Substrate of data acquisition device

Abstract

The utility model discloses a substrate of a data acquisition device, which belongs to the technical field of data acquisition and comprises a main control module, an oscillation starting module, an oscillation pickup module, a vibrating wire sensor acquisition interface module, an NTC (Negative Temperature Coefficient) resistance acquisition module, a power supply module, an acquisition channel selection module and a three-stage lightning protection and surge resistance module. According to the utility model, the NTC resistance value acquisition module is improved, so that the resistance value of the NTC thermistor can be measured without measuring the total voltage v of the measuring circuit, and the problem of large detection error caused by calculating the NTC resistance value by adopting the total voltage v of the circuit is avoided. According to the utility model, a three-stage lightning protection and surge resistance module is arranged on the acquisition interface module of the vibrating wire sensor, and a special design is adopted, so that a plurality of acquisition channels share one group of lightning protection devices, a good lightning protection effect can be achieved, the equipment size is reduced, and the production cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of data acquisition, in particular to a substrate of a data acquisition device. Background Art

[0002] The vibrating string sensor acquisition device is a common data acquisition device. It excites the vibrating string in the vibrating string sensor to vibrate and then measures the frequency of the vibrating string. Since there is a specific relationship between the frequency of the vibrating string and the physical quantity it is subjected to (such as pressure, strain, displacement, temperature, etc.), the data acquisition device converts the measured frequency into the corresponding physical quantity value according to a predetermined mathematical model.

[0003] The existing vibrating string sensor acquisition device, its substrate (mainboard) is generally provided with a main control module, a power module, an oscillation module, a vibration pickup module, a vibrating string sensor acquisition interface and an NTC resistance acquisition module, etc. The measurement principle of the NTC resistance acquisition module is: connect the NTC in series with a 10KΩ resistor, and then use the ADC to collect the voltage across the NTC thermistor, and then calculate the current resistance of the thermistor. Among them, v is the voltage loaded in the entire circuit, r is the current resistance of the NTC thermistor, and v1 is the voltage across the NTC thermistor. According to the formula U = IR and v = ((v-v1) / 10000)*r, it is derived that: r = 10000*v / (v-v1).

[0004] It can be seen that to calculate r, you need to know the values ​​of v and v1. v1 can be collected by ADC, while v is obtained through peripheral circuits (DC-DC step-down devices). Due to the consistency of peripheral circuit devices (such as the error of resistor values), the voltage v obtained by each device through the hardware circuit will have a certain deviation. However, when writing software, v often takes a fixed value, resulting in a large error between the final calculated r and the actual resistance value of the NTC thermistor.

[0005] In addition, vibrating string sensors are generally installed outdoors and connected to vibrating string sensor acquisition devices through wires. Outdoor sensors are easily affected and damaged by lightning, which can damage the vibrating string sensor acquisition devices and cause equipment failure. Currently, most vibrating string sensor acquisition devices have built-in lightning protection devices or use external lightning arresters, which have certain lightning protection and surge resistance capabilities. However, the current multi-channel vibrating string sensor acquisition devices in the industry generally have the following problems in product design: (1) The surge pulse energy is discharged slowly, with only a first-level TVS (transient voltage suppression diode) tube protection or a second-level TVS plus GDT (ceramic gas discharge tube) protection; (2) Each vibrating string data acquisition channel needs to be protected at multiple levels, which is not only costly, but also increases the size of the equipment; therefore, it is necessary to improve the existing technology. Utility Model Content

[0006] The utility model proposes a substrate for a data acquisition device. By improving the NTC resistance acquisition module, the resistance of the NTC thermistor can be measured without measuring the total voltage v of the measurement circuit, so as to solve the problem that the existing NTC resistance detection circuit uses the total circuit voltage v to calculate the NTC resistance, resulting in large detection errors. The utility model also adds multi-stage lightning protection devices to the vibrating string sensor acquisition interface module, and through special design, multiple acquisition channels share a set of lightning protection devices, which can not only achieve good lightning protection effects, but also reduce the volume of the equipment and reduce production costs.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the utility model is:

[0008] A substrate of a data acquisition device comprises a main control module and an oscillating module, a vibration pickup module, a vibrating string sensor acquisition interface module, an NTC resistance acquisition module and a power supply module, all of which are connected to the main control module, wherein the oscillating module, the vibration pickup module and the NTC resistance acquisition module are all connected to the vibrating string sensor acquisition interface module;

[0009] The NTC resistance value acquisition module includes a fixed value resistor 1, a fixed value resistor 2, an NTC thermistor and a switch module; the fixed value resistor 1 and the NTC thermistor are connected in series to form a test circuit 1, and the fixed value resistor 2 and the NTC thermistor are connected in series to form a test circuit 2;

[0010] The power module and the main control module are both connected to the switch module. Under the control of the main control module, the switch module performs an on-off action to load the output voltage of the power module to the test circuit 1 or the test circuit 2;

[0011] One end of the NTC thermistor connected to the fixed value resistor 1 and the fixed value resistor 2 is connected to the signal acquisition end of the main control module, and the other end is grounded.

[0012] Furthermore, the resistance of the fixed-value resistor 1 is 10 kΩ, and the resistance of the fixed-value resistor 2 is 1 kΩ.

[0013] Furthermore, the switch module is an analog switch, and its model is TS5A3160DBVR.

[0014] Furthermore, the substrate also includes an RS485 interface module connected to the main control module.

[0015] Furthermore, the substrate also includes an LED indicator light connected to the main control module.

[0016] Furthermore, the substrate also includes a debugging and burning interface module connected to the main control module.

[0017] Furthermore, the substrate also includes an acquisition channel selection module and a three-level lightning protection and surge protection module; the vibrating string sensor acquisition interface module has multiple acquisition channels, and is connected to an acquisition channel selection module for selecting the corresponding acquisition channel to be turned on or off, and the acquisition channel selection module is connected to the main control module; the three-level lightning protection and surge protection module includes multiple first-level TVS protection circuits, second-level MOV protection circuits, third-level GDT protection circuits, current limiting devices and grounding circuits; multiple first-level TVS protection circuits are respectively connected to multiple acquisition channels; the second-level MOV protection circuit, the third-level GDT protection circuit and the current limiting device are arranged in parallel to form a common circuit; the common circuit is connected to the rear stage of the multiple first-level TVS protection circuits, and is connected to the grounding circuit.

[0018] Furthermore, the first-level TVS protection circuit includes at least two TVSs, the acquisition channel is connected to two or four signal lines, and each signal line is connected in parallel with the TVS; the second-level MOV protection circuit includes MOV, the third-level GDT protection circuit includes GDT, the current limiting device is a current limiting resistor, the MOV, GDT, and current limiting resistor are arranged in parallel, one end of which is connected to the TVS of multiple acquisition channels, and the other end is connected to the ground circuit.

[0019] Furthermore, the main control module is a single chip microcomputer.

[0020] Due to the adoption of the above technical solution, the utility model has the following beneficial effects:

[0021] 1. The utility model can measure the resistance value of the NTC thermistor without measuring the total voltage v of the measuring circuit, thus avoiding the problem of large detection error caused by calculating the NTC resistance value by measuring the total voltage v of the measuring circuit in the prior art, and effectively improving the accuracy of NTC resistance value measurement.

[0022] 2. The detection circuit proposed in the utility model also has the advantages of simple structure, low cost, strong stability, etc. It can be applied in application scenarios under various conditions and has good practicality.

[0023] 3. The utility model adopts a three-level lightning protection and surge resistance design to solve the problem that the vibrating string acquisition terminal is easily damaged and the surge pulse energy is slowly discharged when it is installed outdoors by lightning, ensuring the safety of equipment and facilities and effectively reducing the risk of safety accidents.

[0024] 4. The vibrating string sensor acquisition interface module of the utility model has multiple acquisition channels, and the multiple acquisition channels share the second-level and third-level lightning protection circuits, which greatly reduces the production cost and volume of the equipment while ensuring the functionality.

[0025] 5. The utility model is provided with an acquisition channel selection module, which is used to select the corresponding acquisition channel to be opened or closed. For sensors that are not working, the corresponding acquisition channel can be closed, and the connection between the sensor and the acquisition terminal can be disconnected to ensure the safety of the acquisition terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 A block diagram of the composition of the substrate proposed in the embodiment of the utility model;

[0027] Figure 2 This is a circuit schematic diagram of the NTC resistance value acquisition module proposed in the embodiment of the utility model;

[0028] Figure 3 The circuit schematic diagram of the RS485 interface module proposed by the utility model embodiment;

[0029] Figure 4 This is a circuit diagram of the main control module proposed in the embodiment of the utility model;

[0030] Figure 5 A circuit schematic diagram of a power module proposed in an embodiment of the utility model;

[0031] Figure 6 A circuit schematic diagram of the oscillating module proposed in the embodiment of the utility model;

[0032] Figure 7 A circuit schematic diagram of the vibration pickup module proposed in the embodiment of the utility model;

[0033] Figure 8 The circuit schematic diagram of the three-level lightning protection and surge protection module proposed in the embodiment of the utility model;

[0034] Fig. 9 This is a block diagram of the composition of the three-level lightning protection and surge protection module proposed in the embodiment of the utility model; DETAILED DESCRIPTION

[0035] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0036] Example

[0037] like Figure 1As shown, a substrate of a data acquisition device includes a main control module and an oscillating module, a vibration pickup module, a vibrating string sensor acquisition interface module, an NTC resistance acquisition module, a power module, an RS485 interface module, an LED indicator light, and a debugging and burning interface module, all of which are connected to the main control module.

[0038] The oscillation starting module, vibration pickup module, and NTC resistance value acquisition module are all connected to the vibrating string sensor acquisition interface module. The vibrating string sensor acquisition interface module is an interface connected to an external vibrating string sensor. The main control module reads the frequency information and temperature information of the sensor through this interface. Specifically, the main control module generates PWM pulses of different frequencies. After passing through the oscillation starting module, it outputs +5V and -5V pulses. The sensor is swept and excited through the vibrating string sensor acquisition interface. When the frequency of the excitation pulse is close to the frequency of the vibrating string in the sensor, the vibrating string vibrates and generates a sinusoidal wave signal of a specific frequency. After the sinusoidal wave signal enters the vibrating string sensor acquisition interface, the vibration pickup module performs op amp and filtering operations, and converts the sinusoidal wave signal into a level pulse signal. The main control module obtains the frequency information by capturing and calculating the level pulse signal. For the circuit schematic diagram of the oscillation starting module, see Figure 6 , the circuit schematic diagram of the vibration pickup module is shown in Figure 7 The main control module monitors the resistance of the NTC thermistor through the NTC resistance acquisition module, and calculates the temperature value based on the specific relationship between the resistance of the NTC thermistor and the temperature.

[0039] like Figure 2 As shown, the NTC resistance acquisition module includes a fixed resistor 1, a fixed resistor 2, an NTC thermistor, and a switch module. The fixed resistor 1 and the NTC thermistor are connected in series to form a test circuit 1, and the fixed resistor 2 and the NTC thermistor are connected in series to form a test circuit 2. In this embodiment, the resistance of the fixed resistor 1 is 10kΩ, and the resistance of the fixed resistor 2 is 1kΩ.

[0040] The power module and the main control module are both connected to the switch module. Under the control of the main control module, the switch module performs on-off actions and loads the output voltage of the power module to test circuit 1 or test circuit 2. In this embodiment, the switch module is an analog switch, and its model is TS5A3160DBVR. Figure 4 , the circuit diagram of the power module is shown in Figure 5 .

[0041] One end of the NTC thermistor connected to the fixed resistor 1 and the fixed resistor 2 is connected to the signal acquisition end of the main control module, and the other end is grounded. The main control module collects the voltage across the NTC thermistor through ADC.

[0042] The working principle of the NTC resistance value acquisition module is:

[0043] First, the main control module controls the switch module to load the output voltage of the power module to the test circuit 1. At the same time, the main control module collects the voltage across the NTC thermistor through the ADC. Since the resistance of the fixed resistor 1 is 10kΩ=10000Ω, formula (1) is obtained:

[0044] v / (10000+r)=v1 / r, so: vr=v1(10000+r) (1)

[0045] Among them, v is the voltage value loaded on the entire circuit, r is the resistance value of the NTC thermistor, and v1 is the voltage value across the NTC thermistor resistance measured when a 10KΩ resistor is connected in series.

[0046] Then, the main control module controls the switch module to load the output voltage of the power module to the test circuit 2, and the test circuit 1 is disconnected. At the same time, the main control module collects the voltage across the NTC thermistor through the ADC. Since the resistance of the fixed resistor 2 is 1kΩ=1000Ω, formula (2) is obtained:

[0047] v / (1000+r) = v2 / r, and we can deduce that: vr = v2(1000+r) (2)

[0048] Among them, v2 is the voltage value across the NTC thermistor measured when a 1KΩ resistor is connected in series.

[0049] Finally, from formula (1) and formula (2), we can derive formula (3), (4), (5), and (6):

[0050] v1(10000+r) =v2(1000+r) (3)

[0051] 10000*v1+v1*r=1000*v2+v2*r (4)

[0052] 10000*v1-1000*v2=(v2-v1)r (5)

[0053] Finally, we get: r = (10000*v1-1000*v2) / (v2-v1)(6)

[0054] It can be seen from formula (6) that v does not need to be introduced in the calculation process of r. The only variables are v1 and v2. Both v1 and v2 are acquired by the same main control module through ADC acquisition, avoiding the problem of device consistency.

[0055] The utility model does not need to measure the total voltage v of the measurement circuit, but can also measure the resistance value of the NTC thermistor, thus avoiding the problem of large detection errors caused by using the total voltage v of the measurement circuit to calculate the NTC resistance value in the prior art, and effectively improving the accuracy of the NTC resistance value measurement. In addition, the detection circuit proposed by the utility model also has the advantages of simple structure, low cost, strong stability, etc., and can be applied to application scenarios under various conditions, and has good practicality.

[0056] like Figure 1 , 8 As shown in , the substrate also includes a collection channel selection module and a three-level lightning protection and surge protection module. The vibrating string sensor collection interface module has multiple collection channels, and is connected to a collection channel selection module for selecting the corresponding collection channel to be turned on or off, and the collection channel selection module is connected to the main control module. Each collection channel can be connected to a vibrating string sensor through a certain number of signal lines.

[0057] The three-level lightning protection and surge protection module includes multiple first-level TVS protection circuits, second-level MOV protection circuits, third-level GDT protection circuits, current limiting devices and grounding circuits. Multiple first-level TVS protection circuits are respectively connected to multiple acquisition channels. The second-level MOV protection circuit, the third-level GDT protection circuit and the current limiting device are arranged in parallel to form a common circuit. The common circuit is connected to the rear stage of multiple first-level TVS protection circuits and is connected to the grounding circuit.

[0058] The surge protection circuit, which is composed of a first-level TVS protection circuit, a current limiting device, a second-level MOV protection circuit, and a third-level GDT protection circuit, withstands surge pulses induced on the signal line connected to the vibrating string sensor, prevents the surge pulses from entering the channel selection circuit, and discharges the surge pulse energy through the grounding protection circuit.

[0059] Among them, the first-level TVS protection circuit includes at least two TVSs, the acquisition channel is connected to two or four signal lines, and each signal line is connected in parallel with a TVS. In this embodiment, the acquisition channel is connected to the vibrating string sensor through four signal lines, and each signal line is connected in parallel with a TVS. The second-level MOV protection circuit includes MOV, the third-level GDT protection circuit includes GDT, the current limiting device is a current limiting resistor, MOV, GDT, and current limiting resistor are arranged in parallel, one end of which is connected to the TVS of multiple acquisition channels, and the other end is connected to the ground circuit.

[0060] The three-level lightning protection circuit is composed of GDT, MOV, and current limiting devices connected in parallel and then in series with TVS. The multiple signal lines connected to the acquisition channel are connected to multiple TVSs respectively. Since the conduction response speed TVS>MOV>GDT, when the surge pulse energy passes through the lightning protection and anti-surge circuit, the voltage first reaches the clamping voltage of TVS, and TVS is turned on first. However, due to the existence of the current limiting device, the voltage at both ends of the current limiting device will gradually increase. When it reaches the clamping voltage of MOV, MOV will then turn on and start to discharge the surge pulse energy. If the energy cannot be discharged in a very short time, the voltage at both ends of the current limiting device will continue to increase until it reaches the breakdown voltage of GDT. At this time, GDT is turned on to discharge a large amount of surge pulse energy.

[0061] Each signal line connected to the vibrating string sensor is connected in series to the second and third level protection circuits through a parallel TVS. Since the clamping voltage of the TVS is greater than the signal voltage of the vibrating string sensor, it will not have any effect on the channel selection circuit during normal use. When the signal line is entangled with the induced surge pulse, the voltage between the signal line and the ground is higher than the clamping voltage of the TVS, and the TVS is turned on, diverting the surge pulse energy to the second and third level protection circuits, thereby protecting the safety of the channel selection circuit.

[0062] Current limiting devices usually use large-value resistors, whose main function is to raise the voltage across the current limiting device, so that the voltage across the parallel MOV and GDT is higher than the clamping voltage of the MOV and the breakdown voltage of the GDT, thereby turning on the second-level and third-level protection circuits to discharge energy.

[0063] When the voltage across the MOV is higher than the clamping voltage of the MOV, the response time of the MOV is tens of nanoseconds, and the MOV changes from a high-resistance state to a conductive state, allowing the surge pulse energy to flow into the grounding circuit.

[0064] When the voltage across the GDT is higher than the breakdown voltage of the GDT, the response time of the GDT is several hundred nanoseconds, and the GDT changes from a high-resistance state to a conducting state, allowing the surge pulse energy to flow into the grounding circuit. The response speed of the GDT is slower than that of the MOV, but the discharge speed is higher than that of the MOV. Therefore, the GDT is used as the third-level protection to cooperate with the MOV to discharge the surge pulse energy.

[0065] The grounding circuit is used to divert surge pulse energy to the ground to protect the safety of equipment and lines.

[0066] The channel selection module and the main control module control the designated acquisition channel to connect with the vibration starting module and the vibration picking module according to the instructions issued by the main control gateway, and the connections of other channels will be disconnected. In this embodiment, a relay is used to control the connection between the signal line and the data acquisition device. When the vibrating string sensor is not needed to work, the connection between the signal line and the data acquisition device is disconnected, and the safety of the data acquisition device can be guaranteed even if surge pulse energy is transmitted from the signal line. When it is necessary to collect the value of the channel, the control relay connects the connection between the corresponding signal line and the data acquisition device. After the collection is completed, the control relay disconnects the connection between the corresponding signal line and the data acquisition device.

[0067] The utility model adopts a three-level lightning protection and surge protection design to solve the problem that the vibrating string data acquisition device is easily damaged and the surge pulse energy is slowly discharged when it is installed outdoors and struck by lightning, ensuring the safety of equipment and facilities and effectively reducing the risk of safety accidents. The vibrating string sensor acquisition interface module of the utility model has multiple acquisition channels, and multiple acquisition channels share the second and third level lightning protection circuits, which greatly reduces the production cost and volume of the equipment while ensuring the function.

[0068] The functions of other modules are briefly described below:

[0069] RS485 interface module, used to receive commands and configuration information sent by the master gateway. LED indicator, used to indicate the working status, flashes slowly when in standby mode, and stays on when performing frequency acquisition and NTC resistance value detection. Debugging and burning interface module, used for program debugging and program burning.

[0070] The above description is a detailed description of the preferred feasible embodiment of the utility model, but the embodiment is not used to limit the scope of the patent application of the utility model. All equivalent changes or modified changes completed under the technical spirit suggested by the utility model should fall within the patent scope covered by the utility model.

Claims

1. A substrate of a data acquisition device, comprising a main control module and an oscillating module, a vibration pickup module, a vibrating string sensor acquisition interface module, an NTC resistance acquisition module and a power supply module, all of which are connected to the main control module, wherein the oscillating module, the vibration pickup module and the NTC resistance acquisition module are all connected to the vibrating string sensor acquisition interface module, and characterized in that: The NTC resistance value acquisition module includes a fixed value resistor 1, a fixed value resistor 2, an NTC thermistor and a switch module; the fixed value resistor 1 and the NTC thermistor are connected in series to form a test circuit 1, and the fixed value resistor 2 and the NTC thermistor are connected in series to form a test circuit 2; The power module and the main control module are both connected to the switch module. Under the control of the main control module, the switch module performs an on-off action to load the output voltage of the power module to the test circuit 1 or the test circuit 2; One end of the NTC thermistor connected to the fixed value resistor 1 and the fixed value resistor 2 is connected to the signal acquisition end of the main control module, and the other end is grounded.

2. The substrate of a data acquisition device according to claim 1, characterized in that: The resistance of the fixed resistor 1 is 10 kΩ, and the resistance of the fixed resistor 2 is 1 kΩ.

3. The substrate of a data acquisition device according to claim 2, characterized in that: The switch module is an analog switch, and its model is TS5A3160DBVR.

4. The substrate of a data acquisition device according to claim 1, characterized in that: The base plate also includes an RS485 interface module connected to the main control module.

5. The substrate of a data acquisition device according to claim 1, characterized in that: The base plate also includes an LED indicator light connected to the main control module.

6. The substrate of a data acquisition device according to claim 1, characterized in that: The base plate also includes a debugging and burning interface module connected to the main control module.

7. The substrate of a data acquisition device according to claim 1, characterized in that: The substrate also includes an acquisition channel selection module and a three-level lightning protection and surge protection module; the vibrating string sensor acquisition interface module has multiple acquisition channels, and is connected to an acquisition channel selection module for selecting the corresponding acquisition channel to be turned on or off, and the acquisition channel selection module is connected to the main control module; the three-level lightning protection and surge protection module includes multiple first-level TVS protection circuits, second-level MOV protection circuits, third-level GDT protection circuits, current limiting devices and grounding circuits; multiple first-level TVS protection circuits are respectively connected to multiple acquisition channels; the second-level MOV protection circuit, the third-level GDT protection circuit and the current limiting device are arranged in parallel to form a common circuit; the common circuit is connected to the rear stage of the multiple first-level TVS protection circuits, and is connected to the grounding circuit.

8. The substrate of a data acquisition device according to claim 7, characterized in that: The first-level TVS protection circuit includes at least two TVSs, the acquisition channel is connected to two or four signal lines, and each signal line is connected in parallel with the TVS; the second-level MOV protection circuit includes MOV, the third-level GDT protection circuit includes GDT, the current limiting device is a current limiting resistor, the MOV, GDT, and current limiting resistor are arranged in parallel, one end of which is connected to the TVS of multiple acquisition channels, and the other end is connected to the ground circuit.

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