CN214201695U

CN214201695U - 64-channel electronic switch voltage resistance measuring device

Info

Publication number: CN214201695U
Application number: CN202022258851.XU
Authority: CN
Inventors: 李盛平; 汪金达; 蔡振宇
Original assignee: Intelligent Automation Equipment Zhuhai Co Ltd
Current assignee: Intelligent Automation Equipment Zhuhai Co Ltd; Intelligent Automation Zhuhai Co Ltd
Priority date: 2020-10-12
Filing date: 2020-10-12
Publication date: 2021-09-14
Anticipated expiration: 2030-10-12

Abstract

The utility model provides a low cost, small, high accuracy, efficient 64 passageway electronic switch voltage resistance measuring device. The utility model discloses an input/output interface, the material that awaits measuring go up the electricity and communication interface (J3), measure on the board electricity and communication interface (J4), 4 group 32 select 1 switching circuit, six way switches, programme-controlled constant current source, voltmeter and MCU (1), 32 select 1 switching circuit to include first 16 and select 1 electronic switch (U1), second 16 and select 1 electronic switch (U2) and encoder (U0), input/output interface and 4 group 32 select 1 switching circuit to connect, 4 groups 32 select 1 switching circuit through the switch respectively with programme-controlled constant current source reaches the voltmeter input is connected, programme-controlled constant current source through I2C interface with MCU (1) is connected, the voltmeter through the SPI interface with MCU (1) is connected. The utility model discloses can be applied to the test field.

Description

64-channel electronic switch voltage resistance measuring device

Technical Field

The utility model relates to a measure the field, especially relate to a 64 passageway electronic switch voltage resistance measuring device.

Background

Electronic switches are widely used in modern test equipment and are used for on-off control of signals, current, voltage and the like in the test equipment. However, the quality (contact resistance and stability) of the electronic switch greatly affects the stability and reliability of the testing equipment system, so that more than 10 ten thousand aging and DCR (direct current resistance) tests need to be performed on each batch of electronic switch components, which requires a multi-channel parallel testing system to improve the efficiency and shorten the testing time.

In order to save cost, the industry proposes to reuse the electronic switch on the test equipment on the premise of ensuring quality. This requires 100% testing of these recycled components and the test current is preferably consistent with the actual use. In view of this, it is also necessary to implement programmable adjustment of the current and then to select the good electronic switches according to the test results.

In order to examine the contact impedance and the stability of the electronic switch and improve the testing efficiency, a multi-channel DCR testing system is required to acquire the impedance of each path after each release-press action in real time so as to evaluate the contact stability.

In order to solve the above technical problems, the following schemes are generally adopted in the industry to measure the multi-channel resistance.

1. The current is regulated using an E LOAD, the voltage is measured using a DMM (digital multimeter, such as Keysight 34465 a), the voltage is divided by the current to give a resistance, and a channel switching board is added to achieve multi-channel resistance measurement.

2. The direct current impedance measurement is completed by using a milliohm meter, but the current cannot be adjusted in a program control mode, and the multichannel resistance measurement is realized by adding a channel switching board card.

3. The measurement of the dc impedance is done using an SMU (source measurement unit, e.g. Keithley 2601B), plus a channel switch board to implement multi-channel resistance measurement.

4. A special flying probe tester is used to achieve multi-channel resistance measurements.

However, the above schemes 1 to 3 all use standard instruments, have high cost and low price, only provide single-channel impedance measurement, need to additionally develop a switch board to realize multi-channel measurement, and may use one set of instrument + a plurality of switch boards to expand channels in order to reduce the cost as much as possible, so that the serial test speed is slow, and the serial test is difficult to be widely applied to mass-produced equipment/platforms. In addition, a standard instrument and an external switching board are used, test software needs to coordinate time sequences between various instruments and the board card, the test efficiency is low, and at least 0.5S is needed for measuring one direct current impedance. In addition, the standard instrument used in the schemes 1-3 has large volume and low integration level, and is not suitable for being used in small-size test equipment.

Although the scheme 4 can provide multi-channel resistance measurement, the method is used for open-short circuit testing, and accurate measurement of small resistance (m-omega level) cannot be realized.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that overcome prior art not enough, provide a low cost, small, high accuracy, efficient 64 passageway electronic switch voltage resistance measuring device.

The utility model adopts the technical proposal that: the device comprises an input/output interface, a to-be-detected material charging and first communication interface, a measuring board charging and second communication interface, 4 groups of 32-to-1 switching circuits, a six-way switch, a programmable constant current source, a voltmeter and an MCU, wherein the input/output interface is connected with the 4 groups of 32-to-1 switching circuits, the 4 groups of 32-to-1 switching circuits are respectively connected with the programmable constant current source and the input end of the voltmeter through switches, the programmable constant current source is connected with the MCU through an I2C interface, the voltmeter is connected with the MCU through an SPI interface, the measuring board charging and second communication interfaces are connected with the MCU through a UART interface, the to-be-detected material charging and first communication interface provides power for the to-be-detected material and controls the state of the to-be-detected material, and the MCU is respectively connected with the 32-to-be-selected 1 switching circuits, the programmable constant current source and the voltmeter through an IO interface, the 32-to-1 switching circuit comprises a first 16-to-1 electronic switch, a second 16-to-1 electronic switch and an encoder, wherein the encoder is connected with the first 16-to-1 electronic switch and the second 16-to-1 electronic switch, the encoder performs mutual exclusion on the outputs of the first 16-to-1 electronic switch and the second 16-to-1 electronic switch, the first 16-to-1 electronic switch and the second 16-to-1 electronic switch both perform mutual exclusion on 16 channels of signals, and the input and output interfaces form a 32-channel four-wire voltage resistance measuring system, or a 64-channel two-wire voltage resistance measuring system, or a 64-channel four-wire voltage resistance measuring system.

The input/output interface consists of a 64-channel constant current source interface and a 64-channel differential voltage measurement interface, wherein 1-32 channels of the 64-channel constant current source interface are connected with a first group of 32-to-1 switching circuits, the rest 33-64 channels are connected with a second group of 32-to-1 switching circuits, one output end of the first group of 32-to-1 switching circuits is connected with a positive input electrode of the voltmeter after passing through a first switch, the other output end of the first group of 32-to-1 switching circuits is connected with a high input electrode of the program-controlled constant current source after passing through a second switch, one output end of the second group of 32-to-1 switching circuits is connected with a negative input electrode of the voltmeter after passing through the first switch, the other output end of the second group of 32-to-1 switching circuits is connected with a low input electrode of the program-controlled constant current source after passing through the second switch, and the 1-32 channels of the 64-channel differential voltage measurement interface are connected with a third group of 32-to-1 switching circuits, the rest 33-64 channels are connected with a fourth group of 32-from-1 switching circuits, one output end of the third group of 32-from-1 switching circuits is connected with the low input electrode of the program-controlled constant current source after passing through a third switch, the other output end of the third group of 32-from-1 switching circuits is connected with the negative input electrode of the voltmeter after passing through a fourth switch, one output end of the fourth group of 32-from-1 switching circuits is connected with the high input electrode of the program-controlled constant current source after passing through the third switch, and the other output end of the fourth group of 32-from-1 switching circuits is connected with the positive input electrode of the voltmeter after passing through the fourth switch.

The program-controlled constant current source consists of a power supply, a constant current source circuit and a 16Bits DAC (digital-to-analog converter), wherein the power supply comprises a 30V/1mA power supply and a 1.1V/1A power supply, the constant current source circuit consists of a sampling resistor, an MOS (metal oxide semiconductor) tube and a feedback operational amplifier, and the constant current output current range of the program-controlled constant current source is 1 uA-1A.

The sampling resistor is set to be a three-way switching sampling resistor circuit, and each switching sampling resistor circuit consists of a resistor and a switch.

The voltmeter comprises an input signal conditioning circuit and a 24bits ADC, wherein the input signal conditioning circuit comprises a first following operational amplifier, a voltage division circuit and a second following operational amplifier, the power supply of the input signal conditioning circuit is provided by a low-noise linear voltage stabilizer, and the voltage measurement range of the voltmeter is +/-0.1 mV- +/-5V.

The MCU is selected from a processor with the model number of STM32F 103.

The utility model has the advantages that: the utility model discloses utilize input/output interface, the material that awaits measuring power consumption and first communication interface, measure the board power consumption and second communication interface, 4 groups 32 select 1 switching circuit, six switches, programme-controlled constant current source, voltmeter and MCU's combination constitutes direct voltage resistance measuring device, realize 1uA ~ 100mA current output and-10V- + 10V's voltage measurement, thereby realize 1M omega ~ 1M omega's resistance measurement and diode measurement, in addition 4 groups 32 select 1 circuit, expand 64 passageways with 1 passageway; compared with the prior art, the utility model has the advantages of as follows:

1. the single board provides 64 paths of voltage/resistance/diode measuring channels at most, 512 paths or even 1024 paths of measuring channels can be expanded by a system formed by a plurality of measuring boards, and the single board is very suitable for being used in electronic switch testing equipment;

2. the precision is high, the voltage measurement precision can reach +/-0.1% +/-1 mV within the range of 100 mV-10V, and the voltage measurement precision can reach +/-0.1% +/-0.1 mV within the range of 1 mV-100 mV for mV level signals;

3. the efficiency is high, the utility model only needs 0.1 second for testing the DCR in one path, and at least needs 0.5 second for testing the DCR in one path by the standard instrument and the switching board scheme;

4. the cost is low, if the 64-channel voltage/resistance/diode measurement is needed, the hardware cost of the standard instrument scheme needs more than 1 thousand yuan RMB, and the cost of the testing device of the utility model is within 1 thousand yuan RMB;

5. small volume, with standard instrument patch, system size no less than L W H =400mm 250mm 150mm, the plate scheme size only L W H =80mm 60mm 5mm, the space usage only has instrument scheme 1/400;

therefore, the utility model discloses have the target of realizing high flexibility, high accuracy, high efficiency, low cost, small size, can be used to replace standard DMM milliohmmeter SMU, solve these standard instrument with high costs, test efficiency is low, and is bulky, integrated difficult scheduling problem to in the wide application test equipment, accurate measuring voltage, resistance, diode parameter guarantee product quality.

Drawings

FIG. 1 is a block diagram of a simplified system of the present invention;

FIG. 2 is a simplified schematic diagram of a first 16-to-1 electronic switch U1 of the 32-to-1 switching circuit;

FIG. 3 is a simplified schematic diagram of a second 16-to-1 electronic switch U2 of the 32-to-1 switching circuit;

FIG. 4 is a schematic diagram of the decoder;

FIG. 5 is a simple structure block diagram of the program-controlled constant current source;

FIG. 6 is a schematic diagram of the input signal conditioning circuit;

FIG. 7 is a simplified circuit schematic of the ADC;

FIG. 8 is a schematic diagram of the low noise power supply circuit;

FIG. 9 is a schematic circuit diagram of a core chip of the MCU part;

FIG. 10 is a schematic circuit diagram of the UART communication interface;

FIG. 11 is a circuit schematic of the EEPROM portion;

fig. 12 is a schematic diagram of a GPIO interface of the MCU part.

Detailed Description

The utility model discloses a specifically as follows.

As shown in fig. 1 to 4, the utility model discloses an input/output interface, the material that awaits measuring are gone up the electricity and first communication interface J3, are gone up the electricity and second communication interface J4, 4 groups 32 select 1 switching circuit, six way switches, programme-controlled constant current source, voltmeter and MCU 1 on the measuring board, input/output interface and 4 groups 32 select 1 switching circuit to connect, 4 groups 32 select 1 switching circuit through the switch respectively with programme-controlled constant current source and voltmeter input connection, programme-controlled constant current source pass through I2C interface with MCU 1 is connected, the voltmeter passes through the SPI interface with MCU 1 is connected, on the measuring board electricity and second communication interface J4 pass through the UART interface with MCU 1 is connected, the material is awaited measuring and first communication interface J3 provides the power and carries out state control for the material that awaits measuring, MCU 1 pass through the IO mouth respectively with 32 select 1 switching circuit, The program-controlled constant current source is connected with the voltmeter, the 32-to-1 switching circuit comprises a first 16-to-1 electronic switch U1, a second 16-to-1 electronic switch U2 and an encoder U0, the encoder U0 is connected with the first 16-to-1 electronic switch U1 and the second 16-to-1 electronic switch U2, the encoder U0 performs mutual exclusion on the outputs of the first 16-to-1 electronic switch U1 and the second 16-to-1 electronic switch U2, the first 16-to-1 electronic switch U1 and the second 16-to-1 electronic switch U2 are both 16-channel signals mutually exclusive, and the input and output interfaces form a 32-channel four-wire voltage resistance measuring system, or a 64-channel two-wire voltage resistance measuring system, or a 64-channel four-wire voltage resistance measuring system.

The input/output interface comprises a 64-channel constant current source interface J1 and a 64-channel differential voltage measurement interface J2, the 1-32 channels G1_ 1-G1 _32 of the 64-channel constant current source interface J1 are connected with a first group of the 32-to-1 switching circuit 6_1, the remaining 33-64 channels G2_ 1-G2 _32 are connected with a second group of the 32-to-1 switching circuit 6_2, one output end of the first group of the 32-to-1 switching circuit 6_1 is connected with a positive input electrode VOL _ P of the voltmeter after passing through a first switch S1, the other output end of the first group of the 32-to-1 switching circuit 6_1 is connected with a high input electrode CUR _ HI of the programmable constant current source after passing through a second switch S2, one output end of the second group of the 32-to-1 switching circuit 6_2 is connected with a negative input electrode VOL _ N of the voltmeter after passing through a first switch S1, and the other output end of the second group of the 32-to-1 switching circuit 6_2 of the voltmeter after passing through a second switch S2 A low input electrode CUR _ LO of the current source is connected, 1 to 32 channels G3_1 to G3_32 of the 64-channel differential voltage measurement interface J2 are connected to the 32-selected-1 switching circuit 6_3 of the third group, the remaining 33 to 64 channels G4_1 to G4_32 are connected to the 32-selected-1 switching circuit 6_4 of the fourth group, one output end of the 32-selected-1 switching circuit 6_3 of the third group is connected to the program-controlled low input electrode CUR _ LO of the constant current source through a third switch S3, the other output end of the 32-selected-1 switching circuit 6_3 of the third group is connected to the negative input electrode VOL _ N of the voltage meter through a fourth switch S4, one output end of the 32-selected-1 switching circuit 6_4 of the fourth group is connected to the high input electrode CUR _ HI of the program-controlled constant current source through a third switch S3, and the other output end of the 32-selected-1 switching circuit 6_4 of the fourth group is connected to the positive input electrode VOL _ P4 of the voltage meter.

In the 32-to-1 switching circuit, in order to prevent erroneous operation, 32 signals can be closed at most one at the same time, otherwise, short circuit between external input signals is caused, so hardware mutual exclusion logic must be added, where U1 and U2 are 16-to-1 electronic switches (ADG 1406 of ADI corporation), the highest power supply is 30V, the on-resistance is 9.5 Ω, and a current of 300mA is continuously passed through, and a single chip realizes 16-signal mutual exclusion, but a three-eight decoder chip (74 HC 238) U0 is required to perform mutual exclusion on the outputs of U1 and U2, and a sixth bit IO controls all 32 signals to be completely opened, and the logic truth table is as follows:

TABLE 1 mutual exclusion control circuit truth table

A5	A4	A3	A2	A1	A0	Output of
							0	X	X	X	X	X	U1 and U2 are all disabled and in high impedance state
1	0	0	0	0	0	U1 Enable, U2 Disable, CUR _ VOL _1_ CH1 gating
							1	0	0	1	1	1	U1 Enable, U2 Disable, CUR _ VOL _1_ CH16 gating
1	1	0	0	0	0	U2 Enable, U1 Disable, CUR _ VOL _1_ CH17 gating
							1	1	1	1	1	1	U2 Enable, U1 Disable, CUR _ VOL _1_ CH32 gating

As can be seen from the above table, the circuit can realize the exclusive control of the selection from 32 to 1, and at most one signal in the CUR _ VOL _1_ CH 1-CH 32 is connected with the CUR _ VOL _1 signal at the same time.

In this embodiment, the input/output interfaces J1 and J2 may form a 32-channel four-wire resistor and diode measurement system; can also form 64-channel two-wire resistors, diodes and voltage measurement systems; and by matching with the serial connection design of constant current source signals and materials to be measured in J3, a 64-channel four-wire resistance measurement system can be formed by J1 and J2. The power supply and the IO5_ 1-4 in the J3 are used for supplying power to the material to be measured or controlling the state of the material to be measured, and the J4 provides a power supply input port and a communication interface for the measuring plate. The 4 groups of 32-to-1 switching circuits are completely the same, and have the functions of switching 32 paths of signals to 1 path of signals, selecting a relay during the switching period in order to pass 2A current, adding a 5-32 decoder to realize hardware mutual exclusion in order to prevent short circuit, and then selecting a certain 1 path of signals in the 32 paths through 5 IO ports of the MCU. The S1-S5 switches control the group of switches to select a measurement mode, and specific logics are shown in the following table:

TABLE 2 logic and measurement mode correspondence tables S1-S5

S1	S2	S3	S4	S5	DC resistance test mode
						0	1	0	1	0	32 channel four wire resistance, diode measurement mode, G1&Current of G2, G3&G4 running voltage
1	0	0	0	1	64 channel four wire resistance, diode measurement mode, G1&G2 go voltage, G3&G4 not used
						0	0	0	1	1	64 channel four wire resistance, diode measurement mode, G1&G2 not used, G3&G4 running voltage
1	1	0	0	0	64 channel two wire resistor, diode, Voltage measurement mode, G1&G2 Current and Voltage, G3&G4 not used
						0	0	1	1	0	64 channel two wire resistor, diode, Voltage measurement mode, G1&G2 not used, G3&G4 reference current and voltage

As shown in fig. 7, the program-controlled constant current source comprises a constant current source circuit (comprising a sampling resistor, a MOS transistor and an operational amplifier feedback) and a 16Bits DAC (e.g., AD 5667), and can realize 1 uA-1A constant current output under the control of an MCU IO port and I2C. The voltmeter consists of an instrument operational amplifier (such as AD 8253) with programmable gain and a 24bits ADC (such as AD 7172-2), and can realize voltage measurement of +/-0.1 mV to +/-5V. MCU comprises the minimum system of STM32F103, and the IO mouth is used for controlling 1 ~ 5 circuit, and I2C control DAC, SPI control ADC, EEPROM U7 are used for storing integrated circuit board information and calibration data, UART serial ports and bridging board communication.

The program-controlled constant current source comprises a power supply, a constant current source circuit M1 and a DAC U3 of 16Bits, wherein the power supply comprises a 30V/1mA power supply U4 and a 1.1V/1A power supply U5, the constant current source circuit M1 comprises a sampling resistor, an MOS tube Q1 and a feedback operational amplifier U6, and the constant current output current range of the program-controlled constant current source is 1 uA-1A. The sampling resistor is set to be a three-way switching sampling resistor circuit, and each switching sampling resistor circuit consists of a resistor and a switch.

The utility model discloses consider that the action voltage range of diode TVS voltage regulator tube is wider, consider consumer electronics mainboard test demand simultaneously, current highest voltage is the 20V of USBType-C standard, the action voltage of the TVS that parallels on its interface generally is 24V, and the diode class test generally uses the following electric current of 1mA, so U4 sets up to 30V 1mA output, open short circuit resistance DCR for the test, the electric current scope needs 1A to the maximum, in order not to let the circuit that awaits measuring reach normal operating voltage 1.2V in the test procedure, so U5 sets up to 1.1V 1A output. The DAC part is a digital-to-analog converter and is the key for realizing the control of the current value of the constant current source by a program, the output voltage of the DAC can be set to change from 0V to 5V through I2C of the MCU, and the output voltage can be amplified to the range of 0V to 30V through the operational amplifier. The constant current source part is by sampling resistor and switching circuit, P channel MOS pipe, and the feedback circuit is put to the fortune constitutes, and different current measurement range need use different sampling resistor, for example:

r1=1 Ω, corresponding to a current range of 10mA to 1A, and generating a voltage drop Vdrop ranging from 10mV to 1V,

r2=100 Ω, corresponding to the current flow range of 100 uA-10 mA, the voltage drop Vdrop generated on the capacitor is in the range of 10 mV-1V;

r3=10K Ω, corresponding to a current range of 1uA to 100uA, over which a voltage drop Vdrop occurs ranging from 10mV to 1V.

The voltage VU6- = VU4-Vdrop at the inverting terminal of the operational amplifier U6,

the larger the current is, the larger Vdrop is, the smaller VU6 < - >, when VU6 < - > is smaller than VU6 < + >, the operational amplifier outputs high level, the P-channel MOS tube is cut off, and therefore the current of the control loop is reduced;

the smaller the current is, the smaller Vdrop is, the larger VUS-is, when VU 6-is larger than VU6+, the output low level of the operational amplifier is, and the P communication MOS tube is conducted, so that the current of the control loop is increased.

Through the dynamic adjustment of the negative feedback circuit, the P-channel MOS transistor is finally kept in an impedance state, and the current flowing through the load resistor RL is equal to a set value, so that I = (power voltage VU4 or VU 5-VDAC)/sampling resistor (R1 or R2 or R3).

As shown in fig. 6-8, the voltmeter is composed of an input signal conditioning circuit and a 24bits ADC U21, the input signal conditioning circuit is composed of a first following operational amplifier, a voltage dividing circuit and a second following operational amplifier, the power supply of the input signal conditioning circuit is provided by a low noise linear voltage regulator, and the voltage measurement range of the voltmeter is ± 0.1mV to ± 5V.

As shown in FIG. 6, after the operational amplifier following-voltage dividing-following processing circuit, the voltage of-10V- +10V is attenuated to-5V- +5V, thereby matching the ADC input voltage range. As shown in fig. 7, the ADC chip adopts a 24Bits precision ADC manufactured by ADI corporation, has a maximum sampling rate of 250Ksps, and communicates with the MCU through the SPI interface to complete analog-to-digital conversion of the voltage signal. In order to ensure the measurement accuracy and stability, the power supply of this part of the circuit is very important, and fig. 6 shows a schematic diagram of a low-noise power supply circuit. Wherein, U33 is a low noise linear regulator, the output noise of which is only 20uVrms, and supplies power to the operational amplifier circuit and the ADC; u31 is a precision voltage reference, the output noise is less than 1uVp-p, the initial voltage precision is 0.02%, and the temperature drift coefficient is 2 ppm/DEG C, so as to provide the reference voltage for ADC.

As shown in fig. 9 to 12, the MCU 1 is selected from a processor of model STM32F 103. The part consists of the following parts:

1) u17, MCU, is the core of the whole system, finish the voltage reading through SPI control ADC, regulate the output current value through I2C control DAC, control 1 circuit of selection and constant-current source range through IO port control 32, STMF103 that ST company promoted can meet the demands;

2) u16, for external communication, the board is designed with UART communication interface, which is convenient for the connection between the board and the whole test system;

3) u18, a storage part, which uses EEPROM chip of I2C interface to save board card hardware/software version, production date, test result, calibration data, etc.;

4) and the UART debugging interface and the SWD debugging interface are used for MCU program burning and debugging.

The electronic switch of the utility model has no mechanical contact, does not have the problem of mechanical aging, and theoretically has infinite switching life times; because the 16-to-1 electronic switch is a natural mutual exclusion structure and has high integration level, the circuit design is simple, and the occupied space is only 1/10 of the relay scheme; and no mechanical action is generated in the switching process, so that the switching speed is higher, and the measuring time is shortened.

Claims

1. A64-channel electronic switch voltage resistance measuring device is characterized in that: the device comprises an input/output interface, a to-be-detected material charging and first communication interface (J3), a measuring plate charging and second communication interface (J4), 4 groups of 32-to-1 switching circuits, a six-way switch, a program-controlled constant current source, a voltmeter and an MCU (1), wherein the input/output interface is connected with the 4 groups of 32-to-1 switching circuits, the 4 groups of 32-to-1 switching circuits are respectively connected with the program-controlled constant current source and the input end of the voltmeter through switches, the program-controlled constant current source is connected with the MCU (1) through an I2C interface, the voltmeter is connected with the MCU (1) through an SPI interface, the measuring plate charging and second communication interface (J4) is connected with the MCU (1) through an UART interface, the to-be-detected material charging and first communication interface (J3) provides power for the to-be-detected material and performs state control on-to-be-detected material, and the MCU (1) is respectively connected with the 32-to-be-selected 1 switching circuit, the IO interface, The program-controlled constant current source is connected with the voltmeter, the 32-to-1 switching circuit comprises a first 16-to-1 electronic switch (U1), a second 16-to-1 electronic switch (U2) and an encoder (U0), the encoder (U0) is connected with the first 16-to-1 electronic switch (U1) and the second 16-to-1 electronic switch (U2), the encoder (U0) performs mutual exclusion on the outputs of the first 16-to-1 electronic switch (U1) and the second 16-to-1 electronic switch (U2), the first 16-to-1 electronic switch (U1) and the second 16-to-1 electronic switch (U2) perform mutual exclusion on 16 signals, and the input and output interface forms a 32-channel four-wire voltage resistance measurement system, or a 64-channel four-wire voltage resistance measurement system.

2. A 64-channel electronic switch voltage resistance measuring device according to claim 1, wherein: the input/output interface consists of a 64-channel constant current source interface (J1) and a 64-channel differential voltage measurement interface (J2), 1-32 channels (G1 _ 1-G1 _ 32) of the 64-channel constant current source interface (J1) are connected with a first group of 32-to-1 switching circuits (6 _ 1), the rest 33-64 channels (G2 _ 1-G2 _ 32) are connected with a second group of 32-to-1 switching circuits (6 _ 2), one output end of the first group of 32-to-1 switching circuits (6 _ 1) is connected with a positive input electrode (VOL _ P) of the voltmeter after passing through a first switch (S1), the other output end of the first group of 32-to-1 switching circuits (6 _ 1) is connected with a high input electrode (CUR _ HI) of the programmable constant current source after passing through a second switch (S2), one output end of the second group of the 32-to-1 switching circuits (6 _ 2) is connected with a negative input electrode (VOL _ N) of the voltmeter after passing through a first switch (1), the other output end of the second group of the 32-to-1 switching circuit (6 _ 2) is connected with the low input electrode (CUR _ LO) of the programmable constant current source after passing through a second switch (S2), the 1-32 channels (G3 _ 1-G3 _ 32) of the 64-channel differential voltage measurement interface (J2) are connected with the 32-to-1 switching circuit (6 _ 3) of the third group, the remaining 33-64 channels (G4 _ 1-G4 _ 32) are connected with the 32-to-1 switching circuit (6 _ 4) of the fourth group, one output end of the 32-to-1 switching circuit (6 _ 3) of the third group is connected with the low input electrode (CUR _ LO) of the programmable constant current source after passing through a third switch (S3), the other output end of the 32-to-1 switching circuit (6 _ 3) of the third group is connected with the negative input electrode (VOL _ N) of the voltage meter after passing through a fourth switch (S4), and the other output end of the 32-to-1 switching circuit (6 _ 4) of the third group after passing through a third switch (S3) of the fourth switch (S4) And the high input electrode (CUR _ HI) of the program-controlled constant current source is connected, and the other output end of the fourth group of the 32-to-1 switching circuits (6 _ 4) is connected with the positive input electrode (VOL _ P) of the voltmeter after passing through a fourth switch (S4).

3. A 64-channel electronic switch voltage resistance measuring device according to claim 2, wherein: the program-controlled constant current source comprises a power supply, a constant current source circuit (M1) and a DAC (U3) of 16Bits, wherein the power supply comprises a 30V/1mA power supply (U4) and a 1.1V/1A power supply (U5), the constant current source circuit (M1) comprises a sampling resistor, an MOS (Q1) and a feedback operational amplifier (U6), and the constant current output current range of the program-controlled constant current source is 1 uA-1A.

4. A 64-channel electronic switch voltage resistance measuring device according to claim 3, wherein: the sampling resistor is set to be a three-way switching sampling resistor circuit, and each switching sampling resistor circuit consists of a resistor and a switch.

5. A 64-channel electronic switch voltage resistance measuring device according to claim 1, wherein: the voltmeter comprises an input signal conditioning circuit and a 24bits ADC (U21), wherein the input signal conditioning circuit comprises a first following operational amplifier, a voltage division circuit and a second following operational amplifier, the power supply of the input signal conditioning circuit is provided by a low-noise linear voltage stabilizer, and the voltage measurement range of the voltmeter is +/-0.1 mV- +/-5V.

6. A 64-channel electronic switch voltage resistance measuring device according to claim 1, wherein: the MCU (1) is selected from a processor with the model number of STM32F 103.