CN1075552A - Numeral instrument for measuring earth resistance - Google Patents

Numeral instrument for measuring earth resistance Download PDF

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Publication number
CN1075552A
CN1075552A CN 92114685 CN92114685A CN1075552A CN 1075552 A CN1075552 A CN 1075552A CN 92114685 CN92114685 CN 92114685 CN 92114685 A CN92114685 A CN 92114685A CN 1075552 A CN1075552 A CN 1075552A
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switch
resistance
constant current
earth resistance
source
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胡学军
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Abstract

The present invention relates to numeral instrument for measuring earth resistance, it is made up of feed circuit, square wave alternation pulsation constant current source, high resistant input buffer, rejection filter, switch synchronizing indicator, low-pass filter, A/D converter, display etc., and square wave alternation pulsation constant current source is that amplitude can be provided is the many-valued pulsation constant current source of 10mA, 1mA, 0.1mA or other amplitude.Advantage of the present invention is, has been completely free of the tactic pattern of existing ground connection megger, used alternation pulsation constant current technology, thereby guaranteed measuring accuracy, in the employing, large scale integrated circuit, makes that device volume is little, circuit performance is reliable and stable.

Description

Numeral instrument for measuring earth resistance
The present invention relates to a kind of pick-up unit of measuring the grounding resistance of various earthing device, particularly a kind of numeral instrument for measuring earth resistance.
At present, detect the instrument of the grounding resistance of earthing device, it mainly is the earthing test megger, ZC-8 as the production of news from Beijing Watch Factory, it adopts current and voltage method to measure, this device produces the exchange current of test usefulness with hand generator, the alternating voltage that this exchange current produces in tested resistance is fetched in the table through the potential test utmost point, compare with the same electric current alternating voltage that mutual inductor obtains in showing again, use the phase sensitive detection principle, by regulating the mode of magneto-electric ammeter pointer balance, read measurement result from indicating graduation, because the inclination angle that instrument is placed is different and the influence at observation balanced pointers visual angle, and operating personnel's rocking when shaking megger, make that measuring read value has than mistake.Especially there is stray earth current when tested zone, when perhaps the auxiliary earth resistance in the test changes, the accuracy of measurement result will be had a strong impact on, in this case, the cumulative maximum error of measuring (representing with class index) reaches 400%, obviously, such margin of error is the needs of incompatibility engineering and maintenance work.
Purpose of the present invention is exactly at above-mentioned the deficiencies in the prior art, proposes a kind of new numeral instrument for measuring earth resistance.
Technical solution of the present invention is, it is characterized in that, feed circuit have been adopted, square wave alternation pulsation constant current source, high resistant input buffer, rejection filter, switch synchronizing indicator, low-pass filter, A/D converter, feed circuit link to each other with many-valued direct-flow voltage regulation source, many-valued direct-flow voltage regulation source and many-valued pulsating volage source and square wave alternation pulsation constant current source connect, high resistant input buffer and rejection filter and wave detector connect, wave detector and A/D converter connect, rejection filter links to each other f with the switch synchronizing indicator.Oscillator links to each other with the switch synchronizing indicator with many-valued pulsating volage source respectively, and the switch synchronizing indicator links to each other with low-pass filter, and low-pass filter and A/D converter connect, and A/D converter and display join.The input end of high resistant input buffer is furnished with potential probes.
It is characterized in that it is 10mA, 1mA, 0.1mA(or other amplitude that square wave alternation pulsation constant current source provides amplitude) many-valued pulsation constant current source, it is furnished with the electric current output stage.
It is characterized in that low-pass filter connects by switch and A/D converter.
Basic design of the present invention is, inject measuring current through tested earthing device to the earth from an electric current utmost point, this measuring current has the alternation pulsating current of a fixed frequency, get back to the measurement mechanism proposed by the invention from another electrode again, because this electric current can produce corresponding alternation pulsating volage on the stake resistance of tested earthing device of flowing through, after this voltage is retrieved measurement mechanism, deliver to rejection filter through the high resistant input buffer, filtering 50Hz power frequency is disturbed, remove to control relevant analog switch with the switching frequency identical again with alternation pulsation constant current, carry out the switch synchronous detection to fetching useful pulsating volage, electric signal after the detection is through the low pass filter filters out mixed and disorderly undesired signal different with measurement mechanism work test frequency, guarantee to pass through with the DC voltage that frequency difference goes out, send this to A/D converter with the DC voltage that tested grounding resistance of transmission resistance is directly proportional at last, from digital indicator, directly read the stake resistance resistance of surveying.
According to this design, its measuring process is:
A, to send a frequency by the electric current utmost point of the present invention be f.Alternation pulsating current I., the positive and negative amplitude of this electric current, width equate and are steady state value that it is at the stake resistance R of tested earthing device EVoltage U of last generation.＝I。.R E。
B, through the current potential of the present invention input utmost point voltage at earth potential probe place is fetched in the present invention, behind the filtering 50Hz power frequency component, in frequency f.Control under carry out switch and detect.Because the voltage that is taken into is U.The electric signal that combines with the stray voltage of other various frequencies, thereby with f.The electric signal U that detects for switching frequency IIn will contain the corresponding composition of various stray voltages, U I=U D+ U A
U wherein DBe direct current signal, it is U.In frequency f.The electric signal of the direct current composition that allowance below nominal size goes out, obviously U DSize be proportional to I.And R E, U ABe non-f.The stray voltage detecting signal of frequency, its frequency is: f.+f X1，f。-f X1，f。+f X2，f。-f X2…f。+f Xn，f。-f Xn(f X1～f XnBe power frequency and other various frequencies), its amplitude is proportional to the magnitude of voltage of corresponding frequencies in the potential probes place ground voltage.
C, with U XBe added to the input end of low-pass filter, set low pass filter cutoff frequency f LFar below U XLow-limit frequency in the frequency, thereby that will obtain at the output terminal of low-pass filter is a DC voltage KU D(K is the transmission coefficient of low-pass filter), obviously the size of this voltage only depends on I.And R EValue because I.Amplitude be definite value, so just obtained its value only with R EBe correlated with and linear voltage, i.e. U C=CR E(C=KI.）。
D, Uc is sent into A/D converter, from digital indicator, directly read R EValue.
The invention has the advantages that, it has been completely free of the tactic pattern of present ground connection megger, adopted alternation pulsation constant current technology, make the current value that is used to test keep stable, and remove the outmoded mode that the manpower work done produces measuring current, make device volume little easy to operate, the present invention is provided with the high resistant input buffer, greatly reduce the measuring error that the change of potential pole auxiliary earth resistance causes, adopted the rejection filter of 50Hz, can make more than the 50Hz power frequency interference signals decay 40db, thereby the signal to noise ratio (S/N ratio) and the measuring accuracy of device have been improved, make the complete machine antijamming capability further strengthen with switch detection frequently, the measurement result after the A/D conversion can directly read by display, has avoided the artificial collimation error.The main circuit device that the present invention uses all adopts universal big medium scale integration (MSI), circuit performance is reliable and stable, scope intrinsic resolution 0.1～2000 can reach 0.001,0.01,0.1,1, and relative error is no more than 3%, the present invention can use powered battery, have portable function, in sum, the present invention is the comparatively desirable measurement mechanism that replaces traditional earthing test megger.
Fig. 1, overall circuit block scheme of the present invention
Fig. 2, the electrical schematic diagram in many-valued pulsating volage of the present invention source
Fig. 3, the electrical schematic diagram of square wave alternation pulsation constant current source of the present invention
Fig. 4, the electrical schematic diagram of high resistant input buffer of the present invention
Fig. 5, the electrical schematic diagram of the high resistant input buffer of another kind of form of the present invention
Fig. 6, the electrical schematic diagram of rejection filter of the present invention
Fig. 7, switch synchronizing indicator electrical schematic diagram of the present invention
Fig. 8, the electrical schematic diagram of low-pass filter of the present invention
Fig. 9, basic structure synoptic diagram of the present invention
Figure 10, the rear view of basic structure synoptic diagram of the present invention
Figure 11, the cut-open view of the rear view A-A of basic structure synoptic diagram of the present invention
Figure 12, the B-B of the rear view of basic structure synoptic diagram of the present invention is to cut-open view
Embodiments of the invention are described below with reference to the accompanying drawings:
As shown in Figure 1, the present invention is by square wave alternation pulsation constant current source 1, many-valued pulsating volage source 2, many-valued direct-flow voltage regulation source 3, DC power-supply circuit 4, high resistant input buffer 5, rejection filter 6, switch synchronizing indicator 7, low-pass filter 8, A/D converter 9, display 10, f.Oscillator 12 is formed.DC power-supply circuit 4 adopts 9 volts of power supplys, supplying with full machine work uses, many-valued direct-flow voltage regulation source 3 connects with DC power-supply circuit 4, the output terminal of many-valued direct-flow voltage regulation source 3 connects with many-valued pulsating volage source 2 and square wave alternation pulsation constant current source 1 respectively, different working direct current voltage stabilizings is provided, many-valued pulsating volage source 2 connects square wave alternation pulsation constant current source 1, provides alternating constant-current required pulsating volage, f.Oscillator 12 connects with many-valued pulsating volage source 2 and switch synchronizing indicator 7, provides with the frequency control signal to two element circuits respectively.High resistant input buffer 5 connects with rejection filter 6, wave detector 11 respectively, rejection filter 6 connects with switch synchronizing indicator 7, switch synchronizing indicator 7 joins with low-pass filter 8, low-pass filter 8 and wave detector 11 by switch K with connect with A/D converter 9 respectively, A/D converter 9 connects digital indicator 10.Measuring the required measuring current of earthing pole earth resistance resistance is that electric current utmost point C end is sent by the output terminal of square wave alternation pulsation constant current source 1, from another electrode E(or C 2) flow back in the machine, the relevant voltage that produces in its earth between earth potential best earth point is from E(or C 2), P holds (P 1, P 2End) fetch in the machine, deliver to rejection filter 6 and wave detector 11 after high resistant input buffer 5, wave detector 11 is used for the detection to the power frequency ground voltage, and its value is sent into A/D converter 9 and converted power frequency ground voltage value to.After the rejection filter 6 filtering 50Hz power frequencies, useful test signal is sent into switch synchronizing indicator 7, and in frequency f.Control under be detected, the signal that detects send low-pass filter 8 again, after the filtering AC signal, its useful direct current signal is admitted to A/D converter 9, can the tested earth resistance resistance of direct-reading from digital indicator 10.
As shown in Figure 2, many-valued pulsating volage source 2 is by resistance R 1, R 2, R 3, R 4, R 5, R 6, R 7, R 8, analog gate G 1, G 2, inverting amplifier A 1, current source A 2, selector switch 8 and triode T 1, T 2Form R 1One termination analog gate G 1Input end D, R 1The other end and R 3And A 1End of oppisite phase join A 1In-phase end pass through R 2The device ground of meeting sb. at the airport, R 3Other end fishplate bar phase amplifier A 1Output terminal be analog gate G 2Input end, analog gate G 1Control end G 1', analog gate G 2Control end G 2' be subjected to the control of switching signal, analog gate G 1, G 2Output terminal with meeting R 4, R 4Another termination A 2In-phase input end, at A 2In-phase input end and machine ground between be connected to capacitor C 1, at A 2Inverting input be connected to switch S, select different stake resistance R by switch S S1R Sn, triode T 1, T 2Base stage with being connected on A 2Output terminal, R 5, R 6With being connected on T 1Collector, R 7, R 8With being connected on T 2Collector, R 5, R 6Tap power supply+V 1,+V 2, R 7, R 8Tap power supply-V 1,-V 2, T 1, T 2The emitter of two pipes is connected to A mutually 2Inverting input.A wherein 1Be 1: 1 inverting amplifier, its output voltage is-V R, V R,-V RThrough G 1, G 2Analog gate is at G 1', G 2Deliver to A under the control of ' switching signal 2In-phase input end, A 2Be the one-level current source, select A through switch S 2The different stake resistance of end of oppisite phase can obtain the T that flows through 1, T 2Different current values, this electric current is at T 1, T 2Collector alternately produce required fixed ampllitude voltage.R 5=R 7, R 6=R 8Thereby, at T 1, T 2Collector obtain the alternate pulsation voltage of symmetry.Different R through the switch S selection SValue can obtain different pulsating volage values, R 4, C 1Thereby constitute delay circuit and make V R,-V RThrough G 1, G 2, pass through R 4, C 1A is delivered in time-delay again 2In-phase input end, A has slowed down 2The rate of change of output current zero passage satisfies T 1, T 2Conducting have time enough at interval, R 5, R 6, R 7, R 8With positive and negative V 1, V 2Connect.
As shown in Figure 3, square wave alternation pulsation constant current source 1 is by A 3, A 4, T 3, T 4, R 9, R 10Form A 3, A 4In-phase input end A, B meet T respectively 1, T 2The collector of pipe, inverting input meet T respectively 3, T 4The emitter of pipe, A 3, A 4Output terminal meet T respectively 3, T 4The base stage of pipe, T 3, T 4The collector of pipe links to each other and constitutes output terminal C, R 9Be connected on T 3The emitter of pipe and+V 1Between, R 10Be connected on T 4The emitter of pipe and-V 1Between.Along with the variation of A, B point alternate pulsation voltage, T 3, T 4The pipe alternate conduction is ended, and output terminal C is an electric current output stage of square wave alternation pulsation constant current source 1, and another electrode is machine ground E, (if will be named as C in the type of four electrodes 2, the amplitude of electric current only with A, B point voltage amplitude and R 9, R 10Resistance relevant.V 2Absolute value greater than V 1, make T 1Collector potential is higher than+V in off period 1, T 2Its collector potential is lower than-V in off period 1, to guarantee T 3, T 4The alternately break-make of pipe.
High resistant input buffer 5 as shown in Figure 4 is a kind of type circuit of three test electrodes, and only the follower of forming for the one-level transport and placing device has an input end P and an output terminal F, and this transport and placing device can adopt CA 3140The general-purpose device of one class because the employing of follower, makes input impedance that P orders up to 10 11More than, thereby greatly reduced the change of potential test utmost point auxiliary earth resistance and the measuring error that causes.
High resistant input buffer 5 as shown in Figure 5 is type circuit of a kind of four survey electrodes, by two independent follower A 7And A 8With a differential amplifier A 9Connect composition.Two input utmost point P, P are arranged 2, an output stage F.
Rejection filter 6 as shown in Figure 6, it is a typical R C twin-T network structure, centre frequency 50Hz can reach more than the 40dB in the decay on the centre frequency, can improve the signal to noise ratio (S/N ratio) of measured signal like this.
As shown in Figure 7, switch synchronizing indicator 7 is by A 10, A 11, A 12, G 3, G 4, R 17, R 18, R 19, R 20, R 21, R 22, C 2, C 3Form A 10And respective element composition low-pass amplifier, the amplitude that the restriction higher hamonic wave is disturbed, frequency is by R 18With C 2Product decision, A 11And corresponding resistor constitutes 1: 1 inverting amplifier, A 10, A 11Output be added to analog switch G respectively 3, G 4An input end, G 3, G 4Another output terminal and connect after again through R 22, C 3To A 12Output is at G 3', G 4Finish the switch synchronous detection under the control of ' switching signal, because A 11Be 1: 1 phase inverter, A 10Accumulation in the past belongs to shift error also can be at C 3Last elimination.R 22, C 3Constitute the single order low pass simultaneously.Square wave alternation pulsating volage and undesired signal that the square wave alternation pulsating current of being exported by instrument produces on tested earth resistance together enter in the machine, and filtering power frequency 50Hz is added in the H point after disturbing, through A 10After doing the homophase amplification, the one tunnel directly delivers to analog gate G 3Input end, the one tunnel again through A 11Do to deliver to analog gate G after 1: 1 anti-phase 4Input end, G 3', G 4' be the switch control end, the frequency of its frequency and square wave alternation pulsating current is same frequency, and G 3', G 4' signal be anti-phase, like this, at G 3, G 4The analog gate output terminal, except that the tested one-tenth direct current signal of homogenous frequency signal, all the other all non-homogenous frequency signals all become alternating signal, through R 22, C 3A smothing filtering is by A 12Output.C 2, R 18Constitute the single order low pass, to suppress the amplitude of higher hamonic wave undesired signal.G wherein 3, G 4Available CD 4066Analog gate.
As shown in Figure 8, low-pass filter 8 is by R 23, R 24, R 25, R 26, C 4, C 5, A 13Form, its cutoff frequency is by R 24, R 25, C 4, C 5Decision, the direct current enlargement factor is by R 24/ R 23Decision, A 13Can adopt CA 3140One class operational amplifier.
What deserves to be mentioned is G 1', G 2', G 3', G 4' switch controlling signal be same frequency, differ fixing pulse signal, wherein G 1' with G 2' anti-phase, G 3' with G 4' anti-phase, frequency is the fixed frequency between the 310Hz-610Hz.
According to Fig. 1, Fig. 2, Fig. 3, Fig. 4, (or Fig. 5), Fig. 6, the same-sign of the input and output end points that Fig. 7 provides links up foregoing circuit, has just constituted the overall circuit figure of the embodiment of the present invention's recommendation, is enough to reproduce the present invention according to this overall circuit schematic diagram.
As Fig. 9, Figure 10, Figure 11, basic structure of the present invention shown in Figure 12, that the overall circuit schematic diagram (shown in preceding Fig. 1～7) that proposes according to technical solution of the present invention provides is with DC power-supply circuit 4, many-valued direct-flow voltage regulation source 3, many-valued pulsating volage source 2, square wave alternation pulsation constant current source 1, high resistant input buffer 5, rejection filter 6, switch synchronizing indicator 7, low filter 8, A/D converter 9, display 10, f.Oscillator 12, wave detector 11 is packed in the casing 13, range switch 15 is housed on the shell 13, power switch 16, current start switch 23, external direct current power supply jack 24, alternator indicator 22, E utmost point jack 17, P utmost point jack 18, C utmost point jack 19, numeral display window 21, nameplate 20, range switch 15 is a switch S, K, it is a multi-gear switch, can select upper limit range respectively is 2,20,200 and ground voltage test (0～19.99V), E, P, C utmost point jack respectively with the E of circuit, P, the C end points links to each other, and shell 13 is by loam cake 35, lower cover 32 is formed, by screw 25,37 are connected as a single entity.Shell 13 is a plastic pressuring piece, battery case 26 is arranged on the lower cover 32, battery case lid 27 is arranged on the battery case 26, have power feeder 28,30 to draw from battery case 26, join by plug-in unit 29,31 and circuit board 36, circuit board 36 is fixedly mounted in the shell 13, loam cake 35, lower cover 32 inside surfaces all are equipped with radome 28, and the machine ground on the circuit board 36 is connected with radome 28 on the lower cover 32 by electroconductive elastic sheet 34, and the various components and parts of circuit 1～12 are installed on the circuit board 36.Circuit board 36 is reasonable in design.Various components and parts are universal, and display adopts 3 1/2 LCDs, and dc power supply is 9V, select No. 5 batteries of 6 joints for use or pass through the power supply of external direct current power supply jack 24 external direct current power supplies.
Basic test working condition of the present invention is: according to the situation of tested earthing device, an auxiliary current utmost point C is set, an auxiliary potential pole P, tested earth polar is linked the E utmost point jack 17 of instrument with lead, auxiliary current utmost point C links the C utmost point jack 19 of instrument, auxiliary potential pole P links potential pole jack 18, energized is selected suitable range with range switch, and starting current is after alternator indicator 23 becomes clear, square wave alternation pulsation constant current is just by E feed-in the earth, flow back to instrument from C, and at E, produce corresponding square wave alternating voltage between P, because current amplitude is constant, so the amplitude of square-wave voltage is only relevant with tested earth resistance resistance, and be directly proportional E, this square-wave voltage between P together with voltage intrusively together from E, the P end is taken in the machine, through filtering, the switch synchronous detection, after the filtering, obtain a direct supply U again C=CR E(C=KI.，I。Be current amplitude), with voltage U CDeliver to the input end and the suitably selected A/D converter 9(ICL of A/D converter 9 7106) reference voltage can be from digital indicator 10(liquid crystal display) go up the grounding resistance that direct-reading goes out tested earthing device, owing to adopted high resistant input buffer 5, greatly reduced of the influence of potential test utmost point auxiliary earth changes in resistance, simultaneously again because the output voltage V of many-valued direct-flow voltage regulation source 3 to the test value accuracy 1Absolute value satisfy following relationship formula: V 1＞V.+ Ic(rmax+Rcmax)+V SWherein: V.For maximum allows the interference voltage value,
Rmax is maximum tested grounding resistance
Rcmax is a maximum current utmost point auxiliary earth resistance value,
V SBe T 1, T 2The triode saturation voltage drop
Ic 1Be pulsation constant current amplitude.
Thereby can guarantee that the interference voltage in the maximum ground voltage scope that allows can not impact test.
The results showed that measurement result of the present invention is better than the accuracy and the precision of existing earth resistance device greatly, we can say, the desirable earthing test device of megger traditionally that substitutes really of the present invention.

Claims (10)

1, numeral instrument for measuring earth resistance, it is characterized in that adopting feed circuit (4), square wave alternation pulsation constant current source (1), high resistant input buffer (5), rejection filter (6), switch synchronizing indicator (7), low pass filter (8), A/D converter (9), wherein, DC power-supply circuit (4) links to each other with many-valued direct-flow voltage regulation source (3), many-valued direct-flow voltage regulation source (3) links to each other with square wave alternation pulsation constant current source (1) with many-valued pulsating volage source (2), high resistant input buffer (5) links to each other with wave detector (11) with rejection filter (6), rejection filter (6) links to each other with switch synchronizing indicator (7), switch synchronizing indicator (7) links to each other with low-pass filter (8), low-pass filter (8) links to each other with A/D converter (9) through switch K, A/D converter (9) joins f with digital indicator (10).Oscillator (12) connects with many-valued pulsating volage source (2) and switch synchronizing indicator (7).
According to the described numeral instrument for measuring earth resistance of claim 1, it is characterized in that 2, many-valued pulsating volage source (2) is by R 1, R 2, R 3, R 4, R 5, R 6, R 7, R 8, C 1, A 1, A 2, G 1, G 2Deng composition, A wherein 1Be 1: 1 inverting amplifier, its output voltage is-V R, V RWith-V RThrough G 1, G 2Analog gate is at G 1', G 2Deliver to A under the control of ' switching signal 2In-phase input end, A 2Be the one-level current source, select A through switch S 2The grounding resistance that end of oppisite phase is different can obtain the T that flows through 1, T 2Different current values, this electric current is at T 1, T 2Collector alternately produce required fixed ampllitude voltage.
3, according to the described digitally resistance of claim 2 table, it is characterized in that V R,-V RThrough G 1, G 2, pass through R 4, C 1Deliver to A after the time-delay 2In-phase input end so that T 1, T 2Conducting have time enough at interval.
4, according to the described numeral instrument for measuring earth resistance of claim 2, it is characterized in that T 1Collector has R 5Connect+V 1, R 6Connect+V 2, T 2Collector has R 7Connect-V 1, R 8Connect-V 2, V 2Absolute value greater than V 1, make T 1Collector potential is higher than+V in off period 1, T 2Its collector potential is lower than-V in off period 1, to ensure T 3, T 4Alternately break-make.
According to the described numeral instrument for measuring earth resistance of claim 1, it is characterized in that 5, square wave alternation pulsation constant current source (1) is by A 3, A 4, T 3, T 4, R 9, R 10Form A 3, A 4In-phase input end meet T respectively 1, T 2Collector; Output terminal meets T respectively 3, T 4Base stage, inverting input meets T respectively 3, T 4Emitter, T 3, T 4Emitter resistance R 9, R 10Connect respectively+V 1With-V 1, T 3, T 4Collector link to each other, constitute an electric current utmost point C of square wave alternation pulsation constant current source (1), another electric current very machine ground E(four electrode types is named C 2).
According to the described numeral instrument for measuring earth resistance of claim 1, it is characterized in that 6, the high resistant input buffer (5) of three test pole types is by a follower A 5With the wave detector A that is connected on thereafter 6Form, the high resistant input buffer (5) of four test pole types is by two follower A 7, A 8With a differential amplifier A 9Form.
According to the described numeral instrument for measuring earth resistance of claim 1, it is characterized in that 7, rejection filter (6) is made of common RC twin-T network, centre frequency is 50Hz.
According to the described numeral instrument for measuring earth resistance of claim 1, it is characterized in that 8, switch synchronizing indicator (7) is by A 10, A 11, A 12, G 3, G 4, R 17, R 18, R 19, R 20, R 21, R 22, C 2, C 3Form A 10And respective element composition low-pass amplifier, the amplitude that the restriction higher hamonic wave is disturbed, frequency is by R 18With C 2Product decision, A 11And related resistors constitutes 1: 1 inverting amplifier, A 10, A 11Output be added to analog switch G respectively 3, G 4An input end, G 3, G 4Another output terminal and connect after again through R 22, C 3To A 12Output is at G 3', G 4Finish the switch synchronous detection under the control of ' switching signal, because A 11Be 1: 1 phase inverter, A 10Accumulation drift error in the past also can be at C 3Last elimination, R 22, C 3Constitute the one-level low pass simultaneously.
9, according to claim 2 or 8 described numeral instrument for measuring earth resistance, it is characterized in that G 1', G 2', G 3', G 4' switch controlling signal be same frequency, differ fixing pulse signal, wherein G 1' with G 2' anti-phase, G 3' with G 4' anti-phase, frequency is the fixed frequency between 310Hz～610Hz.
10, according to the described ground resistance meter of claim 1, it is characterized in that the output voltage V of many-valued direct-flow voltage regulation source 3 1Absolute value satisfy the following relationship formula,
V 1＞V 0+Ic（r max+Rc max）+Vs
V wherein 0For maximum allows the interference voltage value
Rmax is maximum tested grounding resistance
Rc is a maximum current utmost point auxiliary earth resistance value
Vs is T 1, T 2The triode saturation voltage drop
Ic is pulsation constant current amplitude.
CN 92114685 1992-12-15 1992-12-15 Numeral instrument for measuring earth resistance Pending CN1075552A (en)

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Cited By (7)

* Cited by examiner, † Cited by third party
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CN100410678C (en) * 1998-09-11 2008-08-13 基思·S·钱普林 Method and apparatus for measuring complex impedance of cells and batteries
CN102981053A (en) * 2012-11-20 2013-03-20 天津锐意泰克汽车电子有限公司 Secondary resistance detection circuit of ignition coil
CN103063928A (en) * 2013-01-29 2013-04-24 湖南继善高科技有限公司 System for testing earth grounding resistance, and digital coherent detection method
CN105044467A (en) * 2015-05-25 2015-11-11 苏州市华安普电力工程有限公司 Multifunctional earth resistance tester
CN107328997A (en) * 2017-07-10 2017-11-07 西安兴汇电力科技有限公司 A kind of grid grounding impedance measurement method
US11217039B2 (en) * 2014-11-11 2022-01-04 FreePoint Technologies Inc. System and method for determining and reporting value added activity data
CN117169755A (en) * 2023-11-02 2023-12-05 青岛艾诺仪器有限公司 AC impedance measuring system and measuring method

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN100410678C (en) * 1998-09-11 2008-08-13 基思·S·钱普林 Method and apparatus for measuring complex impedance of cells and batteries
CN102981053A (en) * 2012-11-20 2013-03-20 天津锐意泰克汽车电子有限公司 Secondary resistance detection circuit of ignition coil
CN102981053B (en) * 2012-11-20 2015-03-04 天津锐意泰克汽车电子有限公司 Secondary resistance detection circuit of ignition coil
CN103063928A (en) * 2013-01-29 2013-04-24 湖南继善高科技有限公司 System for testing earth grounding resistance, and digital coherent detection method
CN103063928B (en) * 2013-01-29 2015-05-20 湖南继善高科技有限公司 System for testing earth grounding resistance, and digital coherent detection method
US11217039B2 (en) * 2014-11-11 2022-01-04 FreePoint Technologies Inc. System and method for determining and reporting value added activity data
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