CN1321315C - Flexible strain signal spot colletion system - Google Patents

Flexible strain signal spot colletion system Download PDF

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Publication number
CN1321315C
CN1321315C CNB2005100402706A CN200510040270A CN1321315C CN 1321315 C CN1321315 C CN 1321315C CN B2005100402706 A CNB2005100402706 A CN B2005100402706A CN 200510040270 A CN200510040270 A CN 200510040270A CN 1321315 C CN1321315 C CN 1321315C
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China
Prior art keywords
reed switch
bridge
switch relay
resistance
programmable amplifier
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Expired - Fee Related
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CNB2005100402706A
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CN1693838A (en
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郭万林
冯谦
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Nanjing University of Aeronautics and Astronautics
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Nanjing University of Aeronautics and Astronautics
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Abstract

The present invention relates to a flexible strain signal on-site collecting system which belongs to the fields of testing and measuring techniques and communication techniques. The system has the function of flexible Wheatstone bridge configuration and a field bus interface. The present invention is mainly composed of a flexible bridge configuring module composed of a plurality of standard resistors and a reed tube relay, a two-stage program control amplifier, a high precision analog-to-digital converter, a DSP module, a field bus and other modules, wherein collected strain signals or other forms of voltage signals are accessed into the flexible bridge configuring module, and bridged and amplified signals are converted to digital signals after entering the analog-to-digital converter; the signals are transmitted to a host computer through the field bus interface after being processed by the DSP module. The present invention has the advantages of advanced technique, small volume and good applicability, and can be used for the measurement and signal collection of strain foil with various resistance values and the collection of other forms of voltage signals; moreover, the field bus interface can be used for forming a data collecting network.

Description

Flexible strain signal spot colletion system
Technical field
The invention belongs to thermometrically technology, communication technical field, be specifically related to a kind of flexible strain signal spot colletion system, have the Wheatstone bridge configuration feature and the field-bus interface of flexibility.
Background technology
Strain measurement is one of experimental technique that most widely used general and practicality is the strongest in the structure analysis, metal forming formula foil gauge is widely used in various occasions, as Experiments of Machanics, highway bridge detection, weighing technology, and the full machine test of aircraft, and dynamic strain measurement, even impact and acceleration analysis.Generally need form electric bridge (as the direct current Wheatstone bridge) to the measurement of foil gauge and carry out, general, strainmeter all adopts precision measurement resistance to form brachium pontis, and manual adjustment and selection resistance are formed needed electric bridge form.When foil gauge resistance or electric bridge form change, must readjust electric bridge.This gathers when larger at strain signal, and the group bridge, to adjust workload big, in case the also difficulty of investigation that breaks down.Also there is the shortcoming that volume is big, be unfavorable for networking formation distributed capture in traditional strain testing measurement means.
In metering circuit, usually need with sensor to signal amplify, but take into account under the situation of big dynamic range and higher signal precision, use the amplifier of fixed gain to be difficult to satisfy the requirement of expecting, use gain-programmed amplifier then can satisfy this requirement well.Neither can be too little because of input signal, amplifier " is owed range ", causes and lose more valid data position when analog to digital conversion, influences measuring accuracy, also can not cause amplifier " overrange " owing to input signal is bigger, causes distorted signals.This is particularly important in intelligence instrument.
What the hardware systems framework mode of signals collecting and processing adopted substantially is the scheme of " measuring and controlling card+industrial computer ", promptly inserts in the industrial computer with ready-made signals collecting integrated circuit board.This mode has good stability, advantages such as highly versatile.But the equipment volume of this mode is generally bigger, and the collection scale is that port number is generally less.When collection was larger, equipment volume was a lot, system complex, and expense is higher.
Fieldbus is the product that computer network adapts to the industry spot environment.Fieldbus, connects with bus as network node with single dispersion, digitizing, intelligentized measurement and opertaing device, realizes information exchange, be a new generation digital, disperse and on-the-spot TT﹠C system that standard-sized sheet is put entirely.Field bus technique has layout networking, transmitting digitized, characteristics such as instrument is intelligent, observing and controlling is decentralized, receives worldwide concern, becomes the focus that develops in the industrial measurement and control field.
Summary of the invention
The present invention is a kind of flexible strain signal spot colletion system, has the Wheatstone bridge configuration feature and the field-bus interface of flexibility.The present invention is directed to the thermometrically of resistance strain gage and design, purpose is to realize being applicable to flexibly, flexibly measurement and the signal acquisition method and the system of the direct current Hui Sideng wheatstone bridge of multiple resistance foil gauge commonly used, half-bridge, full-bridge form.By control electric bridge form and programmable amplifier gain, this system also can be used for the collection of other form voltage signals.Its field-bus interface makes it can form collection network easily, as large-scale distributed data acquisition system (DAS).
Flexible strain signal spot colletion system of the present invention, comprise the two-way respectively CAN of being connected in bus interface of DSP module and analog to digital converter, the output of DSP module also links to each other with control flexibility bridge arrangement module, first order programmable amplifier and second level programmable amplifier respectively, the flexibility bridge arrangement module that receives input signals such as strain signal or voltage signal is connected in first order programmable amplifier input end, the output terminal of first order programmable amplifier is connected in the input end of second level programmable amplifier, and the output terminal of second level programmable amplifier links to each other with analog to digital converter.Flexibility bridge arrangement module is made up of some measuring resistances and reed switch relay, wherein measuring resistance is a high-acruracy survey resistance, its resistance is identical with the resistance of several foil gauges commonly used, reed switch relay is used for the different measuring resistance of gating, realizes the measurement under the multiple electric bridge form of multiple resistance.The feeble signal conditioning that the two-stage programmable amplifier is used to make electric bridge output is to the follow-up analog to digital converter allowed band, wherein, require the gain combination of two-stage programmable amplifier to have at least a kind of for " 1 ", so that this unit also can be used for the collection of other form voltage signals.
The principle of work of native system is, strain signal of being gathered or other forms of voltage signal insert flexibility bridge arrangement module, signal after electric bridge and programmable amplifier amplify enters analog to digital converter and converts digital signal to and send into the DSP module, after the DSP resume module, send to host computer by the CAN bus interface.
The present invention is a kind of flexible strain signal spot colletion system, Wheatstone bridge configuration feature and field-bus interface with flexibility, the measurement and the signals collecting of the direct current Hui Sideng wheatstone bridge of the multiple resistance foil gauge that is suitable for using always, half-bridge, full-bridge form, and the collection of other form voltage signals.Because this unit possesses fieldbus (CAN bus) interface, thereby can form large-scale distributed data acquisition network easily.With measuring and controlling card+industrial computer " scheme compare, this unit also has the little lightweight advantage of volume.
Description of drawings
Fig. 1 flexible strain signal spot colletion system structured flowchart.
The circuit theory diagrams of Fig. 2 flexibility wheatstone bridge configuration module.
The circuit theory diagrams of Fig. 3 flexibility half-bridge bridge arrangement module.
The circuit theory diagrams of Fig. 4 flexibility full-bridge bridge arrangement module.
Designation is respectively among Fig. 2~Fig. 4 :+E ,-E is the generating positive and negative voltage of bridge power supply ,+Uo ,-Uo is an electric bridge output generating positive and negative voltage, R 2A, R 2B, R 2C, R 2DBe the measuring resistance of different resistances, R 3, R XBe the measuring resistance with resistance, S 1~S 9Be reed switch relay.
The program control amplification module theory diagram of Fig. 5 two-stage
The interface principle figure of Fig. 6 analog to digital converter and DSP
Fig. 7 flexibility bridge arrangement module embodiment circuit diagram.Among the figure: RL4_1~RL4_9 is a reed switch relay, R 2A, R 2B, R 2C, R 2DBe the measuring resistance of different resistances, R 3, R 4Be the measuring resistance with resistance, R 5, R 6Be resistance, Q51 is a triode, and U51 is a high performance operational amplifier, and U52 is a reference voltage source.
The program control amplification module embodiment of Fig. 8 two-stage circuit diagram.Among the figure: U21, U22 be the different instrument amplifier of parameter for structure is identical, and U23, U24 are identical high performance operational amplifier.
Fig. 9 high precision analogue modular converter embodiment circuit diagram.Among the figure: U31 is an analog to digital converter, and U32 is a reference voltage source, and Y2 is a crystal oscillator.
Embodiment
Structured flowchart of the present invention adopts the dsp chip TMS320LF2407A of Texas Instruments to make the control core as shown in Figure 1, and peripheral circuit has modules such as flexibility bridge arrangement, the program control amplification of two-stage, analog to digital conversion, CAN bus interface.The outside foil gauge that inserts, or voltage signal inserts the bridge arrangement module, enters programmable amplifier then, handled by DSP after analog to digital conversion, and with packing data after the CAN bus transfer is given host computer.The mode of operation and the parameter of flexibility electric bridge and programmable amplifier are controlled by DSP, and DSP can accept the steering order of host computer.
1) CAN bus interface
Realize the transmission of data, steering order and status information between unit of the present invention and PC with the two-way CAN bus interface that links to each other of DSP module, and form collection network simple in structure, that cost is low, reliability is high.The CAN bus network adopts the inner integrated CAN2.0B bus controller of DSP and the CAN bus transceiver SN65HVD230 of TI company to realize.
The SN65HVD230 chip is a CAN bus transceiver of TI company, and the 3.3V operating voltage is suitable for being used in the dsp system of TI.SN65HVD230 mainly contains three kinds of mode of operations: fast mode, standby mode, slope control model.Adopted slope control model cheaply in the present invention.
2) flexibility bridge arrangement
Be connected in the flexibility bridge arrangement module of DSP module and programmable amplifier respectively, utilize precision resistance and reed switch relay to form as Fig. 2, Fig. 3, electric bridge shown in Figure 4, the feeble signal of electric bridge output is measured after amplification.Symbol among the figure :+E ,-E represent respectively electric bridge for bridge (excitation) positive voltage and negative voltage ,+Uo ,-Uo is that electric bridge is exported positive voltage and negative voltage, S 1~S 9Be reed switch relay.R 3, R 4Be the measuring resistance of similar resistance, when wheatstone bridge measurement and half bridge measurement, use, form half equal arm bridge.R 2A, R 2B, R 2C, R 2DBe the measuring resistance of different resistances, wheatstone bridge used when measuring, and the foil gauge resistance that is inserted must be wherein a kind of, as 120 Ω, 350 Ω etc.
Shown in Figure 2 is the circuit theory diagrams of flexibility wheatstone bridge configuration module, and the composition of its circuit is that bridge power supply output constitutes two shunt circuits; One routing power positive pole+E is through the same resistance resistance R of two series connection 3With R 4The back links to each other with power cathode-E and forms a loop; Another routing power positive pole+E is connected in a reed switch relay S through foil gauge 2After link to each other with power cathode-E again and form another loop, four different resistance measuring resistance R 2A, R 2B, R 2C, R 2DFour series circuits that the reed switch relay of connecting is separately formed are connected in parallel on reed switch relay S separately 2Two ends; On two serial connection points, meet a reed switch relay S with resistance resistance 1, electric bridge output plus terminal and the electric bridge output negative terminal reed switch relay of respectively hanging oneself is connected in first order programmable amplifier.S 1~S 9The closure or openness state see Table 1.
Shown in Figure 3 is the circuit theory diagrams of flexibility half-bridge configuration module, with the difference of Fig. 2 is that foil gauge makes the metering circuit that two foil gauges of connecting are formed the half-bridge form in second loop, next is to have removed four parallel resistances of the different resistance measuring resistances in the frame of broken lines among the figure, and S 1~S 9The closure or openness state see Table 1.
Shown in Figure 4 is the circuit theory diagrams of flexibility full bridge configuration module, is no longer through two same resistance resistance R of connecting in first loop with the difference of Fig. 2 and Fig. 3 3With R 4, but through the foil gauge 3 and the foil gauge 4 of two series connection; Through behind the foil gauge 1 and foil gauge 2 of other two series connection, converge with first loop, in second loop through reed switch relay S 2Be connected in the electric bridge negative pole, therefore, this circuit has not only removed by two with resistance measuring resistance R 3With R 4(the R among the figure in the frame of broken lines 3With R 4) the back loop of forming of series connection, also removed the parallel circuit of the different resistance measuring resistances in the frame of broken lines among the figure simultaneously, and S 1~S 9The closure or openness state see Table 1.
By the open and close of control analog switch, can realize strain measurement among the above-mentioned figure to the multiple resistance resistance strain gage of different electric bridge forms, and the measurement of other voltage signals.When measuring as the wheatstone bridge of Fig. 2, insert 1 foil gauge from the outside, establishing the measuring resistance of mating with its resistance is R 2A, reed switch relay S then 1, S 3, S 7, S 8Closure, other unlatchings.As what carry out is not the strain-ga(u)ge transducer signals collecting, or the electric bridge form signals collecting of other types sensor, but directly inserts the voltage-type signal, then reed switch relay S 7, S 8Closure, S 1, S 9Open.
Table 1 is measured the corresponding relation of the state of type and analog switch
(" X "---two states all can for " 1 "---closed condition, " 0 "---opening.)
Measure type S 1 S 2 S 3 S 4 S 5 S 6 S 7 S 8 S 9
Full-bridge 0 1 0 0 0 0 1 1 0
Half-bridge 1 1 0 0 0 0 1 1 0
Single armed R 2A 1 0 1 0 0 0 1 1 0
Single armed R 2B 1 0 0 1 0 0 1 1 0
Single armed R 2C 1 0 0 0 1 0 1 1 0
Single armed R 2D 1 0 0 0 0 1 1 1 0
Shown in Figure 7 is the circuit diagram of the embodiment of flexibility bridge arrangement module, and RL4_1~RL4_9 is a reed switch relay among the figure, R 3, R 4Be the measuring resistance of similar resistance, R 2A, R 2B, R 2C, R 2DBe the measuring resistance of different resistances, R 5, R 6Be resistance, Q51 is a triode, and U51 is a high performance operational amplifier, and U52 is a reference voltage source.
3) two-stage programmable amplifier
The first order that links to each other with the DSP module and second level programmable amplifier use digital programmable gain instrument amplifier PGAxxx to form two-stage amplifier respectively, its multistage variation in 1~8000V/V scope that gains, the output signal of electric bridge inserts first order programmable amplifier, and (Fig. 2~Fig. 4), the signal after the amplification enters analog to digital converter conversion after low-pass filtering.The two-stage programmable amplifier theory diagram of forming as shown in Figure 5.
PGAxxx is the digital gain instrumentation amplifier of compiling, have low maladjustment voltage, high input impedance, high cmrr and low noise, it is high performance programme-controlled instrument amplifier, be applied to the very high long numeric data acquisition system of work under bad environment and accuracy requirement, be particularly suitable for process control, instrument, data processing and Medical Instruments.Its gain is controlled after driving by digital input and output (I/O) port of DSP in the present invention by the logic level decision of A0, A1 two pins.
Fig. 8 is the circuit diagram of two-stage programmable amplifier, and U21, U22 are digital programmable gain instrument amplifier among the figure, and U23, U24 are identical high performance operational amplifier.After being the instrument amplifier series connection, its output exports analog to digital converter to through low-pass filter circuit.
4) analog to digital converter
The signal of amplification and filtering circuit output changes the receptible digital signal of DSP into through analog to digital converter.This unit is selected ADxxxx for use, and it is for 24 high precision ∑s of the 4 passages-Δ pattern number converter of band SPI (Setial Peripheral Interface) serial line interface, with it Pin inserts external interrupt 1 (XINT1) pin of DSP, and by the startup of the cycle interruption control transformation of DSP.Its theory diagram as shown in Figure 6, circuit diagram is as shown in Figure 9.U31 among the figure is an analog to digital converter, adopts the ADxxxx chip, and U32 is a reference voltage source, and Y2 is a crystal oscillator.DSP selects the TMS320LF2407A chip
The present invention is a kind of flexibility strain signal collection in worksite unit, Wheatstone bridge configuration feature and field-bus interface with flexibility, the measurement and the signals collecting of the direct current Hui Sideng wheatstone bridge of the multiple resistance foil gauge that is suitable for using always, half-bridge, full-bridge form, and the collection of other form voltage signals.Because this unit possesses fieldbus (CAN bus) interface, thereby can form large-scale distributed data acquisition network easily.With measuring and controlling card+industrial computer " scheme compare, this unit also has the little lightweight advantage of volume.

Claims (5)

1. flexible strain signal spot colletion system, it is characterized in that, comprise the two-way respectively CAN of being connected in bus interface of DSP module and analog to digital converter, the DSP module is also controlled respectively and is connected in flexibility bridge arrangement module, first order programmable amplifier and second level programmable amplifier, the flexibility bridge arrangement module that receives the input signal of strain signal or voltage signal is connected in first order programmable amplifier input end, the output terminal of first order programmable amplifier is connected in the input end of second level programmable amplifier, and the output terminal of second level programmable amplifier links to each other with analog to digital converter.
2. flexible strain signal spot colletion system according to claim 1, it is characterized in that, the wheatstone bridge circuit of flexibility bridge arrangement module, bridge power supply output constitutes two shunt circuits: the routing power positive pole loop of formation that links to each other with power cathode behind the same resistance resistance of two series connection; Another routing power positive pole links to each other with power cathode after foil gauge is connected in a reed switch relay S2 again and forms another loop; Four series arms being made up of the measuring resistance of four different resistances all are connected in parallel on above-mentioned reed switch relay S2 two ends, and the composition of these four series arms is respectively: measuring resistance R 2ASeries connection reed switch relay S 3Measuring resistance R 2BSeries connection reed switch relay S 4Measuring resistance R 2CSeries connection reed switch relay S 5Measuring resistance R 2DSeries connection reed switch relay S 6, two with the serial connection of resistance resistance o'clock through a reed switch relay S 1Be connected in the electric bridge output plus terminal, the electric bridge output plus terminal is through reed switch relay S 7After be connected in first order programmable amplifier, electric bridge output negative terminal is through reed switch relay S 8After be connected in first order programmable amplifier equally.
3. flexible strain signal spot colletion system according to claim 1, it is characterized in that, the half-bridge circuit of flexibility bridge arrangement module, bridge power supply output constitutes two shunt circuits: the routing power positive pole loop of formation that links to each other with power cathode behind the same resistance resistance of two series connection; Another routing power positive pole is connected in a reed switch relay S through the foil gauge of two series connection 2The back links to each other with power cathode and forms another loop; Two with the serial connection of resistance resistance o'clock through a reed switch relay S 1Be connected in the electric bridge output plus terminal, the electric bridge output plus terminal is through tongue tube electrical equipment S 7After be connected in first order programmable amplifier; Electric bridge output negative terminal is through reed switch relay S 8After be connected in first order programmable amplifier equally.
4. flexible strain signal spot colletion system according to claim 1 is characterized in that, the full-bridge circuit of flexibility bridge arrangement module, and bridge power supply output constitutes two shunt circuits: loop is the foil gauge through two series connection; Through behind the foil gauge of other two series connection, converge with first loop, in another loop through a reed switch relay S 2Be connected in power cathode; At the electric bridge output plus terminal through reed switch relay S 7After be connected in first order programmable amplifier, electric bridge output negative terminal is through reed switch relay S 8After be connected in first order programmable amplifier equally.
5. flexible strain signal spot colletion system according to claim 1 is characterized in that: the DSP module of this system has connected the CAN bus that is used for field network communication.
CNB2005100402706A 2005-05-27 2005-05-27 Flexible strain signal spot colletion system Expired - Fee Related CN1321315C (en)

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