Method and system for testing response time of analog input card

Abstract

The invention provides an analog input card response time testing method and system, and belongs to the technical field of distributed control system testing. The method comprises the following steps: determining the sampling time of the analog input card according to the one-time closing time and one-time opening time of the signal generator; acquiring a voltage waveform of the sampling resistor and an output waveform of the digital quantity output card in at least one sampling time under the condition that the signal generator is switched on and off according to the switching-on time and the switching-off time, and respectively taking the voltage waveform and the output waveform as a first waveform and a second waveform; and in the same sampling time, taking the difference value of the time corresponding to the same position on the first waveform and the second waveform as the response time of the analog quantity input card. According to the invention, an independent test circuit is not required to be designed, a conventional test instrument is directly used, the sampling time and the response time of the analog quantity input card can be accurately tested, and the universality is relatively high.

Description

Technical Field

[0001] This invention belongs to the field of distributed control system testing technology, and particularly relates to a method and system for testing the response time of analog input cards. Background Technology

[0002] Analog input cards (AI cards) play a crucial role in industrial automation, process control, high-risk industry applications, nuclear power protection systems, and data acquisition. By converting analog signals (including 4-20mA current signals, RTD signals, thermocouple signals, and voltage signals) into digital signals, they enable precise monitoring and control of various physical quantities. The response time of an analog input card refers to the time required for the output signal to reach a steady state after a change in the input signal. This metric is critical for ensuring the accuracy and reliability of the system, especially in applications with high precision and safety requirements, such as distributed control systems (DCS) in thermal power plants.

[0003] The response time of analog input cards can be obtained through both theoretical analysis and actual measurement. Theoretical analysis generally yields the maximum response time, while actual testing verifies this theoretical value. The theoretical response time requires adding delays from the controller scan cycle, CPU-card data exchange cycle, opto-isolation, and A / D conversion time. Furthermore, considering the possibility that the signal input might miss a full controller scan cycle, this cycle needs to be multiplied by two. Therefore, the theoretical response time is always longer than the actual measured time. Thus, developing an effective method for testing the actual response time of analog input cards is crucial.

[0004] Current methods for measuring the response time of analog input cards, such as the test method mentioned in Huo Jianbo's paper "Design and Implementation of DCS Analog Control Loop Response Time Test", are simple and use very few testing devices. However, they do not take into account the sampling time of the analog input card channel. This is because the response time can only be correctly measured within a sampling period; otherwise, the measured time will be too large. Summary of the Invention

[0005] This invention provides a method and system for testing the response time of analog input cards, in order to solve the problem that the test times are too large in the prior art because the sampling time of the analog input card channel is not taken into account.

[0006] In a first aspect, the present invention provides a method for testing the response time of an analog input card, which is applied to an analog input card response time testing device; the testing device includes a signal generator; the signal generator is connected in parallel with a current source and a sampling resistor of the analog input card; the analog input card is electrically connected to a digital output card;

[0007] The analog input card response time test method includes:

[0008] The sampling time of the analog input card is determined based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal.

[0009] When the signal generator switches on and off according to the closing time and opening time, the voltage waveform of the sampling resistor and the output waveform of the digital output card are acquired within at least one sampling time, and used as the first waveform and the second waveform, respectively.

[0010] Within the same sampling time, the difference between the times corresponding to the same position on the first waveform and the second waveform is taken as the response time of the analog input card.

[0011] Optionally, determining the sampling time of the analog input card based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal, includes:

[0012] Obtain the current value of the sampling resistor when the signal generator is closed and open;

[0013] When the number of changes in the current value of the sampling resistor is equal to the sum of the number of times the signal generator closes and opens, the sum of the closing time and the opening time of the signal generator is taken as the sampling time of the analog input card.

[0014] Optionally, the signal generator is connected in series with an external resistor, and the signal generator and the external resistor are connected in parallel with the current source and the sampling resistor, respectively.

[0015] Optionally, the resistance value of the external resistor is equal to the resistance value of the sampling resistor.

[0016] Secondly, the present invention provides an analog input card response time testing system, applied to an analog input card response time testing device; the testing device includes a signal generator; the signal generator is connected in parallel with a current source and a sampling resistor of the analog input card; the analog input card is electrically connected to a digital output card;

[0017] The analog input card response time testing system includes:

[0018] The first determining module is used to determine the sampling time of the analog input card based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal.

[0019] The acquisition module is used to acquire the voltage waveform of the sampling resistor and the output waveform of the digital output card within at least one sampling time when the signal generator is switched on and off according to the closing time and the opening time, so as to serve as the first waveform and the second waveform, respectively.

[0020] The second determining module is used to take the time difference between the corresponding positions on the first waveform and the second waveform as the response time of the analog input card within the same sampling time.

[0021] Optionally, the first determining module includes:

[0022] An acquisition unit is used to acquire the current value of the sampling resistor when the signal generator is closed and open;

[0023] The determining unit is configured to, when the number of changes in the current value of the sampling resistor is equal to the sum of the number of times the signal generator closes and the number of times it opens, use the sum of the closing time and the opening time of the signal generator as the sampling time of the analog input card.

[0024] Optionally, the signal generator is connected in series with an external resistor, and the signal generator and the external resistor are connected in parallel with the current source and the sampling resistor, respectively.

[0025] Optionally, the resistance value of the external resistor is equal to the resistance value of the sampling resistor.

[0026] Thirdly, the present invention provides a computer device, including a processor and a memory; wherein, when the processor executes a computer program stored in the memory, it implements the steps of the analog input card response time testing method described in the first aspect.

[0027] Fourthly, the present invention provides a computer-readable storage medium, characterized in that it is used to store a computer program; when the computer program is executed by a processor, it implements the steps of the analog input card response time testing method described in the first aspect.

[0028] This invention provides a method and system for testing the response time of analog input cards. The method does not require the design of a separate test circuit; it can directly use conventional test instruments to accurately test the sampling time and response time of analog input cards. The accuracy of the response time depends on the accuracy of the signal generator. The response time of analog input cards in commonly used distributed control systems can all be tested using the solution of this invention, which has strong versatility. Attached Figure Description

[0029] To more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A flowchart illustrating a method for testing the response time of an analog input card according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the analog input card response time testing device provided in an embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram showing how the output value of the analog input card is converted by the calculation block and then accumulated by the calculation accumulation block, as provided in this embodiment of the invention.

[0033] Figure 4 This is a waveform diagram of the numerical values ​​displayed by the DCS system provided in an embodiment of the present invention;

[0034] Figure 5 A waveform diagram of the input voltage of the analog input card provided in an embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the output waveform of the computing block output driving digital output card provided in an embodiment of the present invention;

[0036] Figure 7 A schematic diagram illustrating the response time of an analog input card provided in an embodiment of the present invention;

[0037] Figure 8 This is a schematic diagram of an analog input card response time testing system provided in an embodiment of the present invention. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] The analog input card response time test of this invention is based on a DCS (Distributed Control System), which includes host monitoring software, various function blocks (including calculation blocks and calculation accumulation blocks), (AI) analog input cards, and (DO) digital output cards. Conventional testing instruments are also used, including a current source, oscilloscope, (SOE) signal generator, and resistance box.

[0040] The supervisory control and data acquisition (SCADA) software is the human-machine interface of the DCS distributed control system. It can monitor and control in real time, manage centrally, record and analyze data, etc. In this invention, it is used to display the input values ​​of the AI ​​analog input card, the output values ​​of the DO digital output card, and the logical operations of the calculation block and the calculation accumulation block.

[0041] The calculation block is a built-in function block in a DCS distributed control system, used to output corresponding values ​​from input values ​​through different calculation methods. In this invention, different input values ​​from the AI ​​analog input card are converted into FLASE and TRUE values ​​for output, which are then used to drive the output of the DO digital output card.

[0042] The calculation and accumulation block is a built-in function block in the DCS distributed control system, used to accumulate the number of changes in the input value and output the total number of changes. In this invention, the number of changes recorded by the calculation and accumulation block is compared with the number of changes set by the SOE signal generator.

[0043] AI analog input card is an analog input card for DCS distributed control system. It is used to convert the analog quantity of the controlled object into a digital signal that the computer can recognize. It generally inputs a 4-20mA current signal and displays a value of 0-1 in the upper-level monitoring software of DCS distributed control system. Some values ​​are shown in Table 1. In this invention, the analog input card is the object being tested.

[0044] Table 1. Correspondence between input current and displayed values ​​in the DCS distributed control system.

[0045]

[0046] The DO digital output card is a digital output card for a DCS distributed control system. It is used to convert the switch signals represented by binary codes output by the computer into switch signals that can control the production process or display the status. In this invention, it is used as an output signal to participate in the calculation of response time.

[0047] The SOE signal generator can periodically generate on / off signals with an accuracy of 1ms. For example, in the test circuit of this invention, a constant current value of 16mA is input. When the SOE signal generator switches on and off, the current value flowing through the AI ​​analog input card will change periodically.

[0048] The resistor box can be adjusted to different resistance values. In this invention, the resistance value adjusted by the resistor box can be consistent with the sampling resistance value of the AI ​​analog input card. The specific resistance value can be obtained from the design (or manufacturing) manufacturer of the AI ​​analog input card.

[0049] Example 1

[0050] This invention provides a method for testing the response time of analog input cards, applicable to an analog input card response time testing device, such as... Figure 2 and Figure 6 As shown; the test device includes a signal generator 1; the signal generator 1 is connected in parallel with a current source 2 and a sampling resistor 4 of an analog input card 3; the analog input card 3 is electrically connected to a digital output card 5 through a calculation block.

[0051] The analog input card 3 (AI card) has a sampling resistor 4 for each input channel, and the resistance value of the sampling resistor 4 varies from manufacturer to manufacturer. A signal generator 1 and an external resistor 6 with the same resistance value R as the sampling resistor 4 are connected in parallel outside a certain input channel.

[0052] like Figure 1 As shown, the analog input card response time test method includes:

[0053] Step 101: Determine the sampling time of the analog input card based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal.

[0054] For example, this step includes obtaining the current value of the sampling resistor when the signal generator is closed and open.

[0055] When the number of changes in the current value of the sampling resistor is equal to the sum of the number of times the signal generator closes and opens, the sum of the closing time and the opening time of the signal generator is taken as the sampling time of the analog input card. It should be noted that the closing time is the duration from the moment the signal generator closes to the moment it opens, the opening time is the duration from the moment it opens to the moment it closes, and the sampling time refers to a period of time, i.e., the sampling duration.

[0056] When a constant current of 16mA is input using a current source, and the SOE signal generator is disconnected, the current only flows through the sampling resistor inside the AI ​​card. The signal acquired by the AI ​​card is 16mA, and the value displayed by the AI ​​card in the upper-level monitoring software is 0.75.

[0057] When the SOE signal generator is closed, the current flowing through the sampling resistor inside the AI ​​card is 8mA, and the value displayed by the AI ​​card in the upper-level monitoring software is 0.25.

[0058] As the SOE signal generator periodically switches on and off, the input voltage u at the input terminal also changes periodically. This periodic change in the input voltage can be displayed using an oscilloscope.

[0059] like Figure 3 As shown, the display value of the AI ​​card is input to the calculation block. The calculation block determines whether the input value is greater than 0.7 and sets the output to FALSE. When the input value is less than 0.3, the output is set to TRUE. The output value is then sent to the calculation accumulation block.

[0060] When the input value of the accumulator changes (from FALSE to TRUE or vice versa), it automatically increments by 1, and continues to accumulate. Its output value is the number of times the input value has changed.

[0061] For example, if the SOE signal generator is set to switch on and off 100 times, the current flowing through the sampling resistor of the AI ​​card will also change 100 times. If the AI ​​card collects the data every time, the calculation block will change from FALSE to TRUE 100 times, and the calculation accumulation block can record 100.

[0062] Therefore, when the SOE signal generator changes (period) too quickly (shortly), the AI ​​card may not be able to capture all current changes, and the accumulated value will be less than the number of on / off cycles set by the SOE signal generator. Therefore, the change period of the SOE signal generator can be changed (gradually increasing from 1ms) until the accumulated value is exactly equal to the number of on / off cycles set by the SOE signal generator. At this point, the set period of the SOE signal generator is recorded as T0, and the sampling time of the AI ​​card is T, where T = 2·T0. Figure 4 As shown.

[0063] Step 102: When the signal generator switches on and off according to the closing time and opening time, the voltage waveform of the sampling resistor and the output waveform of the digital output card are acquired within at least one sampling time, and used as the first waveform and the second waveform, respectively.

[0064] If there are multiple sampling times in this step, these sampling times can be continuous or intermittent.

[0065] like Figure 5 As shown, because the input current in the circuit is a constant current of I = 16mA, and the load resistor (when the SOE signal generator is off, the load resistor is the sampling resistor, because the current only flows through the sampling resistor, so the sampling resistor is the current load; when the SOE signal generator is on, the load resistor is the sampling resistor and the external resistor, because the current flows through both resistors simultaneously, and because the two resistors have the same resistance value, the current flowing through both the sampling resistor and the external resistor is 8mA), the input voltage value is IR or IR / 2. After determining the sampling time, an oscilloscope can be used to display the waveform of the input voltage change (i.e., the first waveform), as shown... Figure 7 The upper part is shown.

[0066] like Figure 6 As shown, in Figure 3 Based on this, the FALSE or TRUE value output by the calculation block is used as a signal input to the DO digital output card for relay output. At this time, an oscilloscope connected to the relay output terminal can also obtain the periodic change of the DO digital output card's output voltage waveform (i.e., the second waveform), such as... Figure 7 The lower half is shown.

[0067] Step 103: Within the same sampling time, the difference between the times corresponding to the same position on the first waveform and the second waveform is taken as the response time of the analog input card.

[0068] like Figure 7 As shown, within the same sampling time (the same time period), there is a time difference between the two waveforms (the first waveform and the second waveform). This difference is the response time ΔT of the AI ​​analog input card. The specific value of ΔT can be read directly on the oscilloscope.

[0069] In summary, this embodiment provides a method for testing the response time of analog input cards. It eliminates the need for a separate test circuit and allows for accurate testing of the sampling and response times of analog input cards using conventional testing instruments. The accuracy of the response time depends on the precision of the signal generator, typically in the millisecond range. This invention can be used to test the response time of analog input cards in common distributed control systems, demonstrating strong versatility.

[0070] Example 2

[0071] Based on the same inventive concept as Embodiment 1, this embodiment provides an analog input card response time testing system. Since the principle of this system in solving the problem is similar to the analog input card response time testing method provided in Embodiment 1, the implementation of this system can refer to the implementation of the analog input card response time testing method provided in Embodiment 1.

[0072] like Figure 8 As shown, the analog input card response time testing system includes:

[0073] The first determining module 10 is used to determine the sampling time of the analog input card based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal.

[0074] The acquisition module 20 is used to acquire the voltage waveform of the sampling resistor and the output waveform of the digital output card within at least one sampling time when the signal generator is switched on and off according to the closing time and opening time, so as to serve as the first waveform and the second waveform, respectively.

[0075] The second determining module 30 is used to take the time difference between the corresponding positions on the first waveform and the second waveform as the response time of the analog input card within the same sampling time.

[0076] For example, the first determining module includes:

[0077] The acquisition unit is used to acquire the current value of the sampling resistor when the signal generator is closed and open.

[0078] The determining unit is configured to, when the number of changes in the current value of the sampling resistor is equal to the sum of the number of times the signal generator closes and the number of times it opens, use the sum of the closing time and the opening time of the signal generator as the sampling time of the analog input card.

[0079] For more detailed information on the working process of each of the above modules, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0080] Example 3

[0081] This embodiment provides a computer device, including a processor and a memory; wherein, when the processor executes the computer program stored in the memory, it implements the steps of the analog input card response time test method described in Embodiment 1.

[0082] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0083] Example 4

[0084] This embodiment provides a computer-readable storage medium for storing a computer program; when the computer program is executed by a processor, it implements the steps of the analog input card response time test method described in Embodiment 1.

[0085] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0086] Example 5

[0087] This embodiment provides a computer program product, including computer-executable instructions or a computer program. When the computer-executable instructions or the computer program are executed by a processor, they implement the steps of the analog input card response time test method described in Embodiment 1.

[0088] For a more detailed explanation of the above method, please refer to the relevant content disclosed in Example 1, which will not be repeated here.

[0089] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the systems, devices, storage media, and computer program products disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the descriptions are relatively simple, and relevant parts can be referred to the method section.

[0090] Those skilled in the art will clearly understand that the techniques in the embodiments of the present invention can be implemented using software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solutions in the embodiments of the present invention, or the parts that contribute to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or certain parts of the embodiments of the present invention.

[0091] In some embodiments, computer-executable instructions may take the form of programs, software, software modules, scripts, or code, written in any form of programming language (including compiled or interpreted languages, or declarative or procedural languages), and may be deployed in any form, including as stand-alone programs or as modules, components, subroutines, or other units suitable for use in a computing environment.

[0092] As an example, computer-executable instructions may, but do not necessarily, correspond to files in a file system. They may be stored as part of a file that holds other programs or data, for example, in one or more scripts in a Hyper Text Markup Language (HTML) document, in a single file dedicated to the program in question, or in multiple co-located files (e.g., files that store one or more modules, subroutines, or code sections).

[0093] As an example, computer-executable instructions can be deployed to execute on a single electronic device, or on multiple electronic devices located at one location, or on multiple electronic devices distributed across multiple locations and interconnected via a communication network.

[0094] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for testing the response time of an analog input card, applied to an analog input card response time testing device; the testing device includes a signal generator; the signal generator is connected in parallel with a current source and a sampling resistor of the analog input card; the analog input card is electrically connected to a digital output card; The method for testing the response time of the analog input card is characterized in that... include: The sampling time of the analog input card is determined based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal. When the signal generator switches on and off according to the closing time and opening time, the voltage waveform of the sampling resistor and the output waveform of the digital output card are acquired within at least one sampling time, and used as the first waveform and the second waveform, respectively. Within the same sampling time, the difference between the times corresponding to the same position on the first waveform and the second waveform is taken as the response time of the analog input card.

2. The method for testing the response time of an analog input card according to claim 1, characterized in that, The step of determining the sampling time of the analog input card based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal, includes: Obtain the current value of the sampling resistor when the signal generator is closed and open; When the number of changes in the current value of the sampling resistor is equal to the sum of the number of times the signal generator closes and opens, the sum of the closing time and the opening time of the signal generator is taken as the sampling time of the analog input card.

3. The method for testing the response time of an analog input card according to claim 1, characterized in that, The signal generator is connected in series with an external resistor, and the signal generator and the external resistor are connected in parallel with the current source and the sampling resistor, respectively.

4. The method for testing the response time of an analog input card according to claim 3, characterized in that, The resistance value of the external resistor is equal to the resistance value of the sampling resistor.

5. An analog input card response time testing system, applied to an analog input card response time testing device; the testing device includes a signal generator; the signal generator is connected in parallel with a current source and a sampling resistor of the analog input card; the analog input card is electrically connected to a digital output card; The analog input card response time testing system is characterized in that... include: The first determining module is used to determine the sampling time of the analog input card based on the closing time and opening time of the signal generator; wherein the closing time and opening time of the signal generator are numerically equal. The acquisition module is used to acquire the voltage waveform of the sampling resistor and the output waveform of the digital output card within at least one sampling time when the signal generator is switched on and off according to the closing time and the opening time, so as to serve as the first waveform and the second waveform, respectively. The second determining module is used to take the time difference between the corresponding positions on the first waveform and the second waveform as the response time of the analog input card within the same sampling time.

6. The analog input card response time testing system according to claim 5, characterized in that, The first determining module includes: An acquisition unit is used to acquire the current value of the sampling resistor when the signal generator is closed and open; The determining unit is configured to, when the number of changes in the current value of the sampling resistor is equal to the sum of the number of times the signal generator closes and the number of times it opens, use the sum of the closing time and the opening time of the signal generator as the sampling time of the analog input card.

7. The analog input card response time testing system according to claim 5, characterized in that, The signal generator is connected in series with an external resistor, and the signal generator and the external resistor are connected in parallel with the current source and the sampling resistor, respectively.

8. The analog input card response time testing system according to claim 7, characterized in that, The resistance value of the external resistor is equal to the resistance value of the sampling resistor.

9. A computer device, characterized in that, It includes a processor and a memory; wherein, when the processor executes the computer program stored in the memory, it implements the steps of the analog input card response time test method according to any one of claims 1-4.

10. A computer-readable storage medium, characterized in that, Used to store computer programs; when the computer programs are executed by a processor, they implement the steps of the analog input card response time test method according to any one of claims 1-4.

Images