion direction determination unit and a microprocessor unit, the output terminal of the constant frequency and constant amplitude signal generating unit is connected to the input terminal of the channel gating and LVDT drive unit, and the output terminal of the channel gating and LVDT drive unit Connected to the input end of the access gated low noise preamplifier unit, and the output end of the access gated low noise preamplifier unit is respectively connected to the input end of the true effective value fast sampling unit and the motion The input terminal of the direction determination unit is connected, the output terminal of the true effective value rapid sampling unit and the output terminal of the motion direction determination unit are respectively connected to the input terminal of the microprocessor unit, and the output of the microprocessor unit The terminals are respectively connected to the input terminal of the channel gating and LVDT drive unit and the input terminal of the program-controlled gain unit, the output terminal of the program-controlled gain unit and the input terminal of the access gated low-noise preamplifier unit connection.

Further, the constant frequency and constant amplitude signal generating unit includes an integrated analog switch and a zero-drift operational amplifier, and the square wave signal output by the microprocessor unit controls the on and off of the integrated analog switch, so that the integrated analog switch outputs The signal is a constant-frequency and constant-amplitude square wave signal, and the zero-drift operational amplifier is connected to the integrated analog switch for converting a 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 drive unit includes an integrated analog switch and an integrated funnel instrument amplifier, and the microprocessor unit controls the integrated analog switch to connect a constant frequency and constant amplitude bipolar sine wave signal to all The input terminal of the integrated funnel instrument amplifier is used to enable the microprocessor unit to obtain the response coefficient of the connected LVDT sensor.

Further, the access gate low-noise preamplifier unit includes a zero-drift low-noise variable gain instrument amplifier and a resistor, and the microprocessor unit is the zero-drift low-noise variable gain instrument according to the stored sensitivity value. The amplifier selects the resistance with gain matching to adjust the response coefficient of the LVDT sensor.

Further, the true effective value fast sampling unit includes an integrated true effective value chip for quickly converting the output sine wave signal of the gated low-noise preamplifier unit into a high-precision DC signal.

Further, the motion direction determining unit includes three integrated operational amplifiers and an integrated comparator. The two signals in response to the double-ended output of the LVDT sensor are respectively amplified by the integrated operational amplifier, and the two amplified signals pass through another The integrated operational amplifier performs proportional difference, and an output signal of the integrated operational amplifier is used as an input signal of a quasi-zero-crossing comparator formed by the integrated comparator.

Further, it also includes a display and communication unit, which is connected to the microprocessor unit.

Multi-channel adaptive high-precision LVDT data acquisition and measurement methods, including:

Obtain the clock signal;

Based on the clock signal, collect the output signal of the sensor after the sensitivity is corrected;

Obtain detection information of the sensor based on the output signal, where the detection information includes a measurement value and a movement direction;

Wherein, the sensor is an LVDT sensor.

Further, said acquiring a clock signal includes:

Set working parameters;

Based on the working parameters, the clock signal is obtained.

Further, the setting working parameters includes one of the following ways:

JTAG interface to set working parameters;

Human-computer interaction to set working parameters;

GPRS remote wireless data interaction sets working parameters.

Further, the working parameters include one or more combinations of the following methods:

Alarm information of the number of sensors, acquisition frequency, acquisition time, and upper and lower limits of the measured value.

Further, the clock signal is a frequency-stabilized signal obtained by dividing the frequency of a crystal oscillator.

Further, the collecting, based on the clock signal, the output signal of the sensor after the sensitivity is corrected includes:

Acquire the excitation signal of the sensor.

Further, the obtaining the excitation signal of the sensor includes:

Chop the reference source to obtain a digital signal;

Extracting the fundamental wave of the digital signal;

The fundamental wave is amplified to obtain the excitation signal of the sensor.

Further, the obtaining the measurement value of the sensor based on the output signal includes:

Amplify the output signal to obtain the measurement signal;

Purify the measurement signal;

Convert the measurement signal to a DC signal.

Further, the obtaining the movement direction of the sensor based on the output signal includes:

Based on the comparison of the two-terminal output response signals of the sensor, the movement direction information of the sensor is obtained.

Further, the comparison of the two-terminal output response signals of the sensor includes:

Amplify the difference between the two double-ended output response signals.

Further, the calibrating the sensitivity of the sensor includes:

The sensitivity of the sensor is adjusted to be equal to the standard value, where the standard value is set.

Further, the adjusting the sensitivity of the sensor to be equal to the standard value includes:

Adjust the magnification corresponding to the sensitivity of the sensor.

Further, the adjusting the magnification corresponding to the sensitivity of the sensor includes:

Switch the selection resistance to adjust the magnification.

Due to the adoption of the above-mentioned technical processing and measurement methods, the effect of the present invention is obvious:

1. Using zero-drift instrument amplifier and linear compensation to obtain more accurate measurement data.

2. The fast true effective value processing method is adopted to obtain and convert the output signal of the LVDT sensor.

3. The gain of the data conditioning circuit of the present invention has an adaptive function to the LVDT sensor that is connected to the present invention and has various input to output responses (sensitivity).

4. The present invention has a self-calibration function for various input-output response (sensitivity) LVDT sensors connected.

5. Adopting solar energy and industrial network hybrid power supply to charge the configured large-capacity lithium battery pack, in principle, there is no need for manual intervention in the long-term operation of the system.

6. Using crystal frequency division to provide the LVDT sensor with an extremely accurate original excitation signal, using an integrated analog switch to chop the reference source to stabilize the amplitude of the original excitation signal, and using multiple feedback bandpass filtering to extract the original excitation signal The fundamental wave and dual reference sources provide accurate input excitation signals for the LVDT sensor.

7. Use Bluetooth, LORA, GPRS wireless methods to provide users with communication services; use network ports, RS485 methods to provide users with wired communication services.

8. The present invention adopts LCD touch screen and remote wireless GPRS mode to provide users with human-computer interaction.

In order to further understand the performance and features of the present invention, a detailed description will be given in conjunction with the following embodiments and drawings.

Description of the drawings

Figure 1 is a structural block diagram of the multi-channel adaptive high-precision LVDT data acquisition and measurement system of the present invention;

2 is a circuit diagram of the connection between the constant frequency constant amplitude signal generating unit and the channel gating and LVDT driving unit of the present invention;

FIG. 3 is a circuit diagram of the integrated analog switch IC20 of the present invention;

4 is a circuit diagram of the integrated analog switch IC21 of the present invention;

FIG. 5 is a circuit diagram of the integrated analog switch IC22 of the present invention;

FIG. 6 is a circuit diagram of the integrated analog switch IC23 of the present invention;

FIG. 7 is a circuit diagram of the integrated analog switch IC24 of the present invention;

FIG. 8 is a circuit diagram of the integrated analog switch IC25 of the present invention;

FIG. 9 is a circuit diagram of the integrated analog switch IC26 of the present invention;

10 is a circuit diagram of the connection between the gated low-noise preamplifier unit and the true effective value fast sampling unit according to the present invention;

Figure 11 is a circuit diagram of the microprocessor IC12 of the present invention;

Figure 12 is a circuit diagram of the motion direction determining unit of the present invention;

Figure 13 is a circuit diagram of the microprocessor IC14 of the present invention;

FIG. 14 is a circuit diagram of the high-precision integrated reference source IC13 of the present invention;

15 is a circuit diagram of the integrated boost converter chip IC4 of the present invention;

16 is a circuit diagram of the integrated boost converter chip IC5, the integrated low dropout chip IC6 and the integrated low dropout chip IC7 of the present invention;

Figure 17 is a circuit diagram of the integrated step-down chip IC8 of the present invention;

18 is a circuit diagram of the connection between the integrated polarity conversion chip IC9 and the negative power supply low dropout chip IC10 of the present invention;

Figure 19 is a diagram of the solar charging circuit of the present invention;

Fig. 20 is a circuit diagram of the AC-DC conversion circuit of the present invention.

detailed description

The main technical parameters of the embodiment of the present invention are: a, 32LVDT sampling channel. b. An LVDT sensor with free movable ends is used, and the two ends of the LVDT sensor are fixed on the object to be measured, and the length of the two ends (fixed ends) of the LVDT is 150 mm. c. It adopts GPRS remote wireless data interaction and Bluetooth short-range data interaction. d. The axis movement direction of the measured object is consistent with the movement direction of the LVDT sensor's oblique iron. e. The measuring environment temperature range is -10℃-65℃. f. The interval between two adjacent samples is 1 hour.

Please refer to Figure 2 to Figure 20. A multi-channel self-adaptive self-calibration high-precision LVDT data acquisition and measurement system, consisting of a constant frequency and constant amplitude signal generating unit 1, a channel strobe and LVDT drive unit 2, a gated low noise preamplifier unit 3, and a programmable gain unit 4. The true effective value rapid sampling unit 5, the movement direction determination unit 6, the microprocessor unit 7, the display and communication unit 8, the conversion power supply unit 9, and the hybrid charging unit 10.

Please continue to refer to Figure 2 to Figure 20. The constant frequency and constant amplitude signal generating unit 1 provides a sine wave excitation signal source with stable frequency and stable amplitude for the LVDT sensor. The realization principle is to use the 2.5KHz output square wave signal obtained by the microprocessor frequency division to chop the reference voltage source through the low output impedance integrated analog switch, and then use the second-order bandpass filter to transform the constant frequency and constant amplitude chopping signal It is a bipolar sine wave signal VIN; therefore, the sine wave signal VIN is also a constant frequency and constant amplitude. The input of the constant frequency and constant amplitude signal generating unit 1 is connected to the output of the microprocessor unit 7 and the hybrid charging and power conversion power supply 9, and the output is connected to the channel gating and the input of the LVDT driving unit 2 in sequence.

The channel gating and LVDT driving unit 2 is used to sequentially connect the LVDT sensors to the circuit through the integrated analog switch with low output impedance under the control of the microprocessor, and use the funnel-type instrument amplifier to amplify and drive the LVDT sensor. When the present invention is in the initialization state, first the microprocessor in the microprocessor unit 7 controls the analog switch to switch the constant frequency constant amplitude bipolar sine wave signal VIN (frequency 2.5KHz, amplitude 3.0VRMS) is connected to the input terminal of the funnel instrument amplifier with a gain coefficient of 0.8, that is, VIN0.8, so as to obtain the output response Y0.8N of a certain connected LVDT sensor N under the gain coefficient of 0.8, and store Y0.8N in The microprocessor memory in the microprocessor unit 7; then, under the control of the microprocessor, the constant frequency and constant amplitude bipolar sine wave signal output by the constant frequency and constant amplitude signal generating unit 1 is connected to the funnel type instrument amplifier The input terminal with a gain coefficient of 0.4, namely VIN0.4, obtains the output response Y0.4N of a certain connected LVDT sensor with a gain coefficient of 0.4, and stores Y0.4N in the microprocessor memory in the microprocessor unit 7. ;Combined with the 0.8 and 0.4 attenuation coefficients given to the input bipolar sine wave signal:

The microprocessor calculates

The response coefficient of the LVDT sensor is obtained; the above operations are repeated in sequence until the response coefficients of all connected sensors are obtained. At the same time, the microprocessor selects the gain coefficient of the corresponding signal conditioning circuit when a certain LVDT sensor N is gated and connected according to the obtained response coefficients of each LVDT, thus realizing the self-calibration, The purpose of line gain adaptation.

The access gated low-noise preamplifier unit 3 and the program-controlled gain unit 4 are used to give corresponding amplification gains to each successively connected LVDT. The input of the gated low-noise preamplifier unit 3 is connected to the channel gate and the output of the LVDT drive unit 2 in sequence, and the zero-drift low-noise variable gain instrument amplifier in the gated low-noise preamplifier unit 3 is used as For the amplification task, the gain is determined by the peripheral gain matching resistance controlled by the microprocessor. The output of the preamplifier is connected to the input of the true effective value fast sampling unit 5 and the movement direction determining unit 6. When a certain LVDT sensor is selected and connected, the microprocessor in the microprocessor unit 7 selects the correlation for the zero-drift low-noise variable gain instrument amplifier according to the sensitivity value of the LVDT sensor stored in the memory during initialization. The gain matching resistance.

The input of the motion direction determination unit 6 is connected to the output of the gated low-noise preamplifier unit 3, and its output is connected to the input of the microprocessor unit 7. The motion direction determining unit 6 is used to determine the direction (compression or extension) of the deformation of the measured object under the action of external force.

The true effective value fast sampling unit 5 consists of a true effective value integrated circuit and an ultra-low output impedance integrated analog switch. Its input is connected to the output of the gated low-noise preamplifier unit 3, and its output is connected to the input of the microprocessor unit 7. Sequence connection. The true effective value fast sampling unit 5 is used to convert the output sinusoidal signal connected to the gated low-noise preamplifier unit 3 into a DC voltage, supplemented by the fast discharge of the high-speed ultra-low output impedance integrated analog switch to complete the fast sampling function.

The display and communication unit 8 is used to realize wired, short-distance and long-distance wireless communication, and realize the two-way interaction of data and control instructions. The input is connected to the output of the microprocessor unit 7, and its output is connected to the RS485, GPRS, LORA, BLUETEETH communication modules.

The hybrid charging and power conversion power supply 9 is used to provide multiple sets of high-quality regulated power supplies for all the constituent units of the present invention, and to provide AC or solar hybrid charging functions for the configured large-capacity lithium battery pack.

Please continue to refer to Figure 2 to Figure 20. The composition and principle of each circuit unit of the present invention will be described in further detail below.

As shown in Figure 2, the constant frequency and constant amplitude signal generating unit 1 consists of a low output impedance integrated analog switch IC15 (ADG801), a zero-drift operational amplifier IC16: A (AD8639), resistors R46, R47, R48, R49, R50 , Composed of capacitors C58, C59, and C60. The power input (VDD) and signal input of the low output impedance integrated analog switch IC15 (ADG801) are connected to the reference source +3R, so when the low output impedance integrated analog switch IC15 (ADG801) is turned on, its signal output (D) The output signal amplitude is +3R. The 2.5KHz square wave signal (OSC) output by the microprocessor unit 7 controls the on and off of the low output impedance integrated analog switch IC15 (ADG801), so its output +3R reference source is chopped into a series of 2.5KHz frequency and amplitude +3R constant frequency constant amplitude square wave signal. Zero-drift operational amplifier IC16: A (AD8639) and its peripheral passive components form a multiple feedback bandpass filter with a center frequency of 2.5KHz. Therefore, zero-drift operational amplifier IC16: A (AD8639) outputs a constant frequency and constant amplitude The bipolar sine wave ensures the stability of the LVDT excitation signal.

The following description is based on the linkage relationship of circuit processing, so the channel gating and LVDT driving unit 2 and the access gating low-noise preamplifier unit 3 are described together.

As shown in Figures 2 to 4, the channel gating and LVDT drive unit 2 consists of integrated low output impedance analog switch IC17 (ADG1636), integrated funnel instrument amplifier IC18 (AD8475), integrated analog switch IC19 (ADG1636), It is composed of integrated analog switch IC20 (ADG1606) and integrated analog switch IC21 (ADG1606).

As shown in Figure 5 to Figure 10, the access gate low noise preamplifier unit 3 consists of integrated analog switches IC22 (ADG1606), IC23 (ADG1606), IC24 (ADG1606), IC25 (ADG1606), IC26 (ADG1636) ), IC27 (ADG1408), zero-drift instrument amplifier IC28 (INA188), zero-drift operational amplifier IC16: B (AD8639), resistors R51, R52, R53, R54, R55, R56, R57, R58, R59, R60, R61, R62, R63, R64, R65, R66, R67, R68, R69, R70, R71, R72, R73, R74, R75, R76, R77, capacitors C61, C62, C63 and other components.

It is described in three initialization phases:

Initialization stage 1: It is assumed that the KS and VDCW values of the general-purpose LVDT sensor have been obtained by the aforementioned method, and they are permanently stored in the microprocessor memory.

Each sensor must perform an initialization process when it is connected to the system for the first time. When the system is restarted after a power failure, the present invention will prompt the interactive information "whether initialization is needed" through the configured touch display screen. The purpose of initialization is to obtain the output response coefficient of each connected LVDT sensor, and compare it with the sensitivity of the general LVDT sensor stored in the microprocessor IC12 (STM32H750) in the microprocessor unit 7 (based on SDVG20 from Shenzhen Xinwei Technology Development Co., Ltd.) -The VA measuring range is 2.5 mm and the product is the benchmark) to determine the calculation of the output signal of each connected sensor (automatic calculation by the microprocessor), and provide the appropriate pre-gain for the single sensor.

When the initialization phase is executed, first, the microprocessor unit 7 sends a high level (CS) to the "1, 9" enable terminal pins of the integrated analog switch IC17 (ADG1636), and enables "1, 9" of IC19 (ADG1636) The terminal pin sends a high level (CS1), and sends a high level (ENK) to the "1, 9" enable pins of the integrated analog switch IC26 (ADG1636). Send "0, 0" to the terminals "17, 16, 15, 14" of the integrated analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (ADG1606), C25 (ADG1606) ,0,0" logic level, send ENA enable signal as high level "1", and send ENB enable signal as high level "0". Send "0, 0, 0" (selected gain is 2) to the channel strobe terminal (1, 16, 15) of the integrated analog switch IC27 (ADG1408), and send it to the enable terminal "2" of IC27 (ADG1408) High level "1". The above setting means: do not use extended 33~64 channels (when the enable pin "2" of IC27 (ADG1408) is low level "0", it means use extended 33~64 channels), select 1~16 channels in turn The first (channel 1) LVDT sensor, the input of the funnel instrument amplifier is set to 0.8 gain coefficient VIN0.8, the selected channel strobe and LVDT drive unit 2 default gain is "2" times, determine the first (Channel 1) The output response of the LVDT when the input gain of the funnel instrument amplifier is 0.8 is V1S0.8; this value is "permanently" stored in the memory of the microprocessor IC12 (STM32H750) in the microprocessor unit 7. Then, other conditions remain unchanged, the microprocessor unit 7 integrates the analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (DG1606), IC25 (ADG1606) terminal pin "17" , 16, 15, 14" send out the "1, 0, 0, 0" strobe signal, that is, select the second (channel 2) LVDT sensor; determine that the input gain of the second LVDT in the funnel instrument amplifier is 0.8 (VIN0. The output at 8) responds to V2S0.8; this value is "permanently" stored in the memory of the microprocessor IC12 (STM32H750) in the microprocessor unit 7. Until the strobe signal changes to "1, 1, 1, 1,", that is, the output response of the sixteenth (channel 16) connected to the LVDT sensor when the input gain of the funnel instrument amplifier is 0.8 (VIN0.8) is measured. V16S0.8, and save.

Then, the microprocessor unit 7 sends a high level (CS) to the "1, 9" enable terminal of the integrated analog switch IC17 (ADG1636), and sends a low level (CS) to the "1, 9" enable terminal of IC19 (ADG1636). Level "0" (CS1), send a high level (ENK) to the "1, 9" enable pins of the integrated analog switch IC26 (ADG1636). Send "0, 0" to the terminals "17, 16, 15, 14" of the integrated analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (ADG1606), C25 (ADG1606) ,0,0" logic level, send ENA enable signal as high level "0", send ENB enable signal as high level "1". Send "0, 0, 0" to the channel gate pins (1, 16, 15) of the integrated analog switch IC27 (ADG1408) (the selected gain is 2), and send it to the enable pin "2" of IC27 (ADG1408) High level "1". The above setting means: do not use extended 33-64 channels (when the enable pin "2" of IC27 (ADG1408) is low level "0", it means use extended 33-64 channels), select 17-32 channels in turn The input of the seventeenth (channel 17) LVDT sensor and funnel instrument amplifier is set to 0.8 (VIN0.8) gain coefficient, the selected channel strobe and the default gain of the LVDT drive unit 2 is "2" times. The output response of the seventeenth (channel 17) LVDT when the input gain of the funnel instrument amplifier is 0.8 (VIN0.8) is V17S0.8; this value is "permanently" stored in the microprocessor IC12 in the microprocessor unit 7 (STM32H750) memory. Then, other conditions remain unchanged, the microprocessor unit 7 integrates the analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (DG1606), IC25 (ADG1606) terminal pin "17" , 16, 15, 14" sends out the "1, 0, 0, 0" strobe signal, that is, the eighteenth (channel 18) LVDT sensor is selected; the input gain of the eighteenth LVDT in the funnel instrument amplifier is determined to be 0.8 ( The output at VIN0.8) responds to V18S0.8; this value is "permanently" stored in the memory of the microprocessor IC12 (STM32H750) in the microprocessor unit 7. Until the strobe signal changes to "1, 1, 1, 1,), that is, the output of the thirty-second (channel 32) connected to the LVDT sensor when the input gain of the funnel instrument amplifier is 0.8 (VIN0.8) is measured. Respond to V32S0.8 and save.

Initialization phase 2: When the initialization phase is executed, first, the microprocessor unit 7 sends a low level “0” (CS) to the “1, 9” enable terminals of the integrated analog switch IC17 (ADG1636), and then sends a low level “0” (CS) to the IC19 (ADG1636). The "1, 9" enable pin sends a high level (CS1), and the "1, 9" enable pin of the integrated analog switch IC26 (ADG1636) sends a high level (ENK). Send "0, 0" to the terminals "17, 16, 15, 14" of the integrated analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (ADG1606), C25 (ADG1606) ,0,0" logic level, send ENA enable signal as high level "1", send ENB enable signal as high level "0". Send "0, 0, 0" to the channel gate pins (1, 16, 15) of the integrated analog switch IC27 (ADG1408) (the selected gain is 2), and send it to the enable pin "2" of IC27 (ADG1408) High level "1". The above setting means: do not use extended 33~64 channels (when the enable pin "2" of IC27 (ADG1408) is low level "0", it means use extended 33~64 channels), select 1~16 channels in turn The first (channel 1) LVDT sensor, the input of the funnel instrument amplifier is set to 0.4 (VIN0.4) gain coefficient, the selected channel strobe and the default gain of the LVDT drive unit 2 are "2" times. The output response of a (channel 1) LVDT when the input gain of the funnel instrument amplifier is 0.4 is V1S0.4; this value is "permanently" stored in the memory of the microprocessor IC12 (STM32H750) in the microprocessor unit 7. Then, other conditions remain unchanged, the microprocessor unit 7 integrates the analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (DG1606), IC25 (ADG1606) terminal pin "17" , 16, 15, 14" send out the "1, 0, 0, 0" strobe signal, that is, select the second (channel 2) LVDT sensor; determine that the input gain of the second LVDT in the funnel instrument amplifier is 0.4 (VIN0. The output at 4) responds to V2S0.4; this value is "permanently" stored in the memory of the microprocessor IC12 (STM32H750) in the microprocessor unit 7. Until the strobe signal changes to "1, 1, 1, 1,), that is, the output response of the sixteenth (channel 16) connected to the LVDT sensor when the input gain of the funnel instrument amplifier is 0.4 (VIN0.4) is measured V16S0.4, and save.

Then, the microprocessor unit 7 sends a low level "0" (CS) to the "1, 9" enable terminal of the integrated analog switch IC17 (ADG1636), and sends a low level "0" (CS) to the "1, 9" enable terminal of IC19 (ADG1636) The pin sends a low level "0" (CS1), and sends a high level (ENK) to the "1, 9" enable pins of the integrated analog switch IC26 (ADG1636). Send "0, 0" to the terminals "17, 16, 15, 14" of the integrated analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (ADG1606), C25 (ADG1606) ,0,0" logic level, send ENA enable signal as high level "0", send ENB enable signal as high level "1". Send "0, 0, 0" to the channel gate pins (1, 16, 15) of the integrated analog switch IC27 (ADG1408) (the selected gain is 2), and send it to the enable pin "2" of IC27 (ADG1408) High level "1". The above setting means: do not use extended 33-64 channels (when the enable pin "2" of IC27 (ADG1408) is low level "0", it means use extended 33-64 channels), select 17-32 channels in turn The input of the seventeenth (channel 17) LVDT sensor and funnel instrument amplifier is set to 0.4 (VIN0.4) gain coefficient, the selected channel strobe and the default gain of the LVDT drive unit 2 is "2" times. The output response of the seventeenth (channel 17) LVDT when the input gain of the funnel instrument amplifier is 0.4 (VIN0.4) is V17S0.4; this value is "permanently" stored in the microprocessor IC12 in the microprocessor unit 7 (STM32H750) memory. Then, other conditions remain unchanged, the microprocessor unit 7 integrates the analog switch IC20 (ADG1606), IC21 (ADG1606), IC22 (ADG1606), IC23 (ADG1606), IC24 (DG1606), IC25 (ADG1606) terminal pin "17" , 16, 15, 14" sends out the "1, 0, 0, 0" strobe signal, that is, the eighteenth (channel 18) LVDT sensor is selected; the input gain of the eighteenth LVDT in the funnel instrument amplifier is determined to be 0.4( The output at VIN0.4) responds to V18S0.4; this value is "permanently" stored in the memory of the microprocessor IC12 (STM32H750) in the microprocessor unit 7. Until the strobe signal changes to "1, 1, 1, 1,", that is, the output of the thirty-second (channel 32) connected to the LVDT sensor when the input gain of the funnel instrument amplifier is 0.4 (VIN0.4) is measured. Respond to V32S0.4 and save.

Initialization phase three: During the initialization phase three, the microprocessor IC12 (STM32H750) in the microprocessor unit 7 calculates the above-mentioned data collected:

Among them: KN ~ the output response coefficient of the Nth sensor, N = 1, 2, ... 32. When the present invention is initialized and enters the normal measurement mode, the KN value determines the sensitivity of each connected sensor, determines the calculation method of the corresponding LVDT sensor output response, and determines the access gate low-noise preamplifier unit 3. Program-controlled gain Appropriate gain to be provided by unit 4. The present invention relates to the automatic calibration of various LVDT sensors. According to the SDVG20-VA product of Shenzhen Xinwei Technology Development Co., Ltd. whose range is 2.5 mm, this sensor has the highest sensitivity in the same series of products of the company, so it is connected to the gate The low-noise preamplifier unit 3 and the programmable gain unit 4 provide the lowest 2 times gain for it. Gain adaptive control is implemented through the following process: It is known that the microprocessor IC12 (STM32H750) in the microprocessor 7 stores the output response coefficients KS and VDCW values of the SDVG20-VA product with a range of 2.5 mm. The calculation is based on the aforementioned Self-adaptive and self-calibration methods can obtain the measured values of other connected LVDT sensors besides the general LVDT sensor.

When a certain LVDT sensor is connected to the system, and the output response coefficient KX is obtained after initialization. The gain calculation formula of the zero-drift instrument amplifier IC27 (INA188) connected to the gated low-noise preamplifier unit 3 is G=1+50KΩ/RG, where G is the gain, and RG is the set zero-drift instrument amplifier IC27 (INA188) ) External matching resistor for gain. In the present invention, the gain BX automatically corresponding to the gated low-noise preamplifier unit 3 is determined according to the KX value obtained when a certain sensor is initialized, and the zero-drift instrument amplifier IC28 (INA188) is selected by BX through the microprocessor calculation and judgment. The sensor should be provided with BN gain. The microprocessor selects the relevant channel of the integrated analog switch IC25 (ADG1636) according to the BN value. The output of the channel is connected to the corresponding resistor network in series, and the selected resistor network is zero. The external gain matching resistor of drift instrument amplifier IC28 (INA188). The microprocessor selects the relevant channels of the integrated analog switch IC25 (ADG1636) according to the following description: calculate αX=KX/KS (usually, always satisfy the relationship 1≤αX), according to αX, do βX=1/αX operation, βX is It is the gain coefficient required by the connected sensor. The microprocessor stores the coefficient βN (N=1, 2, ... 8) (β1, β2, β3, β4, β5, β6, β7, β8,) corresponding gain (2, 4, 8, 10, 15, 20) , 40, 81), compare βX, βN≤βX≤βN+1, if βX=βN or βN+1, then βX takes the value of βN or βN+1; if βN<βX<βN+1, then take the value of βN. The microprocessor IC12 (STM32H750) will always maintain these βX values unless it is reinitialized or restarted after a power failure. The microprocessor calculates the measured value of a certain connected LVDT sensor: assuming that the quantized reading value is converted into CN, the gated low-noise preamplifier unit 3 is connected to provide βN gain for it, and the actual initialization is βX, then the final measured value is corrected to CN ×(βX/βN).

As shown in Figure 10, the true effective value fast sampling unit 5 consists of integrated true effective value chip IC29 (AD8436), ultra-low output impedance integrated analog switch chip IC30 (ADG801), resistors R78, R79, R80, capacitors C64, It is composed of C65, C66, C67, C68, C69, and C70; it is used to quickly convert the output sine wave signal connected to the gated low-noise preamplifier unit 3 into a high-precision DC signal. The output (direct current signal) of the true effective value fast sampling unit 5 is connected to the A/D input terminal of the microprocessor unit 7. Traditionally, the phase-sensitive detection method is used to obtain the output signal of the LVDT sensor. Considering the high-precision signal processing occasions, the phase-sensitive detection method requires the use of crystal diodes in the circuit, and the disadvantageous characteristics of the diodes in small signal processing (forward voltage drop, drift of forward voltage drop with ambient temperature), which is really effective Fast value sampling can effectively avoid the disadvantages of phase-sensitive detection. In the present invention, the integrated true effective value conversion chip AD8436 is used to convert the sine wave into direct current. In order to ensure that the integrated true effective value conversion chip AD8436 outputs a low-noise DC signal, it is necessary to add a filtering link with a larger inertia coefficient at its output end, which will affect the subsequent A/D sampling sampling rate. In order to solve the contradiction between high-precision signal processing and fast sampling, the present invention adopts a method of quickly releasing stored charge for the inertial element network connected in series at the output end of the integrated true effective value conversion chip AD8436: the implementation method is to use a piece of output impedance of only 0.4Ω Integrated analog switch chip IC29 (ADG801), after the microprocessor completes the A/D conversion of the low-noise DC signal output from the true RMS conversion chip AD8436, quickly releases the inertial filter network connected to the output terminal of the true RMS conversion chip AD8436 The residual voltage. Through this technical means, the sampling rate can be increased from 1HZ/sec to 1KHz/sec.

As shown in FIG. 12, the motion direction determining unit 6 is used to determine the motion direction of the armature when the LVDT sensor receives an external force. The present invention uses the VOA and VOB signals obtained from the double-ended output response of the LVDT sensor with respect to the circuit reference ground to determine the direction of armature movement: the double-ended output response of the LVDT sensor VOA-VOB is used as a differential signal for data measurement, VOA It is two signals with the same output phase as VOB. The LVDT sensor consists of an excitation input line package and two identical output line packages TA and TB. The two output line packages TA and TB are symmetrically located on the two sides of the input excitation line package. Suppose their outputs to the circuit reference ground are VOA and VOB respectively. When the midpoint of the armature is at the midpoint of the excitation line package of the LVDT sensor, the output response VOA and VOB are differentially processed, and the output is zero at this time; when the armature moves away from the midpoint to the TA direction under the action of external force, the VOA output amplitude Increase, the VOB output amplitude decreases. Therefore, the movement direction of the armature can be judged by using the positive or negative half-wave of VOA and VOB: when the full-wave rectification value of VOA minus the full-wave rectification value of VOB is greater than zero, the armature moves toward TA, and vice versa. In the example, in order to minimize the impact on the measurement data, the VOA and VOB signals are respectively integrated with operational amplifiers IC31: A (OPA1654) and IC31: D (OPA1654) for in-phase follow-up processing with high impedance input. Integrated operational amplifier IC31: B (OPA1654), IC31: C (OPA1654), resistors R81, R82, R83, R86, R87, R88, diodes D15, D16, D17, D18 constitute a two-way precision rectifier circuit, for the integrated operational amplifier The outputs of IC31: A (OPA1654) and IC31: D (OPA1654) are respectively subjected to precision full-wave rectification, which changes bipolar sine waves into two pulsating DC signals. The integrated operational amplifier IC32 (AD8638), resistors R84, R85, R89, and R90 constitute a differential proportional amplifier. Two pulsating DC signals VDA and VDB enter the non-inverting and inverting ends of the integrated operational amplifier IC32 (AD8638) through resistors R84 and R89, respectively. end. After the two-channel pulsating DC signal is processed by the proportional difference formed by the integrated operational amplifier IC32 (AD8638), the output signal is used as the input signal of the quasi-zero-crossing comparator formed by the integrated comparator IC33: A (LM293). When VOA-VOB is greater than zero, the integrated comparator IC33: A outputs a high level "1", otherwise, it outputs a low level "0", thus realizing the movement direction judgment of the armature.

As shown in Figure 13 and Figure 14, the microprocessor unit 7 is composed of microprocessor IC14 (STM32F750), high-precision integrated reference source IC13 (ADR4530), reset switch K2, capacitors C47, C48, C49, C50, C51 , C52, C53, C54, C55, C56, C57, resistance R40, R41, R42, R43, R44, R45, Zener diode W2 (2AP9), W3 (2AP9), W4 (2AP9), W5 (2AP9), W6 (2AP9), W7 (2AP9), crystal oscillator JZ1 (32.768KHz), JZ2 (25MHz). The microprocessor unit 7 is used to complete data interaction and macro control of all system operations, such as access channel gating control, sensor sensitivity calibration, adaptive gain control, communication module information interaction and control, and touch screen interaction.

As shown in Figure 11, the display and communication unit 8 of the present invention is equipped with a touch LCD screen to form a human-computer interaction function, and uses the microprocessor IC12 (STM32F750) resource port "89, 90" terminal pins (RX1, TX1). The present invention is equipped with GPRS serial port, using IC12 (STM32F750) resource port "51, 52" terminal pins (RX3, TX3); the present invention is configured with RS485 serial port, using IC12 (STM32F750) resource port "53, 54" terminal pins (RX2) , TX2); The present invention is equipped with a LORA module, using IC12 (STM32F750) resource port "46, 47" terminal pins (RX4, TX4).

As shown in Figure 15 to Figure 18, the conversion power supply 9 consists of integrated boost conversion chips IC4 (TPS55340), IC5 (TPS55340), integrated low dropout chips IC6 (ADP3330-5), IC7 (ADP3330-5), integrated Step-down chip IC8 (LM2594), integrated polarity conversion chip IC9 (TPS63700), negative power low dropout chip IC10 (LT19645-5), chip power inductors L4, L5, L6, L7, resistors R27, R28, R29, R30 , R31, R32, R33, R34, R35, R36, R37, R38, capacitors C18, C18, C20, C20, C20, C20, C20, C20, C20, C20, C20, C20, C30, C30, C30, C30, C30, C30, C30, C30, C30, freewheeling diode D11, D12, D13, D14, switch K1 and other components; provide the required +5P, +5.0, +5D, -5.0, +3.3 volt stability for each component power supply DC power supply. The input voltage of the conversion power source 9 is 3 to 4.2 volts (that is, the output of a single set of lithium battery packs). Among them, +5P provides a DC unit with an output current of up to 1.5A for the large-screen touch LCD screen and GPRS remote wireless communication module; +5.0 and -5.0 provide high stable operating power for the linear circuit of the present invention; +5D is the digital circuit of the present invention Partially provide DC stabilized power supply; +3.3 provides working power supply for the processor.

The hybrid charging unit 10 adopts an AC adapter and a solar power generation method to perform hybrid charging for the lithium battery pack configured in the system. In the charging sequence, the AC adapter is in a priority mode. Generally, the high-capacity lithium battery pack (full charge 4.2V 37.2AH) configured for the system can maintain the normal operation of the system for one month without energy compensation; during this period, the battery pack can be fully charged in only two sunny days. In principle, there is no need for human intervention in the power supply of the system. In special circumstances, an AC adapter can be used to charge the battery pack. When an AC adapter is used to charge the battery pack, the hybrid charging unit will automatically block the solar power output.

As shown in Figure 19, the solar charging part of the hybrid charging unit 10 is composed of a solar charging chip IC1 (BQ24650), resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, capacitors C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, fuses F1, F2, crystal diodes D1 (SS510), D2 (SS510), D3 (SS15), Power field effect tube BG1 (IRF7351), chip power inductor L1, negative temperature coefficient thermistor R8, light-emitting diodes LD1 and LD2. The solar charging part uses a solar panel with an open circuit output voltage of 21.5 volts and a normal output power of 20 watts to charge a 37.2 AH, 4.2 volt lithium battery pack.

As shown in Figure 20, the AC-DC conversion part consists of a single-chip AC-DC conversion chip IC2 (TOP266), three-terminal regulator (TL431), resistors 14, 15, 16, 17, 18, 19, R20, R21, R22, R23, R24, R25, R26, capacitors C12, C13, C14, C15, C16, C17, electrolytic capacitors E1, E2, E3, E4, E5, fuse F3, inductance L2, L3, high frequency transformer T1, linear Optocoupler OP1 (TLV817), crystal diodes D4, D5, D6, D7, D8, D9, D10, transient voltage regulator W1 (P6KE200) and other components. Under normal circumstances, the solar charging part provides the charging power for the lithium battery pack. If solar charging is not available for a long time, you can use an AC-DC adapter to charge; the output of the adapter is designed to be 24 volts, so when the adapter is connected, it will pass the protection Reverse-biased diodes D1 and D2 automatically block the output of solar energy.

The method provided by the present invention realizes the monitoring of high-precision engineering micro-strains, micro-scale changes, mechanical quantities, etc. using various LVDT sensors, and provides a convenient calibration method for occasions where LVDTs are used in a large number of checkpoints, which greatly reduces The cumbersome high-precision calibration of a large number of LVDT sensors provides a fast, high-precision adaptive measurement method for automatic monitoring and detection occasions. The invention is especially suitable for the occasions where the environment of engineering monitoring, nuclear facilities (equipment), aviation equipment, engine, etc. is harsh, requiring high-precision and rapid measurement.

Claims (20)

1. Multi-channel adaptive high-precision LVDT data acquisition and measurement system, which is characterized by including a constant frequency and constant amplitude signal generation unit, channel gating and LVDT drive unit, access gating low-noise preamplifier unit, programmable gain unit, true effective Value fast sampling unit, motion direction determination unit and microprocessor unit, the output end of the constant frequency and constant amplitude signal generating unit is connected to the input end of the channel gating and LVDT driving unit, and the channel gating and LVDT driving The output end of the unit is connected to the input end of the access gated low noise preamplifier unit, and the output end of the access gated low noise preamplifier unit is respectively connected to the input end of the true effective value fast sampling unit Is connected to the input terminal of the motion direction determination unit, the output terminal of the true effective value rapid sampling unit and the output terminal of the motion direction determination unit are respectively connected to the input terminal of the microprocessor unit, and the micro-processing The output terminal of the amplifier unit is respectively connected to the input terminal of the channel gating and LVDT drive unit and the input terminal of the programmable gain unit, and the output terminal of the programmable gain unit and the access gate low-noise preamplifier The input terminal of the unit is connected.
2. The multi-channel adaptive high-precision LVDT data acquisition and measurement system according to claim 1, wherein the constant frequency and constant amplitude signal generating unit includes an integrated analog switch and a zero-drift operational amplifier, and the microprocessor unit outputs The square wave signal controls the on and 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. The zero-drift operational amplifier is connected to the integrated analog switch for connecting The square wave signal with constant frequency and constant amplitude is converted into a bipolar sine wave signal with constant frequency and constant amplitude.
3. The multi-channel adaptive high-precision LVDT data acquisition and measurement system according to claim 2, wherein the channel gating and LVDT drive unit includes an integrated analog switch and an integrated funnel instrument amplifier, and the microprocessor unit controls The integrated analog switch connects a bipolar sine wave signal of constant frequency and constant amplitude to the input end of the integrated funnel instrument amplifier, so that the microprocessor unit can obtain the response coefficient of the connected LVDT sensor.
4. The multi-channel adaptive high-precision LVDT data acquisition and measurement system according to claim 3, wherein the access gate low-noise preamplifier unit comprises a zero-drift low-noise variable gain instrument amplifier and a resistor, and The microprocessor unit selects a gain-matched resistor 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.
5. The multi-channel adaptive high-precision LVDT data acquisition and measurement system according to claim 4, wherein the true effective value fast sampling unit includes an integrated true effective value chip, which is used to gate the access before low noise The output sine wave signal of the set amplifying unit is quickly converted into a high-precision DC signal.
6. The multi-channel adaptive high-precision LVDT data acquisition and measurement system according to claim 1, wherein the motion direction determination unit includes three integrated operational amplifiers and one integrated comparator, and two LVDT sensors output two The signals are respectively amplified by the integrated operational amplifier, the two amplified signals are proportionally differentiated by the other integrated operational amplifier, and the output signal of the integrated operational amplifier is used as the quasi-zero-crossing comparator formed by the integrated comparator. input signal.
7. The multi-channel adaptive high-precision LVDT data acquisition and measurement system according to claim 1, further comprising a display and communication unit connected to the microprocessor unit.
8. The multi-channel adaptive high-precision LVDT data acquisition and measurement method is characterized in that it includes: acquiring a clock signal; collecting the output signal of the sensor after sensitivity correction based on the clock signal; and obtaining the detection information of the sensor based on the output signal, The detection information includes the measured value and the direction of movement; wherein, the sensor is an LVDT sensor.
9. 8. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 8, wherein said acquiring the clock signal comprises: setting working parameters; and obtaining the clock signal based on the working parameters.
10. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 9, wherein the setting of the working parameters includes one of the following ways: JTAG interface setting working parameters; human-computer interaction setting working parameters ; GPRS remote wireless data interaction to set working parameters.
11. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 9, wherein the working parameters include one or more combinations of the following methods: number of sensors, acquisition frequency, acquisition time, measurement value Alarm information of the upper and lower limits.
12. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 8, wherein the clock signal is a frequency-stabilized signal obtained by frequency division of a crystal oscillator.
13. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 8, wherein the collecting the output signal of the sensor after the sensitivity is corrected based on the clock signal comprises: obtaining the excitation signal of the sensor.
14. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 13, wherein said acquiring the excitation signal of the sensor comprises: chopping a reference source to obtain a digital signal; and extracting the digital signal The fundamental wave; amplify the fundamental wave to obtain the excitation signal of the sensor.
15. 8. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 8, wherein said obtaining the measurement value of the sensor based on the output signal comprises: amplifying the output signal to obtain the measurement signal; purifying the measurement signal; Convert the measurement signal to a DC signal.
16. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 8, wherein said obtaining the movement direction of the sensor based on the output signal comprises: comparing the response signal based on the two-terminal output of the sensor , To obtain the movement direction information of the sensor.
17. 16. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 16, wherein the comparison of the two-terminal output response signals of the sensor comprises: amplifying the difference of the comparison of the two two-terminal output response signals.
18. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 8, wherein said calibrating the sensitivity of the sensor comprises: adjusting the sensitivity of the sensor to be equal to a standard value, wherein the The standard value is set.
19. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 18, wherein said adjusting the sensitivity of the sensor to be equal to a standard value comprises: adjusting a magnification corresponding to the sensitivity of the sensor.
20. The multi-channel adaptive high-precision LVDT data acquisition and measurement method according to claim 19, wherein said adjusting the magnification corresponding to the sensitivity of the sensor comprises: switching a selection resistor and adjusting the magnification.

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