Vibrating wire and RS485 interface switchable circuit

Abstract

The utility model provides a vibrating wire and RS485 interface switchable circuit, which comprises a first-stage signal switching module A path, a second-stage signal switching module B path and a third-stage signal switching module C path, and is characterized in that the first-stage signal switching module A path comprises a common signal stage LS1, and the common signal stage LS1 is provided with a first normally-closed contact and a first normally-open contact; the first-stage signal switching module B path comprises a common signal stage LS3, and the common signal stage LS3 is provided with a second normally closed contact and a second normally open contact; the second-stage signal switching module A path comprises an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) and a common signal stage LS17, the common signal stage LS17 is provided with a third normally closed contact and a third normally open contact, and the common signal stage LS17 is connected with the first normally open contact; and the second-stage signal switching module B path comprises a common signal stage LS19, the common signal stage LS19 is provided with a fourth normally closed contact and a fourth normally open contact, the common signal stage LS19 is connected with the second normally open contact, and the flexibility of the equipment in field use is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of structural safety monitoring, in particular to a vibrating string and RS485 interface switchable circuit. Background Art

[0002] The monitoring sensors used in the structural safety monitoring site mainly include two categories: one is the vibrating string sensor, which outputs AC voltage signals; the other is the sensor with digital signal output via RS485 interface.

[0003] Current monitoring equipment generally uses independent channel design for the measurement of these two types of sensors, that is, a vibrating string signal measurement channel is designed for vibrating string sensors, and an RS485 signal channel is designed for RS485 sensors.

[0004] The problem with the existing technology is that since the number and type of field monitoring sensors vary according to different scenarios, the current solution of fixed measurement attribute channels is not flexible enough, and channels may be idle due to too many or too few sensors of a certain type. For example, if 6 vibrating string acquisition channels and 2 RS485 measurement channels are required on site, an 8-channel acquisition device with any configuration can be used to meet the requirements. Any 6 of the 8 channels can be configured as vibrating string channels, and the remaining 2 channels can be configured as RS485 channels. If the current fixed measurement channel method is used, such as an 8-channel data acquisition instrument with a combination of 4 vibrating strings and 4 RS485 channels, at least two such acquisition instruments are required to meet the 6-channel vibrating string signal measurement, and the two acquisition instruments waste a total of 2 vibrating string channels and 6 RS485 channels. Utility Model Content

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a vibrating string and RS485 interface switchable circuit, aiming to solve the technical problems mentioned in the background technology.

[0006] In order to achieve the above purpose, the utility model is implemented through the following technical solutions:

[0007] A vibrating string and RS485 interface switchable circuit, comprising:

[0008] A first-stage signal switching module A path, wherein the first-stage signal switching module A path comprises a common signal stage LS1, wherein the common signal stage LS1 is connected to a vibrating-wire sensor signal power line or an RS485 sensor power supply line, and wherein the common signal stage LS1 has a first normally closed contact and a first normally open contact;

[0009] The first-level signal switching module B path includes a common signal level LS3, the common signal level LS3 is connected to the vibrating wire sensor temperature signal line or the RS485 sensor data transmission line, and the common signal level LS3 has a second normally closed contact and a second normally open contact;

[0010] A second-stage signal switching module A path, the second-stage signal switching module A path includes a MOSFET tube and a common signal stage LS17, the MOSFET tube is used to provide a pulsed enable signal to the vibrating string sensor and a constant enable signal to the RS485 sensor, the common signal stage LS17 has a third normally closed contact connected to the vibrating string signal chain and a third normally open contact connected to the MOSFET tube, and the common signal stage LS17 is connected to the first normally open contact;

[0011] The second-level signal switching module B path, the second-level signal switching module B path includes a common signal level LS19, the common signal level LS19 has a fourth normally closed contact connected to the temperature signal chain, and a fourth normally open contact connected to the RS485 driver, the common signal level LS19 is connected to the second normally open contact.

[0012] According to one aspect of the above technical solution, the common signal level LS1 has pin 3 and pin 6, the first normally closed contact has pin 2 and pin 7, the first normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS1 are connected to the vibrating string sensor signal power line or the RS485 sensor power supply line, pin 3 and pin 6 of the common signal level LS1 are respectively connected to pin 2 and pin 7 of the first normally closed contact, and pin 3 and pin 6 of the common signal level LS1 are respectively connected to pin 4 and pin 5 of the first normally open contact.

[0013] According to one aspect of the above technical solution, the common signal level LS3 has pin 3 and pin 6, the second normally closed contact has pin 2 and pin 7, the second normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS3 are connected to the vibrating string sensor signal power line or the RS485 sensor power supply line, pin 3 and pin 6 of the common signal level LS3 are respectively connected to pin 2 and pin 7 of the second normally closed contact, and pin 3 and pin 6 of the common signal level LS3 are respectively connected to pin 4 and pin 5 of the second normally open contact.

[0014] According to one aspect of the above technical solution, the common signal level LS1 and the common signal level LS3 are respectively provided with a freewheeling diode D2 and a freewheeling diode D4, and the freewheeling diode D2 and the freewheeling diode D4 are used to absorb the current generated by the reverse electromotive force of the signal relay coil when it is in action.

[0015] According to one aspect of the above technical solution, the common signal level LS17 has pin 3 and pin 6, the third normally closed contact has pin 2 and pin 7, and the third normally open contact has pin 4 and pin 5. Pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the first normally open contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 2 and pin 7 of the third normally closed contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the third normally open contact.

[0016] According to one aspect of the above technical solution, the common signal level LS19 has pin 3 and pin 6, the fourth normally closed contact has pin 2 and pin 7, the fourth normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS19 are respectively connected to pin 4 and pin 5 of the second normally open contact, pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 2 and pin 7 of the fourth normally closed contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the fourth normally open contact.

[0017] According to one aspect of the above technical solution, the common signal level LS17 is provided with freewheeling diodes D19 and D20, and a resistor R43, the freewheeling diode D19 and the resistor R43 are used to absorb the pulse current generated by the reverse electromotive force induced by the vibrating string sensor coil, and the freewheeling diode D20 is used to absorb the current generated by the reverse electromotive force of the signal relay coil when it is in action.

[0018] According to one aspect of the above technical solution, the first-level signal switching module A also includes a first drive circuit, the first drive circuit includes a resistor R3, a resistor R5, and a transistor Q1, and the first drive circuit is used to switch the first normally closed contact and the first normally open contact. The first-level signal switching module B also includes a second drive circuit, the second drive circuit includes a resistor R2, a resistor R7, and a transistor Q3, and the second drive circuit is used to switch the second normally closed contact and the second normally open contact. The second-level signal switching module A includes a third drive circuit, the third drive circuit includes a resistor R44, a resistor R45, and a transistor Q19, and the third drive circuit is used to switch the third normally closed contact and the third normally open contact. The second-level signal switching module B includes a fourth drive circuit, the fourth drive circuit includes a resistor R59, a resistor R61, and a transistor Q61, and the fourth drive circuit is used to switch the fourth normally closed contact and the fourth normally open contact.

[0019] According to one aspect of the above technical solution, the vibrating string and RS485 switchable circuit further includes a microcontroller, and the microcontroller is electrically connected to the first drive circuit, the second drive circuit, the third drive circuit, the fourth drive circuit, and the MOSFET tube respectively.

[0020] According to one aspect of the above technical solution, the MOSFET tube includes a neutral line T2, a transistor Q18, a resistor R36, a resistor R37, a resistor R40, and a resistor R41.

[0021] Compared with the prior art, the beneficial effects of the utility model are:

[0022] By setting the first-level signal switching module A and the first-level signal switching module B, when different sensors need to be used according to the on-site conditions, the common signal level LS1 and the common signal level LS3 can be connected to the vibrating string sensor temperature signal line or the RS485 sensor data transmission line at the same time. When there is no need to use the sensor to collect signals, the circuit is switched to the first normally closed contact and the second normally closed contact. When the sensor needs to be used to collect signals, the circuit is switched to the first normally open contact and the second normally open contact, and then connected to the common signal level LS17 and the common signal level LS19, the second-level signal switching module A and the second-level signal switching module B. When connected When the sensor is a vibrating string sensor, first switch to the third normally open contact, excite the vibrating string sensor through the MOSFET tube, then switch to the third normally closed contact, condition and measure the vibrating string signal through the vibrating string signal chain, and switch to the fourth normally closed contact at the same time to make the temperature signal chain work, so as to measure the thermometer inside the vibrating string sensor. When the sensor is an RS485 sensor, switch to the third normally open contact, so that the MOSFET tube provides a constant enable signal to the RS485 sensor, and provides a constant power supply to the RS485 sensor. At the same time, switch to the fourth normally open contact, connect the RS485 driver, and read the data of the RS485 sensor.

[0023] This utility model patent designs a switchable circuit between a vibrating string and an RS485 interface, so that any channel of a multi-channel device can be configured as a vibrating string sensor measurement channel or an RS485 sensor measurement channel, thereby improving the flexibility of the device in on-site use and avoiding channel idleness and waste due to channel limitations. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a system block diagram of a vibrating string and RS485 interface switchable circuit in an embodiment of the utility model;

[0025] Figure 2 This is a circuit diagram of the first-level signal switching module A in the embodiment of the utility model;

[0026] Figure 3This is a circuit diagram of the first-level signal switching module B in the embodiment of the utility model;

[0027] Figure 4 This is a circuit diagram of the A path of the second-level signal switching module in the embodiment of the utility model;

[0028] Figure 5 This is a circuit diagram of the second-level signal switching module B in the embodiment of the utility model;

[0029] Description of main component symbols:

[0030]

[0031]

[0032] The following specific implementation manner will further illustrate the present utility model in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0033] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0034] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art in the technical field of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0036] See also Figures 1 to 5 , shown is a vibrating string and RS485 interface switchable circuit in the first embodiment of the utility model, comprising:

[0037] A first-stage signal switching module A path 1, wherein the first-stage signal switching module A path 1 comprises a common signal stage LS1, wherein the common signal stage LS1 is connected to a vibrating-wire sensor signal power line or an RS485 sensor power supply line, and wherein the common signal stage LS1 has a first normally closed contact and a first normally open contact;

[0038] The first-stage signal switching module B-way 2 comprises a common signal stage LS3, the common signal stage LS3 is connected to the vibrating-wire sensor temperature signal line or the RS485 sensor data transmission line, and the common signal stage LS3 has a second normally closed contact and a second normally open contact;

[0039] The second-stage signal switching module A path 3 includes a MOSFET tube 5 and a common signal stage LS17, wherein the MOSFET tube 5 is used to provide a pulsed enable signal to the vibrating string sensor and a constant enable signal to the RS485 sensor, and the common signal stage LS17 has a third normally closed contact connected to the vibrating string signal chain 6 and a third normally open contact connected to the MOSFET tube 5, and the common signal stage LS17 is connected to the first normally open contact;

[0040] The second-level signal switching module B path 4, the second-level signal switching module B path 4 includes a common signal level LS19, the common signal level LS19 has a fourth normally closed contact connected to the temperature signal chain 7, and a fourth normally open contact connected to the RS485 driver 8, the common signal level LS19 is connected to the second normally open contact.

[0041] It can be understood that by setting the first-level signal switching module A path 1 and the first-level signal switching module B path 2, when different sensors need to be used according to the on-site conditions, the common signal level LS1 and the common signal level LS3 can be connected to the vibrating string sensor temperature signal line or the RS485 sensor data transmission line at the same time. When there is no need to use the sensor to collect signals, the circuit is switched to the first normally closed contact and the second normally closed contact. When the sensor needs to be used to collect signals, the circuit is switched to the first normally open contact and the second normally open contact, and then connected to the common signal level LS17 and the common signal level LS19, the second-level signal switching module A path 3 and the second-level signal switching module B path 4, when When a vibrating string sensor is connected, first switch to the third normally open contact, excite the vibrating string sensor through MOSFET tube 5, then switch to the third normally closed contact, condition and measure the vibrating string signal through the vibrating string signal chain 6, and switch to the fourth normally closed contact at the same time to make the temperature signal chain 7 work, so as to measure the thermometer inside the vibrating string sensor. When an RS485 sensor is connected, switch to the third normally open contact, so that MOSFET tube 5 provides a constant enable signal to the RS485 sensor, and provides a constant power supply to the RS485 sensor. At the same time, switch to the fourth normally open contact, connect the RS485 driver 8, and read the data of the RS485 sensor.

[0042] This utility model patent designs a switchable circuit between a vibrating string and an RS485 interface, so that any channel of a multi-channel device can be configured as a vibrating string sensor measurement channel or an RS485 sensor measurement channel, thereby improving the flexibility of the device in on-site use and avoiding channel idleness and waste due to channel limitations.

[0043] It should be noted that the general vibrating string sensor measurement interface requires two sets of wires: two wires for the vibrating string signal and two wires for the temperature signal, a total of two sets of four-core wires. The RS485 sensor measurement interface also requires two sets of wires: two wires to provide power to the sensor and two signal wires for the RS485 bus, also two sets of four-core wires. The signals of the vibrating string sensor and the RS485 sensor are similar and symmetrical.

[0044] To avoid channel crosstalk and conflict, signal switching should meet the following conditions:

[0045] (1) The channels that are not connected to the signal chain are open by default;

[0046] (2) When a channel is connected to a signal chain, other signal chains are physically isolated from the channel (i.e., high impedance or open circuit).

[0047] For further information, please refer again to Figure 2, the common signal level LS1 has pin 3 and pin 6, the first normally closed contact has pin 2 and pin 7, the first normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS1 are connected to the vibrating string sensor signal power line or the RS485 sensor power supply line, pin 3 and pin 6 of the common signal level LS1 are respectively connected to pin 2 and pin 7 of the first normally closed contact, and pin 3 and pin 6 of the common signal level LS1 are respectively connected to pin 4 and pin 5 of the first normally open contact.

[0048] For further information, please refer again to Figure 3 , the common signal level LS3 has pin 3 and pin 6, the second normally closed contact has pin 2 and pin 7, the second normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS3 are connected to the vibrating string sensor signal power line or the RS485 sensor power supply line, pin 3 and pin 6 of the common signal level LS3 are respectively connected to pin 2 and pin 7 of the second normally closed contact, and pin 3 and pin 6 of the common signal level LS3 are respectively connected to pin 4 and pin 5 of the second normally open contact.

[0049] For further information, please refer again to Figure 4 , the common signal level LS17 has pin 3 and pin 6, the third normally closed contact has pin 2 and pin 7, the third normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the first normally open contact, pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 2 and pin 7 of the third normally closed contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the third normally open contact.

[0050] It should be noted that the pin 5 of the third normally open contact is connected to the constant voltage power supply of the MOSFET tube 5, and the pin 4 is grounded, thereby forming an excitation circuit of the vibrating string sensor.

[0051] For further information, please refer again to Figure 5 , the common signal level LS19 has pin 3 and pin 6, the fourth normally closed contact has pin 2 and pin 7, the fourth normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS19 are respectively connected to pin 4 and pin 5 of the second normally open contact, pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 2 and pin 7 of the fourth normally closed contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the fourth normally open contact.

[0052] It should be noted that the pin 4 and the pin 5 of the fourth normally open contact are respectively connected to the two detection signal lines of RS485 to connect to the RS485 driver 8 .

[0053] Preferably, the common signal level LS1 and the common signal level LS3 are respectively provided with a freewheeling diode D2 and a freewheeling diode D4, and the freewheeling diode D2 and the freewheeling diode D4 are used to absorb the current generated by the reverse electromotive force of the signal relay coil when it is in action; the common signal level LS17 is provided with freewheeling diodes D19 and D20, and a resistor R43, the freewheeling diode D19 and the resistor R43 are used to absorb the pulse current generated by the reverse electromotive force induced by the vibrating string sensor coil, and the freewheeling diode D20 is used to absorb the current generated by the reverse electromotive force of the signal relay coil when it is in action.

[0054] Further, the first-level signal switching module A path 1 also includes a first drive circuit, the first drive circuit includes a resistor R3, a resistor R5, and a transistor Q1, and the first drive circuit is used to switch the first normally closed contact and the first normally open contact. The first-level signal switching module B path 2 also includes a second drive circuit, the second drive circuit includes a resistor R2, a resistor R7, and a transistor Q3, and the second drive circuit is used to switch the second normally closed contact and the second normally open contact. The second-level signal switching module A path 3 includes a third drive circuit, and the third drive circuit includes a resistor R 44, resistor R45, and transistor Q19, the third drive circuit is used to switch the third normally closed contact and the third normally open contact, the second-level signal switching module B path 4 includes a fourth drive circuit, the fourth drive circuit includes a resistor R59, a resistor R61, and a transistor Q61, the fourth drive circuit is used to switch the fourth normally closed contact and the fourth normally open contact; the vibrating string and RS485 switchable circuit also includes a microcontroller 9, and the microcontroller 9 is electrically connected to the first drive circuit, the second drive circuit, the third drive circuit, the fourth drive circuit, and the MOSFET tube 5 respectively.

[0055] It can be understood that the utility model sends electrical signals to the first drive circuit, the second drive circuit, the third drive circuit, the fourth drive circuit, and the MOSFET tube 5 through the microcontroller 9 to make them work, and then controls the opening and closing of each normally open contact and normally closed contact through each drive circuit to achieve control of the entire circuit.

[0056] Specifically, the MOSFET tube 5 includes a neutral line T2, a transistor Q18, a resistor R36, a resistor R37, a resistor R40, and a resistor R41.

[0057] In summary, the vibrating string and RS485 interface switchable circuit in the above embodiments of the utility model, by designing a vibrating string and RS485 interface switchable circuit, can realize that any channel of a multi-channel device can be configured as a vibrating string sensor measurement channel or an RS485 sensor measurement channel, thereby improving the flexibility of the device in field use and avoiding channel idleness and waste due to channel restrictions.

[0058] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] The above-mentioned embodiments only express several implementation methods of the utility model, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent of the utility model. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the utility model, and these all belong to the protection scope of the utility model. Therefore, the protection scope of the utility model patent shall be based on the attached claims.

Claims

1. A vibrating string and RS485 interface switchable circuit, characterized in that: include: A first-stage signal switching module A path, wherein the first-stage signal switching module A path comprises a common signal stage LS1, wherein the common signal stage LS1 is connected to a vibrating-wire sensor signal power line or an RS485 sensor power supply line, and wherein the common signal stage LS1 has a first normally closed contact and a first normally open contact; The first-level signal switching module B path includes a common signal level LS3, the common signal level LS3 is connected to the vibrating wire sensor temperature signal line or the RS485 sensor data transmission line, and the common signal level LS3 has a second normally closed contact and a second normally open contact; A second-stage signal switching module A path, the second-stage signal switching module A path includes a MOSFET tube and a common signal stage LS17, the MOSFET tube is used to provide a pulsed enable signal to the vibrating string sensor and a constant enable signal to the RS485 sensor, the common signal stage LS17 has a third normally closed contact connected to the vibrating string signal chain and a third normally open contact connected to the MOSFET tube, and the common signal stage LS17 is connected to the first normally open contact; The second-level signal switching module B path, the second-level signal switching module B path includes a common signal level LS19, the common signal level LS19 has a fourth normally closed contact connected to the temperature signal chain, and a fourth normally open contact connected to the RS485 driver, the common signal level LS19 is connected to the second normally open contact.

2. The vibrating wire and RS485 interface switchable circuit according to claim 1, characterized in that: The common signal level LS1 has pin 3 and pin 6, the first normally closed contact has pin 2 and pin 7, the first normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS1 are connected to the vibrating string sensor signal power line or the RS485 sensor power supply line, pin 3 and pin 6 of the common signal level LS1 are respectively connected to pin 2 and pin 7 of the first normally closed contact, and pin 3 and pin 6 of the common signal level LS1 are respectively connected to pin 4 and pin 5 of the first normally open contact.

3. The vibrating string and RS485 interface switchable circuit according to claim 2, characterized in that: The common signal level LS3 has pin 3 and pin 6, the second normally closed contact has pin 2 and pin 7, the second normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS3 are connected to the vibrating string sensor signal power line or the RS485 sensor power supply line, pin 3 and pin 6 of the common signal level LS3 are respectively connected to pin 2 and pin 7 of the second normally closed contact, and pin 3 and pin 6 of the common signal level LS3 are respectively connected to pin 4 and pin 5 of the second normally open contact.

4. The vibrating string and RS485 interface switchable circuit according to claim 1, characterized in that: The common signal stage LS1 and the common signal stage LS3 are provided with a freewheeling diode D2 and a freewheeling diode D4 respectively. The freewheeling diode D2 and the freewheeling diode D4 are used to absorb the current generated by the reverse electromotive force of the signal relay coil when it is in action.

5. The vibrating wire and RS485 interface switchable circuit according to claim 3, characterized in that: The common signal level LS17 has pin 3 and pin 6, the third normally closed contact has pin 2 and pin 7, and the third normally open contact has pin 4 and pin 5. Pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the first normally open contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 2 and pin 7 of the third normally closed contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the third normally open contact.

6. The vibrating string and RS485 interface switchable circuit according to claim 5, characterized in that: The common signal level LS19 has pin 3 and pin 6, the fourth normally closed contact has pin 2 and pin 7, the fourth normally open contact has pin 4 and pin 5, pin 3 and pin 6 of the common signal level LS19 are respectively connected to pin 4 and pin 5 of the second normally open contact, pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 2 and pin 7 of the fourth normally closed contact, and pin 3 and pin 6 of the common signal level LS17 are respectively connected to pin 4 and pin 5 of the fourth normally open contact.

7. The vibrating string and RS485 interface switchable circuit according to claim 1, characterized in that: The common signal level LS17 is provided with freewheeling diodes D19 and D20, and a resistor R43. The freewheeling diode D19 and the resistor R43 are used to absorb the pulse current generated by the reverse electromotive force induced by the vibrating string sensor coil, and the freewheeling diode D20 is used to absorb the current generated by the reverse electromotive force of the signal relay coil when it is in action.

8. The vibrating string and RS485 interface switchable circuit according to claim 6, characterized in that: The first-level signal switching module A also includes a first drive circuit, which includes a resistor R3, a resistor R5, and a transistor Q1. The first drive circuit is used to switch the first normally closed contact and the first normally open contact. The first-level signal switching module B also includes a second drive circuit, which includes a resistor R2, a resistor R7, and a transistor Q3. The second drive circuit is used to switch the second normally closed contact and the second normally open contact. The second-level signal switching module A includes a third drive circuit, which includes a resistor R44, a resistor R45, and a transistor Q19. The third drive circuit is used to switch the third normally closed contact and the third normally open contact. The second-level signal switching module B includes a fourth drive circuit, which includes a resistor R59, a resistor R61, and a transistor Q61. The fourth drive circuit is used to switch the fourth normally closed contact and the fourth normally open contact.

9. The vibrating string and RS485 interface switchable circuit according to claim 8, characterized in that: The vibrating string and RS485 switchable circuit further comprises a microcontroller, and the microcontroller is electrically connected to the first drive circuit, the second drive circuit, the third drive circuit, the fourth drive circuit, and the MOSFET tube respectively.

10. The vibrating string and RS485 interface switchable circuit according to claim 1, characterized in that: The MOSFET tube includes a neutral line T2, a transistor Q18, a resistor R36, a resistor R37, a resistor R40, and a resistor R41.

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