CN212905145U - High-resistance measuring device capable of automatically adjusting wide measuring range - Google Patents

Abstract

The utility model provides a simple structure, high and accurate high resistance measuring device who can realize the wide measuring range of automatic adjustment of measurement efficiency. The utility model discloses microprocessor control panel (1), signal processing board (2) and passageway switch circuit board (3), be connected through the mode of keeping apart the coupling between microprocessor control panel (1) and signal processing board (2), microprocessor control panel (1) is provided with signal source (11), MCU (12) and system power (13), system power (13) are the power supply of whole device, signal processing board (2) are gone up to be equipped with DC signal source conversion module (22), signal matching channel switches module (23), signal gain adjustment amplifier circuit (24) and ADC analog-to-digital conversion module (25), AC excitation signal and DC signal source conversion module that the coupling got into are kept apart from outlying signal source all switch the module with the signal matching channel and are connected. The utility model discloses can be applied to the test field.

Description

High-resistance measuring device capable of automatically adjusting wide measuring range

Technical Field

The utility model relates to a test field especially relates to a be used for measuring to possess low withstand voltage (operating voltage < 5V) characteristic and impedance range and reach 50M omega to 100T omega (50 x 10)⁶～100×10¹²Ohm) can automatically adjust the high resistance measuring device with wide measuring range.

Background

In the prior art, impedance measurement basically adopts methods such as an electrometer, an SMU, a picometer + voltage source, a high impedance meter and the like. The measurement mode of the electrometer needs to be configured with a voltage source or a current source, so that the high-resistance precise test is realized by using a method of externally connecting a voltage source (source meter) and the electrometer or a picoammeter, thereby obtaining the measurement voltage or current and finally calculating the resistance value by using the ohm law. At present, in the measurement of ultra-high resistance, a plurality of methods are adopted, which are shown in figure 1 and figure 2, and a meter test method using a source meter (a voltage source and a current source) and an electrometer can directly obtain a test value. The high resistance measurement realized by the general electrometer (electrostatic voltmeter) and high resistance meter instruments by the test method shown in fig. 1 and 2 is characterized in that the electrometer (electrostatic voltmeter) and an excitation source (voltage source or current source) are separated. In addition, a source meter and an electrometer are integrated into one instrument by a high-resistance measuring instrument which is popular in the market and is provided with instrument equipment with the model number of B2985A and the like, and then the high resistance is measured by connecting a special matching adapter for the instrument, so that a test value can be directly read on an instrument panel without additional calculation.

However, the prior art has the disadvantages that when the high impedance greater than G omega is measured, the stability time required by the instrument is longer due to the existence of factors such as noise and interference, when an unknown impedance device is measured, the setting adjustment of the gear parameter of a signal source (a voltage source and a current source) can exist, each switching of the gear can be accompanied by a long stability time, so that the measurement efficiency can be reduced, and the disadvantage is more obvious especially in the automatic equipment for batch production; in addition, the inherent standardization characteristics of the instrument reduce the flexibility of testing, and the embedded development and application of the measuring equipment are difficult to realize; the limitation of increasing the application cost is increased.

SUMMERY OF THE UTILITY MODEL

The utility model aims to solve the technical problem that overcome prior art not enough, provide a simple structure, measurement of efficiency height and accurate high can realize the wide measuring range's of automatic adjustment high resistant measuring device.

The technical scheme adopted by the utility model is that the device comprises a microprocessor control board, a signal processing board and a channel switching circuit board, wherein the microprocessor control board is connected with the signal processing board by means of isolation coupling, the microprocessor control board is provided with a signal source, an MCU and a system power supply, the system power supply supplies power for the whole device, the signal processing board is provided with a DC signal source conversion module, a signal matching channel switching module, a signal gain adjusting and amplifying circuit and an ADC analog-to-digital conversion module, the DC signal source conversion module is connected with the signal matching channel switching module, the signal matching channel switching module outputs a signal to the channel switching circuit board, the signal gain adjusting and amplifying circuit is connected with the ADC analog-to-digital conversion module in sequence, the signal gain adjusting and amplifying circuit performs gain adjustment and amplification on a sampling signal output by the channel switching circuit board, the ADC analog-to-digital conversion module outputs signals to the microprocessor control board in an isolation coupling mode, the channel switching circuit board comprises a shunt sampling resistor with multiple gears, a multi-gear resistor selection switch and a second instrument operational amplifier, and a product to be tested is arranged on the channel switching circuit board and is connected with the shunt sampling resistor through the multi-gear resistor selection switch.

The microprocessor control board and the signal processing board respectively realize analog signal isolation, digital signal isolation and control signal isolation through a sinusoidal signal isolation device, an SPI isolation device and a port isolation device.

DC signal source conversion module adopts DAC digital-to-analog conversion module to set for direct current output, DC signal source conversion module still includes reference power supply, high-accuracy voltage divider and passageway switch, reference power supply with high-accuracy voltage divider connects, the output of high-accuracy voltage divider with the passageway switch is connected, the passageway switch exports two ways, is direct current positive voltage output all the way, is direct current negative voltage output all the way, and this two ways output is imported after the switching of fourth relay the passageway switches the circuit board.

The signal matching channel switching module comprises a third relay, a fourth relay, a first electronic switch and a second electronic switch, wherein the first electronic switch and the second electronic switch are arranged on the channel switching circuit board, and the first electronic switch and the second electronic switch selectively switch input alternating current signals, direct current positive voltage signals and direct current negative voltage signals.

The signal gain adjusting and amplifying circuit comprises a sampling signal gain amplifying circuit consisting of an eleventh instrument amplifier and a thirteenth instrument amplifier and an amplifying gain comparing and judging circuit consisting of a seventeenth instrument amplifier and a voltage comparator.

The ADC analog-to-digital conversion module is a collector.

The shunt sampling resistor is divided into four gears, namely Rs1=100M omega, Rs2=1G omega, Rs3=100G omega, and Rs4=1T omega.

And a protection ring is also arranged between the negative input electrode of the second instrument operation and discharge device and the non-connection low end of the product to be tested, and an electromagnetic shielding box is arranged on the periphery of the product to be tested.

The system power supply consists of six power chips UD 1-UD 6.

The utility model has the advantages that: compared with the prior art, the utility model discloses can set up automatically and measure high impedance, low withstand voltage's part, material within 50M omega ~ 100T omega. Compared with the prior art, the method can use a low voltage source to measure and obtain the advantages of higher precision, higher measuring speed and stronger anti-interference capability. And the utility model discloses the hardware of method realizes small, with low costs, so the utility model discloses the equipment that the measurement design was done, small easily realizes the accurate test of high accuracy of this type of high resistant material when quantization production, also is applicable to the verification test in product research and development stage.

Drawings

FIG. 1 is a simplified schematic diagram of a prior art high resistance measurement using an electrometer and an external voltage source;

FIG. 2 is a simplified schematic diagram of a prior art high resistance measurement using an electrometer and an external current source;

FIG. 3 is a block diagram of a simple system of the present invention;

fig. 4 is a schematic diagram of an equivalent circuit of the present invention;

FIG. 5 is a circuit schematic of the system architecture block diagram of FIG. 3;

FIG. 6 is a schematic circuit diagram of the sinusoidal signal isolation device;

FIG. 7 is a circuit schematic of the SPI isolation device;

FIG. 8 is a schematic circuit diagram of the port isolation device;

FIG. 9 is a schematic circuit diagram of the ADC analog-to-digital conversion module;

FIG. 10 is a circuit schematic of the DC signal source conversion module;

FIG. 11 is a circuit schematic of the reference supply and high precision voltage divider;

FIG. 12 is a circuit schematic of the channel switch;

FIG. 13 is a circuit schematic of the first electronic switch;

FIG. 14 is a circuit schematic of the second electronic switch;

fig. 15 is a circuit schematic of the signal gain adjustment amplifying circuit;

fig. 16 is a circuit schematic diagram of the channel switching circuit board;

FIG. 17 is a circuit schematic of a first portion of the system power supply;

FIG. 18 is a circuit schematic of the second portion of the system power supply;

FIG. 19 is a circuit schematic of a third portion of the system power supply;

FIG. 20 is a schematic circuit diagram of a fourth portion of the system power supply;

FIG. 21 is a circuit schematic of a fifth portion of the system power supply;

FIG. 22 is a circuit schematic of a sixth portion of the system power supply;

fig. 23 is a schematic circuit diagram of the electromagnetic shielding box.

Detailed Description

As shown in fig. 3-5, the device includes microprocessor control panel 1, signal processing board 2 and passageway switching circuit board 3, microprocessor control panel 1 with connect through the mode of keeping apart the coupling between the signal processing board 2, microprocessor control panel 1 is provided with signal source 11, MCU12 and system power supply 13, system power supply 13 is the power supply of whole device. In the present embodiment, the model of the MCU12 is STM32F103ZET 6. The signal processing board 2 is provided with a DC signal source conversion module 22, a signal matching channel switching module 23, a signal gain adjusting and amplifying circuit 24 and an ADC analog-to-digital conversion module 25, the DC signal source conversion module 22 is connected to the signal matching channel switching module 23, the AC excitation signal 21 isolated from the peripheral signal source 11 and coupled in is also connected to the signal matching channel switching module 23, the signal matching channel switching module 23 outputs a signal to the channel switching circuit board 3, the signal gain adjusting and amplifying circuit 24 and the ADC analog-to-digital conversion module 25 are connected in sequence, the signal gain adjusting and amplifying circuit 24 and the ADC analog-to-digital conversion module 25 are connected in sequence, and for filtering, a band-pass filter 26 is further disposed between the signal gain adjusting and amplifying circuit 24 and the ADC analog-to-digital conversion module 25, and the chip model of the band-pass filter is AD8422 BRMZ. The signal gain adjustment amplifying circuit 24 performs gain adjustment amplification on a sampling signal output by the channel switching circuit board 3, the ADC analog-to-digital conversion module 25 outputs the signal to the microprocessor control board 1 in an isolation coupling manner, the channel switching circuit board 3 includes a transconductance splitter 32, a shunt sampling resistor Rs with multiple gears, a multi-gear resistor selection switch UK1 and a second instrument operational amplifier U2, and a product Rx to be tested is arranged on the channel switching circuit board 3 and is connected with the multi-gear resistor selection switch UK1 and the shunt sampling resistor Rs through the transconductance splitter 32. In this embodiment, the transconductance shunt is selected from an input bias current electrometer of the type ADA 4530-1.

The microprocessor control board 1 and the signal processing board 2 respectively realize analog signal isolation, digital signal isolation and control signal isolation through a sinusoidal signal isolation device U18, an SPI isolation device U9 and a port isolation device U16. DC signal source conversion module 22 adopts DAC digital-to-analog conversion module U10 to set for direct current output, DC signal source conversion module 22 still includes reference power U22, high-precision voltage divider U21 and passageway switch U15, reference power U22 with high-precision voltage divider U21 connects, high-precision voltage divider U21's output with passageway switch U15 connects, passageway switch U15 outputs two tunnel, is direct current positive voltage output all the way, is direct current negative voltage output all the way, and this two tunnel output switches the back through fourth relay K4 and inputs to passageway switch circuit board 3.

The signal matching channel switching module 23 comprises a third relay K3, a fourth relay K4, and a first electronic switch AD1 and a second electronic switch AD2 which are arranged on the channel switching circuit board 3, wherein the first electronic switch AD1 and the second electronic switch AD2 selectively switch the input alternating current signal, the direct current positive voltage signal and the direct current negative voltage signal. The signal gain adjusting and amplifying circuit 24 comprises a sampling signal gain amplifying circuit consisting of an eleventh instrument amplifier U11 and a thirteenth instrument amplifier U13 and an amplifying gain comparing and judging circuit consisting of a seventeenth instrument amplifier U17 and a voltage comparator U19. The ADC analog-to-digital conversion module 25 is a collector U7. The shunt sampling resistor Rs is divided into four gears, namely Rs1=100M omega, Rs2=1G omega, Rs3=100G omega, and Rs4=1T omega. A protection ring SA is further arranged between the negative input pole of the second instrument operational amplifier U2 and the non-connection low end of the product Rx to be tested, and an electromagnetic shielding box 31 is arranged on the periphery of the product Rx to be tested. The system power supply 13 consists of six power supply chips UD 1-UD 6.

As shown in fig. 4, OP2 in the figure corresponds to U11 in fig. 5. Which shows an equivalent schematic diagram of the device shown in fig. 3, converted to obtain

I=I_RS=V₀/R_S，R_X=V₁/I，V₁=V_REF。

By the aforesaid, the utility model discloses a setting changes the magnitude of the voltage amplitude of VREF and change Rs resistance value, just can change the resistance value range of being surveyed part Rx, also is exactly through setting up Rs and V_REFThe parameters can adjust the measurement range of the high impedance.

As shown in FIG. 4, when Rs sets a resistance, the change in Rx causes OP1 to sample the electrical signal V_ABIf the measured resistance Rx increases, V of the input OP2_ABWill be reduced when V_ABDecreases to V _REF1% to 0.5% of (B), V_ABWill be susceptible to thermal noise, electromagnetic waves, common mode interference, etc., thus directly affecting Vo (like Vout described later) and the final measurement accuracy; at this time, it is necessary to amplify V_ABThe gain, the signal after enlargiing is sent the ADC again and is carried out data acquisition, in order to realize the programmable adjustment of gain, the utility model discloses OP2 lectotype gain controllable instrumentation amplifier, like the gain control table that table 2 instrument fortune was put, can realize that gain programmable control scope is 1 to 1000 times (G =1 ~ 1000).

As shown in fig. 5 to 8, the signal source 11 is a Direct Digital Synthesizer (DDS). Because of the need of the system structuring of the test equipment, the DDS circuit and the microprocessor chip are isolated and placed in the microprocessor control board, so that the data stream of ADC communication and the AC alternating current sine excitation signal source need to be coupled and input through the isolation chip, and the conducted interference of low-frequency common-mode noise is avoided. As shown in the figure, U18 is an isolation design of analog signals, U9 is an isolation design of digital signals, and U16 is an isolation design of control signals, and this design method greatly reduces switching noise (digital noise) interference caused by digital chips such as microprocessors; similarly, the U4 power module in fig. 20 also acts to isolate unknown multi-spectral range noise outside of the high impedance measurement circuit.

As shown in fig. 17 to fig. 22, the utility model discloses consider the noise that anti-interference and conduction disturbance arouse, select the isolation power module of single power input, dual supply ± 12V, 500mA output for use. The utility model relates to a DC work area's voltage suppression ratio performance is very outstanding to fortune in the circuit, nevertheless the utility model discloses still consider alternating current signal because the ascending performance of frequency reduces's characteristics, for the noise that reduces the power rail, the utility model discloses selected LDO chip LT3042 and LT3094 that common mode rejection ratio performance is outstanding as the steady voltage output of dual supply, be used for restraining the switching noise who produces from the isolation power end.

As shown in fig. 9, in the lectotype of ADC analog-to-digital conversion module 25, the utility model discloses synthesize signal acquisition precision and required independent signal channel quantity, the utility model discloses select AD7175 as data collection station, 24 bits, 250KSPS data sampling rate, integrated sigma-delta type analog-to-digital converter is fit for the high resistance measuring signal input of low bandwidth, and built-in digital filter can carry out synchronous suppression to the doubling of frequency (100 Hz/120 Hz) of 50 Hz/60 Hz and power frequency with 27.27 SPS output data rate, and its holding power reaches 86dB, just so fine reduction the utility model discloses receive the radiation influence of power frequency noise. In fig. 9, AIN0 and AIN1 are set to CH1 (channel 1) differential signal inputs, the signal for DC impedance measurement is read from this channel, AIN2 and AIN3 are set to CH2 (channel 2) differential signal inputs, the signal for AC impedance measurement is read from this channel, and V is set_REFBoth the dc and ac sine wave amplitude signals are read from AIN4, which is set to CH3 (channel 3).

As shown in fig. 10, the DC signal source conversion module is implemented by a DAC digital-to-analog converter, and the model thereof is selected from AD5663, which is 16-bit, set from 0-5V rail to rail 250uA, and output in dual channels. V_REFThe test voltage source is set to be 0-5V through the analog output channel A of the chip, and the output current of the chip is only 250uA and is relatively small, so that V is set_REFOne path is sent into a high-resistance measuring loop after being subjected to impedance matching through a U14 buffer, and the other path forms a protection ring circuit through U12. The U10 analog output channel B is used to set the comparison level for the agc, which is implemented by logically comparing the B channel level of U10 with the sampled level output by U17.

As shown in fig. 4, 11 and 12, V_REFThe DC voltage source has two supply modes, one is DAC set value, and can be used for supplying DC voltage to the converterThe parameter setting requirement of automatic control measurement is conveniently met. In addition, the manual measurement control is easy to realize, the U22 reference power supply chip ADR4520 outputs a high-precision voltage of 2.048V, then the U21 carries out high-precision voltage division to generate an output of 1.024V, and the advantage of adopting fixed 1.024V as a source is that the precision is high, the temperature drift is small, and the signal-to-noise ratio is high, and the method can be reflected in the consistency of test data of a plurality of devices. Whether 1.024V is selected as the measurement signal source or the DAC level parameter is set as the measurement signal source can be set by program according to practical application, and if the impedance value of the measured component is in a fixed range, the use of 1.024V is more concise and quicker. The utility model discloses satisfy the measurement of positive negative impedance, the phase inverter circuit is the circuit that is used for providing the negative excitation signal source when measuring the reverse phase impedance.

As shown in fig. 16, on the channel switching circuit board 3, where U1 is an electronic switch, which is a channel control circuit of Rs, both the U1 and U2 adopt the same power rail, and a ± 7.5V dual power supply mode, so as to ensure that the dc impedance can realize the measurement of the forward impedance and the reverse impedance. For the high accuracy and the reliability of assurance circuit, prevent the influence of factors such as noise or electromagnetic interference that circuit loop overlength produced to the core circuit, the utility model discloses peel off out nuclear core part circuit alone, make a completely shielded module, then be connected to through the connector on measuring the mainboard.

The utility model discloses in, on the passageway switches the circuit board, direct current impedance test and alternating current impedance test need realize through the signal channel who switches the relay, the V of direct current impedance test_REFV for testing positive and negative voltage and alternating current impedance_REFThe voltage is switched by electronic switches AD1 and AD2 in FIGS. 13 and 14, and then V meeting the measurement requirement is obtained after signal impedance matching is carried out by U14_REF。

As shown in fig. 3, 4, 5 and 15, on the signal processing board 2, the signal gain adjustment amplifying circuit 24 includes a sampling signal gain amplifying circuit composed of an eleventh instrumentation amplifier U11 and a thirteenth instrumentation amplifier U13, and an amplification gain comparison judging circuit composed of a seventeenth instrumentation amplifier U17 and a voltage comparator U19. The sampling signal gain adjustment amplifying circuit U11 of the measurement channel selects a programmable instrument operational amplifier (here, AD8253 of ADI corporation, or other gain programmable instrument amplifier chips) to realize gain amplification of four gears of 1 time, 10 times, 100 times, and 1000 times (G = 1-1000). In addition, when the AC alternating current impedance is measured, the RC network is disconnected through the switching K2, and the influence of the network on the phase of an alternating current signal is reduced.

The utility model has two working modes of manual and automatic, and V is used manually_REFA fixed value of 1.024V may be selected for use as output by U21 in fig. 11 and 12. If the measurement is automatic, firstly setting the voltage of DAC (shown in figure 10) U10 (default setting is 1V +/-1%), setting the gain to 1 (G = 1) by the programmable controller U11, and controlling the set V through a relay_REFInput to the U2 op amp non-inverting terminal of fig. 16. Thus completing V_REFThe positive pressure of (2) is established. The common mode level of the two ends of the IN + \ IN-of the 1 and 2 pins of the virtual short characteristic of the U2 operational amplifier is kept at the set V_REF(or 1.024V) is unchanged, so the level of the two ends of the product Rx to be tested is also kept at the set V_REFThe upper part is unchanged, so that the tested components (Rx), (Rs), U2 operational amplifier and V_REFThe AGND network forms a series closed loop, and the change of the measured resistance Rx inevitably causes the change of the U11 sampling input voltage in fig. 15, and when the measured resistance is too small, V_outThe voltage exceeds 5V common mode voltage, so that the output of U11 can be clamped and will not increase any more, the data acquisition ADC at the rear end can judge that overflow occurs, the MCU can adjust the U1 programmable port in the graph 16, and the gear position of Rs is increased by one. On the contrary, if the measured resistance is too large, V_outThe voltage will be millivolts and the level V of the output channel B can be simulated by setting the DAC circuit_{OUT_B}As a program control judgment condition, the judgment and comparison parameters from 10mV to 1000mV can be realized according to the linear characteristics of the impedance to be detected. The level obtained by shunting from the tested component Rx can be compared with the V set by the DAC after the output differential level of U11 is output by a U17 precision instrument amplifier_{OUT_B}The level comparison, i.e. the change in Rx causes a change in Vcomp level, Vout = Vcomp, Vcomp > -within the normal measurement rangeV_{OUT_B}Only the resistance of the tested part is increased to Vcomp < V_{OUT_B}When the output level of the U19 is inverted, the changed level is transmitted to the MCU for judgment, and then the MCU adjusts the GAIN control addresses of the U11 programmable ports GAIN _ A0 and GAIN _ A1 in the figure 15, so that the purpose of controlling the GAIN amplification of the U11 voltage signal is achieved.

To sum up, the utility model discloses can solve 50M omega to the automatic range adjustment test of 100T omega within range, reach and accomplish the purpose of measuring rapidly. The utility model is greatly different from the existing testing technology in the market, the equipment designed by the measuring method of the utility model can quickly and accurately complete the high-precision measurement of the measured part, and the working performance is superior; the utility model discloses test method has the scientificity, and the equipment of working out according to this method design, small easily realizes the accurate test of high accuracy of this type of high impedance measurement demand in the production of batches, also is applicable to the verification test and the scientific research pass and so on of product research and development stage.

The utility model is suitable for a surface resistance and the volume resistance test of low withstand voltage insulating material to the insulating direct current impedance of device (material) under test and these characteristic parameters of alternating current impedance all exceed G ohm, reach T ohm even. The method can be applied to analytical instruments and meters and measuring equipment, and measurement in the material research and development process, impedance test of biological medicines, inspection of semiconductor devices and electronic product test. The technology has the characteristic of easy quantitative production test application, and is favorable for obtaining accurate impedance data of the material to be tested in a laboratory or a processing plant and carrying out characteristic analysis and quality monitoring on the material to be tested.

Claims (9)

1. The utility model provides a can realize the high resistance measuring device of wide measuring range of automatic adjustment which characterized in that: the device comprises a microprocessor control board (1), a signal processing board (2) and a channel switching circuit board (3), wherein the microprocessor control board (1) is connected with the signal processing board (2) in an isolation coupling mode, the microprocessor control board (1) is provided with a signal source (11), an MCU (12) and a system power supply (13), the system power supply (13) supplies power to the whole device, the signal processing board (2) is provided with a DC signal source conversion module (22), a signal matching channel switching module (23), a signal gain adjusting and amplifying circuit (24) and an ADC analog-to-digital conversion module (25), the DC signal source conversion module (22) is connected with the signal matching channel switching module (23), the signal matching channel switching module (23) outputs a signal to the channel switching circuit board (3), and the signal gain adjusting and amplifying circuit (24) is sequentially connected with the ADC analog-to-digital conversion module (25), signal gain adjustment amplifier circuit (24) carry out gain adjustment to the sampling signal of passageway switching circuit board (3) output and amplify, ADC analog-to-digital conversion module (25) exports the signal through the mode of isolation coupling on microprocessor control panel (1), passageway switching circuit board (3) are including the reposition of redundant personnel sampling resistance (Rs), many grades of resistance option switch (UK 1) and the second instrument fortune of containing many gears enlarger (U2), and the product (Rx) that awaits measuring sets up on passageway switching circuit board (3) and through many grades of resistance option switch (UK 1) with reposition of redundant personnel sampling resistance (Rs) are connected.

2. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 1, characterized in that: the microprocessor control board (1) and the signal processing board (2) respectively realize analog signal isolation, digital signal isolation and control signal isolation through a sinusoidal signal isolation device (U18), an SPI isolation device (U9) and a port isolation device (U16).

3. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 1, characterized in that: DC signal source conversion module (22) adopts DAC digital-to-analog conversion module (U10) to set for direct current output, DC signal source conversion module (22) still includes reference power supply (U22), high accuracy voltage divider (U21) and passageway switch (U15), reference power supply (U22) with high accuracy voltage divider (U21) are connected, the output of high accuracy voltage divider (U21) with passageway switch (U15) are connected, passageway switch (U15) output two tunnel, are direct current positive voltage output all the way, are direct current negative voltage output all the way, and this two tunnel output switches the back through fourth relay (K4) and inputs to passageway switch circuit board (3).

4. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 3, wherein: the signal matching channel switching module (23) comprises a third relay (K3), a fourth relay (K4) and a first electronic switch (AD 1) and a second electronic switch (AD 2) which are arranged on the channel switching circuit board (3), wherein the first electronic switch (AD 1) and the second electronic switch (AD 2) selectively switch input alternating current signals, direct current positive voltage signals and direct current negative voltage signals.

5. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 1, characterized in that: the signal gain adjusting and amplifying circuit (24) comprises a sampling signal gain amplifying circuit consisting of an eleventh instrument amplifier (U11) and a thirteenth instrument amplifier (U13) and an amplifying gain comparison and judgment circuit consisting of a seventeenth instrument amplifier (U17) and a voltage comparator (U19).

6. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 1, characterized in that: the ADC analog-to-digital conversion module (25) is a collector (U7).

7. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 1, characterized in that: the shunt sampling resistor (Rs) is divided into four gears, namely Rs1=100M omega, Rs2=1G omega, Rs3=100G omega, and Rs4=1T omega.

8. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 1, characterized in that: and a protection ring (SA) is also arranged between the negative input pole of the second instrument operational amplifier (U2) and the non-connection low end of the product (Rx) to be tested, and an electromagnetic shielding box (31) is arranged on the periphery of the product (Rx) to be tested.

9. The high resistance measuring device capable of automatically adjusting a wide measuring range according to claim 1, characterized in that: the system power supply (13) consists of six power supply chips UD 1-UD 6.

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