A multi-type analog quantity input switching circuit, a data acquisition card and an electrical appliance

Abstract

The application relates to a multi-type analog quantity input switching circuit, a data acquisition card and an electrical equipment. The circuit realizes unified processing of multiple types of analog quantity input signals by adopting a single analog switch module to cooperatively control an impedance matching network and a voltage division network. Without separately designing independent signal conditioning channels for each signal type, the number of operational amplifiers, analog-to-digital converters and other components is greatly reduced, and the area occupancy of the circuit board and the material cost are reduced. The traditional mechanical switch or jumper manual switching mode is abandoned, and an electronic analog switch is adopted for rapid switching, and the switching time can reach nanoseconds. The control unit outputs a control signal in real time according to the access signal type, realizes millisecond-level or even microsecond-level mode switching, and meets the rapid response requirement of dynamic signal type identification in an industrial automation system.

Description

Technical Field

[0001] This invention relates to the field of control circuit technology, specifically to a multi-type analog input switching circuit, a data acquisition card, and electrical equipment. Background Technology

[0002] In fields such as industrial automation control, process monitoring, environmental data acquisition, and intelligent equipment manufacturing, the accurate acquisition and processing of analog signals is fundamental to achieving precise control and reliable operation. Field sensors output a variety of analog signals. Among them, 4-20mA current loop signals are widely used in long-distance industrial environments due to their strong anti-interference capabilities and long transmission distances; while 0-10V voltage signals are commonly found within various instruments and controllers due to their simple interface and ease of processing. Therefore, a high-performance analog input system often needs to be capable of processing multiple types of analog signals to meet the sensor access requirements in different application scenarios.

[0003] Currently, the industry mainly adopts the following traditional solutions to address compatibility issues with multiple types of analog inputs: Firstly, a mechanical switching switch is used.

[0004] This is the most intuitive method. Physical DIP switches, jumpers, or relays are installed on the hardware circuit board, allowing operators to manually switch the signal path based on the type of sensor being connected. For example, when connecting a 4-20mA sensor, the operator needs to manually close the switch to connect a precision sampling resistor (e.g., 250Ω) into the circuit to complete the current-to-voltage conversion; while when connecting a 0-10V sensor, the resistor needs to be manually disconnected to prevent it from becoming a load on the voltage signal. The advantage of this approach is its simple circuit structure and low cost.

[0005] However, its drawbacks are also significant: First, mechanical switches suffer from physical wear and contact oxidation, leading to changes in contact resistance and even poor contact after prolonged use, directly affecting signal transmission stability and measurement accuracy. Second, manual switching is inefficient, especially in large-scale distributed control systems (DCS) or programmable logic controller (PLC) systems. Manually configuring hundreds or thousands of input channels one by one is not only time-consuming and labor-intensive but also highly susceptible to human error. Furthermore, mechanical switches have slow response times, failing to meet the demands of intelligent applications requiring dynamic signal type switching. Therefore, this solution is ill-suited to the high reliability, high efficiency, and intelligent operation and maintenance requirements of modern industry.

[0006] Secondly, a multi-channel independent parallel processing scheme is adopted.

[0007] This involves designing independent signal processing links for 4-20mA current signals and 0-10V voltage signals on a single acquisition board. Each link includes independent input protection circuitry, a filtering network, an operational amplifier (op-amp), and an analog-to-digital converter (ADC) channel. The system selects and reads the digital value from the corresponding link based on pre-defined channel attributes.

[0008] The advantage of this approach is that the signal path is fixed, eliminating transient interference issues caused by switching. However, its disadvantages are also significant: First, it results in a serious waste of hardware resources. Each additional signal type requires an extra complete analog front-end (AFE) and ADC channel, leading to an increase in printed circuit board (PCB) area and a surge in the number of components, which in turn drives up the bill of materials (BOM) cost and system power consumption. Second, there are inherent consistency deviations between multiple channels. Even when using the same type of high-precision components, it is difficult to achieve complete consistency in gain error, bias voltage, and temperature drift characteristics between different channels. This poses a significant challenge to system calibration, especially in applications requiring high-precision multi-channel synchronous measurement, where inconsistencies between channels can severely affect the accuracy of the final measurement results. Third, the system structure is complex, wiring is difficult, and electromagnetic compatibility (EMC) design becomes more challenging.

[0009] Third, an electronic analog switch combined with a single channel is used.

[0010] To overcome the shortcomings of mechanical switches, some existing technologies attempt to introduce electronic analog switches (such as CMOS analog switches) to achieve signal path switching. However, such solutions often have design limitations. For example, some solutions simply connect a sampling resistor in parallel at the input, and determine whether to connect the resistor by turning the analog switch on or off.

[0011] However, this approach does not fully consider the coordination and adaptation issues of the subsequent signal conditioning network. When switching to current mode, the voltage drop across the sampling resistor may exceed the linear operating range of the subsequent op-amp, or it may not effectively match the full-scale input voltage of the ADC (such as 0-3.3V or 0-5V). In voltage mode, although the sampling resistor is disconnected, if the subsequent voltage divider network is not designed properly, it may still introduce additional input impedance, affecting the driving capability of the signal source. In addition, some solutions use discrete components to build complex gain switching networks. Although they achieve the function, the circuit topology is complex, there are many parasitic parameters, and the non-ideal characteristics of the analog switch itself, such as the on-resistance (Ron) and leakage current, can introduce new error sources, affecting the acquisition accuracy of small signals.

[0012] In summary, existing multi-type analog input switching technologies face numerous bottlenecks in meeting the growing demands for intelligent, high-precision, and highly integrated industrial applications.

[0013] Mechanical solutions are limited by physical characteristics and cannot meet the requirements of high reliability and intelligence; multi-channel solutions are difficult to popularize due to high cost and consistency issues; and existing electronic switching solutions generally lack systematic and coordinated design of front-end impedance matching and subsequent signal conditioning networks, resulting in limited circuit performance or still complex structure.

[0014] Therefore, the industry urgently needs a multi-type analog input switching circuit that is compact, has a fast switching response, high measurement accuracy, strong system reliability, and can fundamentally solve the problem of inconsistent signal paths. Summary of the Invention

[0015] In view of this, the purpose of the present invention is to provide a multi-type analog input switching circuit, a data acquisition card, and an electrical device to solve the problems of low measurement accuracy, poor system reliability, and complex structure caused by insufficient precision, lack of intelligence, or differences in multi-channel structure in the traditional multi-type analog input acquisition method in the prior art.

[0016] According to a first aspect of the present invention, a multi-type analog input switching circuit is provided, comprising: Analog input port, used to connect at least two different types of analog input signals; Impedance matching network, including at least one sampling resistor; A voltage divider network, comprising multiple voltage divider branches, is used to adjust the voltage ratio of the input signal; the number of voltage divider branches is equal to the number of analog input signal types. The analog switch module is connected to the impedance matching network and the voltage divider network, respectively. The control unit is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0017] Preferably, the multi-type analog input switching circuit further includes: The input filtering module includes a first resistor and a first capacitor connected in parallel. One end of the parallel first resistor and the first capacitor is connected to the analog input port, and the other end is grounded.

[0018] Preferably, when there are multiple sampling resistors, the multiple sampling resistors are connected in parallel.

[0019] Preferably, the analog switch module includes: The multi-channel switching chip has one end of its first analog on / off switch connected to the sampling resistor and the other end grounded; its two ends of the second analog on / off switch are respectively connected to the voltage divider network, and its control terminal is connected to the control unit.

[0020] Preferably, the multi-type analog input switching circuit further includes: a voltage follower and a current-limiting resistor, wherein the voltage follower includes: An operational amplifier has its non-inverting input terminal connected to the analog input port via a second resistor, its inverting input terminal connected to its output terminal via a third resistor and a second capacitor in parallel, and its output terminal connected to the current-limiting resistor.

[0021] Preferably, the voltage divider network includes: The first voltage divider branch includes: a fourth resistor and a fifth resistor, with a voltage divider point formed between the fourth resistor and the fifth resistor, and an external analog-to-digital converter module connected to the voltage divider point; the other end of the fourth resistor is connected to the current-limiting resistor, and the other end of the fifth resistor is grounded. The second voltage divider branch includes the fourth resistor, the fifth resistor, and the sixth resistor, wherein the sixth resistor is connected in parallel across the fourth resistor via the second analog on / off switch of the multi-channel switching chip.

[0022] Preferably, the multi-type analog input switching circuit further includes: The output filtering module includes a seventh resistor and a third capacitor connected in parallel. One end of the parallel seventh resistor and third capacitor is connected between the current-limiting resistor and the voltage divider network, and the other end is grounded.

[0023] Preferably, the analog input signal includes: The first type of analog input signal is a 4-20mA current signal; The second type of analog input signal is a 0-10V voltage signal.

[0024] Preferably, when the first type of analog input signal is connected, the control unit controls the analog switch module to turn on the branch where the impedance matching network is located, so that the sampling resistor is connected to the circuit to realize current-to-voltage conversion, and at the same time selects the second voltage divider branch to perform voltage division processing on the converted voltage signal to output a 0-3.3V voltage signal; When the second type of analog input signal is received, the control unit controls the analog switch module to disconnect the branch where the impedance matching network is located to avoid the sampling resistor from becoming a load on the voltage signal, and at the same time switches to the first voltage divider branch.

[0025] According to a second aspect of the present invention, a data acquisition card is provided, comprising: The above-mentioned multi-type analog input switching circuit.

[0026] According to a third aspect of the present invention, an electrical device is provided, comprising: The aforementioned data acquisition card.

[0027] The technical solutions provided by the embodiments of the present invention may include the following beneficial effects: By employing a single analog switch module to collaboratively control the impedance matching network and voltage divider network, unified processing of various types of analog input signals is achieved. This eliminates the need for designing separate signal conditioning channels for each signal type, significantly reducing the number of operational amplifiers, analog-to-digital converters, and other components, thus lowering circuit board footprint and material costs.

[0028] It abandons the traditional manual switching method using mechanical switches or jumpers, and adopts electronic analog switches for rapid switching, with switching times down to the nanosecond level. The control unit outputs control signals in real time according to the type of input signal, achieving mode switching at the millisecond or even microsecond level, meeting the rapid response requirements for dynamic signal type recognition in industrial automation systems.

[0029] All types of input signals are processed through the same main signal path (same operational amplifier, same analog-to-digital converter), eliminating consistency deviations caused by differences in component parameters (such as gain error, bias voltage, temperature drift, etc.) between different channels in multi-channel solutions. Simultaneously, precise control of the connection and disconnection of the sampling resistor via analog switches avoids the load effect of the sampling resistor on the signal in voltage mode, ensuring interference-free transmission of different signal sources along a unified path, thereby significantly improving measurement accuracy and system stability.

[0030] Electronic analog switches eliminate the problems of mechanical contact wear and oxidation, resulting in a long service life. Furthermore, signal types can be remotely configured via software, eliminating the need for manual on-site operation, thus reducing maintenance costs and enhancing the system's intelligence level.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0033] Figure 1 This is a schematic block diagram illustrating a multi-type analog input switching circuit according to an exemplary embodiment; Figure 2 This is a schematic block diagram of a multi-type analog input switching circuit according to another exemplary embodiment; Figure 3 This is a schematic diagram of a multi-type analog input switching circuit according to an exemplary embodiment; Figures 4-7 yes Figure 3A partially enlarged view of the schematic diagram of the multi-type analog input switching circuit shown. Detailed Implementation

[0034] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with some aspects of the invention as detailed in the appended claims.

[0035] Example 1 Figure 1 This is a schematic block diagram of a multi-type analog input switching circuit according to an exemplary embodiment. See also: Figure 1 The circuit includes: Analog input port 101 is used to connect at least two different types of analog input signals; Impedance matching network 102 includes at least one sampling resistor; The voltage divider network 103 includes multiple voltage divider branches for voltage proportional adjustment of the input signal; the number of voltage divider branches is equal to the number of analog input signal types. The analog switch module 104 is connected to the impedance matching network and the voltage divider network respectively; The control unit 105 is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0036] It should be noted that in industrial settings, PLCs / DCS need to simultaneously connect transmitters with 4-20mA current output (such as pressure, level, and flow sensors) and sensors with 0-10V voltage output (such as temperature and humidity sensors). This circuit can automatically adapt to both types of signals on a single universal input channel, simplifying module design and improving channel utilization.

[0037] In fields such as environmental monitoring, energy management, and building automation, data acquisition equipment often needs to work with sensors from different manufacturers and with different output types. This circuit allows a single acquisition channel to be compatible with multiple signals, reducing the complexity of equipment selection and facilitating system integration and upgrades.

[0038] It is understood that the technical solution provided in this embodiment achieves unified processing of various types of analog input signals by using a single analog switch module to coordinate the control of the impedance matching network and the voltage divider network. This eliminates the need to design separate signal conditioning channels for each signal type, significantly reducing the number of operational amplifiers, analog-to-digital converters, and other components, thereby lowering the circuit board area and material costs.

[0039] It abandons the traditional manual switching method using mechanical switches or jumpers, and adopts electronic analog switches for rapid switching, with switching times down to the nanosecond level. The control unit outputs control signals in real time according to the type of input signal, achieving mode switching at the millisecond or even microsecond level, meeting the rapid response requirements for dynamic signal type recognition in industrial automation systems.

[0040] All types of input signals are processed through the same main signal path (same operational amplifier, same analog-to-digital converter), eliminating consistency deviations caused by differences in component parameters (such as gain error, bias voltage, temperature drift, etc.) between different channels in multi-channel solutions. Simultaneously, precise control of the connection and disconnection of the sampling resistor via analog switches avoids the load effect of the sampling resistor on the signal in voltage mode, ensuring interference-free transmission of different signal sources along a unified path, thereby significantly improving measurement accuracy and system stability.

[0041] Electronic analog switches eliminate the problems of mechanical contact wear and oxidation, resulting in a long service life. Furthermore, signal types can be remotely configured via software, eliminating the need for manual on-site operation, thus reducing maintenance costs and enhancing the system's intelligence level.

[0042] Example 2 Figure 2 This is a schematic block diagram of a multi-type analog input switching circuit according to another exemplary embodiment, see [link to other documentation]. Figure 2 The circuit includes: Analog input port 101 is used to connect at least two different types of analog input signals; Impedance matching network 102 includes at least one sampling resistor R5; The voltage divider network 103 includes multiple voltage divider branches for voltage proportional adjustment of the input signal; the number of voltage divider branches is equal to the number of analog input signal types. The analog switch module 104 is connected to the impedance matching network and the voltage divider network respectively; The control unit 105 is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0043] See Figure 3 and Figure 4The input filtering module 106 includes a first resistor R1 and a first capacitor C1 connected in parallel. One end of the first resistor R1 and the first capacitor C1 connected in parallel is connected to the analog input port, and the other end is grounded.

[0044] It is understandable that the technical solution provided in this embodiment addresses the complex industrial environment where analog input signals are highly susceptible to high-frequency electromagnetic interference (EMI) introduced by frequency converters, motor starts, and high-power equipment. By setting an RC low-pass filter network at the input, the capacitor's characteristic of "passing AC and blocking DC" can be utilized to bypass high-frequency glitches and noise components mixed into the signal to ground, thereby outputting a purer DC or low-frequency signal and significantly improving the system's signal-to-noise ratio.

[0045] According to the Nyquist sampling theorem, anti-aliasing filtering must be applied to the signal before ADC sampling. This low-pass filter effectively limits the bandwidth of the input signal, filters out frequency components higher than half the ADC sampling frequency, and prevents high-frequency noise from folding into the low-frequency region during analog-to-digital conversion (i.e., aliasing). This ensures that the data acquired by the ADC at the back end can accurately reflect the actual values ​​of the analog quantities on site, avoiding the generation of false data.

[0046] In industrial grounding systems, long cables are prone to introducing common-mode interference. An input filter network, in conjunction with a subsequent differential input structure, can effectively attenuate common-mode noise, enhancing the system's survivability in harsh electromagnetic environments.

[0047] Surge voltages or electrostatic discharge (ESD) energy from the input ports are first absorbed and discharged by an RC filter network before entering the core analog switches and precision operational amplifiers. Resistors limit transient currents, and capacitors absorb transient energy, effectively protecting the expensive analog components downstream from damage caused by high-voltage surges.

[0048] A well-designed input filter time constant (determined by the first resistor and internal parasitic capacitance or the first capacitor) can keep the circuit stable when faced with signal changes, avoid oscillations in the subsequent amplifier due to sudden changes in input impedance, and make the system work more stably and reliably.

[0049] Example 3 A multi-type analog input switching circuit is shown according to another exemplary embodiment. The circuit includes: Analog input port, used to connect at least two different types of analog input signals; Impedance matching network, including at least one sampling resistor R5; A voltage divider network includes multiple voltage divider branches for adjusting the voltage ratio of the input signal; the number of voltage divider branches is equal to the number of types of the analog input signal. The analog switch module is connected to the impedance matching network and the voltage divider network, respectively. The control unit is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0050] See Figure 3 and Figure 4 The input filtering module includes a first resistor R1 and a first capacitor C1 connected in parallel. One end of the first resistor R1 and the first capacitor C1 connected in parallel is connected to the analog input port, and the other end is grounded.

[0051] When the impedance matching network includes multiple sampling resistors, the multiple sampling resistors are connected in parallel.

[0052] It is understandable that the technical solution provided in this embodiment will generate Joule heat when a single sampling resistor carries a large current (such as 20mA), causing resistance drift and affecting measurement accuracy. After multiple resistors are connected in parallel, the total power handling capacity increases exponentially with the number of parallel resistors, the current shared by each resistor decreases, and the heat generation is significantly reduced. This suppresses resistance changes caused by self-heating and improves the measurement stability of the circuit under long-term operation or high-temperature environments.

[0053] By connecting multiple high-precision resistors with the same nominal value (e.g., 0.1% accuracy) in parallel, the combined error of the equivalent resistance can be reduced statistically (e.g., two 1kΩ ±0.1% resistors connected in parallel can reduce the theoretical error of the equivalent resistance to ±0.05%). This makes the current-to-voltage conversion scaling factor more accurate, especially suitable for industrial metrology scenarios with stringent measurement accuracy requirements.

[0054] If one of the sampling resistors fails to open due to overcurrent or aging, the remaining parallel resistors can still maintain basic functionality, preventing the entire channel from failing. This redundancy design enhances the circuit's survivability under harsh operating conditions and reduces maintenance frequency.

[0055] By selecting resistors with different resistance values ​​in parallel combination, the equivalent sampling resistance value can be flexibly adjusted to match various current signal ranges (such as 0-20mA, 4-20mA, 0-40mA, etc.). No hardware replacement is required; range adaptation can be achieved simply by configuring the control unit, thus expanding the circuit's versatility.

[0056] Example 4 A multi-type analog input switching circuit is shown according to another exemplary embodiment. The circuit includes: Analog input port, used to connect at least two different types of analog input signals; Impedance matching network, including at least one sampling resistor R5; A voltage divider network includes multiple voltage divider branches for adjusting the voltage ratio of the input signal; the number of voltage divider branches is equal to the number of types of the analog input signal. The analog switch module is connected to the impedance matching network and the voltage divider network, respectively. The control unit is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0057] See Figure 3 and Figure 4 The input filtering module includes a first resistor R1 and a first capacitor C1 connected in parallel. One end of the first resistor R1 and the first capacitor C1 connected in parallel is connected to the analog input port, and the other end is grounded.

[0058] When the impedance matching network includes multiple sampling resistors, the multiple sampling resistors are connected in parallel.

[0059] See Figure 3 and Figure 5 The analog switch module includes: The multi-channel switching chip U1 has one end (pin 2) of its first analog on / off switch connected to the sampling resistor R5, and the other end (pin 1) grounded; the two ends (pin 5 and pin 6) of its second analog on / off switch are respectively connected to the voltage divider network, and the control terminal is connected to the control unit.

[0060] See Figure 3 and Figure 6 In practical application, the multi-type analog input switching circuit further includes: a voltage follower and a current-limiting resistor R8, wherein the voltage follower includes: The operational amplifier has its non-inverting input terminal (pin 3) connected to the analog input port through the second resistor R7, its inverting input terminal (pin 2) connected to its output terminal through the third resistor R9 and the second capacitor C4 in parallel, and its output terminal (pin 1) connected to the current limiting resistor R8.

[0061] See Figure 3 and Figure 7 In practice, the voltage divider network includes: The first voltage divider branch includes: a fourth resistor R11 and a fifth resistor R12, with a voltage divider point formed between the fourth resistor R11 and the fifth resistor R12, and an external analog-to-digital converter module connected to the voltage divider point; the other end of the fourth resistor R11 is connected to the current-limiting resistor R8, and the other end of the fifth resistor R12 is grounded. The second voltage divider branch includes the fourth resistor, the fifth resistor, and the sixth resistor, wherein the sixth resistor R13 is connected in parallel across the fourth resistor R11 via the second analog on / off switch of the multi-channel switching chip.

[0062] Understandably, the technical solution provided in this embodiment introduces a voltage follower composed of an operational amplifier. Its non-inverting input is connected to the analog input port via a second resistor R7, and its inverting input is connected to the output via a parallel third resistor R9 and a second capacitor C4. This voltage follower has extremely high input impedance, drawing almost no current from the signal source, effectively isolating the mutual influence between the preceding circuit and the subsequent voltage divider network. Simultaneously, its extremely low output impedance powerfully drives the subsequent voltage divider network and analog-to-digital converter module, avoiding signal attenuation due to load effects. The parallel resistor and capacitor at the inverting input form a feedback network, which not only stabilizes the op-amp's gain but also provides phase compensation and filtering, suppressing the op-amp's own high-frequency noise.

[0063] The current-limiting resistor R8 is connected in series between the output of the voltage follower and the voltage divider network. When a short circuit or overload occurs in the subsequent circuit, this resistor can limit the current flowing through the output of the op-amp, preventing the op-amp from being damaged by overcurrent, thus improving the reliability and safety of the circuit.

[0064] The first voltage divider branch consists of the fourth resistor R11 and the fifth resistor R12 connected in series, forming a voltage divider point that is directly connected to the external analog-to-digital converter module. This branch is used to process the signal after it has been buffered by the voltage follower. By selecting an appropriate resistor ratio, the signal voltage can be precisely scaled to the full-scale input range of the ADC.

[0065] The second voltage divider branch includes a sixth resistor R13, which is connected in parallel across the fourth resistor R11 via the second analog on / off switch of the multi-channel switching chip. When the second analog on / off switch is on, the sixth resistor R13 is connected in parallel with the fourth resistor R11, changing the voltage division ratio of the first voltage divider branch, thus adapting to the voltage scaling requirements of another signal type. This method of changing the voltage division ratio through parallel resistors eliminates the need for additional operational amplifiers or complex circuits, resulting in a simple structure, low cost, and fast switching speed.

[0066] The two voltage divider branches share the main voltage divider structure consisting of the fourth resistor R11 and the fifth resistor R12. The voltage division ratio is changed only by whether the sixth resistor R13 is connected. The final output signal is led out from the same voltage divider point to the analog-to-digital converter module. This design allows the subsequent ADC to process all types of signals with only one input channel, avoiding the synchronization errors and increased costs caused by multi-channel ADCs, while also simplifying PCB layout and routing.

[0067] The introduction of a voltage follower enables electrical isolation between the preceding signal and the subsequent voltage divider network, ensuring that changes in the subsequent load do not negatively impact the stability of the preceding signal. Furthermore, all switching operations are performed by the control unit via software, eliminating the need for manual intervention, thus reducing maintenance costs and enhancing the system's intelligence and long-term reliability.

[0068] Example 5 A multi-type analog input switching circuit is shown according to another exemplary embodiment. The circuit includes: Analog input port, used to connect at least two different types of analog input signals; Impedance matching network, including at least one sampling resistor R5; A voltage divider network includes multiple voltage divider branches for adjusting the voltage ratio of the input signal; the number of voltage divider branches is equal to the number of types of the analog input signal. The analog switch module is connected to the impedance matching network and the voltage divider network, respectively. The control unit is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0069] The input filtering module includes a first resistor R1 and a first capacitor C1 connected in parallel. One end of the parallel first resistor R1 and first capacitor C1 is connected to the analog input port, and the other end is grounded.

[0070] When the impedance matching network includes multiple sampling resistors, the multiple sampling resistors are connected in parallel.

[0071] The analog switch module includes: The multi-channel switching chip U1 has one end (pin 2) of its first analog on / off switch connected to the sampling resistor R5, and the other end (pin 1) grounded; the two ends (pin 5 and pin 6) of its second analog on / off switch are respectively connected to the voltage divider network, and the control terminal is connected to the control unit.

[0072] In practical applications, the multi-type analog input switching circuit further includes: a voltage follower and a current-limiting resistor R8, wherein the voltage follower includes: The operational amplifier has its non-inverting input terminal (pin 3) connected to the analog input port through the second resistor R7, its inverting input terminal (pin 2) connected to its output terminal through the third resistor R9 and the second capacitor C4 in parallel, and its output terminal (pin 1) connected to the current limiting resistor R8.

[0073] In practice, the voltage divider network includes: The first voltage divider branch includes: a fourth resistor R11 and a fifth resistor R12, with a voltage divider point formed between the fourth resistor R11 and the fifth resistor R12, and an external analog-to-digital converter module connected to the voltage divider point; the other end of the fourth resistor R11 is connected to the current-limiting resistor R8, and the other end of the fifth resistor R12 is grounded. The second voltage divider branch includes the fourth resistor, the fifth resistor, and the sixth resistor, wherein the sixth resistor R13 is connected in parallel across the fourth resistor R11 via the second analog on / off switch of the multi-channel switching chip.

[0074] The multi-type analog input switching circuit also includes: The output filtering module includes a seventh resistor R10 and a third capacitor C5 connected in parallel. One end of the parallel seventh resistor R10 and third capacitor C5 is connected between the current limiting resistor R8 and the voltage divider network, and the other end is grounded.

[0075] It is understood that in the technical solution provided in this embodiment, the seventh resistor R10 and the third capacitor C5 constitute an additional RC low-pass filter, located after the voltage follower output and before the voltage divider network. Although the voltage follower has low output impedance, its output signal may still contain high-frequency noise components from the preceding circuitry or power supply. This filter can effectively bypass these residual high-frequency components to ground, making the signal entering the voltage divider network smoother and cleaner, thereby further improving the accuracy and stability of analog-to-digital conversion.

[0076] In high-speed signal transmission, the leads between the output of the voltage follower and the subsequent voltage divider network may form parasitic inductance and capacitance, causing high-frequency oscillations or ringing. The presence of the third capacitor C5 provides a low-impedance path to ground for high-frequency components, effectively suppressing the generation of parasitic oscillations and ensuring that the circuit remains stable within the operating frequency band.

[0077] The seventh resistor, R10, provides a DC discharge path to ground for the signal node. When the system is first powered on or during analog switch switching, this resistor can force the signal point down to ground potential (0V), preventing random interference or charge accumulation caused by floating and thus avoiding malfunctions in subsequent circuits, ensuring the predictability of the system's behavior during initialization and mode switching.

[0078] The third capacitor C5 provides a low-impedance AC path to ground, which can quickly discharge electrostatic discharge energy accidentally coupled to the signal line to ground, protecting the subsequent precision resistor network and the input pins of the analog-to-digital converter module from damage, and improving the overall electromagnetic compatibility (EMC) level.

[0079] The input filter module (R1, C1) is responsible for filtering out high-frequency interference from the input, while the output filter module (R10, C5) is responsible for purifying the signal output from the voltage follower. The two-stage filtering works together to ensure that the entire signal link, from the input to the voltage divider network, is well suppressed by noise, making it particularly suitable for industrial environments with high concentrations of strong interference sources such as frequency converters and motors.

[0080] Example 6 A multi-type analog input switching circuit is shown according to another exemplary embodiment. The circuit includes: Analog input port, used to connect at least two different types of analog input signals; Impedance matching network, including at least one sampling resistor R5; A voltage divider network includes multiple voltage divider branches for adjusting the voltage ratio of the input signal; the number of voltage divider branches is equal to the number of types of the analog input signal. The analog switch module is connected to the impedance matching network and the voltage divider network, respectively. The control unit is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0081] The input filtering module includes a first resistor R1 and a first capacitor C1 connected in parallel. One end of the parallel first resistor R1 and first capacitor C1 is connected to the analog input port, and the other end is grounded.

[0082] When the impedance matching network includes multiple sampling resistors, the multiple sampling resistors are connected in parallel.

[0083] The analog switch module includes: The multi-channel switching chip U1 has one end (pin 2) of its first analog on / off switch connected to the sampling resistor R5, and the other end (pin 1) grounded; the two ends (pin 5 and pin 6) of its second analog on / off switch are respectively connected to the voltage divider network, and the control terminal is connected to the control unit.

[0084] In practical applications, the multi-type analog input switching circuit further includes: a voltage follower and a current-limiting resistor R8, wherein the voltage follower includes: The operational amplifier has its non-inverting input terminal (pin 3) connected to the analog input port through the second resistor R7, its inverting input terminal (pin 2) connected to its output terminal through the third resistor R9 and the second capacitor C4 in parallel, and its output terminal (pin 1) connected to the current limiting resistor R8.

[0085] In practice, the voltage divider network includes: The first voltage divider branch includes: a fourth resistor R11 and a fifth resistor R12, with a voltage divider point formed between the fourth resistor R11 and the fifth resistor R12, and an external analog-to-digital converter module connected to the voltage divider point; the other end of the fourth resistor R11 is connected to the current-limiting resistor R8, and the other end of the fifth resistor R12 is grounded. The second voltage divider branch includes the fourth resistor, the fifth resistor, and the sixth resistor, wherein the sixth resistor R13 is connected in parallel across the fourth resistor R11 via the second analog on / off switch of the multi-channel switching chip.

[0086] See Figure 3 and Figure 7 The multi-type analog input switching circuit further includes: The output filtering module includes a seventh resistor R10 and a third capacitor C5 connected in parallel. One end of the parallel seventh resistor R10 and third capacitor C5 is connected between the current limiting resistor R8 and the voltage divider network, and the other end is grounded.

[0087] In practical application, the analog input signal includes: The first type of analog input signal is a 4-20mA current signal; The second type of analog input signal is a 0-10V voltage signal.

[0088] When the first type of analog input signal is connected, the control unit controls the analog switch module to turn on the branch where the impedance matching network is located, so that the sampling resistor is connected to the circuit to realize current-to-voltage conversion. At the same time, the second voltage divider branch is selected to perform voltage division processing on the converted voltage signal and output a 0-3.3V voltage signal. When the second type of analog input signal is received, the control unit controls the analog switch module to disconnect the branch where the impedance matching network is located to avoid the sampling resistor from becoming a load on the voltage signal, and at the same time switches to the first voltage divider branch.

[0089] It is understandable that, based on Example 5, Example 6 further defines the specific types of analog input signals (4-20mA current signals and 0-10V voltage signals), and provides corresponding control strategies for the analog switch module and voltage divider branch in two modes: the second voltage divider branch (parallel sixth resistor R13) is selected in current mode, and the first voltage divider branch (no parallel connection) is selected in voltage mode.

[0090] A 4-20mA current signal is converted to a 1-5V voltage via a 250Ω sampling resistor, requiring a relatively large voltage division ratio to reduce it to 0-3.3V; while a 0-10V voltage signal requires a smaller voltage division ratio. By connecting the sixth resistor R13 in parallel with the fourth resistor R11 in the second voltage divider branch, the equivalent resistance of R11 can be effectively reduced, thereby increasing the voltage division ratio (i.e., the ratio of output voltage to input voltage), so that the 1-5V signal is precisely mapped to 0-3.3V; while the first voltage divider branch has no parallel connection, resulting in an even smaller voltage division ratio, so that the 0-10V signal is also mapped to 0-3.3V. This differentiated design ensures that both signals can fully utilize the ADC's full-scale input range to achieve optimal resolution.

[0091] If a single fixed voltage divider ratio is used, the 1-5V converted from the current signal may only occupy a portion of the ADC range (e.g., only 0-1.65V is used), resulting in a relatively increased quantization noise. This embodiment switches the voltage divider branch so that the current signal can also occupy a range close to full scale, thereby achieving a higher signal-to-noise ratio and measurement accuracy with the same number of ADC bits.

[0092] When a 4-20mA current signal is input, the control unit activates the impedance matching network, connecting the precision sampling resistor R5 into the circuit, and simultaneously selecting the second voltage divider branch. After the sampling resistor completes the current-to-voltage conversion, the second voltage divider branch precisely divides the 1-5V signal. The entire process is completed by a passive resistor network, exhibiting extremely high linearity and no additional nonlinear distortion, ensuring the accuracy of current signal acquisition.

[0093] When a 0-10V voltage signal is input, the control unit disconnects the impedance matching network, completely separating the sampling resistor R5 from the main signal path to prevent the 250Ω resistor from forming a voltage divider load on the voltage signal. Simultaneously, the first voltage divider branch (without parallel resistors) is selected. The input impedance of this branch is determined by the fourth resistor R11 and the fifth resistor R12 (typically tens of kilohms), which is much greater than the internal resistance of the voltage signal source. This ensures that the 0-10V signal enters the voltage divider network with its original amplitude, maintaining the accuracy of the voltage measurement.

[0094] The control unit simultaneously controls two on / off switches of the analog switch module via the same control signal: the first switch controls whether the sampling resistor is connected, and the second switch controls whether the sixth resistor R13 is connected in parallel. The two switches are strictly synchronized, requiring no additional timing logic, simplifying software design, and avoiding signal path conflicts or momentary errors caused by asynchronous switching.

[0095] Regardless of which voltage divider branch is chosen, the final output signal is led out from the same voltage divider point (between the fourth resistor R11 and the fifth resistor R12) to the analog-to-digital converter module. The subsequent ADC only needs one input channel to process two signals, avoiding the synchronization errors and cost of multi-channel ADCs, and also simplifying the PCB layout.

[0096] Signal type identification and switching are entirely handled by the control unit through software logic, requiring no manual intervention. The system can automatically configure itself based on the type of connected sensor, or it can be remotely set by a host computer, supporting dynamic switching. This feature allows the equipment to flexibly adapt to different field requirements, making it particularly suitable for smart manufacturing production lines that require frequent sensor or signal type changes.

[0097] Example 7 A data acquisition card according to an exemplary embodiment includes: The above-mentioned multi-type analog input switching circuit.

[0098] See Figure 1 The circuit includes: Analog input port 101 is used to connect at least two different types of analog input signals; Impedance matching network 102 includes at least one sampling resistor; The voltage divider network 103 includes multiple voltage divider branches for voltage proportional adjustment of the input signal; the number of voltage divider branches is equal to the number of analog input signal types. The analog switch module 104 is connected to the impedance matching network and the voltage divider network respectively; The control unit 105 is used to control whether the analog switch module connects the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

[0099] It is understood that this embodiment, by including the aforementioned multi-type analog input switching circuit, achieves unified processing of various types of analog input signals by using a single analog switch module to coordinate the control of the impedance matching network and the voltage divider network. This eliminates the need to design separate signal conditioning channels for each signal type, significantly reducing the number of operational amplifiers, analog-to-digital converters, and other components, thereby lowering the circuit board area and material costs.

[0100] It abandons the traditional manual switching method using mechanical switches or jumpers, and adopts electronic analog switches for rapid switching, with switching times down to the nanosecond level. The control unit outputs control signals in real time according to the type of input signal, achieving mode switching at the millisecond or even microsecond level, meeting the rapid response requirements for dynamic signal type recognition in industrial automation systems.

[0101] All types of input signals are processed through the same main signal path (same operational amplifier, same analog-to-digital converter), eliminating consistency deviations caused by differences in component parameters (such as gain error, bias voltage, temperature drift, etc.) between different channels in multi-channel solutions. Simultaneously, precise control of the connection and disconnection of the sampling resistor via analog switches avoids the load effect of the sampling resistor on the signal in voltage mode, ensuring interference-free transmission of different signal sources along a unified path, thereby significantly improving measurement accuracy and system stability.

[0102] Electronic analog switches eliminate the problems of mechanical contact wear and oxidation, resulting in a long service life. Furthermore, signal types can be remotely configured via software, eliminating the need for manual on-site operation, thus reducing maintenance costs and enhancing the system's intelligence level.

[0103] Example 8 An electrical device according to an exemplary embodiment includes: The aforementioned data acquisition card.

[0104] It is understood that this embodiment includes the aforementioned data acquisition card, which in turn includes the aforementioned multi-type analog input switching circuit. This circuit achieves unified processing of various types of analog input signals by using a single analog switch module to coordinate the control of the impedance matching network and the voltage divider network. This eliminates the need to design independent signal conditioning channels for each signal type, significantly reducing the number of operational amplifiers, analog-to-digital converters, and other components, thus lowering the circuit board area and material costs.

[0105] It abandons the traditional manual switching method using mechanical switches or jumpers, and adopts electronic analog switches for rapid switching, with switching times down to the nanosecond level. The control unit outputs control signals in real time according to the type of input signal, achieving mode switching at the millisecond or even microsecond level, meeting the rapid response requirements for dynamic signal type recognition in industrial automation systems.

[0106] All types of input signals are processed through the same main signal path (same operational amplifier, same analog-to-digital converter), eliminating consistency deviations caused by differences in component parameters (such as gain error, bias voltage, temperature drift, etc.) between different channels in multi-channel solutions. Simultaneously, precise control of the connection and disconnection of the sampling resistor via analog switches avoids the load effect of the sampling resistor on the signal in voltage mode, ensuring interference-free transmission of different signal sources along a unified path, thereby significantly improving measurement accuracy and system stability.

[0107] Electronic analog switches eliminate the problems of mechanical contact wear and oxidation, resulting in a long service life. Furthermore, signal types can be remotely configured via software, eliminating the need for manual on-site operation, thus reducing maintenance costs and enhancing the system's intelligence level.

[0108] It is understood that the same or similar parts in the above embodiments can be referred to each other, and the contents not described in detail in some embodiments can be referred to the same or similar contents in other embodiments.

[0109] It should be noted that in the description of this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means at least two.

[0110] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0111] It should be understood that various parts of the present invention can be implemented in hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented in software or firmware stored in memory and executed by a suitable instruction execution system. For example, if implemented in hardware, as in another embodiment, it can be implemented using any one or a combination of the following techniques known in the art: discrete logic circuits having logic gates for implementing logical functions on data signals, application-specific integrated circuits (ASICs) having suitable combinational logic gates, programmable gate arrays (PGAs), field-programmable gate arrays (FPGAs), etc.

[0112] Those skilled in the art will understand that all or part of the steps of the methods in the above embodiments can be implemented by a program instructing related hardware. The program can be stored in a computer-readable storage medium, and when executed, the program includes one or a combination of the steps of the method embodiments.

[0113] Furthermore, the functional units in the various embodiments of the present invention can be integrated into a processing module, or each unit can exist physically separately, or two or more units can be integrated into a module. The integrated module can be implemented in hardware or as a software functional module. If the integrated module is implemented as a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.

[0114] The storage media mentioned above can be read-only memory, disk, or optical disk, etc.

[0115] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0116] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A multi-type analog input switching circuit, characterized in that, include: Analog input port, used to connect at least two different types of analog input signals; Impedance matching network, including at least one sampling resistor; A voltage divider network, comprising multiple voltage divider branches, is used to adjust the voltage ratio of the input signal; the number of voltage divider branches is equal to the number of analog input signal types. The analog switch module is connected to the impedance matching network and the voltage divider network, respectively. The control unit is used to control whether the analog switch module connects to the impedance matching network and selects the matching voltage divider branch output according to the type of the currently connected analog input signal.

2. The multi-type analog input switching circuit according to claim 1, characterized in that, Also includes: The input filtering module includes a first resistor and a first capacitor connected in parallel. One end of the parallel first resistor and the first capacitor is connected to the analog input port, and the other end is grounded.

3. The multi-type analog input switching circuit according to claim 1, characterized in that, When there are multiple sampling resistors, the multiple sampling resistors are connected in parallel.

4. The multi-type analog input switching circuit according to claim 1, characterized in that, The analog switch module includes: The multi-channel switching chip has one end of its first analog on / off switch connected to the sampling resistor and the other end grounded; its two ends of the second analog on / off switch are respectively connected to the voltage divider network, and its control terminal is connected to the control unit.

5. The multi-type analog input switching circuit according to claim 4, characterized in that, Also includes: A voltage follower and a current-limiting resistor, wherein the voltage follower includes: An operational amplifier has its non-inverting input terminal connected to the analog input port via a second resistor, its inverting input terminal connected to its output terminal via a third resistor and a second capacitor in parallel, and its output terminal connected to the current-limiting resistor.

6. The multi-type analog input switching circuit according to claim 5, characterized in that, The voltage divider network includes: The first voltage divider branch includes: a fourth resistor and a fifth resistor, with a voltage divider point formed between the fourth resistor and the fifth resistor, and an external analog-to-digital converter module connected to the voltage divider point; the other end of the fourth resistor is connected to the current-limiting resistor, and the other end of the fifth resistor is grounded. The second voltage divider branch includes the fourth resistor, the fifth resistor, and the sixth resistor, wherein the sixth resistor is connected in parallel across the fourth resistor via the second analog on / off switch of the multi-channel switching chip.

7. The multi-type analog input switching circuit according to claim 6, characterized in that, Also includes: The output filtering module includes a seventh resistor and a third capacitor connected in parallel. One end of the parallel seventh resistor and third capacitor is connected between the current-limiting resistor and the voltage divider network, and the other end is grounded.

8. The multi-type analog input switching circuit according to any one of claims 1 to 7, characterized in that, The analog input signal includes: The first type of analog input signal is a 4-20mA current signal; The second type of analog input signal is a 0-10V voltage signal.

9. The multi-type analog input switching circuit according to claim 8, characterized in that, When the first type of analog input signal is connected, the control unit controls the analog switch module to turn on the branch where the impedance matching network is located, so that the sampling resistor is connected to the circuit to realize current-to-voltage conversion. At the same time, the second voltage divider branch is selected to perform voltage divider processing on the converted voltage signal and output a 0-3.3V voltage signal. When the second type of analog input signal is received, the control unit controls the analog switch module to disconnect the branch where the impedance matching network is located to avoid the sampling resistor from becoming a load on the voltage signal, and at the same time switches to the first voltage divider branch.

10. A data acquisition card, characterized in that, include: The multi-type analog input switching circuit according to any one of claims 1 to 9.

11. An electrical appliance, characterized in that, include: The data acquisition card as described in claim 10.

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