A displacement sensor analog output circuit based on the principle of differential transformer

Abstract

The utility model discloses a kind of displacement sensor analog output circuit based on differential transformer principle, it is related to signal analog output field, including isolation interface module, internal excitation source, excitation collection module, output module and control module, the isolation interface module is connected with excitation collection module and output module, the control module is connected with internal excitation source, excitation collection module and output module, the internal excitation source is connected with excitation collection module;External excitation signal is input to excitation collection module by isolation interface module, excitation collection module collects external excitation signal and is transmitted to the output module, or internal excitation source generates internal excitation signal and is transmitted to the output module by excitation collection module, control module controls output module to generate output signal according to external excitation signal or internal excitation signal, and output signal is output by isolation interface module. The circuit can flexibly control analog displacement output, and output precision is high.

Description

Technical Field

[0001] This utility model relates to the field of analog signal output, and in particular to an analog output circuit for a displacement sensor based on the principle of differential transformer. Background Technology

[0002] Displacement sensors based on the differential transformer principle mainly include LVDT / RVDT displacement sensors. These are high-precision displacement sensors that convert mechanical displacement into an electrical signal output through the movement of an iron core. They have wide applications in aerospace, precision machinery manufacturing, and medical fields. Because the output signal of an LVDT / RVDT displacement sensor is a differential signal, traditional instruments cannot directly simulate the LVDT / RVDT sensor signal. Therefore, an LVDT / RVDT simulator is needed to replace the actual LVDT / RVDT displacement sensor for equipment debugging and testing.

[0003] Currently, National Instruments (NI) is the leading technology provider for LVDT / RVDT emulators. NI has long dominated the high-end market, and its PXI-MFB series modular emulation cards support emulation of various sensor types, including LVDT / RVDT, with an accuracy of 0.1%FS. However, these cards are expensive and subject to export controls. Traditional domestic methods for LVDT / RVDT output simulation employ differential input rectifier circuits and phase-sensitive circuits. These methods are complex, susceptible to interference, and difficult to debug. Utility Model Content

[0004] In response to the aforementioned problems and technical requirements, the applicant has proposed a displacement sensor analog output circuit based on the principle of differential transformer.

[0005] The technical solution of this utility model is as follows: A displacement sensor analog output circuit based on the differential transformer principle includes an isolation interface module, an internal excitation source, an excitation acquisition module, an output module, and a control module. The isolation interface module is connected to the excitation acquisition module and the output module. The control module is connected to the internal excitation source, the excitation acquisition module and the output module. The internal excitation source is connected to the excitation acquisition module and the excitation acquisition module is connected to the output module. An external excitation signal is input to the excitation acquisition module through an isolation interface module. The excitation acquisition module acquires the external excitation signal and transmits it to the output module. Alternatively, the internal excitation source generates an internal excitation signal and transmits it to the output module through the excitation acquisition module. The control module controls the output module to generate an output signal based on the external or internal excitation signal. The output signal is output through the isolation interface module.

[0006] A further technical solution is that the isolation interface module includes an input interface circuit, and the excitation acquisition module includes an excitation acquisition circuit connected to the input interface circuit; The input interface circuit includes a transformer T1 and a resistor R1. The external excitation signal is input to the primary winding of the transformer T1. One end of the primary winding of the transformer T1 is connected to the other end of the primary winding through the resistor R1. One end of the secondary winding of the transformer T1 is connected to analog ground, and the other end of the secondary winding of the transformer T1 is connected to the excitation acquisition circuit.

[0007] A further technical solution is that the excitation acquisition circuit includes a signal conditioning circuit, a frequency acquisition circuit, and an ADC circuit. The signal conditioning circuit includes operational amplifier N2A, operational amplifier N2B, resistors R8, R10, R11, and R13, capacitor C15, and interface XP1. The non-inverting input terminal of the operational amplifier N2A is connected to the other end of the secondary winding of the transformer T1 in the input interface circuit. The non-inverting input terminal of the operational amplifier N2A is also connected to analog ground through resistor R13. The inverting input terminal of the operational amplifier N2A is connected to the output terminal of the operational amplifier N2A. The output terminal of the operational amplifier N2A is connected to the non-inverting input terminal of the operational amplifier N2B and one end of the capacitor C15 through resistor R11. The other end of the capacitor C15 is connected to analog ground. The inverting input terminal of the operational amplifier N2B is connected to analog ground through resistor R10, and is connected to the output terminal of the operational amplifier N2B and the first pin of interface XP1 through resistor R8.

[0008] A further technical solution is that the frequency acquisition circuit includes resistors R23, R24, and R25, an optocoupler E3, and a comparator N25B, wherein... The non-inverting input of comparator N25B is connected to the output of operational amplifier N2A through resistor R25. The inverting input of comparator N25B is connected to analog ground. The output of comparator N25B is connected to the negative terminal of the primary LED of optocoupler E3. The positive terminal of the primary LED of optocoupler E3 is connected to analog ground through resistor R24. The emitter of the secondary phototransistor of optocoupler E3 is connected to digital ground. The collector of the secondary phototransistor of optocoupler E3 is connected to the power supply voltage through resistor R23.

[0009] A further technical solution is that the ADC circuit includes an ADC chip, an interface XP9, resistors R232, R233, R234, R235, and R236, capacitors C269, C270, C271, and C272, wherein... The ADC chip model includes AD7606. The 49th pin of the ADC chip is connected to the second pin of the XP9 interface. The second pin of the XP9 interface is connected to the third pin. The third pin of the XP9 interface is connected to the output terminal of the operational amplifier N2B. The first pin of the interface XP9 is connected to voltage VREF through resistor R232, and the first pin of the interface XP9 is also connected to analog ground through resistor R233. The sixth pin of the ADC chip is connected to digital ground through resistor R234, the thirty-sixth pin of the ADC chip is connected to analog ground through capacitor C272, the forty-fifth and forty-fourth pins of the ADC chip are connected to analog ground through capacitor C269, the forty-second pin of the ADC chip is connected to analog ground through capacitor C270, the thirty-ninth pin of the ADC chip is connected to analog ground through capacitor C271, the thirty-fourth pin of the ADC chip is connected to digital ground through resistor R236, and the sixteenth to twenty-second, twenty-fourth to twenty-fifth, and twenty-seventh to thirty-third pins of the ADC chip are connected to the control module.

[0010] A further technical solution is that the internal excitation source includes an internal excitation source circuit connected to the excitation acquisition circuit. The internal excitation source circuit includes a crystal oscillator G1, a DDS chip, operational amplifiers N1A and N1B, capacitors C1, C2, C5, C6, C7, C8, C9, C10, C13, and C14, and resistors R1, R2, R3, R4, and R7. The DDS chip model includes AD9835. The third pin of the crystal oscillator G1 is connected to the sixth pin of the DDS chip through resistor R4. The fourteenth pin of the DDS chip is connected to analog ground through capacitor C13. Resistor R5 is connected in parallel with capacitor C13. The fourteenth pin of the DDS chip is connected to the non-inverting input of operational amplifier N1A. The inverting input of operational amplifier N1A is connected to the output, and is connected through capacitor C9, one end of capacitor C10, one end of resistor R3, and one end of resistor R6. The other end of capacitor C10 is connected to the output of operational amplifier N1A. The other end of resistor R6 is connected to analog ground. The other end of resistor R3 is connected to the non-inverting input of operational amplifier N1B. The non-inverting input of operational amplifier N1B is connected to analog ground through capacitor C14. The inverting input of operational amplifier N1B is connected to analog ground through resistor R7 and is connected to the output of operational amplifier N1B through resistor R1. The output of operational amplifier N1B is connected to the third pin of interface XP1 in the excitation acquisition circuit.

[0011] A further technical solution is that the first pin of the DDS chip is connected to analog ground through resistor R2, the third pin of the DDS chip is connected to analog ground through capacitor C7, the fourth pin of the DDS chip is connected to a 5V digital power supply and connected to digital ground through capacitor C1, the fifteenth pin of the DDS chip is connected to a 5V analog power supply and connected to analog ground through capacitor C2, and the seventh to ninth pins of the DDS chip are connected to the control module.

[0012] The further technical solution is that the output module includes a DAC chip, operational amplifier N3A, operational amplifier N3B, capacitor C18, resistor R22, capacitor C21 and resistor R26. The DAC chip is model AD7847. Pins 12 to 24 of the DAC chip are connected to the control module, and pins 3 and 10 of the DAC chip are connected to pin 2 of interface XP1 in the excitation acquisition circuit. The fourth pin of the DAC chip is connected to one end of capacitor C18, and the other end of capacitor C18 is connected to the non-inverting input of operational amplifier N3A and connected to analog ground through resistor R22. The inverting input of operational amplifier N3A is connected to the output of operational amplifier N3A. The ninth pin of the DAC chip is connected to one end of capacitor C21, and the other end of capacitor C21 is connected to the non-inverting input of operational amplifier N3B and connected to analog ground through resistor R26. The inverting input of operational amplifier N3B is connected to the output of operational amplifier N3B.

[0013] A further technical solution is that the isolation interface module also includes a VA output interface circuit and a VB output interface circuit; The VA output interface circuit includes a transformer T5, a resistor R5, and a resistor R9. One end of the primary winding of the transformer T5 is connected to the output terminal of the operational amplifier N3A, and one end of the primary winding of the transformer T5 is connected to the other end of the primary winding through the resistor R9. The other end of the primary winding is connected to analog ground. One end of the secondary winding of the transformer T5 is connected to the other end of the secondary winding through the resistor R5. The VB output interface circuit includes a transformer T9, a resistor R13, and a resistor R14. One end of the primary winding of the transformer T9 is connected to the output terminal of the operational amplifier N3B, and one end of the primary winding of the transformer T9 is connected to the other end of the primary winding through the resistor R13. The other end of the primary winding is connected to analog ground. One end of the secondary winding of the transformer T9 is connected to the other end of the secondary winding through the resistor R14. A further technical solution is that the control module includes an FPGA chip.

[0014] The beneficial technical effects of this utility model are: The displacement sensor analog output circuit based on the differential transformer principle provided by this invention has a simple structure, high control precision, and can flexibly control the analog displacement output with high accuracy. Furthermore, the input and output interfaces are isolated to prevent external factors from affecting accuracy. This circuit also has an internal excitation source, which helps save testing resources. Attached Figure Description

[0015] Figure 1 This is a structural block diagram of one embodiment of the displacement sensor analog output circuit based on the differential transformer principle provided by this utility model.

[0016] Figure 2 This is a circuit schematic diagram of one embodiment of the input interface circuit provided by this utility model.

[0017] Figure 3 This is a circuit schematic diagram of one embodiment of the signal conditioning circuit provided by this utility model.

[0018] Figure 4 This is a circuit schematic diagram of one embodiment of the frequency acquisition circuit provided by this utility model.

[0019] Figure 5 This is a circuit schematic diagram of one embodiment of the ADC circuit provided by this utility model.

[0020] Figure 6 This is a circuit schematic diagram of one embodiment of the internal excitation source circuit provided by this utility model.

[0021] Figure 7 This is a pin diagram of one embodiment of the DAC chip provided by this utility model.

[0022] Figure 8 This is a circuit diagram of one embodiment of the VA output circuit of the LVDT / RVDT sensor provided by this utility model.

[0023] Figure 9 This is a circuit diagram of one embodiment of the VB output circuit of the LVDT / RVDT sensor provided by this utility model.

[0024] Figure 10 This is a circuit schematic diagram of one embodiment of the VA output interface circuit for the LVDT / RVDT sensor provided by this utility model.

[0025] Figure 11 This is a circuit schematic diagram of one embodiment of the LVDT / RVDT sensor VB output interface circuit provided by this utility model. Detailed Implementation

[0026] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0027] This invention provides a displacement sensor analog output circuit based on the differential transformer principle, including an isolation interface module, an internal excitation source, an excitation acquisition module, an output module, and a control module. Please refer to [reference needed]. Figure 1 The isolation interface module is connected to the excitation acquisition module and the output module. The control module is connected to the internal excitation source, the excitation acquisition module and the output module. The internal excitation source is connected to the excitation acquisition module and the excitation acquisition module is connected to the output module. An external excitation signal is input to the excitation acquisition module through an isolation interface module. The excitation acquisition module acquires the external excitation signal and transmits it to the output module. Alternatively, the internal excitation source generates an internal excitation signal and transmits it to the output module through the excitation acquisition module. The control module controls the output module to generate an output signal based on the external or internal excitation signal. The output signal is output through the isolation interface module.

[0028] Specifically, the external excitation signal is input through the isolation interface module and enters the excitation acquisition circuit, simultaneously serving as the external reference source for the output module. The internal excitation source serves as the internal reference source for the output module; in specific applications, the reference source can be selected via jumpers. The control module can be an FPGA. The control module receives commands from the host computer via the CPCI interface and then controls the output module to generate the set voltage amplitude (output signal) via a parallel bus. This signal is output through the isolation interface module to simulate the output signal of a displacement sensor based on the differential transformer principle. When an external excitation source is selected, the output signal is in phase and frequency with the external excitation signal. When an internal excitation source is selected, the frequency and phase of the output signal can be customized via the host computer. The specific structure of each module and the method of selecting the reference source via jumpers are described below.

[0029] Furthermore, the isolation interface module includes an input interface circuit, and the excitation acquisition module includes an excitation acquisition circuit connected to the input interface circuit; as shown below. Figure 2 As shown, the input interface circuit includes a transformer T1 and a resistor R1. One end of the primary winding of transformer T1 is connected to the other end of the primary winding through resistor R1. The external excitation signal is input to the primary winding of transformer T1. Specifically, the external excitation signal can be in the form of a differential signal, such as... Figure 2 As shown, the two ends of the primary winding of transformer T1 are connected to external excitation signals EXC0+ and EXC0- respectively. One end of the secondary winding of transformer T1 is connected to analog ground, and the other end of the secondary winding of transformer T1 is connected to the excitation acquisition circuit.

[0030] The excitation acquisition circuit includes a signal conditioning circuit, a frequency acquisition circuit, and an ADC circuit. The external excitation signal is filtered out for noise by the signal conditioning circuit, which increases the input impedance to a voltage range suitable for acquisition by the ADC circuit. Please refer to [reference needed]. Figure 3 The signal conditioning circuit includes operational amplifier N2A, operational amplifier N2B, resistors R8, R10, R11, and R13, capacitor C15, and interface XP1. The non-inverting input of operational amplifier N2A is connected to the other end of the secondary winding of transformer T1 in the input interface circuit, and receives the external excitation signal (EXC0_S) after isolation conversion. The non-inverting input of operational amplifier N2A is also connected to analog ground through resistor R13. The inverting input of operational amplifier N2A is connected to the output of operational amplifier N2A. The output of operational amplifier N2A is connected to the non-inverting input of operational amplifier N2B and one end of capacitor C15 through resistor R11. The other end of capacitor C15 is connected to analog ground. The inverting input of operational amplifier N2B is connected to analog ground through resistor R10, and to the output of operational amplifier N2B and the first pin of interface XP1 through resistor R8. The positive and negative power supply terminals of operational amplifiers N2A and N2B are connected to +15V and -15V power supplies, respectively, and the positive and negative power supply terminals of operational amplifiers N2A and N2B are connected to analog ground through capacitors C16 and C17, respectively.

[0031] Further, please refer to Figure 4 The frequency acquisition circuit includes resistors R23, R24, and R25, an optocoupler E3, and a comparator N25B. The non-inverting input of comparator N25B is connected to the output of operational amplifier N2A via resistor R25. The inverting input of comparator N25B is connected to analog ground. The output of comparator N25B is connected to the negative terminal of the primary LED of optocoupler E3. The positive terminal of the primary LED of optocoupler E3 is connected to analog ground via resistor R24. The emitter of the secondary phototransistor of optocoupler E3 is connected to digital ground. The collector of the secondary phototransistor of optocoupler E3 is connected to the power supply voltage via resistor R23 and is also connected to the control module. The frequency acquisition circuit uses comparator N25B to convert the input AC signal into a DC pulse signal, which is then isolated by the optocoupler before being sent to the control module for frequency acquisition.

[0032] Further, please refer to Figure 5The ADC circuit includes an ADC chip, an interface XP9, resistors R232, R233, R234, R235, and R236, and capacitors C269, C270, C271, and C272. The ADC chip, model AD7606, is an 8-channel, 16-bit resolution synchronous sampling ADC chip characterized by high precision and low power consumption. Pin 49 of the ADC chip is connected to pin 2 of interface XP9. Pin 2 of interface XP9 is connected to pin 3, and pin 3 of interface XP9 is connected to the output of operational amplifier N2B. The signal EXC0_AD, conditioned by the signal conditioning circuit, is input to pin V1 of the ADC chip via interface XP9, where it undergoes analog-to-digital conversion before being transmitted to the control module.

[0033] The first pin of the XP9 interface is connected to a 2.5V voltage VREF via resistor R232. The first pin of the XP9 interface is also connected to analog ground via resistor R233. The circuit connected to the first pin of the XP9 interface is used for testing and other purposes. The sixth pin of the ADC chip is connected to digital ground via resistor R234. The seventh and eighth pins of the ADC chip are connected to a 3.3V digital power supply via resistor R235. Pins 37-38 and 48 of the ADC chip are connected to a 5V analog power supply. The thirty-sixth pin of the ADC chip is connected to analog ground via capacitor C272. Pins 45 and 44 of the ADC chip are connected to analog ground via capacitor C269. The forty-second pin of the ADC chip is connected to analog ground via capacitor C270. The thirty-ninth pin of the ADC chip is connected to analog ground via capacitor C271. The thirty-fourth pin of the ADC chip is connected to digital ground via resistor R236. Pins 16-22, 24-25, and 27-33 of the ADC chip (i.e., AD_DB0-AD_DB15) are connected to the control module.

[0034] The 5V analog power supply is also grounded through a group of capacitors connected to ground. In this embodiment, the group of capacitors connected to ground includes capacitors C273, C274, C275, C276, and C277 connected in parallel. The 3.3V analog power supply is grounded through a pair of capacitors connected to ground.

[0035] Furthermore, the internal excitation source includes an internal excitation source circuit connected to the excitation acquisition circuit, please refer to [reference needed]. Figure 6The internal excitation source circuit includes a crystal oscillator G1, a DDS chip, operational amplifiers N1A and N1B, capacitors C1, C2, C5, C6, C7, C8, C9, C10, C13, and C14, and resistors R1, R2, R3, R4, and R7. The DDS chip models include AD9835 and AD9850, which integrate a programmable DDS system, a 10-bit digital-to-analog converter, and a high-speed comparator, forming a complete digital programmable frequency synthesis system. In this embodiment, the AD9835 generates a 3kHz, 5Vrms sine wave signal as the internal excitation signal, which is then output to the output module after signal conditioning. Specifically, the third pin of the crystal oscillator G1 is connected to the sixth pin of the DDS chip through resistor R4. The fourth pin of the crystal oscillator G1 is connected to a 5V digital power supply and then connected to digital ground through capacitors C6 and C8. The fourteenth pin of the DDS chip is connected to analog ground through capacitor C13. Resistor R5 and capacitor C13 are connected in parallel. The fourteenth pin of the DDS chip is connected to the non-inverting input of operational amplifier N1A. The inverting input of operational amplifier N1A is connected to the output, and is connected through capacitors C9 and C10, one end of resistor R3, and capacitor C10. One end of resistor R6 is connected to the analog ground, and the other end of capacitor C10 is connected to the output of operational amplifier N1A. The other end of resistor R6 is connected to analog ground, and the other end of resistor R3 is connected to the non-inverting input of operational amplifier N1B. The non-inverting input of operational amplifier N1B is connected to analog ground through capacitor C14. The inverting input of operational amplifier N1B is connected to analog ground through resistor R7 and to the output of operational amplifier N1B through resistor R1. The output of operational amplifier N1B is connected to the third pin of interface XP1 in the excitation acquisition circuit.

[0036] The first pin of the DDS chip is connected to analog ground through resistor R2, the third pin of the DDS chip is connected to analog ground through capacitor C7, the fourth pin of the DDS chip is connected to a 5V digital power supply and connected to digital ground through capacitor C1, the fifteenth pin of the DDS chip is connected to a 5V analog power supply and connected to analog ground through capacitor C2, and the seventh to ninth pins of the DDS chip are connected to the control module for receiving control commands.

[0037] Please refer to Figure 7 The output module includes a DAC chip, operational amplifier N3A, operational amplifier N3B, capacitor C18, resistor R22, capacitor C21, and resistor R26. The DAC chip, model AD7847, is a dual-channel 12-bit resolution multiplier DAC chip with an integrated output amplifier. It achieves full rated performance without external adjustment. Pins 12 to 24 of the DAC chip are connected to the control module, as are pins 1 and 2. Pins 3 (VREEFA) and 10 (VREEFB) of the DAC chip are connected to pin 2 of interface XP1 in the excitation acquisition circuit. Pins 6 and 7 of the DAC chip are connected to +15V and -15V analog power supplies, respectively, and are grounded via capacitors C22 and C23, respectively. The reference source is selected via jumpers. Specifically, connecting pins 1 and 2 of interface XP1 in the signal conditioning circuit with a connecting cable selects an external excitation source as the reference source; connecting pins 3 and 2 of interface XP1 in the signal conditioning circuit with a connecting cable selects an internal excitation source as the reference source.

[0038] The operational amplifier N3A, capacitor C18, and resistor R22 constitute the VA output circuit. Please refer to [reference needed]. Figure 8 The fourth pin of the DAC chip is connected to one end of capacitor C18, and the other end of capacitor C18 is connected to the non-inverting input of operational amplifier N3A and connected to analog ground through resistor R22. The inverting input of operational amplifier N3A is connected to the output of operational amplifier N3A. The operational amplifier N3B, capacitor C21, and resistor R26 constitute the VB output circuit. Please refer to [reference needed]. Figure 9 The ninth pin of the DAC chip is connected to one end of capacitor C21, and the other end of capacitor C21 is connected to the non-inverting input of operational amplifier N3B and then connected to analog ground through resistor R26. The inverting input of operational amplifier N3B is connected to the output of operational amplifier N3B. The positive and negative power supply terminals of operational amplifiers N3A and N3B are connected to +15V and -15V power supplies, respectively, and the positive and negative power supply terminals of operational amplifiers N23A and N32B are connected to analog ground through capacitors C24 and C25, respectively.

[0039] Furthermore, the isolation interface module also includes a VA output interface circuit and a VB output interface circuit; please refer to... Figure 10 The VA output interface circuit includes a transformer T5, a resistor R5, and a resistor R9. One end of the primary winding of the transformer T5 is connected to the output terminal of the operational amplifier N3A, and one end of the primary winding of the transformer T5 is connected to the other end of the primary winding through the resistor R9. The other end of the primary winding is connected to analog ground. One end of the secondary winding of the transformer T5 is connected to the other end of the secondary winding through the resistor R5. Please refer to Figure 11The VB output interface circuit includes a transformer T9, a resistor R13, and a resistor R14. One end of the primary winding of the transformer T9 is connected to the output terminal of the operational amplifier N3B, and one end of the primary winding of the transformer T9 is connected to the other end of the primary winding through the resistor R13. The other end of the primary winding is connected to analog ground. One end of the secondary winding of the transformer T9 is connected to the other end of the secondary winding through the resistor R14. Specifically, in the isolation interface circuit, the turns ratio of the primary winding to the secondary winding of transformers T1, T5, and T9 is 1:1, which isolates the input external excitation signal and the output signal, while the transformer can also closely resemble the state of the real sensor.

[0040] In the description of this specification, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. The descriptions using terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples and the features of different embodiments / modes or examples described in this specification.

[0041] The above descriptions are merely preferred embodiments of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that can be directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A displacement sensor analog output circuit based on the differential transformer principle, characterized in that, It includes an isolation interface module, an internal excitation source, an excitation acquisition module, an output module, and a control module, among which, The isolation interface module is connected to the excitation acquisition module and the output module. The control module is connected to the internal excitation source, the excitation acquisition module and the output module. The internal excitation source is connected to the excitation acquisition module and the excitation acquisition module is connected to the output module. An external excitation signal is input to the excitation acquisition module through an isolation interface module. The excitation acquisition module acquires the external excitation signal and transmits it to the output module. Alternatively, the internal excitation source generates an internal excitation signal and transmits it to the output module through the excitation acquisition module. The control module controls the output module to generate an output signal based on the external or internal excitation signal. The output signal is output through the isolation interface module.

2. The displacement sensor analog output circuit based on the differential transformer principle according to claim 1, characterized in that, The isolation interface module includes an input interface circuit, and the excitation acquisition module includes an excitation acquisition circuit connected to the input interface circuit. The input interface circuit includes a transformer T1 and a resistor R1. The external excitation signal is input to the primary winding of the transformer T1. One end of the primary winding of the transformer T1 is connected to the other end of the primary winding through the resistor R1. One end of the secondary winding of the transformer T1 is connected to analog ground, and the other end of the secondary winding of the transformer T1 is connected to the excitation acquisition circuit.

3. The displacement sensor analog output circuit based on the differential transformer principle according to claim 2, characterized in that, The excitation acquisition circuit includes a signal conditioning circuit, a frequency acquisition circuit, and an ADC circuit. The signal conditioning circuit includes operational amplifier N2A, operational amplifier N2B, resistors R8, R10, R11, and R13, capacitor C15, and interface XP1. The non-inverting input terminal of the operational amplifier N2A is connected to the other end of the secondary winding of the transformer T1 in the input interface circuit. The non-inverting input terminal of the operational amplifier N2A is also connected to analog ground through resistor R13. The inverting input terminal of the operational amplifier N2A is connected to the output terminal of the operational amplifier N2A. The output terminal of the operational amplifier N2A is connected to the non-inverting input terminal of the operational amplifier N2B and one end of the capacitor C15 through resistor R11. The other end of the capacitor C15 is connected to analog ground. The inverting input terminal of the operational amplifier N2B is connected to analog ground through resistor R10, and is connected to the output terminal of the operational amplifier N2B and the first pin of interface XP1 through resistor R8.

4. The displacement sensor analog output circuit based on the differential transformer principle according to claim 3, characterized in that, The frequency acquisition circuit includes resistors R23, R24, and R25, an optocoupler E3, and a comparator N25B. The non-inverting input of comparator N25B is connected to the output of operational amplifier N2A through resistor R25. The inverting input of comparator N25B is connected to analog ground. The output of comparator N25B is connected to the negative terminal of the primary LED of optocoupler E3. The positive terminal of the primary LED of optocoupler E3 is connected to analog ground through resistor R24. The emitter of the secondary phototransistor of optocoupler E3 is connected to digital ground. The collector of the secondary phototransistor of optocoupler E3 is connected to the power supply voltage through resistor R23.

5. The displacement sensor analog output circuit based on the differential transformer principle according to claim 4, characterized in that, The ADC circuit includes an ADC chip, an interface XP9, resistors R232, R233, R234, R235, and R236, and capacitors C269, C270, C271, and C272. The ADC chip model includes AD7606. The 49th pin of the ADC chip is connected to the second pin of the XP9 interface. The second pin of the XP9 interface is connected to the third pin. The third pin of the XP9 interface is connected to the output terminal of the operational amplifier N2B. The first pin of the interface XP9 is connected to voltage VREF through resistor R232, and the first pin of the interface XP9 is also connected to analog ground through resistor R233. The sixth pin of the ADC chip is connected to digital ground through resistor R234, the thirty-sixth pin of the ADC chip is connected to analog ground through capacitor C272, the forty-fifth and forty-fourth pins of the ADC chip are connected to analog ground through capacitor C269, the forty-second pin of the ADC chip is connected to analog ground through capacitor C270, the thirty-ninth pin of the ADC chip is connected to analog ground through capacitor C271, the thirty-fourth pin of the ADC chip is connected to digital ground through resistor R236, and the sixteenth to twenty-second, twenty-fourth to twenty-fifth, and twenty-seventh to thirty-third pins of the ADC chip are connected to the control module.

6. The displacement sensor analog output circuit based on the differential transformer principle according to claim 3, characterized in that, The internal excitation source includes an internal excitation source circuit connected to the excitation acquisition circuit. The internal excitation source circuit includes a crystal oscillator G1, a DDS chip, operational amplifiers N1A and N1B, capacitors C1, C2, C5, C6, C7, C8, C9, C10, C13, and C14, and resistors R1, R2, R3, R4, and R7. The DDS chip model includes AD9835. The third pin of the crystal oscillator G1 is connected to the sixth pin of the DDS chip through resistor R4. The fourteenth pin of the DDS chip is connected to analog ground through capacitor C13. Resistor R5 is connected in parallel with capacitor C13. The fourteenth pin of the DDS chip is connected to the non-inverting input of operational amplifier N1A. The inverting input of operational amplifier N1A is connected to the output, and is connected through capacitor C9, one end of capacitor C10, one end of resistor R3, and one end of resistor R6. The other end of capacitor C10 is connected to the output of operational amplifier N1A. The other end of resistor R6 is connected to analog ground. The other end of resistor R3 is connected to the non-inverting input of operational amplifier N1B. The non-inverting input of operational amplifier N1B is connected to analog ground through capacitor C14. The inverting input of operational amplifier N1B is connected to analog ground through resistor R7 and is connected to the output of operational amplifier N1B through resistor R1. The output of operational amplifier N1B is connected to the third pin of interface XP1 in the excitation acquisition circuit.

7. The displacement sensor analog output circuit based on the differential transformer principle according to claim 6, characterized in that, The first pin of the DDS chip is connected to analog ground through resistor R2, the third pin of the DDS chip is connected to analog ground through capacitor C7, the fourth pin of the DDS chip is connected to a 5V digital power supply and connected to digital ground through capacitor C1, the fifteenth pin of the DDS chip is connected to a 5V analog power supply and connected to analog ground through capacitor C2, and the seventh to ninth pins of the DDS chip are connected to the control module.

8. The displacement sensor analog output circuit based on the differential transformer principle according to claim 6, characterized in that, The output module includes a DAC chip, operational amplifier N3A, operational amplifier N3B, capacitor C18, resistor R22, capacitor C21, and resistor R26. The DAC chip is model AD7847. Pins 12 to 24 of the DAC chip are connected to the control module, and pins 3 and 10 of the DAC chip are connected to pin 2 of interface XP1 in the excitation acquisition circuit. The fourth pin of the DAC chip is connected to one end of capacitor C18, and the other end of capacitor C18 is connected to the non-inverting input of operational amplifier N3A and connected to analog ground through resistor R22. The inverting input of operational amplifier N3A is connected to the output of operational amplifier N3A. The ninth pin of the DAC chip is connected to one end of capacitor C21, and the other end of capacitor C21 is connected to the non-inverting input of operational amplifier N3B and connected to analog ground through resistor R26. The inverting input of operational amplifier N3B is connected to the output of operational amplifier N3B.

9. The displacement sensor analog output circuit based on the differential transformer principle according to claim 8, characterized in that, The isolation interface module also includes a VA output interface circuit and a VB output interface circuit; The VA output interface circuit includes a transformer T5, a resistor R5, and a resistor R9. One end of the primary winding of the transformer T5 is connected to the output terminal of the operational amplifier N3A, and one end of the primary winding of the transformer T5 is connected to the other end of the primary winding through the resistor R9. The other end of the primary winding is connected to analog ground. One end of the secondary winding of the transformer T5 is connected to the other end of the secondary winding through the resistor R5. The VB output interface circuit includes a transformer T9, a resistor R13, and a resistor R14. One end of the primary winding of the transformer T9 is connected to the output terminal of the operational amplifier N3B, and one end of the primary winding of the transformer T9 is connected to the other end of the primary winding through the resistor R13. The other end of the primary winding is connected to analog ground. One end of the secondary winding of the transformer T9 is connected to the other end of the secondary winding through the resistor R14.

10. The displacement sensor analog output circuit based on the differential transformer principle according to claim 1, characterized in that, The control module includes an FPGA chip.

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