Device, system and method for testing input impedance

Abstract

The invention provides an input impedance testing device, system and method, and belongs to the technical field of electronics. The problem of poor stability in the prior art is solved. The input impedance testing device comprises a shell with a cavity inside, and is characterized in that a testing module used for impedance testing is connected in the shell, the shell is further provided with a power interface and a testing interface, the device further comprises a patch cord, the power interface and the testing interface are both connected with the testing module, and the patch cord is connected with the testing module. The inner end of the patch cord is detachably connected to the test interface, and the outer end of the patch cord is used for being connected with a device to be tested. The input impedance test system is characterized in that the input impedance test system comprises an input impedance test device and a power supply module, the power supply module comprises a plurality of linear power supply modules and a switching power supply module, and voltage converted by the power supply module is input to the test module. The method for testing the input impedance comprises the following steps of: A, sending data; and B, electric block position switching. The device and the system are high in applicability, and the method is simple and convenient to operate.

Description

Technical Field

[0001] The invention belongs to the field of electronic technology and relates to a device, system and method for testing input impedance. Background Art

[0002] After each type of PCB (Printed Circuit Board) is produced, the corresponding chips and electronic components are installed according to the circuit diagram. After the electronic components are soldered and installed, the circuit board cannot be directly powered on for testing. The input impedance of the power supply and the corresponding test points needs to be tested. Only when the input impedance value meets the test requirements can the next power-on debugging step be carried out.

[0003] Most of the existing technical solutions currently use a multimeter to measure the input impedance at both ends of the test point manually, manually record the input impedance measurement results and manually determine whether the test point meets the requirements.

[0004] It can be seen that the above test method is complicated to operate, inefficient, and manual measurement is prone to errors. In order to solve the above problems, many factories also have corresponding input impedance test equipment, but these input impedance test equipment usually only have the ability to test one type of circuit board. When the circuit board is modified, the input impedance test equipment needs to be redesigned, which has poor applicability. Summary of the invention

[0005] The first object of the present invention is to provide a testing device for input impedance with high applicability in view of the above-mentioned problems existing in the prior art.

[0006] A second object of the present invention is to provide a testing system using the input impedance of the above-mentioned testing device.

[0007] The third object of the present invention is to provide a method for testing input impedance.

[0008] The first object of the present invention can be achieved by the following technical solutions: A device for testing input impedance comprises a shell with a hollow interior, characterized in that a test module for performing impedance testing is connected inside the shell, the shell also has a power interface and a test interface, the device also comprises an adapter wire, the power interface and the test interface are both connected to the test module, the inner end of the adapter wire is detachably connected to the test interface, and the outer end of the adapter wire is used to connect to a device to be tested.

[0009] In the above-mentioned input impedance testing device, the power interface includes a USB interface and a DC power input interface. The USB interface is used to connect to a host computer and realize data communication. The test module also has an identification processing unit. When the identification processing unit identifies that the USB power supply is insufficient, the identification processing unit will switch to the DC power interface for power supply.

[0010] In the above-mentioned input impedance testing device, the interior of the shell is a cavity with an opening at the top, the upper port of the shell is provided with an openable and closable cover, and the above-mentioned testing module is located in the inner cavity of the shell.

[0011] In the above-mentioned input impedance test device, the test module includes an input impedance test device and a power supply module, and the power supply module includes a plurality of linear power supply modules and a switching power supply module. The voltage converted by the power supply module is input to the input impedance test device. In the above-mentioned input impedance test system, the test module has a control unit, a switch matrix unit, a standard resistance unit, a digital-to-analog conversion unit, an analog-to-digital conversion unit and a USB communication unit.

[0012] In the above-mentioned input impedance test system, the control unit is composed of an FPGA and its peripheral circuits to form a minimum system. The peripheral circuits include a FLASH memory, an external active crystal oscillator, a filter capacitor, a reset button, etc. The above-mentioned FPGA is a Field-Programmable Gate Array.

[0013] In the above-mentioned input impedance test system, the standard resistance unit consists of two parts: a low-temperature drift, high-precision standard resistor and a signal relay. The standard resistors are 100 ohms, 1K ohms, 10K ohms, 100K ohms, 1M ohms and 10M ohms. Switching between different standard resistors can be achieved by switching relays.

[0014] In the above-mentioned input impedance test system, the switch matrix unit is composed of 204 relay modules, and the normally open pin of each relay module is connected to the input impedance test interface.

[0015] In the above-mentioned input impedance test system, the digital-to-analog conversion unit is mainly composed of a digital-to-analog conversion chip and peripheral circuits, and is connected to the control unit via a 16-bit parallel communication interface to realize the control of analog output.

[0016] A method for testing input impedance, characterized in that the method comprises the following steps: A. Data transmission: The host computer sends data to the control unit, and the control unit analyzes the data to see if it is valid. If it is invalid, the host computer resends the corresponding data. If it is valid, the corresponding analog quantity is output through the digital-to-analog conversion unit; B. Switching of resistance gear position: The analog quantity output by the digital-to-analog conversion unit enters the standard resistance unit. After the standard resistance unit switches to the corresponding resistance gear position, the above resistance information is collected through the analog-to-digital conversion unit. The control unit determines whether its resistance gear position matches. If it does not match, the standard resistance unit switches the corresponding gear position again. If it matches, the analog-to-digital conversion unit and the control unit will collect and calculate the input impedance value of the channel. After the calculation is completed, the measured input impedance value will be sent to the host computer to end the test operation.

[0017] Compared with the prior art, the input impedance testing device can test the input impedance of various types of circuit boards, and has relatively high applicability.

[0018] The input impedance test system can achieve wide-range, high-precision measurement through circuit improvement and algorithm upgrade. The measurement range is 0~40M ohms, the accuracy of 0~4M ohms is 0.5%, and the accuracy of 4M~40M ohms is 1.5%. It can meet the testing requirements of most types of circuit boards and further improve its applicability.

[0019] When measuring the input impedance of the circuit, use a USB data cable to connect the input impedance test device to the host computer, use a test cable to click the automatic test button of the host computer to realize the automatic test of the input impedance of the device under test. Since the adapter cable can be replaced according to the actual situation, the device can also test the test pieces with different interfaces.

[0020] During the measurement process, the traditional measurement method sets the output power supply voltage through the control unit, and then calculates the input impedance value to be measured through the voltage value. However, during use, the actual output voltage value has a significant deviation from the set value. However, the present invention uses a dual-channel ADC to synchronously collect the output power supply voltage and the voltage at both ends of the test point, which can eliminate the error caused by external interference and improve the measurement accuracy of the input impedance.

[0021] The traditional mean filtering method can effectively remove jitter but cannot effectively process larger outliers, while the median filtering can effectively remove outliers but cannot remove jitter very well. The present invention combines the actual collected data and adopts the mode mean filtering method, which can effectively eliminate larger outliers and remove jitter at the same time, thereby further improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1It is a three-dimensional structural schematic diagram of the input impedance testing device.

[0023] Figure 2 It is a schematic diagram of the three-dimensional structure of the input impedance testing device in another direction.

[0024] Figure 3 It is a schematic diagram of the structure of the adapter cable.

[0025] Figure 4 It is the principle block diagram of the input impedance test system.

[0026] Figure 5 It is the principle block diagram of the switch matrix unit.

[0027] Figure 6 This is the schematic diagram of the digital-to-analog conversion module.

[0028] Figure 7 This is the schematic diagram of the analog-to-digital conversion module.

[0029] Figure 8 It is a schematic diagram of the three-dimensional structure supporting the heat dissipation structure.

[0030] In the figure, 1, housing; 2, test module; 3, power interface; 4, test interface; 5, adapter cable; 6, bottom plate; 7, heat sink; 7a, connecting section; 7a1, overflow groove; 7b, avoidance part; 8, positioning plate; 9, water cooling pipe. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that when a component is referred to as being "mounted on" another component, it may be directly mounted on the other component or there may be a central component. When a component is considered to be "set on" another component, it may be directly set on the other component or there may be a central component at the same time. When a component is considered to be "fixed to" another component, it may be directly fixed on the other component or there may be a central component at the same time.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "or / and" used herein includes any and all combinations of one or more related listed items.

[0034] like Figure 1 and Figure 2 and Figure 3 and Figure 4 and Figure 5 and Figure 6 and Figure 7 As shown, the input impedance testing device includes a shell 1 with a cavity inside, a test module 2 for impedance testing is connected inside the shell 1, a test module 2 for impedance testing is connected inside the shell 1, the shell 1 also has a power interface 3 and a test interface 4, the device also includes a transfer line 5, the power interface 3 and the test interface 4 are both connected to the test module 2, the inner end of the transfer line 5 is detachably connected to the test interface 4, and the outer end of the transfer line 5 is used to connect to the device to be tested.

[0035] The power interface 3 includes a USB interface and a DC power input interface. The USB interface is used to connect to the host computer and realize data communication. The test module also has an identification processing unit. When the identification processing unit identifies that the USB power supply is insufficient, the identification processing unit will switch to the DC power interface for power supply.

[0036] The shell 1 is hollow inside and open at the top. The shell 1 has an openable and closable cover at the upper port. The test module 2 is located in the inner cavity of the shell.

[0037] like Figure 4 and Figure 5 and Figure 6 and Figure 7 As shown, the test module 2 includes an input impedance test device and a power supply module. The power supply module includes a plurality of linear power supply modules and a switching power supply module. The voltage transformed by the power supply module is input to the input impedance test device.

[0038] The test module 2 includes a control unit, a switch matrix unit, a standard resistance unit, a digital-to-analog conversion unit, an analog-to-digital conversion unit and a USB communication unit.

[0039] The control unit is composed of a minimum system consisting of an FPGA and its peripheral circuits, wherein the peripheral circuits include a FLASH memory, an external active crystal oscillator, a filter capacitor, a reset button, etc. The FPGA is a Field-Programmable Gate Array.

[0040] The standard resistor unit consists of two parts: a low-temperature drift, high-precision standard resistor and a signal relay. The standard resistors include 100 ohms, 1K ohms, 10K ohms, 100K ohms, 1M ohms and 10M ohms. Switching between different standard resistors can be achieved by switching the relay.

[0041] The switch matrix unit is composed of 204 relay modules, and the normally open pin of each relay module is connected to the input impedance test interface.

[0042] The digital-to-analog conversion unit is mainly composed of a digital-to-analog conversion chip and peripheral circuits, and is connected to the control unit via a 16-bit parallel communication interface to realize the control of analog output.

[0043] The input impedance test method includes the following steps: A. Data transmission: The host computer sends data to the control unit, and the control unit analyzes the data to see if it is valid. If it is invalid, the host computer resends the corresponding data. If it is valid, the corresponding analog quantity is output through the digital-to-analog conversion unit; B. Switching of resistance gear position: The analog quantity output by the digital-to-analog conversion unit enters the standard resistance unit. After the standard resistance unit switches to the corresponding resistance gear position, the above resistance information is collected through the analog-to-digital conversion unit. The control unit determines whether its resistance gear position matches. If it does not match, the standard resistance unit switches the corresponding gear position again. If it matches, the analog-to-digital conversion unit and the control unit will collect and calculate the input impedance value of the channel. After the calculation is completed, the measured input impedance value will be sent to the host computer to end the test operation.

[0044] The device is mainly used to test the input impedance before power-on after the PCB circuit board is assembled with electronic components. Compared with the traditional manual measurement method, the device can realize multi-channel and automatic measurement, effectively improving the test efficiency. The device reserves a USB communication interface, a DC power input interface, and three input impedance test interfaces. The connection relationship between the device, the host computer, and the device to be tested is shown in the figure.

[0045] The shell consists of an upper cover and a lower cover. The impedance test system circuit board is fixed to the lower cover of the impedance tester by four M3 screws, and the upper cover and the lower cover are connected by snaps. The USB interface is connected to the host computer to achieve data communication. The power input interface is connected to the power adapter. When the USB power supply is not enough to drive the impedance test system, the system will automatically identify and switch to the power adapter power supply mode to ensure that all test functions can be executed smoothly and ensure that the accuracy of the test results and the stability of the system will not be affected by insufficient power supply.

[0046] The universal multi-channel input impedance automatic test device uses 3M's N10268-52E3PC socket as the input impedance test interface, and the matching standard plug model is 10168-900APL. In view of the differences in the test interfaces of different products under test (DUT, Device Under Test), in order to ensure the smooth progress of the test, a special adapter cable is required to act as a bridge to achieve an effective connection between the test device and the product under test. One end of the adapter cable needs to perfectly match the input impedance test interface of the test device (i.e., N10268-52E3PC socket) to ensure that the 10168-900APL plug can be inserted firmly and accurately to ensure the integrity and stability of signal transmission. The other end of the adapter cable needs to be designed according to the actual test interface of the product under test. Therefore, when testing unused products under test, the device only needs to replace the adapter cable to complete the test, which has good versatility. The interior of the adapter cable should adopt a high-quality coaxial structure to ensure the integrity and impedance matching of the signal during the test process. This includes selecting appropriate insulation materials, conductor materials, and shielding layer designs to reduce signal attenuation, reflections, and interference to ensure the accuracy of test results.

[0047] The input impedance automated test system consists of three input impedance test interfaces, one power input interface, one USB interface, a control unit, a power module, a switch matrix unit, a standard resistance unit, a digital-to-analog conversion unit, an analog-to-digital conversion unit and a USB communication unit.

[0048] The power module mainly realizes the function of stepping down and stabilizing the external input power supply. The stepped-down power supply is provided to the control unit, switch matrix unit, standard resistor unit, digital-to-analog conversion unit, and analog-to-digital conversion unit in the system, and the power supply of the USB communication unit is directly provided by the USB interface. Based on the dual power selection circuit, when the USB power supply is insufficient to drive the impedance test system, the power module will switch to the power adapter power supply mode. According to the power supply characteristics of the subsequent circuit, the present invention selects a linear power supply module and a switching power supply module to realize the step-down processing of the input power supply, wherein the linear power supply module inputs the stepped-down voltage to the analog-to-digital conversion unit and the digital-to-analog conversion unit, because the analog-to-digital conversion unit and the digital-to-analog conversion unit have higher requirements for the quality of the power supply, and the output voltage of the linear power supply is almost unaffected by the load change, and the ripple and noise are also very small, which can well meet the power supply requirements of the digital-to-analog conversion unit and the analog-to-digital conversion unit. The switching power supply module inputs the stepped-down voltage to the control unit, the switch matrix unit, and the standard resistor unit, because the control unit, the switch matrix unit, and the standard resistor unit do not have high requirements for the quality of the power supply, and the switching power supply has the advantages of small size, light weight, and high efficiency, so that the input impedance automatic test equipment can be designed to be more compact and portable. In order to ensure the accuracy of measurement, the power supply voltages between different modules and units are independent of each other, and the digital power supply and analog power supply isolation design is carried out in the circuit to effectively avoid crosstalk between signals.

[0049] The control unit is a minimum system consisting of FPGA and peripheral circuits. The peripheral circuits include FLASH memory, external active crystal oscillator, reset unit, JTAG download unit, filter capacitor, etc.

[0050] The control unit is connected to the switch matrix unit, the standard resistor unit, the digital-to-analog conversion module, the analog-to-digital conversion module and the USB communication module. The control unit realizes the switching of different relay modules in the switch matrix unit by controlling the high and low levels of the output pins, thereby realizing the function of multi-channel input impedance acquisition. The control unit realizes the switching of the relay module in the standard resistor unit by controlling the high and low levels of the output pins, thereby realizing the multi-range measurement function. The control unit and the digital-to-analog conversion module and the analog-to-digital conversion module all realize the configuration of the reference voltage value and the acquisition of the voltage through parallel communication. The control unit and the USB communication module realize the sending and receiving of data through a serial communication device (UART).

[0051] The standard resistor unit uses low temperature drift and high precision resistor elements to ensure the accuracy and stability of the measurement. In order to meet the common input impedance measurement requirements in engineering, this system selects six standard resistors with different resistance values: 100 ohms, 1K ohms, 10K ohms, 100K ohms, 1M ohms and 10M ohms. These standard resistors correspond to the following six measurement ranges: 0-400 ohm range, using 100 ohm standard resistor; 400 ohms to 4K ohm range, using 1K ohm standard resistor; 4K ohms to 40K ohms range, using 10K ohm standard resistor; 40K ohms to 400K ohms range, using 100K ohm standard resistor; 400K ohms to 4M ohms range, using 1M ohm standard resistor; 4M ohms to 40M ohms range, using 10M ohm standard resistor.

[0052] In the standard resistor unit, each standard resistor is connected to the circuit through a relay module. The initial state of the relay module is set to the normally closed ground state, that is, it is disconnected by default. When measuring the input impedance, the control unit will accurately control the relay module through its IO pin according to the specific value of the input impedance to be measured, so as to flexibly switch the connected standard resistor position to ensure the accuracy and adaptability of the measurement results.

[0053] The switch matrix unit consists of 204 relay modules, and each relay module is connected to a pin in the test interface one by one.

[0054] The relay module uses the fifth generation signal relay, which has the characteristics of fast action speed, good working stability, small size and ultra-low power consumption. The control unit can directly drive the relay module. The relay module is a monostable relay. When the coil is energized, the relay is set, and when the coil is de-energized, it is reset. In the present invention, all relays are designed with a grounded normally closed pin in the reset state.

[0055] One end of the input impedance to be measured is connected to the first pin of the test interface. In this connection state, the control unit will control the relay module corresponding to the first pin to perform a setting operation according to the parsed instruction. This operation will cause the digital-to-analog conversion unit, the standard resistance unit, the relay module and the input impedance to be measured to form a closed loop.

[0056] In order to measure the size of the input impedance to be measured, the digital-to-analog conversion unit will output a known voltage value and apply it to the input end of the analog-to-digital conversion unit through the loop. At the same time, the analog-to-digital conversion unit will measure the voltage value and send it to the controller. Since the loop contains a standard resistor and the input impedance to be measured, the resistance value of the impedance to be measured can be calculated from the measured voltage value according to Ohm's law and the voltage divider principle.

[0057] The same measurement principle also applies to the input impedances to be measured corresponding to other test interfaces. The control unit only needs to set the corresponding relay module according to the host computer instruction to achieve input impedance measurement of different channels. In this way, the entire test system can flexibly switch measurement channels and accurately measure multiple input impedances to be measured.

[0058] In actual debugging, in order to ensure the accuracy and stability of the measurement, it may be necessary to calibrate and compensate the measurement circuit to eliminate the influence of various factors on the measurement results.

[0059] The digital-to-analog conversion unit converts the digital quantity input by the control unit into an analog quantity according to the weight through a resistor network, and then converts it into an analog quantity proportional to the digital quantity through an adding circuit. In order to ensure the measurement accuracy, the present invention uses a digital-to-analog conversion module with a resolution of 16 bits and an integral nonlinearity of ±12LSB, which can achieve high-resolution and high-stability analog output.

[0060] The analog-to-digital conversion module samples, holds, quantizes, and encodes analog quantities to obtain digital quantities, and sends the digital quantities to the control unit through parallel communication to complete data processing and uploading.

[0061] In order to ensure the high precision of input impedance measurement, the present invention specially selects a dual-channel, 16-bit successive approximation analog-to-digital conversion module, whose maximum integral nonlinearity is only ±1.25 LSB. This choice is intended to improve the accuracy and stability of the measurement. In the traditional input impedance measurement method, the voltage value of the input end of the impedance to be measured is usually directly obtained through the analog-to-digital conversion module, and then the difference between the set power supply voltage and the measured voltage value is used to calculate the input impedance to be measured in combination with Ohm's law. However, this method is easily affected by the external environment and the interference of the circuit itself, resulting in instability of the set power supply voltage, which in turn produces measurement errors.

[0062] In order to overcome this defect, the present invention innovatively adopts the idea of ​​differential measurement and is equipped with an analog-to-digital conversion module with dual-channel synchronous acquisition. One of the channels is specifically used to measure the voltage value of the input end of the input impedance to be measured, while the other channel is used to monitor the actual output voltage value (i.e., the power supply voltage value) of the digital-to-analog conversion module in real time. By collecting data through these two channels at the same time and performing differential processing, we can effectively eliminate the voltage fluctuation error caused by external interference or internal factors of the circuit. Specifically, when the voltage at the end to be measured is fluctuated by external interference, since the two channels are synchronously collected, this fluctuation will be reflected in the measured values ​​of the input end voltage of the input impedance to be measured and the power supply voltage at the same time. Through differential processing, this common fluctuation component will be offset, thereby ensuring the accuracy of the measurement result. In addition, if there is an error between the voltage value actually output by the digital-to-analog conversion module itself and the theoretical value, the present invention can also be corrected by the actual voltage value collected. In this way, it can be ensured that the internal circuit will not generate an error source, further improving the accuracy and reliability of the measurement.

[0063] The input impedance calculation method of the present invention is described as follows: First, the digital-to-analog conversion module (DAC) outputs a known voltage value U0, which is applied to the input impedance Rx to be measured and the standard resistor R through the circuit. The voltage value across the input impedance Rx to be measured is recorded as U1, and the resistance value of the standard resistor R is dynamically matched according to the input impedance to be measured.

[0064] The matching mechanism of the standard resistor R is as follows: In the initial state, the standard resistance unit relay module is preferentially switched to the standard resistance of 10M ohms.

[0065] The control unit monitors the ratio of the voltage value U0 output by the digital-to-analog conversion module to the voltage value U1 across the impedance to be measured. If the ratio is greater than 3.5, the relay module switches to the standard resistance of 1M ohm; if the ratio is not greater than 3.5, the current relay module is kept closed, that is, kept at the 10M ohm position, and the automatic switching of the resistance position ends.

[0066] If the relay module has switched to the 1M ohm position, the control unit monitors the ratio again. If the ratio is still greater than 3.5, the relay module continues to switch to the standard resistance of 100K ohms; if the ratio is not greater than 3.5, the current relay module is kept closed, that is, kept at the 1M ohm position, and the automatic switching of the resistance position ends.

[0067] By analogy, when the ratio is always greater than 3.5, the relay module will switch to smaller standard resistance positions in sequence until it switches to the 100 ohm standard resistance, and the resistance position switching is automatically completed.

[0068] After the automatic switching of the resistance position is completed, the control unit will collect and save the voltage values ​​U0 and U1 at this time. Then, the size of the input impedance Rx to be measured is calculated using Ohm's law and the voltage division principle. Since there is a voltage division relationship between the standard resistor R and the impedance Rx to be measured in the circuit, the input impedance Rx to be measured can be calculated using the following formula:

[0069] The software flow of the universal multi-channel input impedance automatic test system is: First, the host computer sends test instructions and parameters to the control unit according to the set measurement program, including the packet header, the channel number of the input impedance to be measured, the check code and other information. The control unit receives the data sent by the host computer and parses it to determine the specific requirements and steps of the test. The control unit checks the validity of the parsed data to ensure that the data is correct. If the data is invalid, it returns to the previous step to receive and parse the data again.

[0070] According to the test requirements, the control unit outputs a known voltage value through the digital-to-analog conversion unit. The voltage value output by the digital-to-analog conversion unit is applied to the test circuit composed of the input impedance to be tested and the standard resistance unit. The control unit switches the switch matrix relay module according to the needs of the test channel to connect the input impedance to be tested to the test circuit.

[0071] The analog-to-digital conversion unit measures the voltage value across the input impedance to be measured and converts it into a digital signal, while collecting the original voltage value output by the digital-to-analog conversion unit. The control unit receives the data collected by the analog-to-digital conversion unit through the parallel communication interface, and according to the collected data, through the matching mechanism of the standard resistor, the control unit switches to a standard resistor of appropriate resistance through the relay module.

[0072] After switching to a standard resistor with a suitable resistance value, the control unit calculates the current input impedance based on the collected voltage data, and packages the data and sends it to the host computer. After receiving the information from the test equipment, the host computer parses the data to obtain the input impedance value of the channel, and compares it with the preset input impedance value to determine whether the input impedance of the channel meets the requirements.

[0073] In addition to the hardware improvements, the present invention also improves the measurement method in the system. The traditional mean filtering method can effectively remove jitter but cannot effectively handle large outliers, while the median filtering method can effectively remove outliers but cannot remove jitter very well. The present invention will combine the actual collected data and adopt the mode mean filtering method, which can effectively remove large outliers and remove jitter at the same time. The specific process is:

[0074] First, the actual voltage value is collected by the analog-to-digital conversion unit and converted into a digital value. The control unit stores the data and ensures that the number of acquisitions is greater than or equal to 20 times. Then, the average value of these 20 sets of data is taken, and the maximum and minimum values ​​of the abnormal data are determined by multiplying the abnormal value comparison coefficient, so as to obtain the abnormal data comparison range. Then, check whether there are values ​​exceeding the abnormal data comparison range in the 20 sets of data collected. If there are no abnormal values ​​in the data, the current data is retained and not eliminated. If there are abnormal values ​​in the data, these abnormal values ​​are eliminated and only the data within the normal range is retained. The data after the abnormal values ​​are eliminated is averaged again and multiplied by the mode comparison coefficient to obtain the mode range. Check whether the data after the abnormal values ​​are eliminated is within the mode comparison range. If the data is within the mode range, the current data is retained; if the data is not within the mode range, the data that does not meet the conditions is eliminated. The data finally retained is averaged to obtain the final filtering result, and the final filtering result (average value) is output as the processed data value.

[0075] In this embodiment, one end of the adapter is a DB15 connector, and the other end is a 10168-900APL connector.

[0076] like Figure 8 As shown, the shell 1 is hollow inside and open at the top, and the test module 2 includes a substrate and corresponding electrical components connected to the substrate. The electrical components are located outside the substrate and are adjacent to the open end of the shell. A supporting heat dissipation structure is provided between the inner side of the substrate and the bottom of the shell 1.

[0077] The supporting heat dissipation structure includes a base plate, a heat sink and a water cooling assembly. The base plate maintains surface contact with the bottom of the shell. The heat sink has a downwardly folded connecting section at the edge. The connecting section is fixedly connected to the base plate by fasteners. A positioning plate is also fixedly connected to the bottom of the heat sink. The water cooling pipe of the water cooling assembly is tightly pressed between the positioning plate and the heat sink. The above-mentioned base plate is against the heat sink and the two are in surface contact.

[0078] It also includes an overflow groove extending from the edge of the heat sink to the connecting section.

[0079] The heat sink is also provided with a recessed avoidance portion at the edge thereof. The fastener is passed through the avoidance portion and the heat sink to fix the heat sink to the positioning plate, and the upper end of the fastener is flush with the upper part of the heat sink.

[0080] The bottom plate is frame-shaped.

[0081] The bottom plate is in contact with the bottom surface of the housing, and the heat sink is in contact with the substrate surface. During the operation of the water cooling assembly, the temperature of the substrate can be appropriately reduced through the heat sink.

[0082] When the temperature difference is too large, water mist will be generated at the bottom of the substrate, and the water mist will steadily flow into the bottom of the shell along the overflow groove to avoid excessive water accumulation at the substrate.

[0083] At the same time, the frame-shaped bottom plate prevents excessive water from remaining between the bottom plate and the outer shell, making it easy to clear the accumulated water during maintenance operations.

[0084] Of course, the main function of this supporting heat dissipation structure is to dissipate heat. The generation of water accumulation is an individual special case. In most operations, it will only effectively reduce the substrate temperature and will not continuously generate water accumulation. This structure is only a backup plan for extreme situations and can respond immediately when extreme situations occur.

[0085] Meanwhile, the water cooling assembly is an existing device having a water cooling pipe, and therefore, the specific technical features of the water cooling assembly will not be described in detail in the embodiments.

[0086] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0087] Those skilled in the art should recognize that the above embodiments are only used to illustrate the present invention, and are not intended to limit the present invention. As long as they are within the spirit of the present invention, appropriate changes and modifications to the above embodiments are within the scope of protection claimed by the present invention.

Claims

1. A device for testing input impedance, comprising a housing with a cavity inside, characterized in that: A test module for performing impedance testing is connected inside the shell, and the shell also has a power interface and a test interface. The device also includes an adapter cable, and the power interface and the test interface are both connected to the test module. The inner end of the adapter cable is detachably connected to the test interface, and the outer end of the adapter cable is used to connect to the device to be tested.

2. The input impedance testing device according to claim 1, characterized in that: The power interface includes a USB interface and a DC power input interface. The USB interface is used to connect to a host computer and realize data communication. The test module also has an identification processing unit. When the identification processing unit identifies that the USB power supply is insufficient, the identification processing unit will switch to the DC power interface for power supply.

3. The input impedance testing device according to claim 2, characterized in that: The interior of the shell is a cavity with an opening at the top, and an openable and closable cover is provided at the upper port of the shell. The test module is located in the inner cavity of the shell.

4. The input impedance testing system according to claim 3, characterized in that: The test module includes an input impedance test device and a power supply module. The power supply module includes a plurality of linear power supply modules and a switching power supply module. The voltage converted by the power supply module is input to the input impedance test device.

5. The input impedance testing system according to claim 4, characterized in that: The test module includes a control unit, a switch matrix unit, a standard resistance unit, a digital-to-analog conversion unit, an analog-to-digital conversion unit and a USB communication unit.

6. The input impedance testing system according to claim 5, characterized in that: The control unit is composed of a minimum system consisting of an FPGA and its peripheral circuits, wherein the peripheral circuits include a FLASH memory, an external active crystal oscillator, a filter capacitor, a reset button, etc. The FPGA is a Field-Programmable Gate Array.

7. The input impedance testing system according to claim 6, characterized in that: The standard resistor unit consists of two parts: a low-temperature drift, high-precision standard resistor and a signal relay. The standard resistors include 100 ohms, 1K ohms, 10K ohms, 100K ohms, 1M ohms and 10M ohms. Switching between different standard resistors can be achieved by switching the relay.

8. The input impedance testing system according to claim 7, characterized in that: The switch matrix unit is composed of 204 relay modules, and the normally open pin of each relay module is connected to the input impedance test interface.

9. The input impedance testing system according to claim 8, characterized in that: The digital-to-analog conversion unit is mainly composed of a digital-to-analog conversion chip and peripheral circuits, and is connected to the control unit via a 16-bit parallel communication interface to realize the control of analog output.

10. The method for testing input impedance according to claim 4, characterized in that: The method comprises the following steps: A. Data transmission: The host computer sends data to the control unit, and the control unit analyzes the data to see if it is valid. If it is invalid, the host computer resends the corresponding data. If it is valid, the corresponding analog quantity is output through the digital-to-analog conversion unit; B. Switching of resistance gear position: The analog quantity output by the digital-to-analog conversion unit enters the standard resistance unit. After the standard resistance unit switches to the corresponding resistance gear position, the above resistance information is collected through the analog-to-digital conversion unit. The control unit determines whether its resistance gear position matches. If it does not match, the standard resistance unit switches the corresponding gear position again. If it matches, the analog-to-digital conversion unit and the control unit will collect and calculate the input impedance value of the channel. After the calculation is completed, the measured input impedance value will be sent to the host computer to end the test operation.

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