CN111190054B - Ultrahigh resistance value measuring circuit and device for alternating current characteristic detection - Google Patents
Ultrahigh resistance value measuring circuit and device for alternating current characteristic detection Download PDFInfo
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- CN111190054B CN111190054B CN202010193688.5A CN202010193688A CN111190054B CN 111190054 B CN111190054 B CN 111190054B CN 202010193688 A CN202010193688 A CN 202010193688A CN 111190054 B CN111190054 B CN 111190054B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/14—Measuring resistance by measuring current or voltage obtained from a reference source
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/025—Measuring very high resistances, e.g. isolation resistances, i.e. megohm-meters
Abstract
The invention discloses a super high resistance value measuring circuit and a device for detecting alternating current characteristics, wherein the circuit comprises a voltage signal generating circuit for generating a reference sine wave voltage signal for a measuring circuit and a signal amplifying circuit for amplifying a current signal of the measuring circuit; the signal amplification circuit comprises an operational amplifier and a negative feedback resistor connected to the operational amplifier, the resistance value of the negative feedback resistor is 10-1000G ohms, the current noise of the operational amplifier is less than or equal to 1, and the input bias current is less than or equal to 1pA. Under the alternating current measurement reference circuit, the amplification circuit is improved, the high resistance value can be quickly measured, the resistance value of a test sample can be scanned and measured in a frequency domain, and research and development designers are helped to quickly analyze parasitic parameters of a researched amplification device in the frequency domain.
Description
Technical Field
The invention relates to the field of resistance measuring devices, in particular to an ultrahigh resistance value measuring circuit and device for alternating current characteristic detection.
Background
The ultra-high resistance value measuring device with the resistance value of more than 1G omega is a device for measuring ultra-weak current from pA to fA level under lower voltage so as to measure the ultra-high resistance value, is widely applied to the fields of photoelectric sensors, electrochemistry, piezoelectric materials and the like, and plays an indispensable important role in research work such as sensor circuit design, process research and development, material characteristic detection and the like. Taking an infrared photoelectric sensor as an example, because the ultra-weak photocurrent of the fA level needs to be amplified to mV level signals required by subsequent processing circuits such as an ADC, a feedback resistor exceeding 1G ohm needs to be used in a transimpedance circuit, and some resistors even reach a resistance value of 100G to 1T. Such huge feedback resistance value will make the weak leakage current and parasitic resistance in each link of traditional PCB process and design non-negligible, and the three common non-negligible parasitic resistances are: 1. the electrical property material itself parasitic resistance; 2. PCB board and parasitic resistance produced in its pasting process; 3. the input impedance of the operational amplifier and other components. Therefore, an ultra-high resistance detection circuit and an instrument are required to measure parasitic parameters and adjust design of each link in design and development, so that the photoelectric sensor can achieve a fast and stable working state and an optimal signal-to-noise ratio.
The super-high resistance measuring instruments sold on the market at present use direct current micro-current signal detection as a standard, and achieve the measuring level of low noise and high sensitivity through longer detection time, but only detect direct current signals, that is, only detect the resistance value of parasitic resistance under direct current voltage. For the field of infrared photoelectric sensing signal amplification, weak alternating current signals need to be amplified and processed, for example, civil products need to be processed under alternating current signals of 1 to 10HZ, and military products need to be processed under alternating current signals of dozens of HZ to hundreds of HZ; various parasitic resistors have different resistance characteristics under direct current, alternating current and different frequency points. Therefore, the commercial direct current ultrahigh resistance detection instrument cannot completely meet the requirements of the research and development field of the infrared photoelectric sensor amplification system.
Disclosure of Invention
The present invention provides an ultra-high resistance measurement circuit and device for detecting ac characteristics.
The invention is realized by the following technical scheme:
an ultra-high resistance value measuring circuit for detecting alternating current characteristics comprises a voltage signal generating circuit for generating a reference sine wave voltage signal for a measuring circuit and a signal amplifying circuit for amplifying a current signal of the measuring circuit;
the signal amplification circuit comprises an operational amplifier and a negative feedback resistor connected to the operational amplifier, the resistance value of the negative feedback resistor is 10-1000G ohm, and the current noise of the operational amplifier is less than or equal to
And the input bias current is 1pA or less.
According to the scheme, the alternating voltage signal is adopted to replace a traditional direct current level signal to serve as a measurement reference signal, and the improvement of the resistance value of the sample under the direct current signal to the resistance value under the alternating current signal can be measured only. Under the AC measurement reference circuit, the amplifying circuit is improved, so that the high resistance value can be quickly measured, the resistance value of a test sample can be scanned and measured in the frequency domain, and research and development designers are helped to quickly analyze the parasitic parameters of the researched amplifying device in the frequency domain.
A super-high resistance value measuring device for detecting alternating current characteristics comprises a shell, a shielding shell detachably connected with the shell, a circuit board integrated with a measuring circuit and a test sample socket connected to the circuit board and arranged in the shielding shell. The existing direct current micro-current measuring device uses a long cable to link a test box structure, and the test system has a complex structure and high manufacturing cost; this measuring device adopts the encapsulation of above-mentioned integral type structure, has replaced the structure that traditional long cable linked the test box, has simplified test system's structure and manufacturing cost, greatly reduced test system's price and research and development cost.
Compared with the prior art, the invention has the following advantages and beneficial effects:
1. according to the invention, under the AC measurement reference circuit, the amplification circuit is improved, so that the high resistance value can be rapidly measured, the resistance value of the test sample can be scanned and measured in the frequency domain, and the research and development designer is helped to rapidly analyze the parasitic parameters of the researched amplification device in the frequency domain.
2. The measuring device is packaged by adopting the integrated structure, so that the structure and the manufacturing cost of the test system are simplified, and the price and the research and development cost of the test system are greatly reduced.
Drawings
The accompanying drawings, which are included to provide a further understanding of the embodiments of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principles of the invention.
Fig. 1 is a schematic circuit diagram of the present invention.
Fig. 2 is a perspective view of a package of the present invention.
Fig. 3 is an exploded view of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to examples and accompanying drawings, and the exemplary embodiments and descriptions thereof are only used for explaining the present invention and are not used as limitations of the present invention.
Example 1
An ultra-high resistance value measuring circuit for ac characteristic detection as shown in fig. 1 includes a voltage signal generating circuit DAC for generating a reference sine wave voltage signal for a measuring circuit and a signal amplifying circuit for amplifying a current signal of the measuring circuit; the signal amplification circuit comprises an operational amplifier and a negative feedback resistor connected to the operational amplifier, the signal amplification circuit is an ultramicro alternating current signal amplification circuit, the resistance value of the negative feedback resistor Rfb is 10-1000G ohm, and the current noise of the operational amplifier OPA is less than or equal to
And the input bias current is less than or equal to 1pA. One end of a detected sample RX to be measured is connected with the output end of a voltage signal generating circuit DAC, the other end of the detected sample RX is connected with the inverted input end of an operational amplifier OPA, and a sine wave voltage signal V1 with standard amplitude generated by the voltage signal generating circuit DAC can generate a weak sine wave current signal on RX; the resistance of a detection sample RX is more than 1G omega, the current signal is in a level from PA to fA, the weak current signal needs to be amplified by a transimpedance amplification circuit with an overlarge feedback resistance, and due to the fact that the feedback resistance is extremely large, the operational amplifier used by the transimpedance amplification circuit needs to use a high-performance operational amplifier with ultralow current noise and ultralow input bias current, and the gain-bandwidth product of the operational amplifier with the performance is usually in an MHZ level. The resistance value of the negative feedback resistor Rfb is controlled between 10G ohm and 1000G ohm, and the current noise of the operational amplifier OPA is controlled at
The present invention is suitable for use in amplification and processing of weak ac signals.
Example 2
Based on the above-mentioned embodimentIn principle, the applicant selects the operational amplifier with the negative feedback resistor with different resistance values and different current noise coefficients continuously, and prefers an optimal implementation mode under the condition of considering parameters such as bandwidth, gain, signal-to-noise ratio and the like, namely on the basis of the circuit structure, the resistance value of the negative feedback resistor is 100G ohm, and the current noise of the operational amplifier is 0.4
And the input bias current is 0.2pA. Because 100HZ alternating current signals need to be amplified, the bandwidth of the trans-impedance amplifier must reach 100HZ, and the bandwidth of the high-gain feedback resistance amplifying circuit is greatly influenced by parameters such as operational amplification performance, circuit board parasitic capacitance and the like; meanwhile, the selection of the resistance value of the feedback resistor is very important, the requirements of comprehensive gain and bandwidth, the requirements of signal to noise ratio, the resistance value of an actual resistor device and the magnitude of parasitic parameters are met, and the ultra-high resistance feedback resistor of 100G ohm is very suitable for being applied to the example. Based on the above principle, the resistance of the resistor to be measured is equal to 100G Ω ÷ V2 × V1.
Different from the low-frequency transimpedance amplification circuit of a common direct-current high-impedance instrument in the market, in order to keep the ultrahigh gain, high signal-to-noise ratio and the stability of a loop, the low-frequency ultrahigh-impedance transimpedance amplification circuit can be connected with a PF-level feedback capacitor in parallel at two ends of a feedback loop, namely a feedback resistor, so that the loop is stable. However, in this example, to meet the 100HZ bandwidth requirement, the commercial capacitors are too large and only the PCB parasitic capacitance of less than 0.1PF is needed to meet the loop compensation requirement of the transimpedance amplifier, but because of this, the PCB design needs to be more precise, and the parasitic capacitance of the PCB will have a great influence on the system loop and bandwidth. The circuit of the negative input end of the operational amplifier is the most important, and the wiring from the measured sample to the feedback resistor to the negative input end of the operational amplifier needs to be strictly shielded by an equipotential shielding ring, and the parasitic capacitance of the wiring needs to be strictly controlled. Finally, the 100G gain and 100HZ bandwidth ultra-micro alternating current signal amplifying circuit can be achieved.
Example 3
Besides ensuring the performance realization of the invention in the aspects of component selection and PCB design, the electrical connection between the amplifying circuit and the tested sample is very important, the shorter the electrical connection is, the shorter the interference noise of the amplifying system is, and meanwhile, the whole system needs to be completely grounded to shield 50HZ power frequency interference; in addition, the measuring device needs to have high air tightness to shield the measuring result from the influence of atmospheric humidity and the like. The traditional instrument and meter uses a high-performance triaxial cable to meet the connection requirement, a core amplifying circuit is singly shielded, and the core amplifying circuit is connected with a measurement sample shielding tool through the triaxial cable. This is costly and the convenience of measurement is not strong. Therefore, based on the above measuring circuit, the present embodiment discloses an ultra-high resistance value measuring device for detecting ac characteristics, and referring to fig. 2 and fig. 3, the measuring device includes a housing, a shielding case 4 detachably connected to the housing, a circuit board 2 integrated with the measuring circuit, and a test sample socket 3 connected to the circuit board 2 and disposed in the shielding case 4. Specifically, the housing comprises an upper housing 11 and a lower housing 12, which play a role in shielding and sealing; the shielding case 4 is formed in a cylindrical shape, and an open end thereof is connected to the upper case 11 through a screw structure to be quickly attached to and detached from the case, thereby accomplishing electromagnetic shielding and airtightness. The test sample socket 3 can be made of a high-insulation Teflon material, can be conveniently inserted and detached with a sample to be tested, simultaneously ensures ultralow leakage property, can be welded on the circuit board 2 and directly connected with the ultramicro current amplifying circuit, greatly reduces the length of a key signal link, and reduces parasitic parameters and electromagnetic interference. The input and output cable connections on the circuit board will not include extremely sensitive critical signal links, the input is power and reference voltage, and the output is amplified voltage signal, so that the cost of the input and output cable is greatly reduced, and the device performance is more stable.
When the test device is used, the shielding shell 4 is detached, a prepared test sample such as a large resistor or a PCB sample is inserted into a test sample socket, and then the shielding shell 4 is rotatably installed, so that sufficient electrical connection and airtightness are ensured. The test sample is measured in an environment with good electromagnetic shielding and air tightness, and good signal to noise ratio and test precision are guaranteed.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (2)
1. The ultrahigh resistance value measuring device for detecting the alternating current characteristic is characterized by comprising a measuring circuit, a shell, a shielding shell (4) detachably connected with the shell and a test sample socket (3);
the measuring circuit comprises a voltage signal generating circuit for generating a reference sine wave voltage signal for the measuring circuit and a signal amplifying circuit for amplifying a current signal of the measuring circuit;
the signal amplification circuit comprises an operational amplifier and a negative feedback resistor connected to the operational amplifier, the resistance value of the negative feedback resistor is 10-1000G ohm, and the current noise of the operational amplifier is less than or equal to
The input bias current is less than or equal to 1pA, and the measuring circuit is integrated on the circuit board (2); the casing includes casing (11) and casing (12) down, and test sample socket (3) are arranged in shielding shell (4), and shielding shell (4) are cylindric, and its open end passes through helicitic texture and is connected with last casing (11), and test sample socket (3) adopt high insulating teflon material to make, and test sample socket (3) welding is on circuit board (2).
2. The ultra-high resistance value measuring device for ac characteristic detection according to claim 1, wherein the degeneration resistor has a resistance of 100G ohms and the operational amplifier has a current noise of 100G ohms
And the input bias current is 0.2pA.
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| CN202010193688.5A CN111190054B (en) | 2020-03-18 | 2020-03-18 | Ultrahigh resistance value measuring circuit and device for alternating current characteristic detection |
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| CN202010193688.5A CN111190054B (en) | 2020-03-18 | 2020-03-18 | Ultrahigh resistance value measuring circuit and device for alternating current characteristic detection |
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| CN111190054B true CN111190054B (en) | 2022-12-27 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN1167955C (en) * | 2000-12-16 | 2004-09-22 | 深圳市安圣电气有限公司 | AC method and device for measuring insulation resistance |
| CN203117295U (en) * | 2013-01-24 | 2013-08-07 | 深圳市海洋王照明工程有限公司 | Resistance value detection circuit and device |
| CN106160678B (en) * | 2016-09-06 | 2020-04-21 | 中国核动力研究设计院 | Current sensitive pulse fast amplification system and method and pulse measurement system |
| CN207215905U (en) * | 2017-08-11 | 2018-04-10 | 西安理工大学 | A kind of high-precision AC microresistivity survey instrument |
| CN108267640B (en) * | 2018-01-23 | 2020-05-26 | 北京东方计量测试研究所 | Single-power-supply resistance measuring device |
| CN108594020B (en) * | 2018-04-27 | 2020-05-05 | 陈德文 | Digital display high-sensitivity conductance and high-resistance measuring circuit and method |
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Non-Patent Citations (2)
| Title |
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| A一种宽量程高精度绝缘电阻测量仪设计;王晓俊等;《电子测量与仪器学报》;20120228;第26卷(第2期);第155-160页 * |
| 非线性绝缘介质低频介电响应特性测试技术;郑欢;《中国优秀硕士学位论文全文数据库 工程科技Ⅱ辑》;20080215;第11-15页 * |
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