A method of current testing
By connecting multiple ammeters with different ranges in parallel in the current test circuit and using independent switches, the problems of insufficient test accuracy and equipment damage in dynamic current testing are solved, achieving accurate testing and process continuity throughout the entire current change process, and improving test efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- TIANNENG BATTERY GRP (JIANGXI) CO LTD
- Filing Date
- 2026-04-09
- Publication Date
- 2026-06-12
AI Technical Summary
In the existing technology, dynamic current testing equipment cannot accurately read the values in the low current stage during the high current stage, and it is easy to be damaged by excessive current when replacing the small range ammeter, resulting in insufficient test accuracy and equipment wear and tear, which affects the reliability of the test.
Multiple ammeters with different ranges are connected in parallel in the current test circuit. Each ammeter is connected in series with an independent switch. After the maximum range ammeter is initially read, the circuit switches to the ammeter with the matching range to achieve uninterrupted testing. The electronic switch and control module automatically control the switching on and off.
It enables accurate testing of current changes throughout the entire process, protects small-range ammeters, ensures the continuity of the testing process and the safety of the equipment, and improves testing efficiency.
Smart Images
Figure CN122193670A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of current testing technology, and specifically relates to a method for current testing. Background Technology
[0002] In the field of current testing, for devices whose current changes dynamically over time, such as batteries in constant voltage charging process and detection instruments with large operating current in the early stage and significant decrease in current after stabilization, the current change characteristics place special requirements on testing accuracy and equipment safety.
[0003] In existing technologies, testing such dynamic currents typically involves using a single-range ammeter connected in series. While a large-range ammeter can handle the high current conditions in the early stages of operation, its smaller scale division becomes insufficient as the current decreases, making it difficult to accurately read values during the low-current phase. This results in inadequate testing accuracy and fails to meet the need for precise monitoring of the entire current change process. Replacing the ammeter with a smaller-range one to improve accuracy during the low-current phase requires interrupting the current test circuit. During this interruption, the current in the device under test will return to its initial maximum value. The smaller-range ammeter connected at this time, exceeding its range limit, is highly susceptible to damage from excessive current, leading to equipment wear and test interruption. This approach fails to address the issues of safe testing during high-current phases and accurate testing during low-current phases, severely impacting the reliability of current testing. Therefore, we need to propose a new method for current testing. Summary of the Invention
[0004] To address the above problems, the present invention provides a method for current testing, comprising:
[0005] S1. Set up a current test circuit. Multiple ammeters with different ranges are connected in parallel in the test circuit, and each ammeter is connected in series with an independent switch.
[0006] S2. To perform a current test on the device under test, first close the switch corresponding to the maximum range ammeter so that the maximum range ammeter is connected to the test circuit, and read the current value displayed by the maximum range ammeter.
[0007] S3. Read the current value, select the target ammeter whose range matches the current value, close the switch corresponding to the target ammeter, and connect the target ammeter to the test circuit.
[0008] S4. After closing the switch corresponding to the target ammeter, open the switch corresponding to the maximum range ammeter and read the accurate current value of the device under test through the target ammeter.
[0009] Furthermore, the ranges of the multiple ammeters do not overlap, and the ranges of the multiple ammeters are set in descending order. The range coverage of the multiple ammeters is consistent with the current variation range of the device under test. The device under test is a device whose current changes with time. The device under test includes a battery whose current gradually decreases during constant voltage charging and a detection instrument whose current is large in the early stage and then stabilizes and decreases in the later stage.
[0010] Furthermore, the switch is an electronic switch. When an electronic switch is used, it is electrically connected to an external control module, which controls the on / off state of the electronic switch.
[0011] Furthermore, the specific operation of reading the current value displayed by the maximum range ammeter includes:
[0012] Once the maximum range ammeter is connected to the test circuit and the displayed value stabilizes, record the displayed value as the initial basis for selecting the target ammeter.
[0013] Furthermore, the criterion for selecting a target ammeter whose range matches the current value is as follows:
[0014] The current value is within one-third to two-thirds of the range of the target ammeter, and the target ammeter is the smallest range ammeter among multiple ammeters whose range and current value are closest.
[0015] Furthermore, the timing for disconnecting the switch corresponding to the maximum range ammeter is as follows:
[0016] After closing the switch corresponding to the target ammeter, observe the displayed value of the target ammeter. Once the displayed value of the target ammeter stabilizes, disconnect the switch corresponding to the maximum range ammeter.
[0017] Furthermore, the test circuit also includes a protective resistor, which is connected in series between the total input terminal of multiple parallel ammeters and the device under test, to prevent sudden current changes in the test circuit from damaging the ammeters.
[0018] Furthermore, the accuracy class of the target ammeter is higher than that of the maximum range ammeter. The accuracy class is the ratio of the ammeter's permissible error to its range, and the smaller the ratio, the higher the accuracy class.
[0019] Furthermore, after reading the accurate current value of the device under test through the target ammeter, the method also includes repeating the current test if the current of the device under test continues to change, so as to reselect a target ammeter that matches the changed current and read the new accurate current value.
[0020] Furthermore, the control module is electrically connected to multiple ammeters to receive numerical signals from each ammeter. The switching on / off control and the reading of current values from the ammeters are both automatically executed by the control module.
[0021] The beneficial effects of this invention are:
[0022] This invention avoids the problem of insufficient accuracy when measuring small currents with a single large-range ammeter by setting up multiple sets of parallel ammeters and corresponding switches. It can read accurate values by matching ammeters with corresponding ranges, and achieve accurate testing of the entire current change process. At the same time, by first reading with the largest range ammeter and then switching to the matching range ammeter, the test circuit is not interrupted throughout the process. This protects the small-range ammeter from damage by excessive current, ensures the continuity of the test process, reduces test losses and the risk of process interruption, and enables more accurate testing of the current in each segment without complicated debugging, thus improving the efficiency of current testing.
[0023] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1 A flowchart according to an embodiment of the present invention is shown. Detailed Implementation
[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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, 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.
[0027] like Figure 1 As shown, an embodiment of the present invention provides a method for current testing, comprising:
[0028] S1. Set up a current test circuit. Multiple ammeters with different ranges are connected in parallel in the test circuit, and each ammeter is connected in series with an independent switch. The input terminal of the test circuit is electrically connected to the current output terminal of the device under test, and the output terminal is grounded or connected to the load terminal of the device under test to form a complete current path.
[0029] S2. To test the current of the device under test, first close the switch corresponding to the maximum range ammeter so that the maximum range ammeter is connected to the test circuit. After the ammeter reading stabilizes (the fluctuation of the reading does not exceed ±0.5% in 3 consecutive readings), read the current value displayed by the maximum range ammeter (retain 1 significant digit, such as 5.3A, then record it as 5A).
[0030] S3. Read the current value, select the target ammeter whose range matches the current value, close the switch corresponding to the target ammeter, and connect the target ammeter to the test circuit.
[0031] S4. After closing the switch corresponding to the target ammeter, observe the value displayed on the target ammeter. After the value stabilizes (the change is ≤0.01A for 2 consecutive seconds), disconnect the switch corresponding to the maximum range ammeter and read the accurate current value of the device under test through the target ammeter.
[0032] For example, S1 has no fewer than three ammeters, and the ranges of the three ammeters can be set from high to low as the maximum range 0-10A, the intermediate range 0-6A, or the minimum range 0-1A, while the rated current of the switch is not lower than the maximum range current of the corresponding ammeter.
[0033] In S3, the current value is within 1 / 3 to 2 / 3 of the target ammeter's range. For example, if the current value is 3A, select an ammeter with a range of 0-6A (3A is within the 2-4A range). Then close the switch corresponding to the target ammeter to connect the target ammeter to the test circuit.
[0034] The ranges of multiple ammeters do not overlap, and the ranges of multiple ammeters are set in descending order. The range coverage of multiple ammeters is consistent with the current variation range of the device under test. The device under test is a device whose current changes with time. The device under test includes a battery whose current gradually decreases during constant voltage charging and a detection instrument whose current is large in the early stage and then stabilizes and decreases in the later stage.
[0035] For example, when the current variation range of the device under test is 0.05-10A, the ammeter range is set to 0-10A (maximum), 0-6A (intermediate), and 0-1A (minimum). The lower limit of the 0-10A range does not overlap with the upper limit of the 0-6A range, and the lower limit of the 0-6A range does not overlap with the upper limit of the 0-1A range. The lower limit of the minimum range 0-1A (0A) is less than or equal to the minimum current of the device under test (0.05A), and the upper limit of the maximum range 0-10A (10A) is greater than or equal to the maximum current of the device under test (10A).
[0036] The devices under test that change current over time specifically include: batteries (such as lithium batteries and lead-acid batteries) whose current gradually decreases from an initial high current (such as 5-10A) to a low current (such as 0.1-1A) during constant voltage charging, or detection instruments (such as ambient gas detectors and electronic component fault detectors) whose initial operating current is 8-15A and whose current drops to 0.05-0.5A after stabilization.
[0037] In this embodiment, the switch is an electronic switch. When an electronic switch is used, the electronic switch is electrically connected to an external control module, and the external control module controls the on / off state of the electronic switch.
[0038] Electronic switches can be selected from DC relays (such as HH52P type, rated current 15A) or N-channel MOSFET switches (such as IRF3205 type, on-resistance ≤8mΩ). If electronic switches are not used, mechanical switches can be used, among which rocker switches (such as KCD1 type, rated voltage 250V, rated current 10A) are selected. When electronic switches are used, the electronic switches are electrically connected to external control modules (such as STM32F103C8T6 microcontroller, AT89C51 microcontroller) through I / O ports. The control module outputs high and low level signals to control the on and off of the electronic switches (high level to turn on, low level to turn off, or vice versa).
[0039] The specific steps for reading the current value displayed by the ammeter at its maximum range include:
[0040] After the maximum range ammeter is connected to the test circuit and the displayed value stabilizes, wait 1-3 seconds to ensure that the current flows stably through the ammeter. Manually observe the ammeter pointer / digital display, or collect the ammeter's output signal (such as a 4-20mA analog signal or an RS485 digital signal) through the control module, and record the displayed value as the initial basis for selecting the target ammeter. If it is a pointer-type ammeter, read the scale value pointed to by the pointer (estimate to the next digit after the smallest scale division) as the initial basis for selecting the target ammeter.
[0041] The criteria for selecting a target ammeter whose range matches the current value are:
[0042] The current value is within one-third to two-thirds of the range of the target ammeter, and the target ammeter is the smallest range ammeter among multiple ammeters whose range and current value are closest.
[0043] For example, when the current value is 0.8A, 1 / 3 of the minimum range 0-1A is 0.33A and 2 / 3 is 0.67A. 0.8A is outside the 2 / 3 range of 0-1A. In this case, select the intermediate range 0-6A (1 / 3 is 2A, 0.8A is less than 2A, if this is not met, the current value needs to be reconfirmed. If the current value is 0.5A, 0.5A is within the 0.33-0.67A range of 0-1A, then select the minimum range ammeter of 0-1A).
[0044] The timing for disconnecting the switch corresponding to the maximum range ammeter is as follows:
[0045] After closing the switch corresponding to the target ammeter, observe the displayed value of the target ammeter. When the value changes by ≤0.01A for 2 consecutive seconds (e.g., after the target ammeter displays 2.53A, it remains between 2.52-2.54A within 2 seconds), wait for the displayed value of the target ammeter to stabilize before disconnecting the switch corresponding to the maximum range ammeter. The disconnection operation must be completed in one go to avoid repeated switching on and off causing current fluctuations in the test circuit.
[0046] The test circuit also includes a protective resistor, which is connected in series between the total input terminal of multiple parallel ammeters and the device under test. The resistance value of the protective resistor is determined according to the maximum current of the device under test, and the value range is 1-10Ω (e.g., if the maximum current of the device under test is 10A, the resistance value is 1Ω). The power is selected to be no less than 1.2 times the product of the square of the maximum current and the resistance value (e.g., if it is 10A and 1Ω, the power is 120W). The material is a metal film resistor or a cement resistor, which is used to prevent the ammeters from being damaged by sudden current changes in the test circuit.
[0047] The accuracy class of the target ammeter is higher than that of the ammeter with the maximum range. The accuracy class is the ratio of the ammeter's permissible error to its range, and the smaller the ratio, the higher the accuracy class.
[0048] For example, the ammeter with a maximum range of 0-10A has an accuracy class of 1.0 and an allowable error of ±10A×1.0%=±0.1A, while the target ammeter (such as 0-6A) has an accuracy class of 0.5 and an allowable error of ±6A×0.5%=±0.03A. The absolute value of the allowable error of the target ammeter is less than the absolute value of the allowable error of the ammeter with the maximum range.
[0049] After reading the accurate current value of the device under test through the target ammeter, if the current of the device under test continues to change, such as the current decreasing by 0.2-0.5A every 5 minutes during battery charging, and the current value displayed by the current target ammeter exceeds 1 / 3-2 / 3 of the range, such as the current dropping below 1.5A in the 0-6A range, then repeat steps S2-S4, close the maximum range ammeter switch again to read the current value, repeat the current test, and reselect a target ammeter that matches the changed current to read the new accurate current value.
[0050] The control module is electrically connected to multiple ammeters to receive numerical signals from each ammeter. The switching on / off control and the reading of current values from the ammeters are all automatically executed through the control module.
[0051] The on / off control and current value reading of switches S2-S4 are all automatically executed by the control module. The specific process is as follows:
[0052] The control module first outputs a high-level signal to close the switch of the maximum range ammeter, and at the same time collects the ammeter value at a frequency of 10 times per second. When the value fluctuation is ≤ ±0.5% for 3 consecutive times, it is determined to be stable and the current value is recorded.
[0053] Select the target ammeter according to the preset range and current matching method, output a high-level signal to close the target ammeter switch, and continuously collect the target ammeter value. When the change is ≤0.01A for 2 consecutive seconds, output a low-level signal to open the maximum range ammeter switch, and at the same time store the accurate value of the target ammeter in the module's built-in storage unit or upload it to the host computer (such as a computer) via serial port.
[0054] If the current value collected later exceeds 1 / 3 to 2 / 3 of the current range, the control module will automatically trigger the S2-S4 cycle without manual intervention. By switching the ammeter in stages, accurate current testing can be achieved without interrupting the test circuit or damaging the equipment.
[0055] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for current testing, characterized in that, include: S1. Set up a current test circuit. Multiple ammeters with different ranges are connected in parallel in the test circuit, and each ammeter is connected in series with an independent switch. S2. To perform a current test on the device under test, first close the switch corresponding to the maximum range ammeter so that the maximum range ammeter is connected to the test circuit, and read the current value displayed by the maximum range ammeter. S3. Read the current value, select the target ammeter whose range matches the current value, close the switch corresponding to the target ammeter, and connect the target ammeter to the test circuit. S4. After closing the switch corresponding to the target ammeter, open the switch corresponding to the maximum range ammeter and read the accurate current value of the device under test through the target ammeter.
2. The method for current testing according to claim 1, characterized in that: The ranges of the multiple ammeters do not overlap, and the ranges of the multiple ammeters are set in descending order. The range coverage of the multiple ammeters is consistent with the current variation range of the device under test. The device under test is a device whose current changes with time. The device under test includes a battery whose current gradually decreases during constant voltage charging and a detection instrument whose current is large in the early stage and then stabilizes and decreases in the later stage.
3. The method for current testing according to claim 2, characterized in that: The switch is an electronic switch. When an electronic switch is used, it is electrically connected to an external control module, which controls the switching on and off of the electronic switch.
4. The method for current testing according to claim 3, characterized in that: The specific operation of reading the current value displayed by the maximum range ammeter includes: Once the maximum range ammeter is connected to the test circuit and the displayed value stabilizes, record the displayed value as the initial basis for selecting the target ammeter.
5. A method for current testing according to claim 4, characterized in that: The criteria for selecting a target ammeter whose range matches the current value are as follows: The current value is within one-third to two-thirds of the range of the target ammeter, and the target ammeter is the smallest range ammeter among multiple ammeters whose range and current value are closest.
6. The method for current testing according to claim 5, characterized in that: The timing for disconnecting the switch corresponding to the maximum range ammeter is as follows: After closing the switch corresponding to the target ammeter, observe the displayed value of the target ammeter. Once the displayed value of the target ammeter stabilizes, disconnect the switch corresponding to the maximum range ammeter.
7. A method for current testing according to claim 6, characterized in that: The test circuit also includes a protective resistor, which is connected in series between the total input terminal of multiple parallel ammeters and the device under test, to prevent sudden current changes in the test circuit from damaging the ammeters.
8. A method for current testing according to claim 7, characterized in that: The accuracy class of the target ammeter is higher than that of the ammeter with the maximum range. The accuracy class is the ratio of the ammeter's permissible error to its range, and the smaller the ratio, the higher the accuracy class.
9. A method for current testing according to claim 8, characterized in that: After reading the accurate current value of the device under test using the target ammeter, the test also includes repeating the current test if the current of the device under test continues to change, so as to reselect a target ammeter that matches the changed current and read the new accurate current value.
10. A method for current testing according to claim 9, characterized in that: The control module is electrically connected to multiple ammeters and is used to receive numerical signals from each ammeter. The on / off control of the switch and the reading of the current value of the ammeters are both executed automatically by the control module.