CN103604982A - PXI micro-current detection device - Google Patents

PXI micro-current detection device Download PDF

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Publication number
CN103604982A
CN103604982A CN201310581097.5A CN201310581097A CN103604982A CN 103604982 A CN103604982 A CN 103604982A CN 201310581097 A CN201310581097 A CN 201310581097A CN 103604982 A CN103604982 A CN 103604982A
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circuit
micro
operational amplifier
relay switch
current
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CN201310581097.5A
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Chinese (zh)
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CN103604982B (en
Inventor
薛沛祥
乔宏志
秦赞
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中国电子科技集团公司第四十一研究所
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Abstract

The invention discloses a PXI micro-current detection device. The PXI micro-current detection device comprises a control circuit, a micro-current detection circuit and a power supply circuit. The control circuit comprises an FPGA and a PXI interface. The FPGA receives data from a zero groove controller via the PXI interface and sends control commands to the micro-current detection circuit and the power supply circuit. The micro-current detection circuit comprises an I-V conversion circuit and an ADC acquisition circuit. The I-V conversion circuit is provided with two operational amplifier branches. The two operational amplifier branches are switched to access into the I-V conversion circuit by a relay switch in a time-sharing way via the FPGA through control. A same micro-current signal can be measured twice, and the two results are compared and averaged so that influence on the test results caused by instability of large-resistance feedback resistor performance and instability of bias current temperature characteristics is reduced.

Description

The micro-current sensing means of PXI

Technical field

The present invention relates to the micro-current sensing means of a kind of PXI.

Background technology

In scientific research and production run, such as the measurement of leakage current, insulation resistance and other parameter, the measurement of the photocurrent of photoelectric device, photomultiplier and particle and wave beam monitoring and for determining that semiconductor, sensor and the cable etc. of product performance all must carry out micro-testing current.The key of weak current test is that by micro-current conversion be voltage signal, avoid simultaneously as far as possible or get rid of space radiation and other undesired signals of introducing, only pure micro-current signal is converted to voltage signal, voltage signal is after analog to digital converter conversion, by computer acquisition, then be scaled electric current.Micro-electric current test technology has the difficult point of following two aspects: the one, how the voltage signal that can be gathered by analog to digital converter is changed and zoomed into very faint current signal, and the 2nd, thus how to avoid space radiation and other undesired signals change in the lump and amplify and introduce larger error as far as possible.

Existing micro-testing current equipment be take desk-top instrument as main, and as shown in Figure 1, micro-testing current equipment, is mainly comprised of I-V change-over circuit, ADC Acquisition Circuit and master cpu its theory diagram; Wherein the chief component of I-V change-over circuit is amplifier and feedback resistance commutation circuit, and micro-electric currents of corresponding different size, switch different feedback resistances, make the output voltage of I-V drop on all the time ADC Acquisition Circuit can acquisition range in.Because micro-electric current I is to fA(10 -15a) rank, can arrive greatly μ A rank, so the resistance range of feedback resistance is very large, and can be from 100M Ω to 1T Ω (1 * 10 12Ω); Master cpu switches suitable feedback resistance access I-V change-over circuit according to the collection voltage of ADC Acquisition Circuit, makes the output voltage of I-V change-over circuit drop on the good line acquisition district of ADC Acquisition Circuit, reduces measuring error.

In Fig. 1, the theory diagram of I-V change-over circuit as shown in Figure 2.As shown in Figure 2, amplifier is connected into typical sign-changing amplifier, there is no input resistance.Feedback resistance Rfb is a key element, and its resistance selects to depend on desired sensitivity and noise; If for example the feedback resistance Rfb of circuit reaches 1T, the input current of 1pA will cause the output of 1V so, i.e. sensitivity is 1V/pA; Feedback resistance Rfb is also closely related with current noise, and resistance more theoretical noise is less, for example, select 100G, and theoretical noise limit is 0.25fArms; Certainly, feedback resistance Rfb can not obtain too large, because the bias current Ib of amplifier flows through this resistance completely, produces pressure drop, also produces the disadvantages such as noise, temperature coefficient.

For meeting the different ranges of micro-testing current, feedback resistance Rfb is generally in parallel by the resistance of several varying number levels, and adds switch formation resistor network, as shown in Figure 3, corresponding different micro-current ranges, change-over switch is by corresponding feedback resistance access I-V change-over circuit.The selection of amplifier, most important parameter is exactly bias current Ib, and in micro-testing current, the bias current Ib of amplifier must be as far as possible little, must compensate, returns to zero and offset simultaneously.The effect of feedback capacity Cf has two: offset on the one hand input capacitance, improve the response speed that get on rank; Determine on the other hand constant free time of I-V change-over circuit together with feedback capacity Rf.The value of Cf is less, and the response speed of I-V change-over circuit is higher, but can increase output noise.

Existing micro-testing current equipment, as shown in Figure 4, for convenience of controlling and power supply, micro-current testing circuit and control circuit are integrated on a circuit board, this scheme cannot be carried out complete full encirclement shielding to micro-current testing circuit, the circuit board in shielding box outside still can be introduced extraneous spurious signal, and easily introduces the crosstalk signal on control circuit, and shield effectiveness is general.The area of circuit board is larger, is unfavorable for the miniaturization of instrument and integrated.

In addition, the resistance value ratio of the feedback resistance Rfb in I-V change-over circuit is larger, be not only difficult to buy, and precision is not high, and unstable properties, large resistance resistance has capacitance characteristic in addition, and micro-testing current is impacted; While selecting the amplifier in I-V change-over circuit, although the bias current Ib of amplifier is as far as possible little, yet bias current Ib in fact always exists, and the Rfb resistance in I-V change-over circuit is very large, although Ib is very little, on Rfb, can produce pressure drop, cause the inaccurate of test result; And bias current Ib is unstable, can bring current noise, especially its temperature coefficient is very large, meeting disturbed test result to a great extent, temperature is floated and can be brought very large difficulty to data calibration.

Summary of the invention

For the above-mentioned technical matters existing in prior art, the present invention proposes the micro-current sensing means of a kind of PXI, it adopts following technical scheme:

The micro-current sensing means of PXI, comprise control circuit, micro-current sensing circuit and feed circuit, control circuit comprises FPGA and PXI interface, FPGA is received from the data of Zero greeve controller and is sent control command to micro-current sensing circuit and feed circuit by PXI interface, micro-current sensing circuit comprises I-V change-over circuit and ADC Acquisition Circuit, described I-V change-over circuit comprises two operational amplifier branch roads, i.e. the first operational amplifier branch road and the second operational amplifier branch road; On the first operational amplifier branch road, be provided with the first relay switch and the first operational amplifier, one end of the first relay switch is connected to the reverse input end of the first operational amplifier, the input end grounding in the same way of the first operational amplifier; On the second operational amplifier branch road, be provided with the second relay switch and the second operational amplifier, one end of the second relay switch is connected to the reverse input end of the second operational amplifier, the input end grounding in the same way of the second operational amplifier; The other end of the other end of the first relay switch and the second relay switch is connected and as the input end of I-V change-over circuit, and the output terminal of the output terminal of the first operational amplifier and the second operational amplifier is connected and as the output terminal of I-V change-over circuit; Between the input end of I-V change-over circuit and output terminal, be provided with feedback resistance circuit and feedback capacity circuit; It is upper that the control end of the first relay switch and the second relay switch is connected respectively to FPGA, and FPGA controls the first relay switch and the first operational amplifier branch road and the second operational amplifier branch road access I-V change-over circuit are switched in the second relay switch break-make timesharing.

Further, described control circuit also comprises temperature sensor, EEROM and DA acquisition chip, and it is upper that temperature sensor, EEROM and DA acquisition chip are connected respectively to FPGA, and FPGA gathers the voltage signal of micro-current sensing circuit output by DA acquisition chip.

Further, described micro-current sensing circuit is placed on micro-current detecting plate, control circuit is placed on control circuit board, arranged outside at micro-current detecting plate has a shielding box, micro-current detecting plate is placed in the inside cavity of shielding box completely and is fixed, on shielding box, offer power supply interface and optical coupling isolation control interface, feed circuit are that micro-current sensing circuit is powered by power supply interface, and control circuit is connected with micro-current sensing circuit by optical coupling isolation control interface.

Advantage of the present invention is:

The present invention adopts operational amplifier redundancy, two operational amplifier branch roads are set on I-V change-over circuit, by the timesharing of FPGA pilot relay switch, switch two operational amplifier branch road access I-V change-over circuits, can carry out twice measurement to same micro-current signal, and by two times result comparison be averaged, reduced the unstable impact on test result of bias current temperature characterisitic of large resistance feedback resistance unstable properties and operational amplifier; In addition, in control circuit, increase temperature sensor and EEROM, realize the read-write of calibration data, the corresponding a set of calibration data of each temperature spot, eliminates large resistance feedback resistance unstable properties and the impact on test result greatly of operational amplifier bias current temperature coefficient; By micro-current sensing circuit individual screen technology, micro-current sensing circuit is independent of to control circuit and feed circuit, adopt shielding box to carry out the full shielding of surrounding, get rid of to greatest extent the interference that outer signals is micro-testing current, be beneficial to the volume that dwindles shielding box, in PXI module, realize micro-current detection technology, the desk-top instrument of traditional micro-testing current is reduced into modular instrument, on the basis that guarantees measuring accuracy, dwindle volume, reduced power consumption, improved precision, the modularization that has realized micro current instrument, is more conducive to the integrated of system.

Accompanying drawing explanation

Fig. 1 is the theory diagram of micro-current detecting in prior art;

Fig. 2 is the structural representation of I-V change-over circuit in Fig. 1;

Fig. 3 is the structural representation of feedback resistance circuit in Fig. 2;

Fig. 4 is the shielding construction schematic diagram of micro-current sensing circuit in prior art;

Fig. 5 is the circuit structure block diagram of the micro-current sensing means of PXI in the present invention;

Fig. 6 is the structural representation of I-V change-over circuit in the present invention;

Fig. 7 is the shielding construction schematic diagram of micro-current sensing circuit in the present invention.

Embodiment

Below in conjunction with accompanying drawing and embodiment, the present invention is described in further detail:

In conjunction with shown in Fig. 5 to Fig. 7, the micro-current sensing means of PXI, comprises control circuit, micro-current sensing circuit and feed circuit.Control circuit comprises FPGA and PXI interface, and FPGA is received from the data of Zero greeve controller and sent control command to micro-current sensing circuit and feed circuit by PXI interface.

Micro-current sensing circuit comprises I-V change-over circuit and ADC Acquisition Circuit.I-V change-over circuit comprises two operational amplifier branch roads, i.e. the first operational amplifier branch road and the second operational amplifier branch road.

The one end that is provided with the first relay switch S5 and the first operational amplifier 1, the first relay switch S5 on the first operational amplifier branch road is connected to the reverse input end of the first operational amplifier 1, the input end grounding in the same way of the first operational amplifier 1; The one end that is provided with the second relay switch S6 and the second operational amplifier 2, the second relay switch S6 on the second operational amplifier branch road is connected to the reverse input end of the second operational amplifier 2, the input end grounding in the same way of the second operational amplifier; The other end S6 of the other end of the first relay switch S5 and the second relay switch is connected and as the input end of I-V change-over circuit, and the output terminal of the output terminal of the first operational amplifier and the second operational amplifier is connected and as the output terminal of I-V change-over circuit; Between the input end of I-V change-over circuit and output terminal, be provided with feedback resistance circuit and feedback capacity circuit; It is upper that the first relay switch and the second relay switch are electrically connected to respectively FPGA, and FPGA controls the first relay switch and the first operational amplifier branch road and the second operational amplifier branch road access I-V change-over circuit are switched in the second relay switch break-make timesharing.The first operational amplifier 1 and the second operational amplifier 2 preferably adopt LMC6042 series operational amplifier.Feedback resistance circuit adopts resistance circuit as shown in Figure 3, repeats no more herein.

Two operational amplifier branch roads are set on I-V change-over circuit, by the timesharing of FPGA pilot relay switch, switch two operational amplifier branch road access I-V change-over circuits, same micro-current signal is carried out to twice measurement, the result of twice measurement is respectively I 11and I 12if, ︱ I 11-I 12︱≤I 11/ 10, judge that two times result is close two times result is averaged, as net result; If ︱ is I 11-I 12︱>=I 11/ 10, judge that two times result difference is larger, two times result is abandoned, re-start measurement; Same micro-current signal is carried out to twice conversion judged result through different operational amplifier timesharing, avoided the unstable error causing because of amplifier performance as far as possible, and be equivalent to repeatedly measure and average as a result of, the unstable temperature of bringing of bias current Ib that can reduce large resistance feedback resistance Rfb unstable properties and operational amplifier such as floats at the impact.

In addition, control circuit also comprises temperature sensor, EEROM and DA acquisition chip, and it is upper that temperature sensor, EEROM and DA acquisition chip are connected respectively to FPGA, and FPGA gathers the voltage signal of micro-current sensing circuit output by DA acquisition chip.

In actual alignment, temperature is calibrated as an independent factor.During calibration, at-10 ℃, by micro-current signal I of the known current value of standard micro-current source output 0receive on micro-current sensing circuit, test result is designated as I 1, by calibration data △ I 1=I 0-I 1write EEROM, then, in-10 ℃~40 ℃ temperature ranges, take 0.1 ℃ as stepping, by micro-current signal I of the known current value of standard micro-current source output 0receive this micro-current sensing circuit, test result is designated as I i, by calibration data △ I i=I 0-I iwrite EEROM, 1≤i≤501, can obtain the form of the calibration data shown in table 1 like this.

Temperature spot Input micro-current value Survey micro-current value Calibration data -10℃ I 0 I 1 △I 1 -9.9℃ I 0 I 2 △I 2 39.9℃ I 0 I 500 △I 500 40℃ I 0 I 501 △I 501

Table 1

By the test of the micro-current signal of standard to known current value, test data is calibrated under different temperature spots, and deposit calibration data in EEROM; When reality is tested micro-electric current, the current temperature value gathering according to temperature sensor, will read corresponding to the calibration data under this temperature spot in EEROM, for calibrating actual test result, just can eliminate because temperature is floated the test error bringing.

In addition, micro-current sensing circuit is placed on micro-current detecting plate 3, control circuit is placed on control circuit board 4, arranged outside at micro-current detecting plate 3 has a shielding box 5, micro-current detecting plate is placed in the inside cavity of shielding box completely and is fixed, and offers power supply interface and optical coupling isolation control interface on shielding box, and shielding box 5 is placed in back up pad 6, on control circuit, place PXI interface 7, for Zero greeve controller communication.Feed circuit are that micro-current sensing circuit is powered by power supply interface, and control circuit is connected with micro-current sensing circuit by optical coupling isolation control interface, gets rid of to greatest extent the interference of the spurious signal of control circuit to micro-current testing circuit.

Control circuit and micro-current sensing circuit are placed on two boards, have reduced monolithic board area.Micro-current sensing circuit carries out 360 ° of full encirclements and shields, and can avoid the interference of the spurious signal of outer signals and control circuit to micro-current sensing circuit, has so following two advantages: 1. disturb and reduce, can select the higher element of sensitivity of small size; 2. not during individual screen, for preventing disturbing, the spacing of device is as far as possible large, during individual screen, disturb and reduce, the spacing of device can suitably be dwindled, facilitate micro-current sensing circuit to concentrate, make the shielding box volume-diminished of micro-current sensing circuit, be convenient to be integrated in PXI module.

In PXI module, realize micro-current sense function, independent PXI module possesses the function of micro-current detecting, can utilize the superior function of pci bus, this module can be separately to micro-testing current, also with the PXI module integration that possesses other functions, build easily the test macro of the other types with micro-testing current function, for example, build PXI insulation resistance test system with PXI high-pressure modular, or build photocurrent test macro etc. with PXI photocurrent conditioning module.

Certainly; more than explanation is only preferred embodiment of the present invention; the present invention is not limited to enumerate above-described embodiment; should be noted that; any those of ordinary skill in the art are under the instruction of this instructions; that makes is allly equal to alternative, obvious form of distortion, within all dropping on the essential scope of this instructions, ought to be subject to protection of the present invention.

Claims (3)

  1. The micro-current sensing means of 1.PXI, comprise control circuit, micro-current sensing circuit and feed circuit, control circuit comprises FPGA and PXI interface, FPGA is received from the data of Zero greeve controller and is sent control command to micro-current sensing circuit and feed circuit by PXI interface, micro-current sensing circuit comprises I-V change-over circuit and ADC Acquisition Circuit, it is characterized in that, described I-V change-over circuit comprises two operational amplifier branch roads, i.e. the first operational amplifier branch road and the second operational amplifier branch road; On the first operational amplifier branch road, be provided with the first relay switch and the first operational amplifier, one end of the first relay switch is connected to the reverse input end of the first operational amplifier, the input end grounding in the same way of the first operational amplifier; On the second operational amplifier branch road, be provided with the second relay switch and the second operational amplifier, one end of the second relay switch is connected to the reverse input end of the second operational amplifier, the input end grounding in the same way of the second operational amplifier; The other end of the other end of the first relay switch and the second relay switch is connected and as the input end of I-V change-over circuit, and the output terminal of the output terminal of the first operational amplifier and the second operational amplifier is connected and as the output terminal of I-V change-over circuit; Between the input end of I-V change-over circuit and output terminal, be provided with feedback resistance circuit and feedback capacity circuit; It is upper that the first relay switch and the second relay switch control end are connected respectively to FPGA, and FPGA controls the first relay switch and the second relay switch break-make timesharing is switched in the first operational amplifier branch road and the second operational amplifier branch road access I-V change-over circuit.
  2. 2. the micro-current sensing means of PXI according to claim 1, it is characterized in that, described control circuit also comprises temperature sensor, EEROM and DA acquisition chip, it is upper that temperature sensor, EEROM and DA acquisition chip are connected respectively to FPGA, and FPGA gathers the voltage signal of micro-current sensing circuit output by DA acquisition chip.
  3. 3. the micro-current sensing means of PXI according to claim 1, described micro-current sensing circuit is placed on micro-current detecting plate, control circuit is placed on control circuit board, arranged outside at micro-current detecting plate has a shielding box, micro-current detecting plate is placed in the inside cavity of shielding box completely and is fixed, on shielding box, offer power supply interface and optical coupling isolation control interface, feed circuit are that micro-current sensing circuit is powered by power supply interface, and control circuit is connected with micro-current sensing circuit by optical coupling isolation control interface.
CN201310581097.5A 2013-11-19 2013-11-19 PXI micro-current detection device CN103604982B (en)

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Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104090258A (en) * 2014-03-19 2014-10-08 天津市计量监督检测科学研究院 Micro electric-energy controlling device
CN104597316A (en) * 2015-01-08 2015-05-06 聚光科技(杭州)股份有限公司 Weak current detecting device and method
CN105137162A (en) * 2015-07-28 2015-12-09 东华大学 pA current detector
CN105914836A (en) * 2016-05-24 2016-08-31 北京工业大学 Charging-type portable pA micro current monitoring system
CN106645910A (en) * 2016-12-21 2017-05-10 中国电子科技集团公司第三十二研究所 UA grade slim current test system and method suitable for carrier rocket electronic equipment
CN107390009A (en) * 2017-07-28 2017-11-24 北京无线电计量测试研究所 A kind of micro-current test device and method
CN108226603A (en) * 2016-12-13 2018-06-29 保时捷股份公司 For measuring the device and method of the electric current in electric conductor
CN109799378A (en) * 2019-01-08 2019-05-24 北京交通大学 A kind of micro-current sensing circuit

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CN101907654A (en) * 2010-07-20 2010-12-08 西北核技术研究所 Large dynamic weak current detection device for radiation detection
CN201859176U (en) * 2010-11-05 2011-06-08 漳州国绿太阳能科技有限公司 Direct current micro voltage/micro current detection device
CN102620756A (en) * 2012-03-27 2012-08-01 天津大学 Phase sensitive demodulator (PSD) signal single-channel processing method based on modulated laser, and processing circuit
CN102707128A (en) * 2012-01-10 2012-10-03 河南科技大学 Circuit and method for acquiring alternating signal based on microcontroller

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JPH04317217A (en) * 1991-04-17 1992-11-09 Mitsubishi Electric Corp Current detecting circuit
CN101556169A (en) * 2008-04-07 2009-10-14 中国科学院空间科学与应用研究中心 Micro-current amplifier
CN101907654A (en) * 2010-07-20 2010-12-08 西北核技术研究所 Large dynamic weak current detection device for radiation detection
CN201859176U (en) * 2010-11-05 2011-06-08 漳州国绿太阳能科技有限公司 Direct current micro voltage/micro current detection device
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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104090258A (en) * 2014-03-19 2014-10-08 天津市计量监督检测科学研究院 Micro electric-energy controlling device
CN104090258B (en) * 2014-03-19 2017-01-04 天津市计量监督检测科学研究院 Micro-electric energy control device
CN104597316A (en) * 2015-01-08 2015-05-06 聚光科技(杭州)股份有限公司 Weak current detecting device and method
CN105137162A (en) * 2015-07-28 2015-12-09 东华大学 pA current detector
CN105914836A (en) * 2016-05-24 2016-08-31 北京工业大学 Charging-type portable pA micro current monitoring system
CN105914836B (en) * 2016-05-24 2019-03-22 北京工业大学 Chargeable portable pA micro-current monitors system
CN108226603A (en) * 2016-12-13 2018-06-29 保时捷股份公司 For measuring the device and method of the electric current in electric conductor
CN106645910A (en) * 2016-12-21 2017-05-10 中国电子科技集团公司第三十二研究所 UA grade slim current test system and method suitable for carrier rocket electronic equipment
CN107390009A (en) * 2017-07-28 2017-11-24 北京无线电计量测试研究所 A kind of micro-current test device and method
CN107390009B (en) * 2017-07-28 2019-11-29 北京无线电计量测试研究所 A kind of micro-current test device and method
CN109799378A (en) * 2019-01-08 2019-05-24 北京交通大学 A kind of micro-current sensing circuit

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