Test system suitable for current devices

Abstract

The utility model relates to a kind of test system suitable for current device.It includes standard device, current source and test main piece, test main piece, at least including controller, first conversion processing branch, second conversion processing branch and selection sampling unit, based on the type of the current device to be measured and the current direction state of the current device to be measured and standard device, controller is at least configured first conversion processing branch and standard device connection, and configuration is measured current measuring device and first conversion processing branch or second conversion processing branch adaptive connection, to acquire the required test data by selection sampling unit, and the test data obtained is loaded to controller, to calculate the current measurement accuracy of the current device to be measured by controller.The utility model can effectively realize the high-precision test of current device, improve the adaptive range and test precision of test, improve test speed.

Description

Technical Field

[0001] This utility model relates to a testing system, and more particularly to a testing system suitable for current devices. Background Technology

[0002] Current measuring devices are devices capable of measuring current. They can be categorized into current sensors, current transformers, shunts, etc. There are many types of current sensors. Based on the type of output signal, current sensors can be classified as current output type, voltage output type, or digital output type. Current output type current sensors output a current signal and are generally zero-flux type with closed-loop feedback, possessing high accuracy. These include fluxgate current sensors, magnetic modulation current sensors, or closed-loop Hall current sensors, etc. The output signal equals the input signal divided by the coil turns ratio. Voltage output type current sensors output a voltage signal. Besides converting the closed-loop output current back into a voltage output signal, this also includes open-loop Hall current sensors, shunts, and other sensors that directly output voltage signals. Digital output type current sensors have a built-in processor that converts the measurement signal into a digital output signal and outputs it through a digital interface, such as RS232, RS485, or CAN.

[0003] It should be understood that different types of output signals require different measurement methods from current measuring devices, resulting in differences in measurement accuracy, speed, and cost. Specifically, for various output types of current measuring devices, a transformation ratio can be used as a unified term. For different models of current measuring devices under test, the number of transformation ratios is very large, and the test system needs to adapt to a wide variety of ratios. Furthermore, the measurement range of current measuring devices is also very extensive, commonly ranging from the μA level to the kA level, spanning more than nine orders of magnitude.

[0004] To ensure the accuracy of current measurements, current measuring devices typically undergo factory testing and adjustment to guarantee their accuracy during subsequent use. The wide variety of current sensor types and their broad measurement ranges presents challenges for current sensor testing systems. Furthermore, fluxgate current sensors and magnetically modulated current sensors can achieve measurement accuracies of 10 ppm or higher, exceeding the accuracy of standard sources and meters. Meeting these ultra-high accuracy requirements places high demands on testing systems.

[0005] High-precision testing often involves slow testing speeds. Both stabilizing the output of the standard source and the measurement itself require more time, resulting in decreased efficiency. Generally, the standard source can be a current source, and the standard meter can be a voltmeter or ammeter used for measurement.

[0006] In summary, how to effectively test current measuring devices, adapt to a wide range of output types, achieve a broad measurement range, meet extremely high accuracy requirements, maximize testing speed and efficiency, and reduce costs are urgent technical challenges that need to be addressed. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a testing system suitable for current devices. It can effectively test current devices, especially those with a range from A to kA, thus improving the testing adaptability. It is suitable for current measurement devices of various types, including current output, voltage output, and digital output, providing extremely high testing accuracy, increasing testing speed, and reducing testing costs.

[0008] According to the technical solution provided by this utility model, a testing system suitable for current-driven devices is provided, the testing system comprising:

[0009] The standard device is at least a current output type current measuring device, and the current measurement accuracy of the standard device is not lower than that of the current measuring device under test.

[0010] A current source provides bus current for testing standard devices and devices under test.

[0011] The main test component, used to perform test operations on the current-carrying device under test, includes at least a controller, a first conversion processing branch, a second conversion processing branch, and a selection sampling unit.

[0012] The controller is adapted to connect with the current source, the first conversion processing branch, the second conversion processing branch, and the selection sampling unit to at least configure the current source to generate the bus current required for the test, and to obtain the test data required for the test through the selection sampling unit.

[0013] Based on the type of the device under test and the current direction of the device under test and the standard device, the controller is configured to connect at least the first conversion processing branch to the standard device, and the device under test is configured to be adapted to connect to the first conversion processing branch or the second conversion processing branch, so as to collect the required test data through the selected sampling unit, and load the acquired test data into the controller so that the controller can calculate the current measurement accuracy of the device under test.

[0014] The first conversion processing branch includes a first branch selection switch and a first branch conversion processing component adapted and connected to the first branch selection switch, wherein,

[0015] The first branch selection switch is connected to the controller, and the first branch conversion processing component is connected to the second conversion processing branch and the selection sampling unit.

[0016] The controller configures the connection state of the first branch selection switch to either connect the standard device to the first branch conversion processing component or ground the standard device.

[0017] When only the standard device is connected to the first branch conversion processing component through the first branch selection switch, the first branch conversion processing component converts the reference current output by the standard device for bus current measurement into a corresponding conversion processing reference voltage. Subsequently, the selection sampling unit selects the conversion processing reference voltage and samples it before transmitting it to the controller. Alternatively, the selection sampling unit selects the conversion processing differential voltage generated based on the conversion processing reference voltage and samples it before transmitting it to the controller.

[0018] After the standard device and the device under test are connected to the first branch conversion processing component via the first branch selection switch, the first branch conversion processing component converts the difference between the reference current and the test current into the corresponding conversion processing error voltage. Then, the selection sampling unit selects the conversion processing error voltage and samples it and transmits it to the controller. The test current is the current value output by the bus current measurement using the device under test.

[0019] The first branch conversion processing component includes a measuring resistor and a first branch programmable gain amplifier adapted to and connected to the measuring resistor, wherein,

[0020] One end of the measuring resistor corresponds to the first branch selection switch, and the other end of the measuring resistor is grounded. When the first branch selection switch is connected to the measuring resistor, the output terminal of the standard device is adapted to the measuring resistor to connect the standard device to the first branch conversion processing component.

[0021] The input of the first branch programmable gain amplifier is connected to the measurement resistor adapter, and the output of the first branch programmable gain amplifier is connected to the second conversion processing branch and the selection sampling unit adapter.

[0022] The measuring resistor includes a measuring sub-resistance unit and a measuring resistor switch array adapted and connected to the measuring sub-resistance unit, wherein...

[0023] The measuring sub-resistance unit includes a plurality of measuring sub-resistors arranged in an array. The measuring sub-resistors within the measuring sub-resistance unit are selected by a measuring resistor switch array to configure and form the resistance value of the measuring resistor based on the selected measuring sub-resistors.

[0024] The second conversion processing branch includes a second branch selection switch unit, a load resistor, and a second branch conversion processing component, wherein,

[0025] The output port of the current-under-test device is connected to one end of the load resistor and the second branch conversion processing component. The other end of the load resistor is adapted and connected to the second branch selection switch unit, so that the second branch selection switch unit can select and connect the load resistor to the first branch selection switch, ground the load resistor, or float the load resistor.

[0026] When the load resistor is selected and connected to the first conversion processing component via the second branch selection switch unit, and the standard device is connected to the first conversion processing component via the first branch selection switch, the current under test device and the standard device are adapted and connected to the first conversion processing branch. After that, the first conversion processing component generates the conversion processing error voltage.

[0027] When the load resistor is grounded or floating via the second branch selection switch unit, the test base voltage is processed by the second branch conversion processing component to generate a conversion processing reference voltage. The test base voltage is either directly output by the device under test or generated by converting the test current output by the device under test using the grounded load resistor.

[0028] When the sampling unit selects the conversion processing reference voltage generated by the first conversion processing branch, the test data also includes the conversion processing reference voltage. At this time, the sampling processing unit samples the conversion processing reference voltage and transmits it to the controller, and the test data includes the conversion processing reference voltage and the conversion processing reference voltage.

[0029] When the sampling unit is selected to be the conversion processing differential voltage, the conversion processing differential voltage is generated by the second branch conversion processing component after differential processing of the conversion processing reference voltage and the conversion processing base voltage, and the test data is generated from the conversion processing differential voltage.

[0030] When the sampling unit is selected to convert the error voltage, test data is generated from the conversion error voltage.

[0031] When the sampling unit is selected to convert and process the error voltage, the type of the current device under test is current output type, and the current direction of the current device under test is opposite to that of the standard device.

[0032] When the test data is generated from the conversion-processed differential voltage, or from the conversion-processed reference voltage and the conversion-processed base voltage, the type of the device under test is either current output type or voltage output type.

[0033] When the output type of the current device under test is voltage output, the load resistor is made to float through the second branch selection switch unit.

[0034] The second branch conversion processing component includes a second branch programmable gain amplifier, an inverter, a direction switching switch, and a differential processor, wherein,

[0035] The input terminal of the second branch programmable gain amplifier is connected to the output port of the current measuring device under test. The output terminal of the second branch programmable gain amplifier is connected to the inverter. The output terminals of the second branch programmable gain amplifier and the inverter correspond to the direction switching switch. The direction switching switch is connected to an input terminal of the differential processor and the selection sampling unit, so that the output terminals of the second branch programmable gain amplifier and the inverter can be selected to be connected to the differential processor or the selection sampling unit via the direction switching switch.

[0036] The other input of the differential processor is connected to the first branch conversion processing component.

[0037] The selection sampling unit includes an output selection switch and a voltmeter adapted and connected to the output selection switch. The voltmeter is connected to the controller.

[0038] The output selection switch has at least three selection terminals and one output terminal. The three selection terminals are respectively connected to the direction switching switch, the output terminal of the differential processor, and the first branch conversion processing component. The output terminal is connected to the voltmeter.

[0039] When the output of the current under test device is a digital signal, the output port of the current under test device is directly connected to the controller, and the sampling unit is configured to select the conversion processing reference voltage. After that, the conversion processing reference voltage is sampled and transmitted to the controller.

[0040] The advantages of this invention are as follows: Based on the type of the current device under test and the current direction state between the current device under test and the standard device, the controller is configured to connect at least the first conversion processing branch to the standard device, and the current measuring device under test is configured to be adapted to connect to the first conversion processing branch or the second conversion processing branch, so as to collect the required test data through the selected sampling unit, thereby effectively realizing the testing of the current device, with a high testing adaptability range. When testing the current device, voltage measurement method or current measurement method can be used, reducing the requirements for current source and voltmeter, thereby improving the testing accuracy. Attached Figure Description

[0041] Figure 1 This is a system block diagram of one embodiment of the testing system of this utility model.

[0042] Figure 2 This is a circuit diagram of one embodiment of the present invention for measuring resistance.

[0043] Figure 3This is a circuit diagram of one embodiment of the load resistor of this utility model. Detailed Implementation

[0044] The present invention will be further described below with reference to the specific accompanying drawings and embodiments.

[0045] It should be noted that the most common method used in traditional testing systems for testing current measuring devices is the source-meter method. This involves a standard source outputting a high-precision standard current signal, which passes through the current measuring device under test (DUT). The output signal of the DUT is then measured by a high-precision standard meter. By comparing the output of the standard source with the measurement result of the standard meter, the accuracy of the DUT is calculated. This testing method is limited by the accuracy of the standard source and the standard meter; the testing system's accuracy cannot exceed that of the standard source or the standard meter.

[0046] Generally, high-current standard sources are difficult to make highly accurate and are expensive. Standard meters are also expensive; this makes the entire test system costly and has limited performance, failing to meet the testing requirements of ultra-high-precision current sensors. In addition, traditional testing methods are slow. Factors affecting testing speed include the time required for the standard source output to stabilize and the need for the standard meter to be set to a high resolution, resulting in long measurement times.

[0047] To effectively test current-carrying devices and improve the testing range and accuracy, this invention provides a testing system suitable for current-carrying devices. Specifically, the testing system includes:

[0048] The standard device is at least a current output type current measuring device, and the current measurement accuracy of the standard device is not lower than that of the current measuring device under test.

[0049] A current source provides bus current for testing standard devices and devices under test.

[0050] The main test component, used to perform test operations on the current-carrying device under test, includes at least a controller, a first conversion processing branch, a second conversion processing branch, and a selection sampling unit.

[0051] The controller is adapted to connect with the current source, the first conversion processing branch, the second conversion processing branch, and the selection sampling unit to at least configure the current source to generate the bus current required for the test, and to obtain the test data required for the test through the selection sampling unit.

[0052] Based on the type of the device under test and the current direction of the device under test and the standard device, the controller is configured to connect at least the first conversion processing branch to the standard device, and the device under test is configured to be adapted to connect to the first conversion processing branch or the second conversion processing branch, so as to collect the required test data through the selected sampling unit, and load the acquired test data into the controller so that the controller can calculate the current measurement accuracy of the device under test.

[0053] It should be noted that the current devices that can be tested by the testing system of this utility model may include the current measuring devices or shunts mentioned in the background art above. For example, the current measuring device may be a current sensor or a current transformer, and the type of current device can be selected as needed. In order to improve the adaptability and accuracy of the test, the testing system of this utility model should provide standard devices, wherein the standard devices should be current output type current measuring devices, that is, the standard devices should be selected as current measuring devices, and the standard devices output the measured value in the form of current. In the following description, "current output type" means the same thing; similarly, the meaning of "voltage output type" can be determined, that is, outputting the measured value in the form of voltage. For details, please refer to the description here.

[0054] In practical implementation, the standard device can be selected with a variable turns ratio. The appropriate turns ratio of the standard device is chosen based on the current-to-be-tested device, effectively utilizing the high testing accuracy of the standard device. The form of the variable turns ratio of the standard device can be consistent with existing technologies, such as using switches or relays to switch the number of turns in the secondary winding of the standard sensor coil. Specific examples of variable turns ratio methods will not be provided here. Generally, the current-to-be-tested device is the test object using this utility model's testing system. The current-to-be-tested device should be capable of measuring bus current. For example, the current-to-be-tested device can be a current measuring device or a shunt. The current measuring device can be of current output type or voltage output type, while the shunt type is voltage output type. The standard device should generally be selected with high current measurement accuracy, such as a current measurement accuracy no lower than that of the current measuring device. Therefore, after selecting the current-to-be-tested device, a standard device is selected based on its parameters, ensuring that the selected standard device meets the testing requirements of this utility model.

[0055] Figure 1 The image shows an embodiment of the testing system of this utility model, which is composed of... Figure 1 Therefore, in addition to standard devices and the device under test, a current source should also be included. The current source can provide the bus current for testing, and the bus current can be used as the test current. The current source can adopt existing commonly used forms, and the bus current provided by the current source can be bidirectional DC or AC. The form of the bus current provided can be selected as needed to meet the testing requirements of the device under test.

[0056] To enable testing, the testing system should also include a main testing component, which should include a controller, a first conversion processing branch, a second conversion processing branch, and a selection sampling unit. The controller can utilize existing commonly used control equipment. The controller can be used to calculate and determine the current measurement accuracy of the device under test. Therefore, the purpose of this invention is at least to determine the current measurement accuracy of the device under test. Furthermore, Figure 1 The document also illustrates an embodiment of the test system that includes a human-machine interface (HMI). The HMI is connected to the controller and can display test information such as the accuracy of output current measurement. The HMI can be a commonly used display terminal, such as a touchscreen, and can be selected according to specific needs.

[0057] During testing, the controller can be configured to generate the required bus current using a current source, and the corresponding test data can be acquired by selecting a sampling unit. The controller can then analyze the test data to calculate and determine the current measurement accuracy of the device under test. The method and process of analyzing the test data can be consistent with existing technologies and will not be elaborated here; the specific focus should be on determining the current measurement accuracy of the device under test.

[0058] It should be noted that, in order to obtain test data, the first conversion processing branch and the second conversion processing branch should be connected and coordinated with the standard device and the device under test (DUT). The connection and coordination with the first and second conversion processing branches should be related to the type of the DUT and the current direction of the DUT and the standard device. Specifically, the type of the DUT refers to the measurement output type mentioned above; the current direction refers to whether the current direction of the DUT and the standard device is the same or opposite. The current direction of the standard device and the DUT can be consistent with existing technology and will not be elaborated here. The following will provide a detailed explanation of the type of the DUT, the current direction, and the test operation.

[0059] In practice, when testing the current device under test, the standard device should be connected to at least the first conversion processing branch, and the current device under test can be connected to either the first or second conversion processing branch. It is understood that the connection should be related to the type of the current device under test and the current direction. Thus, it can be seen that the testing of current devices can be effectively realized and the testing range can be improved.

[0060] In one embodiment of this utility model, the first conversion processing branch includes a first branch selection switch and a first branch conversion processing component adapted and connected to the first branch selection switch, wherein...

[0061] The first branch selection switch is connected to the controller, and the first branch conversion processing component is connected to the second conversion processing branch and the selection sampling unit.

[0062] The controller configures the connection state of the first branch selection switch to either connect the standard device to the first branch conversion processing component or ground the standard device.

[0063] When only the standard device is connected to the first branch conversion processing component through the first branch selection switch, the first branch conversion processing component converts the reference current output by the standard device for bus current measurement into a corresponding conversion processing reference voltage. Subsequently, the selection sampling unit selects the conversion processing reference voltage and samples it before transmitting it to the controller. Alternatively, the selection sampling unit selects the conversion processing differential voltage generated based on the conversion processing reference voltage and samples it before transmitting it to the controller.

[0064] After the standard device and the device under test are connected to the first branch conversion processing component via the first branch selection switch, the first branch conversion processing component converts the difference between the reference current and the test current into the corresponding conversion processing error voltage. Then, the selection sampling unit selects the conversion processing error voltage and samples it and transmits it to the controller. The test current is the current value output by the bus current measurement using the device under test.

[0065] Figure 1 The figure shows an embodiment of the first branch selection switch. In the figure, S1 is the first branch selection switch. The first branch selection switch can select a single-pole double-throw switch. The first branch selection switch is connected to the output terminal of the standard device. The output terminal of the standard device can be grounded or connected to the first branch conversion processing component through the first branch selection switch. Generally, the connection state of the first branch selection switch can be controlled by the controller.

[0066] As explained above, the first conversion processing branch can be connected to a standard device, or a standard device and the device under test for current measurement. The following section will further elaborate on this. Figure 1 The situation of the first branch conversion processing component will be explained in detail.

[0067] In one embodiment of this utility model, the first branch conversion processing component includes a measuring resistor and a first branch programmable gain amplifier adapted and connected to the measuring resistor, wherein...

[0068] One end of the measuring resistor corresponds to the first branch selection switch, and the other end of the measuring resistor is grounded. When the first branch selection switch is connected to the measuring resistor, the output terminal of the standard device is adapted to the measuring resistor to connect the standard device to the first branch conversion processing component.

[0069] The input of the first branch programmable gain amplifier is connected to the measurement resistor adapter, and the output of the first branch programmable gain amplifier is connected to the second conversion processing branch and the selection sampling unit adapter.

[0070] Figure 1 In the diagram, Rs is the measuring resistor, and PGA1 is the first branch programmable gain amplifier. The input terminal of the first branch programmable gain amplifier is differentially connected to the measuring resistor. The first branch programmable gain amplifier can adopt the commonly used form. Voltage amplification can be achieved through the first branch programmable gain amplifier, and the amplification factor can be programmably selected. The situation of the first branch programmable gain amplifier can be consistent with the existing ones, and will not be described in detail here.

[0071] In one embodiment of this utility model, the measuring resistor includes a measuring sub-resistance unit and a measuring resistor switch array adapted and connected to the measuring sub-resistance unit, wherein...

[0072] The measuring sub-resistance unit includes a plurality of measuring sub-resistors arranged in an array. The measuring sub-resistors within the measuring sub-resistance unit are selected by a measuring resistor switch array to configure and form the resistance value of the measuring resistor based on the selected measuring sub-resistors.

[0073] Figure 2 An embodiment for measuring resistance is shown in the figure. Figure 2 In this array, R1 and R2 are the sub-resistors being measured, and switches k1 through k6 are the measuring resistor switches within the array. The corresponding measuring sub-resistor can be selected by controlling the switching states of the measuring resistor switches within the array. For example, when switches k1, k3, and k6 are closed, measuring sub-resistor R1 can be selected. Other cases are not listed here. To improve testing accuracy, four-wire resistors should be selected for the measuring resistor switches. Furthermore, the switching states of the measuring resistor switches within the array can be selected and configured by the controller.

[0074] Depend on Figure 1 It can be seen that when the output terminal of standard device 1 is connected to the measuring resistor via the first branch selection switch, since the standard device is a current output type, the reference current output by the standard device can be converted into a reference voltage. The resulting reference voltage should be related to the reference current and the resistance value of the measuring resistor. It is understandable that the reference current can be converted into the required reference voltage by adjusting the turns ratio of the standard device and the resistance value of the measuring resistor. The method for generating the reference voltage can be selected as needed.

[0075] The obtained reference voltage is applied to the first branch programmable gain amplifier for gain amplification. Therefore, the conversion processing of the reference current by the first branch conversion processing component should at least include current-to-voltage conversion and gain amplification. The converted reference voltage can be output after passing through the first branch programmable gain amplifier. It is understood that when generating the converted reference voltage, the selected sampling unit can select the converted reference voltage, sample it, and transmit it to the controller.

[0076] In addition, the conversion processing reference voltage output by the programmable gain amplifier of the first branch can also be applied to the second conversion processing branch to generate a conversion processing differential voltage via the second conversion processing branch. After that, the selection sampling unit selects and samples the conversion processing differential voltage and transmits it to the controller. At this time, the device under test should be connected to the second conversion processing branch.

[0077] Furthermore, to improve the accuracy and convenience of testing, when the type of current device under test is current output type, and the current direction of the current device under test is opposite to that of the standard device, after the standard device is connected to the first branch conversion processing component via the first branch selection switch, the current device under test can also be connected to the first branch conversion processing component via the second branch selection switch. Since the current directions of the two are opposite and the current magnitudes are the same, based on Kirchhoff's current theorem, an approximately zero current difference will be formed at the node where the first branch selection switch and the measuring resistor are connected. This current difference is the difference between the reference current and the test current. Subsequently, it can be converted into a corresponding voltage by the measuring resistor, and after being amplified by the first branch programmable gain amplifier, a conversion processing error voltage can be generated. The selection sampling unit can select and sample the conversion processing error voltage and transmit it to the controller.

[0078] As explained above, when the sampling unit is selected to convert the error voltage, the type of the device under test (DUT) is current output, and the current direction of the DUT is opposite to that of the standard device. Therefore, in this state, the test data should be the conversion error voltage. It should be noted that when the test data is the conversion error voltage, the standard device is used to test the DUT using the current difference method. In this case, the standard device and the DUT should have the same turns ratio to ensure that an approximately zero current difference is formed at the aforementioned node.

[0079] In one embodiment of this utility model, the second conversion processing branch includes a second branch selection switch unit, a load resistor, and a second branch conversion processing component, wherein...

[0080] The output port of the current-under-test device is connected to one end of the load resistor and the second branch conversion processing component. The other end of the load resistor is adapted and connected to the second branch selection switch unit, so that the second branch selection switch unit can select and connect the load resistor to the first branch selection switch, ground the load resistor, or float the load resistor.

[0081] When the load resistor is selected and connected to the first conversion processing component via the second branch selection switch unit, and the standard device is connected to the first conversion processing component via the first branch selection switch, the current under test device and the standard device are adapted and connected to the first conversion processing branch. After that, the first conversion processing component generates the conversion processing error voltage.

[0082] When the load resistor is grounded or floating via the second branch selection switch unit, the test base voltage is processed by the second branch conversion processing component to generate a conversion processing reference voltage. The test base voltage is either directly output by the device under test or generated by converting the test current output by the device under test using the grounded load resistor.

[0083] When the sampling unit selects the conversion processing reference voltage generated by the first conversion processing branch, the test data also includes the conversion processing reference voltage. At this time, the sampling processing unit samples the conversion processing reference voltage and transmits it to the controller, and the test data includes the conversion processing reference voltage and the conversion processing reference voltage.

[0084] When the sampling unit is selected to be the conversion processing differential voltage, the conversion processing differential voltage is generated by the second branch conversion processing component after differential processing of the conversion processing reference voltage and the conversion processing base voltage, and the test data is generated from the conversion processing differential voltage.

[0085] Figure 1 The figure shows an embodiment of the second branch selection switch unit. As can be seen from the figure, the second branch selection switch unit may include switch S2 and switch S3, where RL is a load resistor. One end of switch S2 and one end of switch S3 are connected to one end of the load resistor, and the other end of the load resistor is connected to the output port of the current device under test. The load resistor can be connected to the measuring resistor through switch S2, and the load resistor can be grounded through switch S3.

[0086] It is understandable that when both switches S2 and S3 are open, the load resistor is in a floating state; when switch S2 is closed and switch S3 is open, the load resistor can be connected to the measuring resistor, enabling the connection between the device under test (DUT) and the first branch conversion processing component. When switch S2 is open and switch S3 is closed, the connection between the DUT and the first branch conversion processing component is disconnected, and the load resistor can be grounded. When the load is grounded, current-to-voltage conversion can be achieved using the load resistor. Specifically,

[0087] When the device under test is a current output type, switch S2 can be opened and switch S3 can be closed, or switch S2 can be closed and switch S3 can be opened. When switch S2 is closed and switch S3 is open, the current direction of the device under test is generally the same as the current direction of the standard device. In this case, the above-mentioned current difference measurement method is used for testing. When switch S2 is open and switch S3 is closed, the test current can be converted into the test basic voltage using the load resistor.

[0088] As explained above, when switch S2 is closed and switch S3 is open, the second branch conversion processing component is in a non-operating state; while when switch S2 is open, the second branch conversion processing component is in an operating state. If the type of the current device under test is current output type, and the current direction of the current device under test is the same as the current direction of the standard device, then switch S2 is open and switch S3 is closed. At this time, the test current can be converted into the corresponding test basic voltage through the load resistor. After that, the test basic voltage is processed by the second branch conversion processing component to generate the conversion processing reference voltage.

[0089] When the type of current-to-measure device is voltage output type, since the above current-to-voltage conversion is not required, both switches S2 and S3 can be in the open state, the load resistor is in the floating state, and the current-to-measure device directly generates the test basic voltage. Then, the voltage output by the current-to-measure device is directly converted into the conversion processing reference voltage using the second branch conversion processing component.

[0090] Specifically, after generating the conversion processing reference voltage, the conversion processing reference voltage can be differentially divided with the conversion processing base voltage, and a conversion processing differential voltage is generated after the differential division. It can be understood that when the test data is a conversion processing differential voltage, the voltage difference method is used to test the current-carrying device. When using the voltage difference method or the current difference method for testing, the requirements for the current source can be reduced, the instrument accuracy requirements can be lowered, and a wider data acquisition speed can be used.

[0091] It should be noted that when the voltage difference measurement method is adopted, before differential processing, the reference voltage for conversion processing and the reference voltage for conversion processing should be theoretically calculated to be consistent. For example, the turn ratio of the standard device can be adjusted, and the corresponding resistance values of the measurement resistor and / or load resistor can be adjusted. Specifically, it should be based on making the reference voltage for conversion processing and the reference voltage for conversion processing the same in theory. Of course, when the test data includes the reference voltage for conversion processing and the reference voltage for conversion processing, the reference voltage for conversion processing and the reference voltage for conversion processing should also maintain a theoretically calculated consistent situation.

[0092] As can be seen from the above description, when the current difference measurement method / voltage difference measurement method of the present utility model is used to test the device to be measured for current, a standard device with relatively high precision should be provided. The standard device and the device to be measured for current pass through the same current busbar, and always measure the same busbar current. The measurement result of the device to be measured for current is compared with the measurement result of the standard device by taking the difference. Therefore, when testing with the test system of the present utility model, the comparison reference for testing is the standard device. The standard device determines the upper limit of the measurement precision of the test system. The precision requirements for the standard source and the standard meter can be significantly reduced. That is, the output of the standard source does not need to be very precise, reducing the stabilization time. The standard meter does not need a particularly high resolution either, and the measurement time can also be shortened. Therefore, while obtaining improved precision, the measurement time is shortened.

[0093] The following takes the device to be measured for current with current output as an example to illustrate the principle and advantages of the current difference measurement method of the present utility model. Specifically:

[0094] Let the number of turns of the standard device be M, and the number of turns of the device to be measured for current be M + Δ. Δ is the difference in turns between the device to be measured for current and the standard device. Among them, Δ = 1 represents one more turn, Δ = -1 represents one less turn, and so on. In addition, the ratio error of the device to be measured for current can also be converted into it. At this time, Δ can also be a decimal.

[0095] Let the primary side busbar cable pass through N turns. Then, at the node mentioned above, the current difference measured by the ammeter is:

[0096]

[0097] Among them, I1 is the reference current output by the standard device, I2 is the test current output by the device to be measured for current, and I o is the current difference; the negative sign in I2 indicates that the current direction of the test current is opposite to the current direction of the reference current. O1 and O2 respectively represent the zero - position currents of the standard device and the device to be measured for current. In the above formula (1), O = O1 + O2, and the general value of O is very small.

[0098] When the condition Δ << M is satisfied, for the current difference, there is:

[0099]

[0100] Based on the above explanation, the impact of the accuracy of the current source and the selected voltmeter within the sampling unit on the system accuracy is deduced below, specifically:

[0101] As explained above, the error current is converted into a processing error voltage through a measuring load and supplied to the voltmeter in the selection sampling unit for measurement. Let the conversion error of the measuring resistor be e3, and the bus current output by the current source be I. B The test current I is obtained by measuring the bus current obtained by the device under test using an ammeter. M The ideal output value of the current source is I, with an accuracy error of e1. The voltage measured by the voltmeter is Vo, with an error of e2. Vo = Io / Rs. Then the test error of the test system is:

[0102]

[0103] Substituting formula (3) into formula (1), we get:

[0104]

[0105] From the above derivation, it can be seen that the systematic error ε is a second-order small quantity. Those skilled in the art know that when testing a current-controlled device, the systematic error is mainly affected by the errors of the current source, the meter, and the load resistance. As explained above, through the derivation, when using the current difference measurement method, the systematic error ε is reduced to... This value is generally very small. For high-precision current measuring devices, Δ is typically less than 0.1, and M is on the order of 1000. Less than 1 / 10000. If the current source, meter, and load resistor each have a 1ppm impact on the system's test accuracy, then... The proportional change requires only 1% accuracy from the current source, meter, and load resistor. Those skilled in the art will know that this accuracy requirement is easily achievable. The measurement accuracy of the current source, meter, and load resistor can easily be achieved within 0.1%, and their combined impact on the system's test accuracy will not exceed 1 ppm. Therefore, their impact on test accuracy is negligible. Thus, for the test system of this invention, the bottleneck to test accuracy is the standard components. The accuracy of the standard components essentially determines the system's measurement accuracy. By using standard components with higher measurement accuracy, the accuracy requirements for the current source and meter are greatly reduced. Here, the meter can be the voltmeter mentioned below.

[0106] As can be seen from the above formula, the premise for the effective application of the difference method is that the difference signal is near 0. Specifically, when the difference method is the current difference method, the difference signal should be the difference between the reference current and the test current mentioned above; when the difference method is the voltage difference method, the difference signal should be the difference between the conversion-processed reference voltage and the conversion-processed reference voltage mentioned above. The situation of the difference signal can be referred to the above explanation.

[0107] Because the turns ratios of the current under test (DUT) vary widely and the output of the DUT is specific, the output of the standard device in the test system must be adaptable to various turns ratios. When the turns ratio of the standard device is adjustable, the adjustment range should cover all current-output type DUTs. For voltage-output type DUTs, the reference current output by the standard device needs to be further converted into a reference signal. This is achieved by forming an adjustable resistance-gain network using a measuring resistor and a first-branch programmable gain amplifier. By selecting the turns ratio of the standard device and the resistance-gain network, matching and coverage of all voltage-output type DUTs can be achieved.

[0108] Generally, the installation direction (positive current direction) of the device under test can be determined in advance, but reverse installation is possible. The installation process can be complex and time-consuming. The test system can automatically determine the direction and set the measurement, which is very user-friendly. For example, the current direction can be determined based on the error voltage conversion or differential voltage conversion mentioned above. The specific determination methods and processes will not be illustrated here.

[0109] Based on the above explanation, when the test data is generated by the conversion processing differential voltage, or by the conversion processing reference voltage and the conversion processing base voltage, the type of the device under test is either current output type or voltage output type.

[0110] When the output type of the current device under test is voltage output, the load resistor is made to float through the second branch selection switch unit.

[0111] As explained above, the shunt is a voltage output type. Therefore, when the device under test (DUT) is a shunt, the load resistor should be in a floating state. Since the output of the DUT can also be a digital signal, when the output of the DUT is a digital signal, then:

[0112] The output port of the device under test is directly connected to the controller, and the sampling unit is configured to select the conversion processing reference voltage. After that, the conversion processing reference voltage is sampled and transmitted to the controller.

[0113] Specifically, the digital signal output by the device under test does not need to go through the second conversion processing branch and can be directly loaded into the controller. In this case, in order to form complete test data, a sampling conversion processing reference voltage should be selected. That is, when the output of the device under test is a digital signal, only the standard device is connected to the first branch conversion processing component through the first branch selection switch.

[0114] Figure 3 The figure illustrates one embodiment of the load resistor of this utility model. As shown in the figure, the load resistor may include several parallelly distributed resistor branches and load resistor switches adapted and connected to the resistor branches. Each resistor branch may include a load sub-resistor. Figure 3 In the diagram, R3 and R4 are load sub-resistors within two resistor branches, and q1 to q3 are corresponding load resistor switches. The resistance value of the load resistor can be configured by the switching state of the load resistor switch. Of course, the switching state of the load resistor switch can be controlled by the controller.

[0115] In one embodiment of this utility model, the second branch conversion processing component includes a second branch programmable gain amplifier, an inverter, a direction switching switch, and a differential processor, wherein...

[0116] The input terminal of the second branch programmable gain amplifier is connected to the output port of the current measuring device under test. The output terminal of the second branch programmable gain amplifier is connected to the inverter. The output terminals of the second branch programmable gain amplifier and the inverter correspond to the direction switching switch. The direction switching switch is connected to an input terminal of the differential processor and the selection sampling unit, so that the output terminals of the second branch programmable gain amplifier and the inverter can be selected to be connected to the differential processor or the selection sampling unit via the direction switching switch.

[0117] The other input of the differential processor is connected to the first branch conversion processing component.

[0118] Figure 1 In the diagram, PGA2 is the second branch programmable gain amplifier. Figure 1 The "inverting" in the text refers to an inverter, which can be used to reverse the direction of a voltage signal. S4 is a direction switching switch. Figure 1 The “differential” in this context refers to the differential processor. The programmable gain amplifier, inverter, and differential processor in the second branch can adopt commonly used forms, which can be selected according to the needs, and will not be elaborated here.

[0119] It should be noted that when the current direction of the device under test is opposite to that of the standard device, and the second branch conversion processing component is required, an inverter should be used for inversion. Otherwise, the direction switching switch directly selects the output of the second branch programmable gain amplifier. The differential processor can perform differential processing on the conversion processing reference voltage and the conversion processing reference voltage. The conversion processing reference voltage is the voltage after the direction switching switch. Of course, the conversion processing reference voltage can also be directly selected and sampled by the selection sampling unit. That is, the differential processor can output the conversion processing differential voltage for subsequent selection, sampling, and transmission by the selection sampling unit.

[0120] As can be seen from the above description, when using the test system of this utility model for testing, by changing the turns ratio of the standard device, the resistance value of the measuring resistor, and / or the corresponding gain value of the first branch programmable gain amplifier / second branch programmable gain amplifier, a wide range of adaptability can be provided, so that the differential measurement method can be widely applied to various test circuit devices with different current positive directions, current output type and voltage output type, laying a good foundation for obtaining high test accuracy and high test speed.

[0121] In one embodiment of this utility model, the selection sampling unit includes an output selection switch and a voltmeter adapted and connected to the output selection switch. The voltmeter is connected to a controller.

[0122] The output selection switch has at least three selection terminals and one output terminal. The three selection terminals are respectively connected to the direction switching switch, the output terminal of the differential processor, and the first branch conversion processing component. The output terminal is connected to the voltmeter.

[0123] Figure 1 The figure shows one embodiment of an output selection switch, where S5 is the output selection switch. The figure also shows an embodiment where the output selection switch has four selection terminals. Figure 1 From bottom to top, the four selection terminals are numbered 1 to 4. As shown in the diagram, when the output selection switch selects terminal number 1, the voltmeter can sample the conversion processing reference voltage or conversion processing error voltage and load it into the controller. When the output selection switch selects terminal number 2, the voltmeter can sample the conversion processing differential voltage and load it into the controller. When the output selection switch selects terminal number 3, the voltmeter can sample the conversion processing reference voltage and load it into the controller. When the output selection switch selects terminal number 4, the voltmeter cannot sample any voltage signal.

[0124] Specifically, when using the above-described test system to test the current device under test, the standard device, current source, first conversion processing branch, second conversion processing branch, and corresponding working state of the sampling unit can be configured according to the above description, so as to effectively test the current device under test according to the type of the current device under test and the current direction state. The specific test process can be referred to the above description, and will not be repeated here.

Claims

1. A testing system suitable for current-carrying devices, characterized in that, The testing system includes: The standard device is at least a current output type current measuring device, and the current measurement accuracy of the standard device is not lower than that of the current measuring device under test. A current source provides bus current for testing standard devices and devices under test. The main test component, used to perform test operations on the current-carrying device under test, includes at least a controller, a first conversion processing branch, a second conversion processing branch, and a selection sampling unit. The controller is adapted to connect with the current source, the first conversion processing branch, the second conversion processing branch, and the selection sampling unit to at least configure the current source to generate the bus current required for the test, and to obtain the test data required for the test through the selection sampling unit. Based on the type of the device under test and the current direction of the device under test and the standard device, the controller is configured to connect at least the first conversion processing branch to the standard device, and the device under test is configured to be adapted to connect to the first conversion processing branch or the second conversion processing branch, so as to collect the required test data through the selected sampling unit, and load the acquired test data into the controller so that the controller can calculate the current measurement accuracy of the device under test.

2. The testing system suitable for current-carrying devices according to claim 1, characterized in that: The first conversion processing branch includes a first branch selection switch and a first branch conversion processing component adapted and connected to the first branch selection switch, wherein, The first branch selection switch is connected to the controller, and the first branch conversion processing component is connected to the second conversion processing branch and the selection sampling unit. The controller configures the connection state of the first branch selection switch to either connect the standard device to the first branch conversion processing component or ground the standard device. When only the standard device is connected to the first branch conversion processing component through the first branch selection switch, the first branch conversion processing component converts the reference current output by the standard device for bus current measurement into a corresponding conversion processing reference voltage. Subsequently, the selection sampling unit selects the conversion processing reference voltage and samples it before transmitting it to the controller. Alternatively, the selection sampling unit selects the conversion processing differential voltage generated based on the conversion processing reference voltage and samples it before transmitting it to the controller. After the standard device and the device under test are connected to the first branch conversion processing component via the first branch selection switch, the first branch conversion processing component converts the difference between the reference current and the test current into the corresponding conversion processing error voltage. Then, the selection sampling unit selects the conversion processing error voltage and samples it and transmits it to the controller. The test current is the current value output by the bus current measurement using the device under test.

3. The test system suitable for current devices according to claim 2, characterized in that: The first branch conversion processing component includes a measuring resistor and a first branch programmable gain amplifier adapted to and connected to the measuring resistor, wherein, One end of the measuring resistor corresponds to the first branch selection switch, and the other end of the measuring resistor is grounded. When the first branch selection switch is connected to the measuring resistor, the output terminal of the standard device is adapted to the measuring resistor to connect the standard device to the first branch conversion processing component. The input of the first branch programmable gain amplifier is connected to the measurement resistor adapter, and the output of the first branch programmable gain amplifier is connected to the second conversion processing branch and the selection sampling unit adapter.

4. The test system suitable for current devices according to claim 3, characterized in that: The measuring resistor includes a measuring sub-resistance unit and a measuring resistor switch array adapted and connected to the measuring sub-resistance unit, wherein... The measuring sub-resistance unit includes a plurality of measuring sub-resistors arranged in an array. The measuring sub-resistors within the measuring sub-resistance unit are selected by a measuring resistor switch array to configure and form the resistance value of the measuring resistor based on the selected measuring sub-resistors.

5. The test system suitable for current devices according to any one of claims 2 to 4, characterized in that: The second conversion processing branch includes a second branch selection switch unit, a load resistor, and a second branch conversion processing component, wherein, The output port of the current-under-test device is connected to one end of the load resistor and the second branch conversion processing component. The other end of the load resistor is adapted and connected to the second branch selection switch unit, so that the second branch selection switch unit can select and connect the load resistor to the first branch selection switch, ground the load resistor, or float the load resistor. When the load resistor is selected and connected to the first conversion processing component via the second branch selection switch unit, and the standard device is connected to the first conversion processing component via the first branch selection switch, the current under test device and the standard device are adapted and connected to the first conversion processing branch. After that, the first conversion processing component generates the conversion processing error voltage. When the load resistor is grounded or floating via the second branch selection switch unit, the test base voltage is processed by the second branch conversion processing component to generate a conversion processing reference voltage. The test base voltage is either directly output by the device under test or generated by converting the test current output by the device under test using the grounded load resistor. When the sampling unit selects the conversion processing reference voltage generated by the first conversion processing branch, the test data also includes the conversion processing reference voltage. At this time, the sampling processing unit samples the conversion processing reference voltage and transmits it to the controller, and the test data includes the conversion processing reference voltage and the conversion processing reference voltage. When the sampling unit is selected to be the conversion processing differential voltage, the conversion processing differential voltage is generated by the second branch conversion processing component after differential processing of the conversion processing reference voltage and the conversion processing base voltage, and the test data is generated from the conversion processing differential voltage. When the sampling unit is selected to convert the error voltage, test data is generated from the conversion error voltage.

6. The test system suitable for current devices according to claim 5, characterized in that: When the sampling unit is selected to convert and process the error voltage, the type of the current device under test is current output type, and the current direction of the current device under test is opposite to that of the standard device.

7. The test system suitable for current devices according to claim 5, characterized in that: When the test data is generated from the conversion-processed differential voltage, or from the conversion-processed reference voltage and the conversion-processed base voltage, the type of the device under test is either current output type or voltage output type. When the output type of the current device under test is voltage output, the load resistor is made to float through the second branch selection switch unit.

8. The test system suitable for current devices according to claim 5, characterized in that: The second branch conversion processing component includes a second branch programmable gain amplifier, an inverter, a direction switching switch, and a differential processor, wherein, The input terminal of the second branch programmable gain amplifier is connected to the output port of the current measuring device under test. The output terminal of the second branch programmable gain amplifier is connected to the inverter. The output terminals of the second branch programmable gain amplifier and the inverter correspond to the direction switching switch. The direction switching switch is connected to an input terminal of the differential processor and the selection sampling unit, so that the output terminals of the second branch programmable gain amplifier and the inverter can be selected to be connected to the differential processor or the selection sampling unit via the direction switching switch. The other input of the differential processor is connected to the first branch conversion processing component.

9. The test system suitable for current devices according to claim 8, characterized in that: The selection sampling unit includes an output selection switch and a voltmeter adapted and connected to the output selection switch. The voltmeter is connected to the controller. The output selection switch has at least three selection terminals and one output terminal. The three selection terminals are respectively connected to the direction switching switch, the output terminal of the differential processor, and the first branch conversion processing component. The output terminal is connected to the voltmeter.

10. The test system suitable for current devices according to claim 5, characterized in that: When the output of the current under test device is a digital signal, the output port of the current under test device is directly connected to the controller, and the sampling unit is configured to select the conversion processing reference voltage. After that, the conversion processing reference voltage is sampled and transmitted to the controller.

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