CN210111604U - Lightning protection circuit for signal interface of vibrating wire type acquisition instrument - Google Patents
Lightning protection circuit for signal interface of vibrating wire type acquisition instrument Download PDFInfo
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- CN210111604U CN210111604U CN201922371291.6U CN201922371291U CN210111604U CN 210111604 U CN210111604 U CN 210111604U CN 201922371291 U CN201922371291 U CN 201922371291U CN 210111604 U CN210111604 U CN 210111604U
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Abstract
The utility model relates to a appearance signal interface lightning protection circuit is gathered to vibration wire formula, including vibration wire formula sensor, first order GDT protective device, decoupling device, second grade TVS pipe protective device, anti surge protection earthing device, protected back stage circuit, by first order GDT protective device, decoupling device, the anti surge protection circuit of the full differential vibration wire signal that second grade TVS pipe protective device constitutes, bear the surge pulse of response on the vibration wire formula sensor signal line, prevent that surge pulse from damaging by protected back stage circuit, and protect the surge energy through anti surge protection earthing device. The technical scheme is designed into a two-stage surge protection circuit from the perspective of the electrical characteristics of the vibrating wire signal and the requirements of a rear-stage protection circuit, has small volume and low cost, is completely matched with the surge protection requirements of the vibrating wire signal and a vibrating wire acquisition system in theoretical design, and completely meets the surge protection requirements of LPZ0B-3 in an actual surge level test.
Description
Technical Field
The utility model relates to a civil engineering field is applied to structure safety and health monitoring trade, and more specifically says, relates to a appearance signal interface lightning protection circuit is gathered to vibration wire formula.
Background
At present, the application environments of vibrating wire sensors are basically outdoor and outdoors, such as bridges, dams, slopes and the like, and the application environments cannot avoid the influence of thunderstorm weather, particularly thunder. The influence of lightning on the vibrating wire type data acquisition system is mainly induced lightning, and the induced lightning can generate surge pulse on a signal cable from the vibrating wire type sensor to the vibrating wire type acquisition instrument, so that a signal interface of the vibrating wire type acquisition instrument can be damaged due to the surge, and equipment failure is caused. At present, most of sensor signal interface parts of the vibrating wire acquisition instruments only provide one-level TVS tube protection or even do not have a protection device, the protection grade is weaker, and along with the fact that the reliability of the system is higher and higher in requirement on structural safety monitoring, the surge impact resistance of a data acquisition system is higher and higher in requirement. Except taking into account the protection for the wave inside the collection appearance, also there is the dedicated external lightning protection ware of adoption to protect at present, but external lightning protection ware has several problems: 1. the price is high, the volume is large, and the system integration is inconvenient; 2. wiring is troublesome, and large workload is brought to field engineering installation personnel; 3. the compatibility is poor, and general external special signal lightning protection devices are all designed aiming at special protection of some industrial common signals such as RS485 and the like, and do not have special modules aiming at vibration-string interfaces, so if the matching is not good, not only the protection effect cannot be achieved, but also normal signal measurement can be caused to cause problems.
SUMMERY OF THE UTILITY MODEL
To the problem that exists among the prior art, the utility model aims to provide a appearance signal interface lightning protection circuit is gathered to vibration wire formula to solve the technical problem who mentions in the background art.
In order to solve the above problems, the utility model adopts the following technical proposal.
A lightning protection circuit for a signal interface of a vibrating wire type acquisition instrument comprises a vibrating wire type sensor, a first-stage GDT protection device, a decoupling device, a second-stage TVS tube protection device, an anti-surge protection grounding device and a protected rear-stage circuit, wherein the anti-surge protection circuit for a fully differential vibrating wire signal consists of the first-stage GDT protection device, the decoupling device and the second-stage TVS tube protection device, bears surge pulses induced on a signal line of the vibrating wire type sensor, prevents the surge pulses from damaging the protected rear-stage circuit and releases surge energy through the anti-surge protection grounding device;
the first-stage GDT protection device with three pins and double GDTs, the pair of decoupling devices and the pair of second-stage TVS tube protection devices protect the differential signal interface of the vibrating string type acquisition instrument.
In any of the above schemes, preferably, when the surge pulse signal passes through the surge-resistant circuit module, since the response speed of the TVS tube is faster than that of the GDT, the second-stage TVS tube protection device operates first, and the decoupling device increases the voltage input to the decoupling device side to the breakdown voltage of the first-stage GDT protection device through a certain internal resistance of the decoupling device, and at this time, the first-stage GDT protection device performs a large through-current discharge to play a role in protection.
In any of the above solutions, preferably, the metal casing of the vibrating wire sensor is connected to the shielding layer of the signal cable, and is finally connected to the equipotential connection terminal of the anti-surge protection grounding device.
In any of the above aspects, it is preferable that the maximum withstand voltage of the subsequent circuit is 60V.
In any of the above schemes, preferably, the vibrating wire channel switching adopts a G6K-2F-Y-5V type signal relay.
Compared with the prior art, the utility model has the advantages of:
the utility model discloses an in having solved present trade, only one-level surge protection circuit or not even have in present vibrating wire class collection equipment inside, in the scene that needs the lightning protection, probably need dispose dedicated external signal lightning protection device moreover, but external signal lightning protection device is not only bulky, and the cost is very high moreover, the protection signal of the most important signal lightning protection device and the matching degree problem of vibrating wire signal. The design is specially designed into a two-stage surge protection circuit from the aspect of the electrical characteristics of vibrating wire signals and the requirements of a rear-stage protection circuit, the size is small, the cost is low, the surge protection requirements of the vibrating wire signals and a vibrating wire acquisition system are completely matched from the theoretical design, and the surge protection requirements of LPZ0B-3 are completely met in the actual surge level test.
Drawings
Fig. 1 is a block diagram of a lightning protection interface module of the present invention;
FIG. 2 is a schematic diagram of the lightning protection circuit of the signal interface of the vibrating wire type collecting instrument of the present invention;
figure 3 is the utility model discloses anti surge thick film chip resistor circuit diagram.
The reference numbers in the figures illustrate:
1. vibrating wire formula sensor, 2, first order GDT protective device, 3, decoupling zero device, 4, second grade TVS pipe protective device, 5, anti surge protection earthing device, 6, protected back level circuit.
Detailed Description
The technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiment of the present invention; obviously, the described embodiments are only a part of the embodiments of the present invention, and not all embodiments, and all other embodiments obtained by those skilled in the art without any inventive work are within the scope of the present invention based on the embodiments of the present invention.
Example 1:
referring to fig. 1-3, a lightning protection circuit for signal interface of vibrating wire type collector comprises a vibrating wire type sensor 1, a first stage GDT protection device 2, a decoupling device 3, a second stage TVS tube protection device 4, an anti-surge protection grounding device 5 and a protected rear stage circuit 6, wherein the anti-surge protection circuit for fully differential vibrating wire signal is composed of the first stage GDT protection device 2, the decoupling device 3 and the second stage TVS tube protection device 4, bears surge pulse induced on the signal line of the vibrating wire type sensor 1, prevents the surge pulse from damaging the protected rear stage circuit 6, and releases surge energy through the anti-surge protection grounding device 5.
In the embodiment, a first-stage GDT protection device 2 with three pins and double GDTs, a pair of decoupling devices 3 and a pair of second-stage TVS tube protection devices 4 are used for protecting a differential signal interface of the vibrating wire type acquisition instrument;
in this embodiment, when a surge pulse signal passes through the surge-resistant circuit module, since the response speed of the TVS tube is faster than that of the GDT, the second-stage TVS tube protection device 4 acts first, and the decoupling device 3 increases the voltage input to the decoupling device 3 side to the breakdown voltage of the first-stage GDT protection device 2 through a certain internal resistance of the decoupling device, and at this time, the first-stage GDT protection device 2 performs a large-current discharge to play a role in protection;
in the present embodiment, the metal shell of the vibrating wire sensor 1 is connected to the shielding layer of the signal cable and finally connected to the equipotential connection terminal of the anti-surge protection grounding device 5.
The scheme adopts multi-stage protection and the principle of gradually decreasing surge energy, and achieves the purpose of protecting a signal interface circuit of the vibrating wire acquisition instrument. The system adopts two-stage protection, the first stage adopts a large through-current device, such as a gas discharge tube GDT or a piezoresistor MOV, and the second stage adopts a precise clamping device to ensure that the voltage does not exceed the maximum voltage which can be born by a rear-stage circuit, such as a TVS device. Because the parameters such as response time, breakdown voltage and the like of the first-stage protection device and the second-stage protection device are different, a decoupling device is required to be added between the two-stage protection devices to ensure the cooperative work of the two-stage protection circuits.
The vibrating wire channel is switched by a G6K-2F-Y-5V signal relay, the technical specification shows that the maximum withstand voltage of a post-stage circuit of a signal interface of the vibrating wire type acquisition instrument is 60V (namely VABS), the surge protection circuit is designed according to the maximum withstand voltage, and meanwhile, the maximum working voltage of the protection circuit needs to be determined.
In addition, according to the scene of equipment use and lightning protection requirements, general equipment is installed in a protective box close to an interface or on a similar hillside, and the matched lightning protection grade requirements are as follows: LPZ0B-3 belongs to outdoor ground equipment system, designs according to surge protection requirement of 6KV-3 KA. Therefore, the design of the circuit is designed according to the protection requirement of the level.
The parameter design steps of the two-stage anti-surge device of the vibrating wire signal interface are as follows:
(1) the first stage selects GDT (3R 090M-6 × 8) with 90V breakdown voltage, the actual maximum breakdown voltage is 108V, and 108V corresponds to the residual voltage parameter of the second stage TVS tube protection, i.e. VMAX =108V;
(2) excitation voltage 33V, then VINMAX = 33V;
(3) maximum input safe voltage of circuit VABS = 60V;
(4) the clamping voltage Vc of the TVS is less than or equal to VABS = 60V;
(5) the reverse turn-off voltage VR of the TVS tube is more than or equal to VINMAX =33V, VR =1.1 × 33V =36.3V is selected, and VR =36V is selected;
（6）Ipp=（VMAX-Vc）/2Ω=（108V-36V）/2Ω=36A;
(7) maximum peak pulse power Pppm = Ipp × Vc =36A × 36V =1296W, and a TVS tube of 1500W was actually selected.
According to the above parameters, SMCJ36CA, Vc =58.1V, VR =36V, VBR = 40V @1mA, Ipp =25.9A, Pppm =1500W may be selected. It can be seen that Ipp for SMCJ36CA does not meet the requirements and requires decoupling devices for current limiting. If a decoupling resistance of 1 ohm is chosen, Ipp can be limited to (108V-36V)/3 Ω =24A, which meets the requirements.
A1 ohm resistor requires the selection of an anti-surge thick film chip resistor. The circuit design is shown in fig. 3. In addition, the direct current resistance of the decoupling device cannot influence the measurement of the vibrating wire signal, if the resistance value of the decoupling device is too large, the vibrating wire sensor is possibly difficult to excite, and the already weak signal fed back may be influenced by the attenuation of the decoupling device. The utility model discloses an actual calculation, actual decoupling resistance is 1 ohm, and the coil direct current resistance of general vibrating wire sensor mostly all is more than 100 ohms, can ignore the influence degree of signal, also finds the test of long distance (like 1000 meters) in the actual test, has or not anti surge circuit module can not influence the amplitude of vibrating wire signal, does not influence signal integrality.
FIG. 1 illustrates: two signal lines of vibrating string sensor (1) output fully differential signal, so two arrows represent a pair of difference pair signals with equal size and opposite polarity, the model of three pins can be selected through the first stage GDT, and then the protection circuit of whole signal chain is in a structure of upper and lower symmetry because of fully differential signal after passing through two anti-surge power resistors and finally passing through the accurate voltage clamping of second stage TVS.
FIG. 2 illustrates: the inductance L1 and the resistance R83 in the black box form an equivalent circuit model of the vibrating wire sensor. And F + and F-form a fully differential signal differential pair, and the electrical connecting line at which the fully differential signal differential pair is arranged represents a sensor signal line from the vibrating-wire type sensor to the interface part of the vibrating-wire type acquisition instrument. G17, R78, R79, D47 and D48 form a two-stage anti-surge protection circuit module. LS9 denotes the components of the back stage circuit to be protected. G1 denotes the metal housing of the vibrating wire sensor and the shielding of the signal cable, and G1 denotes the protective earth (anti-surge protective earth) on the vibrating wire pick-up board, the energy bleed circuit for providing the surge pulse. G1 and G2 are connected together at the vibrating wire pick-up interface.
The working principle is as follows:
TVS, transient voltage suppressors, also known as avalanche breakdown diodes. Which is a device with a single PN junction or an integration of multiple PN junctions made using standard semiconductor processes. The TVS has a difference between unidirectional TVS generally applied to a dc power supply circuit and bidirectional TVS applied to a voltage alternating circuit. When the circuit works normally, the unidirectional TVS is in a cut-off state (high-resistance state) and does not influence the normal work of the circuit. When the circuit has abnormal overvoltage and reaches the (avalanche) breakdown voltage of the circuit, the TVS is suddenly changed from the high-resistance state to the low-resistance state, instantaneous overcurrent caused by the abnormal overvoltage is discharged to the ground, and the abnormal overvoltage is clamped within a safety level, so that the rear-stage circuit is protected from being damaged by the abnormal overvoltage. When the abnormal overvoltage disappears, the resistance of the TVS is restored to the high resistance state.
GDT, i.e. ceramic gas discharge tube. The GDT is a device consisting of one or more discharge gaps enclosed in a ceramic tube filled with inert gas. The electrical performance of the GDT depends on factors such as the type of gas, the pressure of the gas, the structure of the internal electrode, the fabrication process, etc. The GDT can bear the surge current impact of dozens of even hundreds of kiloamperes, has extremely low junction capacitance and is applied to protecting electronic equipment and human bodies from being damaged by transient high voltage.
According to the calculation steps in the implementation principle, the parameters of the GDT, the TVS and the decoupling device are selected as follows:
GDT: the model is 3R090M-6 × 8, DC spark-over voltage 90V + -20%, 8/20us 5KA,2.0pF
TVS: model selection SMCJ36CA bidirectional TVS pipe, Vc =58.1V, VR =36V, VBR = 40V @1mA, Ipp =25.9A, Pppm =1500W
Decoupling resistance: model SWR12JTFA1R, 1.5W, 1 ohm, 10/700us surge pulse can bear the highest voltage of 400V, and the utility model provides a design, 1 ohm resistance circulating current is 24A, and the power is 576W, and the power tolerance of this model is 1500W when 10/700us surge pulse.
For the requirement of grounding, after a lightning protection device is configured inside the vibrating wire type acquisition instrument, the anti-surge protection grounding needs to be reliably connected to the real ground, and the requirement of the grounding resistance needs to meet the standard requirement of the national standard, so that the anti-surge effect can be achieved. Meanwhile, the metal shell of the vibrating wire sensor and the shielding layer of the signal cable are connected to the potential connection terminal which is equal to the anti-surge protection grounding device, so that the influence degree of the differential line of the vibrating wire signal on the surge can be further reduced through the electromagnetic shielding principle.
Regarding the selection of decoupling devices:
the first-stage protective device and the second-stage protective device are different in overvoltage device type, different in breakdown voltage and different in response time, so that the two-stage overvoltage protective device can be ensured to work cooperatively only by adding a decoupling element between the two-stage overvoltage protective devices. The decoupling element requires a certain impedance to perform the decoupling function.
The working principle of the decoupling device is that the common second-stage overvoltage protection device adopts a small-current device with low clamping voltage and high response speed, the small-current device is firstly conducted when surge voltage impacts, the decoupling device has certain internal resistance, the voltage in front of the decoupling device is improved to be higher than the breakdown voltage of a first-stage voltage element when large surge current passes through the decoupling device, and the surge current can be discharged and amplified after the first-stage element is conducted, so that the pressure of the second-stage protection device is shared. If no decoupling device is arranged between the two stages of overvoltage protection devices, the second stage of overvoltage protection device is always in a pilot-on state, and when surge current exceeds the power absorption capacity of the second stage of overvoltage protection device, the second stage of overvoltage protection device is damaged.
The decoupling device is selected according to the working current of the line, for example, the working current of some signal circuits is small, a power type resistor or a self-recovery fuse can be selected under the condition of ensuring normal communication, and the decoupling resistor is generally selected within 10 ohms. From the viewpoint of surge protection, the larger the decoupling resistance is, the better the decoupling resistance is, but the decoupling resistance cannot be too large, otherwise, the normal working current of the line can be influenced, and the decoupling resistance needs to be comprehensively considered in the circuit design.
For some low-frequency lines with large input current, an inductor can be selected for decoupling, the calculation formula of the impedance of the inductor is ZL =2 pi fL, and after the impedance value is determined, the size of the inductor can be calculated from the formula.
The above description is only the preferred embodiment of the present invention; the scope of the present invention is not limited thereto. Any person skilled in the art should also be able to cover the technical scope of the present invention by replacing or changing the technical solution and the improvement concept of the present invention with equivalents and modifications within the technical scope of the present invention.
Claims (4)
1. The utility model provides a appearance signal interface lightning protection circuit is gathered to vibration wire formula, includes vibration wire formula sensor (1), first order GDT protective device (2), decoupling device (3), second level TVS pipe protective device (4), anti surge protection earthing device (5) and protected back stage circuit (6), its characterized in that: the anti-surge protection circuit of the fully differential vibrating wire signal, which consists of a first-stage GDT protection device (2), a decoupling device (3) and a second-stage TVS tube protection device (4), bears the surge pulse induced on the signal line of the vibrating wire sensor (1), prevents the surge pulse from damaging a protected rear-stage circuit (6), and releases surge energy through an anti-surge protection grounding device (5);
the first-stage GDT protection device (2) with three pins and double GDTs, the pair of decoupling devices (3) and the pair of second-stage TVS tube protection devices (4) protect differential signal interfaces of the vibrating string type acquisition instrument.
2. The lightning protection circuit for signal interface of vibrating wire collector as claimed in claim 1, wherein: when a surge pulse signal passes through the surge resisting circuit module, as the response speed of the TVS tube is higher than that of the GDT tube, the second-stage TVS tube protection device (4) acts first, and the decoupling device (3) improves the voltage input to the decoupling device (3) side to the breakdown voltage of the first-stage GDT protection device (2) through a certain internal resistance of the decoupling device, at the moment, the first-stage GDT protection device (2) performs large-through-flow discharge.
3. The lightning protection circuit for signal interface of vibrating wire collector as claimed in claim 1, wherein: the metal shell of the vibrating wire sensor (1) is connected with the shielding layer of the signal cable and finally connected to the equipotential connecting terminal of the anti-surge protection grounding device (5).
4. The lightning protection circuit for signal interface of vibrating wire collector as claimed in claim 1, wherein: the maximum withstand voltage of the post-stage circuit (6) is 60V.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922371291.6U CN210111604U (en) | 2019-12-26 | 2019-12-26 | Lightning protection circuit for signal interface of vibrating wire type acquisition instrument |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201922371291.6U CN210111604U (en) | 2019-12-26 | 2019-12-26 | Lightning protection circuit for signal interface of vibrating wire type acquisition instrument |
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| Publication Number | Publication Date |
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| CN210111604U true CN210111604U (en) | 2020-02-21 |
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| CN201922371291.6U Active CN210111604U (en) | 2019-12-26 | 2019-12-26 | Lightning protection circuit for signal interface of vibrating wire type acquisition instrument |
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