Anti-attenuation anti-interference circuit for long-distance transmission of voltage signals

Abstract

The invention provides an anti-attenuation and anti-interference circuit for long-distance transmission of voltage signals. The anti-attenuation and anti-interference circuit comprises a first measuring range adjusting circuit, a zero setting circuit, an isolation amplifying circuit, a U / I conversion circuit, a dynamic feedback compensating circuit, an I / U conversion circuit, a differential sampling circuit, a zero taking circuit and a second measuring range adjusting circuit. According to the invention, attenuation and interference can be effectively resisted in the long-distance transmission process of voltage signals, the accuracy and stability of signal transmission are ensured, meanwhile, a broken line detection function is provided, the fault of a signal transmission line can be found in time, and the strict requirements on high-reliability and low-bit error rate signal transmission in the manufacturing of communication system equipment are met.

Description

Technical Field

[0001] This invention relates to the field of power signal processing and transmission technology, specifically to an anti-attenuation and anti-interference circuit for long-distance transmission of voltage signals. It is particularly suitable for the signal transmission stage in the manufacturing of communication system equipment such as new-generation mobile communication base station equipment and digital program-controlled exchanges, and belongs to the key anti-attenuation and anti-interference technology to ensure stable long-distance transmission of voltage signals during the manufacturing process of the above-mentioned equipment. Background Technology

[0002] In industrial settings, when acquired signals are conditioned into voltage signals and need to be transmitted over long distances, several problems arise. First, because voltage signals are being transmitted, the transmission lines are highly susceptible to noise interference, affecting the accuracy and stability of the signal. Second, the distributed resistance of the transmission lines causes voltage drops, resulting in deviations between the voltage signal received at the receiving end and that at the transmitting end, reducing the accuracy of signal transmission. Furthermore, providing a suitable operating voltage for the instrumentation amplifiers in the field is also a challenge.

[0003] To address the aforementioned issues and avoid the influence of related noise, current is currently widely used for signal transmission in industrial settings. This is because current signals are less susceptible to interference, and the internal resistance of a current source is infinite, meaning that the resistance of the conductor connected in series in the loop does not affect accuracy; hundreds of meters can be transmitted over ordinary twisted-pair cables. However, existing voltage signal transmission methods still have many shortcomings and urgently need improvement. Summary of the Invention

[0004] To address the various problems existing in the prior art, this invention provides an anti-attenuation and anti-interference circuit for long-distance voltage signal transmission. This circuit can effectively resist attenuation and interference during long-distance voltage signal transmission, ensuring the accuracy and stability of signal transmission. Simultaneously, the circuit also has a disconnection detection function, enabling timely detection of faults in the signal transmission line.

[0005] The present invention achieves the above objectives through the following technical solutions: An anti-attenuation and anti-interference circuit for long-distance transmission of voltage signals, characterized in that it comprises: The first range adjustment circuit is used to receive raw voltage signals of different ranges and convert the raw voltage signals of different ranges into the first range voltage signal. The zero-adjustment circuit, when receiving a voltage signal of 0 from the first range, controls the U / I conversion circuit to generate a specified current signal to detect whether the line is broken. An isolation amplifier circuit receives signals transmitted from a zero-adjustment circuit and is used to isolate and amplify voltage signals. U / I conversion circuit is used to convert the voltage signal transmitted by the isolation amplifier circuit into a first current signal; The dynamic feedback compensation circuit is connected in series at the output of the U / I conversion circuit. It acquires the first current signal in real time, compares the voltage drop with the reference voltage, and generates a compensation signal. I / U conversion circuit is used to convert the first current signal transmitted by the U / I conversion circuit into a converted voltage signal; The differential sampling circuit acquires the converted voltage signal transmitted by the I / U conversion circuit based on the principle of resistor voltage division; The zero-taking circuit eliminates the bias voltage added to the converted voltage signal transmitted by the I / U conversion circuit due to the generation of a specified current signal. The second range adjustment circuit adjusts the conversion voltage signal transmitted by the I / U conversion circuit so that its value is within the full range of the sampling chip.

[0006] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided, wherein the current output terminal of the U / I conversion circuit is directly connected to the current input terminal of the I / U conversion circuit through a long-distance transmission line composed of twisted pair or shielded twisted pair; the voltage output terminal of the I / U conversion circuit is connected to the differential sampling circuit through PCB traces or shielded wires. The U / I conversion circuit converts the voltage signal after pre-conditioning into a 4-20mA constant current signal. It utilizes the constant current source characteristics of the current signal to offset the attenuation effect of the distributed resistance of the long-distance transmission line on the signal. The I / U conversion circuit linearly converts the 4-20mA current signal into a converted voltage signal through a precision resistor network. This converted voltage signal serves as the input to the differential sampling circuit, enabling electrical isolation between the transmitting and receiving ends.

[0007] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided. The U / I conversion circuit includes an operational amplifier U1B, resistors R1, R2, R3, R4, R5, and a transistor Q1. The non-inverting input terminal of the operational amplifier U1B is connected to the input voltage signal through resistor R2. U i The inverting input terminal of operational amplifier U1B is connected to the emitter of transistor Q1 through resistor R1, and the inverting input terminal of operational amplifier U1B is grounded through resistor R3. The output terminal of operational amplifier U1B is connected to the base of transistor Q1. The collector of transistor Q1 is connected to the power supply VCC. The emitter of transistor Q1 is connected to one end of resistor R4. The other end of resistor R4 is connected to the output node UB. The output node UB is connected to the non-inverting input terminal of operational amplifier U1B through resistor R5.

[0008] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided. In the U / I conversion circuit, the current flowing through resistor R2 is... I R2 Equal to the current flowing through resistor R5 I R5 ,Right now I R2 = I R5 ,in, I R5 =( U B - U P ) / R5, I R2 =( U i - U P Since R2 = R5, therefore I R2 =( U i - U P ) / R5, resulting in the following formula:

[0009] Based on the virtual short characteristic of operational amplifiers, the voltage at the non-inverting input terminal of operational amplifier U1B is... U P equal to the voltage at the inverting input terminal U N ,Right now U P = U N ; Combining the non-inverting amplifier circuit with resistors R1=R3, the output voltage of operational amplifier U1B satisfies: U A =2 U N ; Substituting the virtual short relation, we obtain the following formula:

[0010] in, and The node voltage is the current flowing through resistor R4. ; Since the resistance of resistor R5 is in the megaohm range, I R5 ≈0, therefore the output current is expressed as:

[0011] When the input voltageU i When the output current varies within the range of 0 to 2V I out Linear correspondence from 0 to 20 mA.

[0012] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided. The differential sampling circuit includes two signal terminals, a differential sampling network, resistors R15 and R16, and an operational amplifier U4B. The differential sampling network includes resistors R12, R13, and R14. The two signal terminals are respectively connected to nodes U1 and U2 for receiving the converted voltage signal transmitted by the I / U conversion circuit. One end of resistor R12 is connected to node U1, and the other end is connected to the non-inverting input terminal of operational amplifier U4B. One end of resistor R15 is connected to the non-inverting input terminal of operational amplifier U4B, and the other end is grounded. One end of resistor R13 is connected to node U2, and the other end is connected to the inverting input terminal of operational amplifier U4B. One end of resistor R16 is connected to the inverting input terminal of operational amplifier U4B, and the other end is connected to the output terminal of operational amplifier U4B. Resistor R14 is connected across nodes U1 and U2.

[0013] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided. In the differential sampling circuit, the voltage at the non-inverting input terminal of operational amplifier U4B is... V 正 The voltage at node U1 is obtained by dividing the voltage across resistors R12 and R15, as shown in the formula: Since operational amplifier U4B operates in the linear region, the voltage at the non-inverting input of operational amplifier U4B is... V 正 voltage at the inverting input terminal V 负 Equal, that is V 正 = V 负 ; The input impedance of operational amplifier U4B approaches infinity, therefore the current flowing through resistor R16 is equal to the current flowing through resistor R13, as shown in the formula:

[0014] When the resistance values ​​of resistors R12, R15, R13, and R16 satisfy... R 12= R 15= R 13= R At 16:00, the output voltage of operational amplifier U4B is expressed as: in, and For nodes and nodes The voltage.

[0015] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided. The zero-adjustment circuit includes a reference voltage source, a resistor R6, a potentiometer PR2, an operational amplifier U2B and a resistor R9. The output terminal of the reference voltage source is connected to the first fixed terminal of the potentiometer PR2 through the resistor R6. The second fixed terminal of the potentiometer PR2 is grounded. The sliding terminal of the potentiometer PR2 is connected to the non-inverting input terminal of the operational amplifier U2B. The inverting input and output terminals of operational amplifier U2B are shorted to form a voltage follower structure; the output terminal of operational amplifier U2B is connected to the isolation amplifier circuit through resistor R9.

[0016] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided, wherein a reference voltage is provided through a reference voltage source in the zero-adjustment circuit. The voltage is divided by resistor R6 and potentiometer PR2, resulting in an adjustable voltage at the sliding contact of potentiometer PR2. The formula is: in, This is the real-time resistance value between the sliding contact of potentiometer PR2 and the ground terminal. The nominal total resistance value of potentiometer PR2 is determined by adjusting the position of the slider of potentiometer PR2. Adjust to the preset value; Using operational amplifier U2B as a voltage follower, and utilizing its virtual short and virtual open characteristics, the voltage divider is transformed... It follows the output to the output terminal without attenuation, that is... = ; When the first range voltage signal input to the zero-adjustment circuit is 0V, adjust potentiometer PR2 to... =K value, at this time the output terminal The output voltage is a K-value voltage, which is converted into a minimum current signal by an isolation amplifier circuit and a U / I conversion circuit. This minimum current signal is used to detect whether the line is broken. If the long-distance transmission line is normal, the U / I conversion circuit outputs the minimum current; if the line is broken, the current signal disappears.

[0017] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided. The first range adjustment circuit includes a terminal J1, a resistor R8, a potentiometer PR1, an operational amplifier U2A, and a resistor R3. The signal terminal J1 is used to receive raw voltage signals of different ranges. Ui The grounding terminal of terminal J1 is grounded; one end of resistor R8 is connected to the signal terminal of terminal J1 and the non-inverting input terminal of operational amplifier U2A, and the other end is grounded; the two fixed terminals of potentiometer PR1 are connected to the inverting input terminal of operational amplifier U2A and ground respectively, the sliding terminal of potentiometer PR1 is connected to one end of resistor R3, and the other end of resistor R3 is connected to the zero-adjustment circuit; the inverting input terminal and the output terminal of operational amplifier U2A are directly connected to form a voltage follower structure.

[0018] In the first range adjustment circuit, the input voltage U i The voltage is applied between the two fixed terminals of potentiometer PR1. By adjusting the position of the sliding terminal of potentiometer PR1, the voltage division ratio is changed so that when... U i When at full scale, the voltage output from the sliding terminal of potentiometer PR1 U P 2 Precision is 1V; Operational amplifier U2A, acting as a voltage follower, utilizes its virtual short and virtual open characteristics to divide the voltage across the sliding contact. U P 2 It follows the output to the output terminal without attenuation, that is... U O = U P2 .

[0019] According to the present invention, a voltage signal long-distance transmission anti-attenuation and anti-interference circuit is provided. The second range adjustment circuit includes an operational amplifier U6B, resistors R21 and R23, and a potentiometer PR4. The non-inverting input terminal of the operational amplifier U6B is connected to a zero-taking circuit through resistor R21; the inverting input terminal of the operational amplifier U6B is connected to the fixed terminals of resistors R23 and potentiometer PR4; the sliding terminal of potentiometer PR4 is connected to the output terminal of the operational amplifier U6B; the output terminal of the operational amplifier U6B is connected to the signal input terminal of a sampling chip for transmitting the range-adjusted voltage signal to the sampling chip. In the second range adjustment circuit, since the input impedance of operational amplifier U6B approaches infinity, the current flowing through resistor R21 is approximately zero. Therefore, the voltage at the non-inverting input terminal of operational amplifier U6B is... Equal to the converted voltage signal output by the I / U conversion circuit ,Right now ; Potentiometer PR4 and resistor R23 are connected in series to form an adjustable voltage divider circuit to convert voltage signals. The input is fed to potentiometer PR4 via resistor R23, and the sliding contact of potentiometer PR4 will change the total resistance. R PR4总 Divided into upper part RPR4上 lower part R PR4下 and satisfy R PR4上 + R PR4下 = R PR4总 The voltage at the inverting input terminal of operational amplifier U6B The voltage division is equal to the voltage across the sliding terminal of potentiometer PR4. Considering the current-limiting effect of resistor R23, the voltage division relationship is as follows: Based on the virtual short characteristic of operational amplifiers = , United = Using the voltage divider formula, the output voltage is obtained. With input voltage Linear amplification relationship:

[0020] By adjusting the position of the sliding end of potentiometer PR4, the change R PR4上 The resistance value is linearly adjusted to adjust the output voltage. The magnification factor.

[0021] Therefore, compared with the prior art, the anti-attenuation and anti-interference circuit for long-distance voltage signal transmission proposed in this invention has the following specific advantages: 1. Traditional voltage-to-current circuits output 0mA when the voltage signal is 0V, making it impossible to effectively detect whether the signal transmission line is broken. This invention, by introducing a zero-adjustment circuit, allows the output current signal to be adjusted to 4mA when the voltage signal is 0V. This improvement makes line break detection possible, greatly enhancing the reliability of signal transmission and maintenance efficiency.

[0022] 2. Traditional U / I conversion circuits often require specialized chips and microcontrollers, which are not only complex to design but also costly. The circuit design of this invention uses common and fewer components, significantly reducing the manufacturing cost of the circuit, while simplifying the circuit design and improving production efficiency.

[0023] 3. This invention strictly controls the upper limit of the output current to below 20mA, meeting explosion-proof requirements. In flammable and explosive environments, the spark energy caused by switching on and off a 20mA current is insufficient to ignite gas, thus greatly improving the safety of the circuit in these environments.

[0024] 4. By introducing an isolation amplifier circuit and a differential sampling circuit, this invention effectively improves the anti-interference capability of voltage signals during long-distance transmission. The isolation amplifier circuit can isolate and amplify voltage signals, reducing the impact of external noise on the signal; the differential sampling circuit can accurately acquire voltage signals, further improving the accuracy and stability of the signal.

[0025] 5. This invention ensures the accuracy of voltage signals during transmission through the design of range adjustment circuit and zero-taking circuit: the range adjustment circuit can convert voltage signals of different ranges into a range suitable for subsequent processing; the zero-taking circuit can subtract the bias voltage added to generate 4mA and restore the original voltage signal, thereby ensuring the accuracy of signal transmission.

[0026] 6. The circuit design of this invention has strong adaptability and can handle voltage signal inputs of different ranges (such as 0~3.3V, 0~5V, or 0~10V). By adjusting the relevant potentiometers, the circuit can easily adapt to voltage signal inputs of various ranges, improving the versatility and flexibility of the circuit.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit according to the present invention.

[0029] Figure 2 This is an application schematic diagram of an embodiment of the anti-attenuation and anti-interference circuit for long-distance transmission of voltage signals according to the present invention.

[0030] Figure 3 This is a first circuit diagram of an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit according to the present invention.

[0031] Figure 4 This is a second circuit diagram of an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit according to the present invention.

[0032] Figure 5 This is a circuit diagram of the U / I conversion circuit in an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit of the present invention.

[0033] Figure 6 This is a circuit diagram of the differential sampling circuit in an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit of the present invention.

[0034] Figure 7 This is a circuit diagram of the zero-adjustment circuit in an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit of the present invention.

[0035] Figure 8 This is a circuit diagram of the first range adjustment circuit in an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit of the present invention.

[0036] Figure 9 This is a circuit diagram of the second range adjustment circuit in an embodiment of a voltage signal long-distance transmission anti-attenuation and anti-interference circuit of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0039] An embodiment of an anti-attenuation and anti-interference circuit for long-distance transmission of voltage signals. See Figures 1 to 9 This embodiment provides an anti-attenuation and anti-interference circuit for long-distance transmission of voltage signals, comprising: The first range adjustment circuit is used to receive raw voltage signals of different ranges and convert them into the first range voltage signal, providing a signal with a uniform range for circuit processing to meet the requirements of different starting signals in long-distance transmission. The zero-adjustment circuit, when receiving a voltage signal of 0 from the first range, controls the U / I conversion circuit to generate a specified current signal to detect whether the line is broken, ensuring that signal interruption problems can be detected in a timely manner during long-distance transmission. The isolation amplifier circuit receives the signal transmitted by the zero-adjustment circuit and is used to isolate and amplify the voltage signal, so that the signal is within the voltage range of 0-2V before being transmitted to the U / I conversion circuit. The isolation amplification process can effectively reduce the interference of external noise on the signal during long-distance transmission and improve the anti-interference capability of signal transmission. U / I conversion circuit is used to convert the voltage signal transmitted by the isolation amplifier circuit into a first current signal, for example, converting it into a 4-20mA current signal and outputting it. At the same time, the current signal is transmitted to the I / U conversion circuit. Using current signal transmission can avoid the voltage drop problem caused by the distributed resistance of the transmission line. Moreover, the internal resistance of the current source is infinite, and the resistance of the wire in series in the loop does not affect the accuracy. It is more suitable for long-distance transmission on ordinary twisted pair cables, and the transmission distance can reach hundreds of meters. The dynamic feedback compensation circuit is connected in series at the output of the U / I conversion circuit. It acquires the first current signal in real time, compares the voltage drop with the reference voltage, and generates a compensation signal. I / U conversion circuit is used to convert the first current signal transmitted by the U / I conversion circuit into a converted voltage signal; The differential sampling circuit acquires the converted voltage signal transmitted by the I / U conversion circuit based on the principle of resistor voltage division; The zero-taking circuit eliminates the bias voltage added to the converted voltage signal transmitted by the I / U conversion circuit due to the generation of a specified current signal; for example, it subtracts the bias voltage added to generate 4mA, thereby eliminating the influence of bias voltage on the signal, improving signal accuracy, and ensuring signal quality after long-distance transmission.

[0040] The second range adjustment circuit regulates the converted voltage signal transmitted by the I / U conversion circuit to ensure its value is within the full-scale range of the sampling chip, thereby better utilizing the sampling chip's range for more accurate sampling. Furthermore, the second range adjustment circuit uses a voltage follower to adjust the potentiometer so that U0 = 1V at full scale, which is then amplified through isolation to become 2V, and further converted into a 20mA current. This adapts to different input voltage ranges of 0~3.3V, 0~5V, or 0~10V, meeting the precise sampling requirements of different sampling chips and ranges during long-distance transmission.

[0041] In this embodiment, the current output terminal of the U / I conversion circuit is directly connected to the current input terminal of the I / U conversion circuit via a long-distance transmission line composed of twisted pair or shielded twisted pair; the voltage output terminal of the I / U conversion circuit is connected to the differential sampling circuit via PCB traces or shielded wires. The U / I conversion circuit converts the voltage signal after pre-conditioning into a 4-20mA constant current signal. Utilizing the constant current source characteristics of the current signal, such as the current source's internal resistance approaching infinity, the distributed resistance of the transmission line connected in series in the loop does not change the current magnitude, thus completely offsetting the signal attenuation effect of the distributed resistance of long-distance transmission lines (transmission distance ≥ 100 meters). Long-distance transmission lines use a twisted-pair structure, which forms a closed current loop through two wires. The electromagnetic coupling characteristics of the twisted pair are used to cancel external common-mode interference, such as 50Hz power frequency noise and radio frequency interference, thereby improving the signal-to-noise ratio of the transmitted signal. The I / U conversion circuit linearly converts a 4-20mA current signal into a converted voltage signal (such as 0-2V or 0-5V) through a precision resistor network (such as low-temperature drift, high-precision resistors). This converted voltage signal serves as the input to the differential sampling circuit, achieving electrical isolation between the transmitting end (such as the sensor / transmitter side) and the receiving end (such as the data acquisition card / controller side) (current signal transmission has no direct electrical connection), thus avoiding signal distortion caused by the potential difference between the two locations.

[0042] In this embodiment, a dynamic feedback compensation circuit is added between the U / I conversion circuit and the I / U conversion circuit, including: A current sampling resistor Rf is connected in series at the output of the U / I conversion circuit to acquire and transmit the current signal in real time. Error amplifier U3 compares the voltage drop across the current sampling resistor (Vf=Iout×Rf) with the reference voltage Vref to generate a compensation signal; Compensation signal injection module: Feeds the compensation signal back to the input of the U / I conversion circuit after optocoupler isolation, and mixes it with the original voltage signal. U i The superposition and dynamic adjustment of the output current of the U / I conversion can offset the current error caused by dynamic resistance changes in the transmission line (such as temperature drift and contact resistance changes).

[0043] Furthermore, the differential sampling circuit, zero-taking circuit, and second range adjustment circuit all use low-noise operational amplifiers, such as OP2177, to reduce the impact of the circuit's own noise on long-distance transmission signals and ensure that the signal-to-noise ratio of the received signal is ≥60dB.

[0044] Furthermore, the MCU periodically detects the output current of the U / I conversion circuit, the sampling error of the differential sampling circuit, and the resistance value of the transmission line to generate fault codes, such as open circuit, overload, and drift. These fault codes, along with real-time sampling data, are encrypted and uploaded to a cloud server, supporting remote monitoring and early warning. This embodiment achieves integrated "transmission + monitoring + early warning" through self-diagnosis and wireless transmission, reducing on-site maintenance costs and is suitable for distributed sensor networks (such as smart city pipeline monitoring and agricultural greenhouse environmental monitoring).

[0045] In this embodiment, as Figure 5 As shown, the U / I conversion circuit includes operational amplifier U1B, resistors R1, R2, R3, R4, R5, and transistor Q1. The non-inverting input terminal of operational amplifier U1B is connected to the input voltage signal through resistor R2. Ui The inverting input terminal of operational amplifier U1B is connected to the emitter of transistor Q1 through resistor R1, and the inverting input terminal of operational amplifier U1B is grounded through resistor R3. The output terminal of operational amplifier U1B is connected to the base of transistor Q1. The collector of transistor Q1 is connected to power supply VCC. The emitter of transistor Q1 is connected to one end of resistor R4. The other end of resistor R4 is connected to output node UB. Output node UB is connected to the non-inverting input terminal of operational amplifier U1B through resistor R5. The output current Iout is drawn from output node UB.

[0046] In this embodiment, the U / I conversion circuit achieves linear voltage-to-current conversion based on Kirchhoff's Current Law (KCL), the virtual short characteristic of operational amplifiers, and the negative feedback amplification principle. Specifically, it includes: UP node KCL equation: Current flowing through resistor R2 I R2 Equal to the current flowing through resistor R5 I R5 ,Right now I R2 = I R5 ,in, I R5 =( U B - U P ) / R5, I R2 =( U i - U P Since R2 = R5, therefore I R2 =( U i - U P By combining equations and simplifying to R5, we obtain the following formula:

[0047] Virtual Short and Negative Feedback Amplification: Based on the virtual short characteristic of operational amplifiers, the voltage at the non-inverting input of operational amplifier U1B... U P equal to the voltage at the inverting input terminal U N ,Right now U P = U N ;Considering the non-inverting amplifier circuit (gain of 2) composed of resistors R1=R3, the output voltage of operational amplifier U1B satisfies: U A=2 U N Substituting the virtual short relation, we obtain the following formula:

[0048] in, and The node voltage is the current flowing through resistor R4. ; KCL equations for UB nodes: Because the resistance of resistor R5 is in the megaohm range (far greater than the 100Ω of R4). I R5 ≈0, therefore the output current is expressed as:

[0049] Based on the above principle, when the input voltage U i When varying within the range of 0 to 2V, the output current Iout can linearly correspond to 0 to 20mA (because R4=100Ω). I out = U i ( / 100Ω) to achieve stable conversion of voltage signals to current signals, adapting to the anti-interference requirements of long-distance transmission.

[0050] In this embodiment, as Figure 6 As shown, the differential sampling circuit includes two signal terminals, a differential sampling network, resistors R15 and R16, and operational amplifier U4B. The differential sampling network includes resistors R12, R13, and R14. The two signal terminals are connected to nodes U1 and U2 respectively, and are used to receive the converted voltage signal transmitted by the I / U conversion circuit. One end of resistor R12 is connected to node U1, and the other end is connected to the non-inverting input of operational amplifier U4B. One end of resistor R15 is connected to the non-inverting input of operational amplifier U4B, and the other end is grounded. One end of resistor R13 is connected to node U2, and the other end is connected to the inverting input of operational amplifier U4B. One end of resistor R16 is connected to the inverting input of operational amplifier U4B, and the other end is connected to the output of operational amplifier U4B. Resistor R14 is connected across nodes U1 and U2. Operational amplifier U4B is model OP2177_3, a high-precision, low-noise operational amplifier.

[0051] In this embodiment, the differential sampling circuit, based on the principle of resistor voltage division, the virtual short characteristic and virtual open characteristic of operational amplifiers, achieves differential and accurate acquisition of voltage signals after long-distance transmission, specifically including: Resistor voltage divider: Voltage at the non-inverting input of operational amplifier U4B V正 The voltage at node U1 is obtained by dividing the voltage across resistors R12 and R15, as shown in the formula: Virtual short characteristic: Because operational amplifier U4B operates in the linear region, the voltage at the non-inverting input terminal of operational amplifier U4B is... V 正 voltage at the inverting input terminal V 负 Equal, that is V 正 = V 负 ; Virtual open circuit characteristic: The input impedance of operational amplifier U4B approaches infinity, therefore the current flowing through resistor R16 is equal to the current flowing through resistor R13, as shown in the formula:

[0052] When the resistance values ​​of resistors R12, R15, R13, and R16 satisfy... R 12= R 15= R 13= R At 16:00, combining the above formulas, we can simplify to obtain: in, and For nodes and nodes The voltage.

[0053] As can be seen, the differential sampling circuit, through its differential input structure (simultaneously acquiring the voltage signals of nodes U1 and U2), utilizes the high common-mode rejection ratio of the operational amplifier to suppress common-mode interference introduced by long-distance transmission lines, such as 50Hz power frequency noise and ground loop interference. At the same time, through precise resistor matching (R12=R15=R13=R16), it achieves linear amplification and accurate restoration of the differential signal, ensuring that the voltage signal acquisition error after long-distance transmission is small.

[0054] In this embodiment, as Figure 7 As shown, the zero-adjustment circuit includes a reference voltage source, a resistor R6, a potentiometer PR2, an operational amplifier U2B, and a resistor R9. The output terminal of the reference voltage source is connected to the first fixed terminal of the potentiometer PR2 through the resistor R6. The second fixed terminal of the potentiometer PR2 is grounded, and the sliding terminal of the potentiometer PR2 is connected to the non-inverting input terminal of the operational amplifier U2B. The inverting input and output terminals of operational amplifier U2B are shorted to form a voltage follower structure; the output terminal of operational amplifier U2B is connected to the isolation amplifier circuit through resistor R9.

[0055] In this embodiment, the zero-adjustment circuit, based on the reference voltage divider principle and the operational amplifier voltage follower characteristic, realizes zero-point calibration and line disconnection detection functions, specifically including: Reference voltage divider: A reference voltage source provides a stable reference voltage, such as 2.5V. This voltage is divided by resistor R6 and potentiometer PR2, resulting in an adjustable voltage divider at the sliding contact of potentiometer PR2. The formula is: in, This is the real-time resistance value between the sliding contact of potentiometer PR2 and the ground terminal. The nominal total resistance value of potentiometer PR2 can be precisely adjusted by changing the position of the slider of potentiometer PR2. U P1 Adjust to the preset value, such as 0.2V; Operational amplifier U2B acts as a voltage follower, utilizing virtual short ( U P1 = U N The characteristics of virtual open circuit (input impedance approaching infinity) and virtual closed circuit (input impedance approaching infinity) will divide the voltage. U P1 It follows the output to the output terminal without attenuation, that is... = At the same time, it achieves signal isolation (avoiding the load of subsequent circuits from affecting the reference voltage source) and impedance matching (high input impedance does not shunt the reference current, and low output impedance drives subsequent circuits). When the voltage signal input to the zero-adjustment circuit is 0V, adjust potentiometer PR2 to... =0.2 V At this time, the output terminal The system outputs a 0.2V voltage, which is transmitted to an isolation amplifier circuit. After amplification (e.g., amplification factor of 2), it becomes a 0.4V voltage, which is then converted into a minimum current signal (e.g., 0.4mA or 4mA) by a U / I conversion circuit, depending on system requirements. This minimum current signal is used to detect whether the line is broken. If the long-distance transmission line is normal, the U / I conversion circuit outputs the minimum current; if the line is broken, the current signal disappears, thus achieving real-time detection of line breakage. At the same time, the minimum current signal ensures that the line breakage detection logic corresponds to a non-zero current for a 0V input, solving the problem in traditional voltage transmission where 0V cannot distinguish between a broken line and a true 0V signal.

[0056] As can be seen, the zero-adjustment circuit in this embodiment solves the problems of large zero-point drift and significant load effect of traditional zero-adjustment circuits through a combination design of reference voltage divider and voltage follower isolation: the reference voltage source provides a stable reference, the potentiometer realizes precise zero-point adjustment, and the voltage follower realizes impedance matching and signal isolation, ensuring that the voltage signal after zeroing is stably transmitted to subsequent circuits; at the same time, the output of the minimum current signal meets the key requirement of long-distance transmission interruption detection, improving the reliability of the system.

[0057] In this embodiment, as Figure 8 As shown, the first range adjustment circuit includes terminal J1, resistor R8, potentiometer PR1, operational amplifier U2A, and resistor R3. Terminal J1 has a signal terminal and a ground terminal. The signal terminal is used to receive the raw voltage signals for different ranges. U i For example, 0~3.3V, 0~5V or 0~10V, the grounding terminal is grounded; one end of resistor R8 is connected to the signal terminal of terminal J1 and the non-inverting input terminal of operational amplifier U2A, and the other end is grounded; the two fixed terminals of potentiometer PR1 are connected to the inverting input terminal of operational amplifier U2A and ground respectively, the sliding terminal of potentiometer PR1 is connected to one end of resistor R3, and the other end of resistor R3 is connected to the zero adjustment circuit; the inverting input terminal and the output terminal of operational amplifier U2A are directly connected to form a voltage follower structure.

[0058] The first range adjustment circuit, based on the potentiometer voltage divider principle and the operational amplifier voltage follower characteristic, achieves unified range conversion of original voltage signals with different ranges. Specifically, it includes: Original voltage signal U i (e.g., 0~10V) is applied between the two fixed terminals of potentiometer PR1. By adjusting the position of the sliding terminal of PR1, the voltage division ratio is changed so that when... U i When at full scale, the voltage output from the sliding contact U P2 Precision is 1V, for example: when U i =10 V At that time, adjust PR1 to make U P2 =1 V ; Operational amplifier U2A, acting as a voltage follower, utilizes the virtual short characteristic (the voltage at the non-inverting input equals the voltage at the inverting input, i.e.) U P2 = U N The virtual open circuit characteristic (input impedance approaches infinity, and the original signal current is not shunted) divides the voltage across the sliding contact. U PFollows the output to the output terminal without attenuation. U O = U P2 Meanwhile, the low output impedance of the voltage follower can drive the subsequent zeroing circuit, avoiding the attenuation of the original signal due to the load effect. As can be seen, through the above voltage division and following process, the original voltage signals of different ranges... U i They are uniformly converted into standard range signals of 0~1V. U O The signal is transmitted to the subsequent zeroing circuit, laying the foundation for standardized processing in subsequent circuits (such as zeroing, isolation amplification, and U / I conversion). The first range adjustment circuit solves the problem of traditional range adjustment circuits requiring hardware replacement to adapt to different ranges by using a combination of potentiometer voltage divider and voltage follower design. In this embodiment, by simply adjusting the sliding end of potentiometer PR1, it can flexibly adapt to various original voltage ranges such as 0~3.3V, 0~5V, and 0~10V, achieving range adaptation without hardware modification, significantly reducing circuit complexity and application cost. At the same time, the isolation effect of the voltage follower avoids the load influence of subsequent circuits on the original signal, ensuring the accuracy of range conversion.

[0059] In this embodiment, as Figure 9 As shown, the second range adjustment circuit includes an operational amplifier U6B, resistors R21 and R23, and a potentiometer PR4. The non-inverting input of the operational amplifier U6B is connected to the zero-taking circuit through resistor R21; the inverting input of the operational amplifier U6B is connected to the fixed terminals of resistor R23 and potentiometer PR4; the sliding terminal of potentiometer PR4 is connected to the output of the operational amplifier U6B; the output of the operational amplifier U6B is connected to the signal input of the sampling chip, used to transmit the range-adjusted voltage signal to the sampling chip.

[0060] The second range adjustment circuit, based on the virtual short and virtual open characteristics of operational amplifiers and the voltage divider principle of potentiometers, achieves precise matching between the voltage signal and the full-scale range of the sampling chip. Specifically, it includes: Virtual open circuit and non-inverting input voltage: Since the input impedance of operational amplifier U6B approaches infinity (virtual open circuit characteristic), the current flowing through resistor R21 is approximately zero. Therefore, the voltage at the non-inverting input terminal of operational amplifier U6B is... Equal to the converted voltage signal output by the I / U conversion circuit ,Right now ; Voltage divider and inverting input voltage: Potentiometer PR4 and resistor R23 are connected in series to form an adjustable voltage divider circuit to convert the voltage signal. The resistor R23 inputs to potentiometer PR4, and the sliding contact of potentiometer PR4 adjusts its total resistance. RPR4总 Divided into upper part R PR4上 lower part R PR4下 and satisfy R PR4上 + R PR4下 = R PR4总 Voltage at the inverting input terminal The voltage division is equal to the voltage across the potentiometer's sliding contact. Considering the current-limiting effect of resistor R23, the voltage division relationship is as follows: Virtual Short and Output Voltage Regulation: Based on the virtual short characteristic of operational amplifiers ( = ), joint = Using the voltage divider formula above, the output voltage can be obtained. With input voltage Linear amplification relationship:

[0061] Since resistors R21 and R23 have the same resistance value, R 21= R 23=10 K Ω±1%, this formula simplifies to a linear adjustment of input voltage × potentiometer voltage division ratio; As can be seen, by adjusting the position of the sliding end of potentiometer PR4, the change R PR4上 The output voltage can be linearly adjusted by changing the resistance value. The amplification factor, for example: when the full scale range of the sampling chip is 0~3.3V, adjust PR4 to make... U O =3.3 V correspond =2 V (Isolation amplified voltage); When the sampling chip's full-scale range is 0~5V, adjust PR4 to... U O =5 V correspond =2 V When the sampling chip's full-scale range is 0~10V, adjust PR4 to... U O =10 V correspond =2 V Finally, the voltage signal after I / U conversion is adjusted to the full-scale range of the sampling chip, ensuring that the sampling chip makes full use of its range resources and improving the sampling accuracy to ≤0.1%, which is far better than the 0.5% error of traditional fixed-range circuits.

[0062] Therefore, the second range adjustment circuit solves the problems of traditional range adjustment circuits requiring hardware resistor replacement and lacking adaptability by using a combination design of fixed resistor + adjustable potentiometer + operational amplifier. It can adapt to sampling chips with different full-scale ranges such as 0~3.3V, 0~5V, and 0~10V without hardware modification simply by adjusting the sliding end of potentiometer PR4. The high input impedance (≥100MΩ) of the operational amplifier avoids the load effect on the I / U conversion circuit and ensures the stability of range adjustment. The precision matching of resistors R21 and R23 ensures the linearity of voltage division and amplification, further improving the accuracy of range adjustment.

[0063] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0064] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A voltage signal long-distance transmission anti-attenuation and anti-interference circuit, characterized in that, include: The first range adjustment circuit is used to receive raw voltage signals of different ranges and convert the raw voltage signals of different ranges into the first range voltage signal. The zero-adjustment circuit, when receiving a voltage signal of 0 from the first range, controls the U / I conversion circuit to generate a specified current signal to detect whether the line is broken. An isolation amplifier circuit receives signals transmitted from a zero-adjustment circuit and is used to isolate and amplify voltage signals. U / I conversion circuit is used to convert the voltage signal transmitted by the isolation amplifier circuit into a first current signal; The dynamic feedback compensation circuit is connected in series at the output of the U / I conversion circuit. It acquires the first current signal in real time, compares the voltage drop with the reference voltage, and generates a compensation signal. I / U conversion circuit is used to convert the first current signal transmitted by the U / I conversion circuit into a converted voltage signal; The differential sampling circuit acquires the converted voltage signal transmitted by the I / U conversion circuit based on the principle of resistor voltage division; The zero-taking circuit eliminates the bias voltage added to the converted voltage signal transmitted by the I / U conversion circuit due to the generation of a specified current signal. The second range adjustment circuit adjusts the conversion voltage signal transmitted by the I / U conversion circuit so that its value is within the full range of the sampling chip.

2. The circuit according to claim 1, characterized in that: The current output terminal of the U / I conversion circuit is directly connected to the current input terminal of the I / U conversion circuit via a long-distance transmission line composed of twisted pair or shielded twisted pair cable; the voltage output terminal of the I / U conversion circuit is connected to the differential sampling circuit via PCB traces or shielded wires. The U / I conversion circuit converts the voltage signal after pre-conditioning into a 4-20mA constant current signal. It utilizes the constant current source characteristics of the current signal to offset the attenuation effect of the distributed resistance of the long-distance transmission line on the signal. The I / U conversion circuit linearly converts the 4-20mA current signal into a converted voltage signal through a precision resistor network. This converted voltage signal serves as the input to the differential sampling circuit, enabling electrical isolation between the transmitting and receiving ends.

3. The circuit according to claim 1, characterized in that: The U / I conversion circuit includes operational amplifier U1B, resistors R1, R2, R3, R4, and R5, and transistor Q1. The non-inverting input of operational amplifier U1B is connected to the input voltage signal through resistor R2. U i The inverting input terminal of operational amplifier U1B is connected to the emitter of transistor Q1 through resistor R1, and the inverting input terminal of operational amplifier U1B is grounded through resistor R3. The output terminal of operational amplifier U1B is connected to the base of transistor Q1. The collector of transistor Q1 is connected to the power supply VCC. The emitter of transistor Q1 is connected to one end of resistor R4. The other end of resistor R4 is connected to the output node UB. The output node UB is connected to the non-inverting input terminal of operational amplifier U1B through resistor R5.

4. The circuit according to claim 3, characterized in that: In the U / I conversion circuit, the current flowing through resistor R2 I R2 Equal to the current flowing through resistor R5 I R5 ,Right now I R2 = I R5 ,in, I R5 =( U B - U P ) / R5, I R2 =( U i - U P Since R2 = R5, therefore I R2 =( U i - U P ) / R5, resulting in the following formula: Based on the virtual short characteristic of operational amplifiers, the voltage at the non-inverting input terminal of operational amplifier U1B is... U P equal to the voltage at the inverting input terminal U N ,Right now U P = U N ; Combining the non-inverting amplifier circuit with resistors R1=R3, the output voltage of operational amplifier U1B satisfies: U A =2 U N ; Substituting the virtual short relation, we obtain the following formula: in, and The node voltage is the current flowing through resistor R4. ; Since the resistance of resistor R5 is in the megaohm range, I R5 ≈0, therefore the output current is expressed as: When the input voltage U i When the output current varies within the range of 0 to 2V I out Linear correspondence from 0 to 20 mA.

5. The circuit according to claim 1, characterized in that: The differential sampling circuit includes two signal terminals, a differential sampling network, resistors R15 and R16, and operational amplifier U4B. The differential sampling network includes resistors R12, R13, and R14. The two signal terminals are connected to nodes U1 and U2 respectively to receive the converted voltage signal transmitted by the I / U conversion circuit. One end of resistor R12 is connected to node U1, and the other end is connected to the non-inverting input of operational amplifier U4B. One end of resistor R15 is connected to the non-inverting input of operational amplifier U4B, and the other end is grounded. One end of resistor R13 is connected to node U2, and the other end is connected to the inverting input of operational amplifier U4B. One end of resistor R16 is connected to the inverting input of operational amplifier U4B, and the other end is connected to the output of operational amplifier U4B. Resistor R14 is connected across nodes U1 and U2.

6. The circuit according to claim 5, characterized in that: In the differential sampling circuit, the voltage at the non-inverting input of operational amplifier U4B is... V 正 The voltage at node U1 is obtained by dividing the voltage across resistors R12 and R15, as shown in the formula: Since operational amplifier U4B operates in the linear region, the voltage at the non-inverting input of operational amplifier U4B is... V 正 voltage at the inverting input terminal V 负 Equal, that is V 正 = V 负 ; The input impedance of operational amplifier U4B approaches infinity, therefore the current flowing through resistor R16 is equal to the current flowing through resistor R13, as shown in the formula: When the resistance values ​​of resistors R12, R15, R13, and R16 satisfy... R 12= R 15= R 13= R At 16:00, the output voltage of operational amplifier U4B is expressed as: in, and For nodes and nodes The voltage.

7. The circuit according to claim 1, characterized in that: The zero-adjustment circuit includes a reference voltage source, a resistor R6, a potentiometer PR2, an operational amplifier U2B, and a resistor R9. The output terminal of the reference voltage source is connected to the first fixed terminal of the potentiometer PR2 through the resistor R6. The second fixed terminal of the potentiometer PR2 is grounded. The sliding terminal of the potentiometer PR2 is connected to the non-inverting input terminal of the operational amplifier U2B. The inverting input and output terminals of operational amplifier U2B are shorted to form a voltage follower structure; the output terminal of operational amplifier U2B is connected to the isolation amplifier circuit through resistor R9.

8. The circuit according to claim 7, characterized in that: In the zero-adjustment circuit, a reference voltage is provided by a reference voltage source. The voltage is divided by resistor R6 and potentiometer PR2, resulting in an adjustable voltage at the sliding contact of potentiometer PR2. The formula is: in, This is the real-time resistance value between the sliding contact of potentiometer PR2 and the ground terminal. The nominal total resistance value of potentiometer PR2 is determined by adjusting the position of the slider of potentiometer PR2. Adjust to the preset value; Using operational amplifier U2B as a voltage follower, and utilizing its virtual short and virtual open characteristics, the voltage divider is transformed... It follows the output to the output terminal without attenuation, that is... = ; When the first range voltage signal input to the zero-adjustment circuit is 0V, adjust potentiometer PR2 to... =K value, at this time the output terminal The output voltage is a K-value voltage, which is converted into a minimum current signal by an isolation amplifier circuit and a U / I conversion circuit. This minimum current signal is used to detect whether the line is broken. If the long-distance transmission line is normal, the U / I conversion circuit outputs the minimum current; if the line is broken, the current signal disappears.

9. The circuit according to any one of claims 1 to 8, characterized in that: The first range adjustment circuit includes terminal J1, resistor R8, potentiometer PR1, operational amplifier U2A, and resistor R3. The signal terminal J1 is used to receive the raw voltage signals for different ranges. U i The grounding terminal of terminal J1 is grounded; one end of resistor R8 is connected to the signal terminal of terminal J1 and the non-inverting input terminal of operational amplifier U2A, and the other end is grounded; the two fixed terminals of potentiometer PR1 are connected to the inverting input terminal of operational amplifier U2A and ground, respectively; the sliding terminal of potentiometer PR1 is connected to one end of resistor R3, and the other end of resistor R3 is connected to the zero-adjustment circuit; the inverting input terminal and the output terminal of operational amplifier U2A are directly connected to form a voltage follower structure. In the first range adjustment circuit, the input voltage U i The voltage is applied between the two fixed terminals of potentiometer PR1. By adjusting the position of the sliding terminal of potentiometer PR1, the voltage division ratio is changed so that when... U i When at full scale, the voltage output from the sliding terminal of potentiometer PR1 U P 2 Precision is 1V; Operational amplifier U2A, acting as a voltage follower, utilizes its virtual short and virtual open characteristics to divide the voltage across the sliding contact. U P 2 It follows the output to the output terminal without attenuation, that is... U O = U P2 .

10. The circuit according to any one of claims 1 to 8, characterized in that: The second range adjustment circuit includes an operational amplifier U6B, resistors R21 and R23, and a potentiometer PR4. The non-inverting input of the operational amplifier U6B is connected to the zero-taking circuit through resistor R21; the inverting input of the operational amplifier U6B is connected to the fixed terminals of resistor R23 and potentiometer PR4; the sliding terminal of potentiometer PR4 is connected to the output of the operational amplifier U6B; the output of the operational amplifier U6B is connected to the signal input of the sampling chip, used to transmit the range-adjusted voltage signal to the sampling chip. In the second range adjustment circuit, since the input impedance of operational amplifier U6B approaches infinity, the current flowing through resistor R21 is approximately zero. Therefore, the voltage at the non-inverting input terminal of operational amplifier U6B is... Equal to the converted voltage signal output by the I / U conversion circuit ,Right now ; Potentiometer PR4 and resistor R23 are connected in series to form an adjustable voltage divider circuit to convert voltage signals. The input is fed to potentiometer PR4 via resistor R23, and the sliding contact of potentiometer PR4 will change the total resistance. R PR4总 Divided into upper part R PR4上 lower part R PR4下 and satisfy R PR4上 + R PR4下 = R PR4总 The voltage at the inverting input terminal of operational amplifier U6B The voltage division is equal to the voltage across the sliding terminal of potentiometer PR4. Considering the current-limiting effect of resistor R23, the voltage division relationship is as follows: Based on the virtual short characteristic of operational amplifiers = , United = Using the voltage divider formula, the output voltage is obtained. With input voltage Linear amplification relationship: By adjusting the position of the sliding end of potentiometer PR4, the change R PR4上 The resistance value is linearly adjusted to adjust the output voltage. The magnification factor.

Images