External reference device for board card calibration and test equipment

Abstract

The utility model relates to an external reference device for board card calibration and test equipment, and the external reference device comprises a reference source interface which is connected with an external reference source; the digital-to-analog conversion module is connected with the reference source interface; the analog-to-digital conversion module is connected with the reference source interface and the digital-to-analog conversion module, and the load resistor module is connected with the reference source interface, the digital-to-analog conversion module and the analog-to-digital conversion module; the calibration circuit group is connected with the reference source interface, the digital-to-analog conversion module, the analog-to-digital conversion module and the load resistor module; a plurality of board card calibration interfaces, wherein each board card calibration interface is connected with the calibration circuit group and a corresponding board card to be calibrated; a load resistor in the load resistor module and the analog-to-digital conversion module are calibrated through an external reference source, the board cards to be calibrated are calibrated through the digital-to-analog conversion module, the calibrated analog-to-digital conversion module and the calibrated load resistor module, precision rechecking does not need to be carried out at the output ends of the board cards, simultaneous calibration of a plurality of board cards to be calibrated is supported, and the calibration accuracy of the board cards to be calibrated is improved. And the calibration efficiency is improved.

Description

Technical Field

[0001] The present application relates to the field of semiconductor testing technologies, and particularly to an external reference device for board calibration and a testing device. Background Art

[0002] Semiconductor automatic testing refers to detecting various parameter indicators of a device under test (DUT) using automatic test equipment (ATE), and rejecting defective products to control the ex-factory quality of semiconductor devices. Before testing the device under test, it is necessary to calibrate and verify the relevant function boards of the automatic test equipment to ensure test accuracy.

[0003] The traditional method for calibrating a test machine board is to complete the calibration using an internal calibration reference circuit. However, there are differences between the internal calibration verification link of the board and the output link of the board. After internal calibration, it is still necessary to perform accuracy recheck at the output end of the board, which has a high time cost and the disadvantage of low calibration efficiency. Summary of the Utility Model

[0004] Based on this, in view of the above problems, it is necessary to provide an external reference device for board calibration and a testing device that can improve calibration efficiency.

[0005] The first aspect of the present application provides an external reference device for board calibration, including:

[0006] A reference source interface for connecting to an external reference source;

[0007] A digital-to-analog conversion module connected to the reference source interface;

[0008] An analog-to-digital conversion module connected to the reference source interface and the digital-to-analog conversion module,

[0009] A load resistance module connected to the reference source interface, the digital-to-analog conversion module, and the analog-to-digital conversion module;

[0010] A calibration circuit group connected to the reference source interface, the digital-to-analog conversion module, the analog-to-digital conversion module, and the load resistance module;

[0011] A plurality of board calibration interfaces, each of which is connected to the calibration circuit group and the corresponding board to be calibrated;

[0012] Wherein, the load resistance in the load resistance module and the analog-to-digital conversion module are calibrated through the external reference source, and the board to be calibrated is calibrated through the digital-to-analog conversion module, the calibrated analog-to-digital conversion module, and the calibrated load resistance module.

[0013] In one embodiment, the load resistance module includes:

[0014] A board voltage calibration load resistance unit, connected to the reference source interface, the digital-to-analog conversion module, the analog-to-digital conversion module, and the calibration line group;

[0015] A board current calibration load resistance unit, connected to the calibration line group;

[0016] Wherein, the load resistance in the board current calibration load resistance unit is calibrated by the external reference source.

[0017] In one embodiment, the external reference device further includes a line switching switch group. The calibration line group is divided into two or more calibration line segments. The number of board calibration interfaces and the number of board current calibration load resistance units are the same as the number of calibration line segments. Each calibration line segment is connected through the line switching switch group, and each calibration line segment is connected to the corresponding board calibration interface and the corresponding board current calibration load resistance unit.

[0018] In one embodiment, the calibration line group includes a high-end output line HF, a high-end measurement line HS, and a low-end measurement line LS. The reference source interface is connected to the high-end output line HF, the high-end measurement line HS, and the low-end measurement line LS.

[0019] In one embodiment, the digital-to-analog conversion module includes a digital-to-analog converter and a first operational amplifier conditioning circuit. The first output end of the digital-to-analog converter is connected to the first input end of the first operational amplifier conditioning circuit. The second output end of the digital-to-analog converter is connected to the second input end of the first operational amplifier conditioning circuit. The first output end of the first operational amplifier conditioning circuit is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface. The second output end of the first operational amplifier conditioning circuit is connected to the low-end measurement line LS and the ground terminal.

[0020] In one embodiment, the analog-to-digital conversion module includes an analog-to-digital converter and a second operational amplifier conditioning circuit. The first input end of the second operational amplifier conditioning circuit is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface. The second input end of the second operational amplifier conditioning circuit is connected to the low-end measurement line LS and the reference source interface. The first output end of the second operational amplifier conditioning circuit is connected to the first input end of the analog-to-digital converter. The second output end of the second operational amplifier conditioning circuit is connected to the second input end of the analog-to-digital converter.

[0021] In one embodiment, the board voltage calibration load resistance unit includes a switch K R∞ and a load resistance R ∞, the load resistor R ∞ is a resistor with a resistance value above megohm; the switch K R∞ has its first end connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface. The second end of the switch K R∞ is connected to the first end of the load resistor R ∞ . The second end of the load resistor R ∞ is connected to the low-end measurement line LS and the ground terminal.

[0022] In one embodiment, the board current calibration load resistor unit includes a plurality of load switching units. Each load switching unit includes a switching switch and a load resistor. The first end of the switching switch is connected to the high-end output line HF and the high-end measurement line HS. The second end of the switching switch is connected to the first end of the load resistor. The second end of the load resistor is connected to the low-end measurement line LS and the ground terminal.

[0023] In one embodiment, the external reference device further includes an interface control switch group. The reference source interface is connected to the digital-to-analog conversion module, the analog-to-digital conversion module, the load resistor module, and the calibration circuit group through the interface control switch group.

[0024] A second aspect of the present application provides a test device, including a test machine. The test machine includes a host computer, a communication module, a board to be calibrated, and the above-mentioned external reference device. The host computer is connected to the communication module. The communication module is connected to the board to be calibrated and the external reference device.

[0025] After calibrating the load resistor and the analog-to-digital conversion module in the load resistor module of the external reference device through an external reference source, the external reference device for board calibration and the test device can calibrate the board to be calibrated through the digital-to-analog conversion module, the calibrated analog-to-digital conversion module, and the calibrated load resistor module. Compared with calibrating using the internal calibration reference circuit of the board, there is no need to perform accuracy recheck at the output end of the board, and it also supports calibrating multiple boards to be calibrated simultaneously, improving the calibration efficiency. Description of the Drawings

[0026] Figure 1 is a structural block diagram of an external reference device in one embodiment;

[0027] Figure 2 is a structural schematic diagram of an external reference device in one embodiment;

[0028] Figure 3 is a schematic diagram of the principle of calibrating and verifying an external reference device using a high-precision multimeter in one embodiment;

[0029] Figure 4 Schematic diagram of the principle for calibrating and verifying multiple circuit boards using an external reference device in one embodiment;

[0030] Figure 5 Block diagram of the test equipment in one embodiment;

[0031] Figure 6 Schematic diagram of the time - sharing and common use of an external reference device by multiple test machines in one embodiment. Specific implementation manners

[0032] In order to make the objectives, technical solutions and advantages of the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used in the description of this application herein are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0034] It can be understood that, in the following embodiments, "connection", if there is an electrical signal or data transfer between the connected circuits, modules, units, etc., should be understood as "electrical connection", "communication connection", etc.

[0035] As used herein, the singular forms "a", "an" and "the" may also include the plural forms unless the context clearly dictates otherwise. It should also be understood that the terms "comprises / include" or "has" etc. specify the presence of the stated features, wholes, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, wholes, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the related listed items.

[0036] In one embodiment, as Figure 1As shown, an external reference device 100 for board calibration is provided, including a reference source interface 110, a digital-to-analog conversion module 120, an analog-to-digital conversion module 130, a load resistor module 140, a calibration circuit group 150, and several board calibration interfaces 160. The reference source interface 110 is used to connect to an external reference source. The digital-to-analog conversion module 120 is connected to the reference source interface 110. The analog-to-digital conversion module 130 is connected to the reference source interface 110 and the digital-to-analog conversion module 120. The load resistor module 140 is connected to the reference source interface 110, the digital-to-analog conversion module 120, and the analog-to-digital conversion module 130. The calibration circuit group 150 is connected to the reference source interface 110, the digital-to-analog conversion module 120, the analog-to-digital conversion module 130, and the load resistor module 140. Each board calibration interface 160 is connected to the calibration circuit group 150 and the corresponding board to be calibrated.

[0037] Among them, the load resistors in the load resistor module 140 and the analog-to-digital conversion module 130 are calibrated through an external reference source. The board to be calibrated is calibrated through the digital-to-analog conversion module 120, the calibrated analog-to-digital conversion module 130, and the calibrated load resistor module 140. The board to be calibrated can be a power supply board or other functional boards of a testing machine. The type of the external reference source is not unique and can be a multimeter or other devices. In this embodiment, the external reference source uses a high-precision multimeter, specifically a six-and-a-half-digit or eight-and-a-half-digit precision multimeter. The number of board calibration interfaces 160 can be one or more than two, supporting the simultaneous calibration and verification of multiple boards to be calibrated.

[0038] Specifically, the calibration circuit group 150 may include a high-end output line HF, a high-end measurement line HS, and a low-end measurement line LS, and the relevant modules are connected through different lines to calibrate and verify the board to be calibrated. Before calibrating and verifying the board to be calibrated using the external reference device 100, it is necessary to calibrate and verify the external reference device 100 through an external reference source first. The digital-to-analog conversion module 120 and the analog-to-digital conversion module 130 can be connected to the upper computer. The upper computer controls the output of the digital-to-analog conversion module 120 and obtains and analyzes the measurement data of the analog-to-digital conversion module 130 to complete the calibration of the external reference device 100 and save the relevant calibration parameters. When applying the external reference device 100 to calibrate the board, the upper computer can also combine the saved calibration parameters, control the output of the digital-to-analog conversion module 120, and obtain and analyze the measurement data of the analog-to-digital conversion module 130 to complete the calibration of the board. In addition, the verification principle of the external reference device 100 and the board is similar to calibration. The difference is that calibration uses the default value for output or measurement to calculate the correction parameters, while verification uses the correction parameters obtained by calibration for output or measurement to evaluate whether the accuracy requirements are met.

[0039] The above-mentioned external reference device 100 can calibrate the board to be calibrated through the digital-to-analog conversion module 120, the calibrated analog-to-digital conversion module 130, and the calibrated load resistance module 140. Compared with calibrating using the internal calibration reference circuit of the board, there is no need to perform accuracy recheck at the output end of the board, and it can also support calibrating multiple boards to be calibrated simultaneously, improving the calibration efficiency.

[0040] Taking the calibration line group including the high-end output line HF, the high-end measurement line HS, and the low-end measurement line LS as an example, the reference source interface 110 can be connected to the high-end output line HF, the high-end measurement line HS, and the low-end measurement line LS, and is connected to other modules through relevant lines. Further, the external reference device 100 further includes an interface control switch group, and the reference source interface 110 is connected to the digital-to-analog conversion module 120, the analog-to-digital conversion module 130, the load resistance module 140, and the calibration line group 150 through the interface control switch group. Among them, the host computer can be connected to the interface control switch group to control the on / off of each switch in the interface control switch group, such as Figure 2 As shown, the interface control switch group can include switch K1, switch K2, switch K3, and switch K4. Switch K1, switch K2, switch K3, and switch K4 can adopt relay switches or other controlled switches. The port HS of the reference source interface 110 is connected to the digital-to-analog conversion module 120, the analog-to-digital conversion module 130, the load resistance module 140, and the high-end measurement line HS through switch K1. The port LS of the reference source interface 110 is connected to the analog-to-digital conversion module 130 and the low-end measurement line LS through switch K2. The port HF of the reference source interface 110 is connected to the digital-to-analog conversion module 120, the analog-to-digital conversion module 130, the load resistance module 140, and the high-end output line HF through switch K3. The port LF of the reference source interface 110 is connected to the ground terminal GND through switch K4. The host computer can be connected to the control terminals of switch K1, switch K2, switch K3, and switch K4, and control the on / off of switch K1, switch K2, switch K3, and switch K4 through the host computer, so as to control the connection of the external reference source.

[0041] In one embodiment, such as Figure 2As shown in the figure, the digital-to-analog conversion module 120 includes a digital-to-analog converter DAC and a first operational amplifier conditioning circuit 122. The first output terminal of the digital-to-analog converter DAC is connected to the first input terminal of the first operational amplifier conditioning circuit 122, and the second output terminal of the digital-to-analog converter DAC is connected to the second input terminal of the first operational amplifier conditioning circuit 122. The first output terminal of the first operational amplifier conditioning circuit 122 is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface 110, specifically connected to the port HS of the reference source interface 110 through the switch K1, and connected to the port HF of the reference source interface 110 through the switch K3. The second output terminal of the first operational amplifier conditioning circuit 122 is connected to the low-end measurement line LS and the ground terminal GND. Among them, the digital-to-analog converter DAC is used to provide an excitation voltage, and the first operational amplifier conditioning circuit 122 is used to remove noise and interference and improve the stability of the excitation voltage. The host computer can be connected to the digital-to-analog converter DAC to control the digital-to-analog converter DAC to output an excitation voltage.

[0042] Furthermore, the analog-to-digital conversion module 130 includes an analog-to-digital converter ADC and a second operational amplifier conditioning circuit 132. The first input terminal of the second operational amplifier conditioning circuit 132 is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface 110, specifically connected to the port HS of the reference source interface 110 through the switch K1, and connected to the port HF of the reference source interface 110 through the switch K3. The second input terminal of the second operational amplifier conditioning circuit 132 is connected to the low-end measurement line LS and the reference source interface 110, specifically connected to the port LS of the reference source interface 110 through K2. The first output terminal of the second operational amplifier conditioning circuit 132 is connected to the first input terminal of the analog-to-digital converter ADC, and the second output terminal of the second operational amplifier conditioning circuit 132 is connected to the second input terminal of the analog-to-digital converter ADC. Among them, the analog-to-digital converter ADC is mainly used to collect the voltage values of the output channels of the board to be calibrated / verified. Its measurement accuracy is higher than that of the board. The second operational amplifier conditioning circuit 132 can be designed according to the output range of the board to be calibrated and the measurement range of the analog-to-digital converter ADC to better match the input range of the analog-to-digital converter ADC and filter and reduce noise for the analog signal at the same time. The host computer can be connected to the analog-to-digital converter ADC to receive the voltage values collected by the analog-to-digital converter ADC.

[0043] In one embodiment, continue to refer to Figure 2 , the load resistance module 140 includes a board voltage calibration load resistance unit 142 and a board current calibration load resistance unit 144. The board voltage calibration load resistance unit 142 is connected to the reference source interface 110, the digital-to-analog conversion module 120, the analog-to-digital conversion module 130, and the calibration line group 150. The board current calibration load resistance unit 144 is connected to the calibration line group 150. Among them, the load resistance in the board current calibration load resistance unit 144 is calibrated by an external reference source.

[0044] Further, the external reference device 100 further includes a line switching switch group. The calibration line group 150 is divided into two or more calibration line segments. The number of board calibration interfaces 160 and board current calibration load resistance units 144 is the same as the number of calibration line segments. The calibration line segments are connected through the line switching switch group, and each calibration line segment is connected to the corresponding board calibration interface 160 and the corresponding board current calibration load resistance unit 144. As Figure 2 shown, K B1-B2 , K B2-B3 , …, K B(N-1)-BN are respectively a group of line switching switch groups, used to connect two adjacent calibration line segments. Each calibration line segment includes three lines: a high-end output line HF, a high-end measurement line HS, and a low-end measurement line LS. The high-end output line HF, the high-end measurement line HS, and the low-end measurement line LS are all connected to the corresponding board calibration interface 160. The host computer can be connected to the line switching switch group K B1-B2 , the line switching switch group K B2-B3 , …, the line switching switch group K B(N-1)-BN . The host computer adjusts the on / off of the switches in each line switching switch group according to the calibration mode to control whether the boards are connected.

[0045] Specifically, the board voltage calibration load resistance unit 142 includes a switch K R∞ and a load resistance R ∞ . The load resistance R ∞ is a resistor with a resistance value above megohm, used to calibrate the board voltage. The first end of the switch K R∞ is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface 110. Specifically, it is connected to the port HS of the reference source interface 110 through the switch K1 and to the port HF of the reference source interface 110 through the switch K3. The second end of the switch K R∞ is connected to the first end of the load resistance R ∞ . The second end of the load resistance R ∞ is connected to the low-end measurement line LS and the ground terminal GND. The switch K R∞ can be a relay switch or other controlled switch. The host computer can be connected to the switch K R∞ to control the on / off of the switch K R∞ , thereby controlling the connection of the load resistance R ∞ .

[0046] Continue to refer to Figure 2, the load resistance unit 144 for board current calibration may specifically include several load switching units. Each load switching unit includes a switching switch and a load resistance. The first end of the switching switch is connected to the high-end output line HF and the high-end measurement line HS. The second end of the switching switch is connected to the first end of the load resistance. The second end of the load resistance is connected to the low-end measurement line LS and the ground terminal GND. Among them, in each load resistance unit 144 for board current calibration, the number of load switching units can be one or more. Taking the load resistance unit 144 for board current calibration including multiple load switching units as an example, as Figure 2 shown, in the first load resistance unit 144 for board current calibration, the switching switch K R11 and the load resistance R 11 constitute a load switching unit,..., the switching switch K R1N and the load resistance R 1N constitute a load switching unit; in the second load resistance unit 144 for board current calibration, the switching switch K R21 and the load resistance R 21 constitute a load switching unit,..., the switching switch K R2N and the load resistance R 2N constitute a load switching unit; in the Nth load resistance unit 144 for board current calibration, the switching switch K RN1 and the load resistance R N1 constitute a load switching unit,..., the switching switch K RNN and the load resistance R NN constitute a load switching unit.

[0047] The load resistances R 11 -R 1N , the load resistances R 21 -R 2N ,..., the load resistances R N1 -R NN correspond to the load resistances of each board respectively and are used to calibrate the board current. Their resistance values can be designed according to the current output and measurement range of the board. The switching switches K R11 -K R1N , the switching switches K R21 -K R2N ,..., the switching switches K RN1 -K RNN can also be relay switches or other controlled switches. The host computer can be connected to the switching switches K R11 -K R1N , the switching switches K R21 -K R2N ,..., the switching switches K RN1 -K RNN , and the corresponding load resistances can be controlled by adjusting the on / off of the switching switches.

[0048] Specifically, the external reference device 100 mainly uses a high-precision multimeter to calibrate the analog-to-digital converter ADC, the second operational amplifier conditioning circuit 132, and the load resistors R 11 -R 1N and the load resistors R 21 -R 2N and so on, up to the load resistors R N1 -R NN in the device. The digital-to-analog converter DAC and the first operational amplifier conditioning circuit 122, as output sources, do not require calibration and can meet the board calibration requirements by using the default values for output. As Figure 3 shown, the calibration of the external reference device 100 mainly includes the following steps:

[0049] (1) Disconnect all relay switches, connect the high-precision multimeter, and then close switch K1, switch K2, switch K3, and switch K4 to prepare for calibrating the reference device.

[0050] (2) Close switch K R∞ to select the maximum load resistor R ∞ . Set the multimeter to the voltage measurement mode, use the digital-to-analog converter DAC to output an excitation voltage, and perform a linear fit on the measured value of the high-precision multimeter and the measured value of the analog-to-digital converter ADC to calculate the offset error Offset and gain error Gain of the analog-to-digital converter ADC.

[0051] (3) Connect all line switching switch groups K B1-B2 , line switching switch groups K B2-B3 , and so on, up to line switching switch groups K B(N-1)-BN . Then close switching switches K R11 -K R1N , switching switches K R21 -K R2N , and so on, up to switching switches K RN1 -K RNN one by one. Set the multimeter to the four-wire resistance measurement mode and read the resistance value of the corresponding load resistor through the measured value of the high-precision multimeter.

[0052] (4) The host computer writes the calculated offset error and gain error of the analog-to-digital converter ADC and the resistance value of the load resistor into the storage unit. When using the external reference device 100 to calibrate the board, directly use the resistance value of the load resistor written in the storage unit, and the measured voltage value (or code value) of the analog-to-digital converter ADC will be corrected according to the offset error Offset and gain error Gain.

[0053] The calibration method of the external reference device 100 is the same as that of calibration. The difference is that calibration uses the default value for output or measurement to calculate the correction parameters. While verification uses the correction parameters obtained from calibration, that is, the calibration value, for output or measurement to evaluate whether the accuracy requirements are met.

[0054] After completing the calibration of the external reference device 100, the calibrated external reference device 100 can be used for multi-board calibration and verification. The calibration and verification of multi-boards can include: multi-board full-channel parallel voltage output and measurement calibration and verification, and board parallel channel serial current output and measurement calibration and verification.

[0055] Among them, the multi-board full-channel parallel voltage output and measurement calibration and verification method can complete the voltage output and measurement calibration and verification of all boards and all channels in the test machine at one time. The time used for calibration and verification is only equivalent to the single-channel calibration and verification time. This method requires the use of the digital-to-analog converter DAC, the first operational amplifier conditioning circuit 122, the analog-to-digital converter ADC, the second operational amplifier conditioning circuit module 132 and related load resistors on the external reference device 100. As Figure 4 shown, the calibration (the same for verification) is mainly divided into the following steps:

[0056] (1) Complete the calibration of the external reference device 100 through the calibration method of the external reference device 100.

[0057] (2) When calibrating each board, it is not necessary to connect a high-precision multimeter. Connect the external reference device 100 to the board to be calibrated in the test machine (including N boards), obtain the number of boards and the number of board channels, and disconnect all relay switches.

[0058] (3) Connect the line switching switch group K B1-B2 , the line switching switch group K B2-B3 , …, the line switching switch group K B(N-1)-BN and the switch K R∞ . At this time, the calibration depends on the load resistor R ∞ , the analog-to-digital converter ADC and the digital-to-analog converter DAC.

[0059] (4) Through the upper computer human-machine interface, select the voltage output measurement (FVMV) calibration mode.

[0060] (5) According to the calibration mode, traverse the voltage levels. In each level, control the relay switches KCH1-KCHN of each channel in all boards to close. At this time, each channel of the board is connected to the board output terminal and is connected to the board calibration interface of the external reference device 100 through the board output terminal.

[0061] (6) First, complete the calibration of the board full-channel voltage measurement (MV). Close the switch K R∞, select the maximum load resistance R ∞ , use the digital-to-analog converter DAC to generate the excitation voltage. All channels of all boards are sampled together, sharing the sampling delay. Take the voltage collected by the analog-to-digital converter ADC in the external reference device 100 as the expected value for each channel of the board, and the voltage collected by the channel itself as the actual value for linear fitting, calculate the offset error and gain error of the voltage measurement (MV) of each channel, and write them into the storage unit.

[0062] (7) Then, complete the full-channel voltage output (FV) calibration of the board. Turn off the excitation voltage output of the digital-to-analog converter DAC on the external reference device 100. Disconnect all the relay switches in the external reference device 100 and all the relay switches of all channels in the board. Output the no-load voltage inside the board. Take the pure theoretical value as the expected value for all channels of all boards, and use the calibrated channel voltage measurement (MV) in step (5) to read back the voltage of the channel itself as the actual value together, and then calculate the offset error and gain error of the voltage output (MV) of each channel and write them into the storage unit. At this time, the accuracy of the channel voltage output mainly depends on the measurement accuracy of the channel voltage.

[0063] For the calibration and verification of the parallel-channel serial current output and measurement of multiple boards, the external reference device 100 can be used to calibrate and verify multiple board channels simultaneously. Among them, the boards are in parallel mode and the channels are in serial mode. This method only needs to use the load resistance of the external reference device 100. As Figure 4 shown, the calibration (the same for verification) is mainly divided into the following steps:

[0064] (1) Complete the calibration of the external reference device 100 through the calibration method of the external reference device 100.

[0065] (2) Complete the calibration of the parallel voltage output and measurement of all channels of multiple boards through the calibration and verification method of the parallel voltage output and measurement of all channels of multiple boards.

[0066] (3) Select the current output measurement (FIMI) calibration mode through the human-computer interaction interface of the upper computer.

[0067] (4) Traverse the current gears according to the calibration mode, and then traverse a single channel of all boards one by one in each gear. The control instructions are sent to the relay switches KCH1-KCHN of each channel of each board one by one. All boards then wait for a certain delay together, that is, the so-called parallel control mode of multiple boards and serial control mode of channels.

[0068] (5) Disconnect the line switching switch group K B1-B2 , the line switching switch group K B2-B3 , …, the line switching switch group K B(N-1)-BN and the switch K R∞, enabling each board to be calibrated using independent load resistors in the external reference device 100. Multiple boards can simultaneously calibrate a single-channel FIMI. At this time, it depends on load resistors other than the load resistor R ∞ except, and does not depend on the analog-to-digital converter ADC and the digital-to-analog converter DAC. First, according to the current range, select the load resistor connected correspondingly by the switch K R1 -K RN in the external reference device 100, and output using the channel FI. The single channels of all boards respectively measure the voltage (MV) and the measured current (MI) samples, and then calculate the current passing through the load resistor by dividing the measured voltage (MV) by the actual resistance value of the load resistor corresponding to each board. At this time, the sampling delay between the boards is shared.

[0069] (6) Current measurement (MI) of multiple boards in a single channel. Using the current passing through the load resistor as the expected value, and the current (MI) collected by the board channel as the actual value for linear fitting.

[0070] (7) Current output (FI) of multiple boards in a single channel. Using the pure theoretical value as the expected value, and the current passing through the load resistor as the actual value for linear fitting.

[0071] (8) Calculate the offset error and gain error of the current measurement (MI) and current output (FI) of each channel of each board respectively, and write them into the storage unit.

[0072] In one embodiment, as Figure 5 shown, a test device is also provided, including a test machine. The test machine includes a host computer 210, a communication module 220, the board to be calibrated, and the above-mentioned external reference device 100. The host computer 210 is connected to the communication module 220, and the communication module 220 is connected to the board to be calibrated and the external reference device 100. Among them, the host computer 210 is connected to the analog-to-digital converter ADC, the digital-to-analog converter DAC, and the relevant relay switches in the external reference device 100 through the communication module 220. The board to be calibrated can be the power board of the test machine or other functional boards. The number of boards to be calibrated can be one or more. For example, it can include the board to be calibrated 1, the board to be calibrated 2,..., the board to be calibrated N. After calibrating the external reference device 100 with the external reference source, the calibrated external reference device 100 can be used to calibrate and verify multiple boards to be calibrated of the test machine simultaneously, including multi-board full-channel parallel voltage output and measurement calibration verification, and board parallel channel serial current output and measurement calibration verification.

[0073] In addition, the number of test machines can also be one or more, as Figure 6As shown, when the test equipment includes multiple test machines, such as test machine 1, test machine 2, …, test machine N, an external reference device 100 can be configured for each test machine. After calibrating each external reference device 100 with an external reference source, the board cards to be calibrated of the test machine where each external reference device 100 is located are calibrated and verified. Alternatively, one external reference device 100 can be configured. After calibration with the external reference source, the external reference device 100 is disassembled and installed on different test machines to calibrate and verify the board cards to be calibrated of each test machine respectively.

[0074] The above-mentioned external reference device for board card calibration and the test equipment use the external reference device to replace the high-precision multimeter for calibration in an environment with multiple test machines and multiple board cards, which can greatly reduce the dependence on the high-precision multimeter. The cost of the external reference device is much lower than the price of the high-precision multimeter, which can meet the requirements such as simultaneous sharing or time-sharing sharing by multiple test machines. Calibrating and verifying at the output end of the board card with the external reference device of the present application is equivalent to directly performing accuracy verification at the output end during use, without the need for in-board calibration and verification and then out-of-board accuracy recheck. For board cards with more channels, the time cost can be greatly reduced. In addition, the external reference device provided in the present application can calibrate and verify the board card in different ways: ① Method for calibrating and verifying parallel voltage output and measurement of all channels of multiple board cards; ② Serial current output and measurement calibration and verification for parallel channels of multiple board cards. Among them, the time required for calibrating and verifying parallel voltage output and measurement of all channels of multiple board cards is only equivalent to the time for single-channel calibration and verification, which greatly improves the calibration and verification efficiency of board cards with more channels, and the more channels there are, the more obvious the improvement is.

[0075] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope described in this specification.

[0076] The above-described embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the utility model patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An external reference device for board calibration, characterized in that, Comprising: A reference source interface for connecting to an external reference source; A digital-to-analog conversion module connected to the reference source interface; An analog-to-digital conversion module connected to the reference source interface and the digital-to-analog conversion module, A load resistance module connected to the reference source interface, the digital-to-analog conversion module, and the analog-to-digital conversion module; A calibration circuit group connected to the reference source interface, the digital-to-analog conversion module, the analog-to-digital conversion module, and the load resistance module; A plurality of board calibration interfaces, each of which is connected to the calibration circuit group and a corresponding board to be calibrated; Wherein, the load resistance in the load resistance module and the analog-to-digital conversion module are calibrated by the external reference source, and the board to be calibrated is calibrated by the digital-to-analog conversion module, the calibrated analog-to-digital conversion module, and the calibrated load resistance module.

2. The external reference device according to claim 1, wherein The load resistance module includes: A board voltage calibration load resistance unit connected to the reference source interface, the digital-to-analog conversion module, the analog-to-digital conversion module, and the calibration circuit group; A board current calibration load resistance unit connected to the calibration circuit group; Wherein, the load resistance in the board current calibration load resistance unit is calibrated by the external reference source.

3. The external reference device according to claim 2, characterized in that It further includes a line switching switch group. The calibration circuit group is divided into two or more calibration circuit segments. The number of the board calibration interfaces and the number of the board current calibration load resistance units are the same as the number of the calibration circuit segments. Each calibration circuit segment is connected through the line switching switch group, and each calibration circuit segment is connected to a corresponding board calibration interface and a corresponding board current calibration load resistance unit.

4. The external reference device according to claim 2, characterized in that, The calibration circuit group includes a high-end output line HF, a high-end measurement line HS, and a low-end measurement line LS. The reference source interface is connected to the high-end output line HF, the high-end measurement line HS, and the low-end measurement line LS.

5. The external reference device according to claim 4, wherein The digital-to-analog conversion module includes a digital-to-analog converter and a first operational amplifier conditioning circuit. The first output end of the digital-to-analog converter is connected to the first input end of the first operational amplifier conditioning circuit. The second output end of the digital-to-analog converter is connected to the second input end of the first operational amplifier conditioning circuit. The first output end of the first operational amplifier conditioning circuit is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface. The second output end of the first operational amplifier conditioning circuit is connected to the low-end measurement line LS and the ground terminal.

6. The external reference device according to claim 4, wherein The analog-to-digital conversion module includes an analog-to-digital converter and a second operational amplifier conditioning circuit. The first input end of the second operational amplifier conditioning circuit is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface. The second input end of the second operational amplifier conditioning circuit is connected to the low-end measurement line LS and the reference source interface. The first output end of the second operational amplifier conditioning circuit is connected to the first input end of the analog-to-digital converter. The second output end of the second operational amplifier conditioning circuit is connected to the second input end of the analog-to-digital converter.

7. The external reference device according to claim 4, characterized in that The board voltage calibration load resistance unit includes a switch K R∞ and a load resistor R ∞ , and the load resistor R ∞ is a resistor with a resistance value above megaohm; the first end of the switch K R∞ is connected to the high-end output line HF, the high-end measurement line HS, and the reference source interface, and the second end of the switch K R∞ is connected to the first end of the load resistor R ∞ , and the second end of the load resistor R ∞ is connected to the low-end measurement line LS and the ground terminal.

8. The external reference device according to claim 4, characterized in that The board current calibration load resistance unit includes a plurality of load switching units. Each load switching unit includes a switching switch and a load resistance. The first end of the switching switch is connected to the high-end output line HF and the high-end measurement line HS. The second end of the switching switch is connected to the first end of the load resistance. The second end of the load resistance is connected to the low-end measurement line LS and the ground terminal.

9. The external reference device according to any one of claims 1-8, characterized in that, It further includes an interface control switch group. The reference source interface is connected to the digital-to-analog conversion module, the analog-to-digital conversion module, the load resistance module, and the calibration line group through the interface control switch group.

10. A test device, characterized in that, It includes a test machine. The test machine includes a host computer, a communication module, a board to be calibrated, and the external reference device according to any one of claims 1-9. The host computer is connected to the communication module. The communication module is connected to the board to be calibrated and the external reference device.

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