CN201681113U

CN201681113U - Voltage measuring apparatus

Info

Publication number: CN201681113U
Application number: CN2009202022781U
Authority: CN
Inventors: 骆晓英
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-12-14
Filing date: 2009-12-14
Publication date: 2010-12-22
Anticipated expiration: 2019-12-14

Abstract

The utility model provides a voltage measuring apparatus for measuring DC voltage, which consists of two stepping discs and one double-slide wire disc. In the voltage measuring apparatus, two measuring discs are connected with a measuring slide wire through a conducting wire. The voltage measuring apparatus can be switched without a switch, so that the voltage measuring apparatus can not be influenced by deviation and thermo-electrical potential. By changing the quantity of working current, the voltage measuring apparatus can obtain three measuring ranges, lead the minimum resolution ratio to be at 0.1muV, and eliminate two auxiliary discs of the first stepping disc.

Description

Voltage-measuring equipment

Technical field

The utility model relates to the instrument that DC voltage is measured.

Background technology

For the voltage-measuring equipment that three measuring disk are arranged, telophragma generally adopts switch to switch, and so just produces the variation of contact resistance, brings restriction to resolution a few days ago.In order to overcome this problem, generally adopt big brush with the increase contact area, and adopt silver-carbon/carbon-copper composite material; The patent No. 200720109906.2,200720107582.9,200720107585.2 discloses has three three-range voltage-measuring equipments of measuring disk to solve the variation new method of switch contact resistance, its first step disc is made up of a measuring disk and two bracket panels, two measuring disk connect the back and are connected between two measurement terminals with slide wire disc, brush on the step disc switch is got rid of outside the measurement loop, do not exist switch to switch between the resistance on three measuring disk, just do not produce variation yet; Because first step disc has three layers, make switch and apparatus structure become complicated, increased the height of instrument simultaneously.

The utility model content

The purpose of this utility model is a kind of three range voltage-measuring equipments of design, and telophragma does not switch by switch in the connection of three measuring disk, and two bracket panels of first step disc cancellation.

The technical solution of the utility model is taked like this:

Electric current is anodal through the resistance on two step discs between node C, the B and one pair of slide wire discs, range selector K from voltage-measuring equipment 1.5V working power ₁On the resistor network formed of resistance, through setting up resistance to 66 Ω resistance R ₀, connect 0～12000 Ω adjustable resistance R again _P1An end, adjustable resistance R _P1Sliding contact connect 0～1000 Ω adjustable resistance R _P2An end, adjustable resistance R _P2Sliding contact connect 0～82 Ω adjustable resistance R _P3An end, adjustable resistance R _P3Sliding contact and adjustable resistance R _P3, adjustable resistance R _P2, adjustable resistance R _P1The other end be connected in parallel on the working power negative pole, form voltage-measuring equipment work loop; It is characterized in that first step disc between node C, the B has only measuring disk I, it has 0,1,2 ... 22 totally 23 gears, connect one of 10 Ω resistance between each grade contact, second step disc is made up of measuring disk II and bracket panel II ', measuring disk II has 0,1,2 ... 10 totally 11 gears, the resistance that 11 11 Ω are arranged above, the 1st resistance R ₁One end welds the 2nd resistance R ₂One end, resistance R ₂The other end welds the 3rd resistance R ₃One end, resistance R ₃The other end welds the 4th resistance R ₄One end, resistance R ₄The other end welds the 5th resistance R ₅One end, resistance R ₅The other end welds the 6th resistance R ₆One end, resistance R ₆The other end welds the 7th resistance R ₇One end, resistance R ₇The other end welds the 8th resistance R ₈One end, resistance R ₈The other end welds the 9th resistance R ₉One end, resistance R ₉The other end welds the 10th resistance R ₁₀One end, resistance R ₁₀The other end welds the 11st resistance R ₁₁One end, the 11st resistance R ₁₁The other end and the 1st resistance R ₁The other end connect resistance R ₁With resistance R ₂Tie point be connected resistance R through 20 Ω resistance with the 1st contact ₂With resistance R ₃Tie point be connected resistance R through 12 Ω resistance with the 2nd contact ₃With resistance R ₄Tie point be connected resistance R through 6 Ω resistance with the 3rd contact ₄With resistance R ₅Tie point be connected resistance R through 2 Ω resistance with the 4th contact ₅With resistance R ₆Tie point be connected resistance R with the 5th contact ₆With resistance R ₇Tie point be connected resistance R with the 6th contact ₇With resistance R ₈Tie point be connected resistance R through 2 Ω resistance with the 7th contact ₈With resistance R ₉Tie point be connected resistance R through 6 Ω resistance with the 8th contact ₉With resistance R ₁₀Tie point be connected resistance R through 12 Ω resistance with the 9th contact ₁₀With resistance R ₁₁Tie point be circuit node A, node A is connected resistance R through 20 Ω resistance with the 10th contact ₁With resistance R ₁₁The point that connects is a Node B, and Node B is connected with the 0th contact through 30 Ω resistance, is the resistance of 10 0.5 Ω on the bracket panel II ' of second step disc, passes through 200 Ω resistance R between the brush of the second step disc measuring disk II and the brush of bracket panel II ' ₁₂Connect, the 3rd dish is two slide wire discs, two slip thickness materials are identical, resistance all is 10 Ω, and wherein one is measurement slip III, and another root is auxiliary slip III ', the index dial of two slide wire discs divides 10 big lattice, the resistance of every big lattice correspondence is 1 Ω, and every big lattice divide 10 little lattice, and the brush on two slide wire resistances is with a slice metallic brush sheet; Bracket panel II ' the 10th contact and 2300 Ω resistance R ₁₃End point in parallel be node C, node C connects voltage-measuring equipment working power positive pole, the brush of bracket panel II ' connects measuring disk I the 22nd contact and connects the 0th contact connected node A of measuring disk I, resistance R ₁₃The other end connect to measure top " 0 " point of slip III, the end " 10 " of measuring slip III is o'clock through 90 Ω resistance R ₁₄Back connecting circuit Node B; Node B connects DPTT double-pole triple throw range selector K ₁K _1-2The normally closed contact of layer, K _1-2Layer * 0.1 range contact and * 1 range contact between by 43655 Ω setting resistance R N ₃And 0～58 Ω adjustable resistance R _P4Connect K _1-2Layer * 1 range contact and * 10 range contacts between by 4364 Ω setting resistance R N ₂And 0～8 Ω adjustable resistance R _P5Connect K _1-2Layer * 10 range contacts and DPTT double-pole triple throw range selector K ₁K _1-1Set up resistance R N by 485 Ω between the normally closed contact of layer ₁And 0～1 Ω adjustable resistance R _P6Connect K _1-1The normally closed contact of layer connects standard cell EN negative pole, K _1-1Layer * 66 Ω resistance R are passed through in 10 range contacts ₀And adjustable resistance R _P1, R _P2, R _P3To the working power negative pole, K _1-1Layer * 10 range contact and K _1-1Layer * 1 range contact between by 1628 Ω resistance R _aConnect K _1-1Layer * 1 range contact and K _1-1Layer * 0.1 range contact between by 16250 Ω resistance R _bConnect, standard cell EN positive pole is through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂With DPTT double-pole triple throw range selector K ₁K _1-2Layer normally closed contact connects; Voltage-measuring equipment is used to connect measured " U _X" two terminals, anodal terminal is connected with the brush of measuring disk I, the negative pole terminal is by galvanometric change-over switch K ₂Be connected with auxiliary slip III '.

By above technical scheme, first step disc has saved two bracket panels, makes potential difference meter simple in structure, volume-diminished, also reduced production cost, in equalizing network, do not passed through switch on the circuit of three measuring disk connections simultaneously, so do not have variation and thermoelectric potential influence; The brush of first step disc and two slide wire discs switches and causes that change in resistance does not influence measurement numerical value, only influences the galvanometer damping, and compares brush with the resistance variations of whole equalizing network and switch and cause that change in resistance can ignore.

Description of drawings

Fig. 1 is the utility model schematic circuit.

In Fig. 1, the measuring disk I of 22 * 10 Ω, expression measuring disk I is made up of the resistance of 22 10 Ω; In like manner, the bracket panel II ' of 10 * 0.5 Ω, expression bracket panel II ' is made up of the resistance of 10 0.5 Ω, and resistance R in the resistance ring network of expression measuring disk II is arranged in the resistance ring network of measuring disk II " 10 * 11 Ω " ₁～resistance R ₁₀Ten resistances all are 11 Ω.

Embodiment

In Fig. 1, measuring disk II is 11 the 11 end to end resistance rings of Ω between node A and Node B, when measuring disk II puts " 5 " or puts " 6 ", the brush of measuring disk II is to being that 5 11 Ω resistance are in parallel with 6 11 Ω resistance between the Node B, back in parallel resistance is 30 Ω to the maximum, other contact of measuring disk II all is connected to 30 Ω to the resistance value between the Node B and is as the criterion, and corresponding point directly are connected on the 5th, 6 contacts and the resistance ring; When measuring disk II put " 4 " or puts " 7 ", the brush of measuring disk II was to being that 4 11 Ω resistance are in parallel with 7 11 Ω resistance between the Node B, and back in parallel resistance is 28 Ω, so the 4th, 7 contacts are connected with corresponding point on the resistance ring through 2 Ω resistance; When measuring disk II put " 3 " or puts " 8 ", the brush of measuring disk II was to being that 3 11 Ω resistance are in parallel with 8 11 Ω resistance between the Node B, and back in parallel resistance is 24 Ω, so the 3rd, 8 contacts are connected with corresponding point on the resistance ring through 6 Ω resistance; When measuring disk II put " 2 " or puts " 9 ", the brush of measuring disk II was to being that 2 11 Ω resistance are in parallel with 9 11 Ω resistance between the Node B, and back in parallel resistance is 18 Ω, so the 2nd, 9 contacts are connected with corresponding point on the resistance ring through 12 Ω resistance; When measuring disk II set or when putting " 10 ", the brush of measuring disk II is to being that 1 11 Ω resistance is in parallel with 10 11 Ω resistance between the Node B, and back in parallel resistance is 10 Ω, so the 1st, 10 contacts are connected with corresponding point on the resistance ring through 20 Ω resistance; When measuring disk II reset, the 0th contact of measuring disk II is between the Node B being the connections of 30 Ω resistance.

The brush of the brush of the measuring disk II of second step disc and bracket panel II ' is synchronous, and during the second step disc reset, the brush of bracket panel II ' is that two resistance that are both 230 Ω are in parallel with resistance value between the Node B, is 115 Ω therefore.

During the second step disc set, the calculating of resistance value need be carried out triangle-star conversion between the brush of bracket panel II ' and the Node B, establishes resistance (R ₂+ R ₃+ ... + R ₉+ R ₁₀) and resistance R ₁₁The both sides resistance is equivalent to resistance r ₁, resistance R ₁₁With resistance R ₁The both sides resistance is equivalent to resistance r ₁' resistance (R ₂+ R ₃+ ... + R ₉+ R ₁₀) and resistance R ₁The both sides resistance is equivalent to resistance r ₁", be equivalent to resistance r ₁, r ₁', r ₁" intersection point is Q ₁:

R then ₁=(R ₂+ R ₃+ ... + R ₉+ R ₁₀) * R ₁₁/ (R ₁+ R ₂+ ... + R ₁₀+ R ₁₁)=9 * 11 * 11/11 * 11 Ω=9 Ω

r ₁’＝R ₁×R ₁₁/(R ₁+R ₂+…+R ₁₀+R ₁₁)＝11×11/11×11Ω＝1Ω

r ₁”＝(R ₂+R ₃+…+R ₉+R ₁₀)×R ₁/(R ₁+R ₂+…+R ₁₀+R ₁₁)＝9×11×11/11×11Ω＝9Ω

Resistance value equals (220 Ω+r between the brush of bracket panel II ' and the Node B ₁) * (200 Ω+20 Ω+r ₁")/(2 * 229) Ω+r ₁'=229 Ω/2+1 Ω=114.5 Ω+1 Ω=115.5 Ω

When second step disc is put " 2 ", the calculating of resistance value between the brush of bracket panel II ' and the Node B: establish resistance (R ₃+ R ₄+ ... + R ₉+ R ₁₀) and resistance R ₁₁The both sides resistance is equivalent to resistance r ₂, resistance R ₁₁With resistance (R ₁+ R ₂) the both sides resistance is equivalent to resistance r ₂' resistance (R ₃+ R ₄+ ... + R ₉+ R ₁₀) and resistance (R ₁+ R ₂) the both sides resistance is equivalent to resistance r ₂", be equivalent to resistance r ₂, r ₂', r ₂" intersection point is Q ₂:

R then ₂=8 Ω r ₂'=2 Ω r ₂"=16 Ω

Resistance value equals (220 Ω+r between the brush of bracket panel II ' and the Node B ₂) * (200 Ω+12 Ω+r ₂")/(2 * 228) Ω+r ₂'=228 Ω/2+2 Ω=114 Ω+2 Ω=116 Ω.

In like manner, when second step disc was put " 3 ", resistance value was 116.5 Ω between the brush of bracket panel II ' and the Node B,

When second step disc was put " 4 ", resistance value was 117 Ω between the brush of bracket panel II ' and the Node B,

When second step disc was put " 5 ", resistance value was 117.5 Ω between the brush of bracket panel II ' and the Node B,

……

When second step disc was put " 10 ", resistance value was 120 Ω between the brush of bracket panel II ' and the Node B.Increase by 0.5 Ω because measuring disk II is connected the every stepping in back with measuring disk I, so the every stepping of bracket panel II ' reduces by 0.5 Ω, it is constant that circuit is always hindered.

Node C is 120 Ω through two step discs to the resistance of Node B, node C process slide wire disc is 2400 Ω to the resistance of Node B, is 2.1mA when voltage-measuring equipment is made current standard, when * 10 ranges, electric current is 2mA on the 120 Ω resistance, and electric current is 0.1mA on the 2400 Ω resistance; According to triangle-star conversion, I is to equivalent resistance r for bracket panel II ' brush process measuring disk _n, r _n', r _n" intersection point Q _n(n=1,2,3 ... 9) resistance and bracket panel II ' brush are through 200 Ω resistance R ₁₂To intersection point Q _nResistance equate, so flow through measuring disk I and 200 Ω resistance R ₁₂Electric current respectively be 1mA; When measuring disk II puts " 10 ", bracket panel II ' brush through measuring disk I to the resistance of node A and bracket panel II ' brush through 200 Ω resistance R ₁₂Resistance to node A all equals 220 Ω, so flow through measuring disk I and 200 Ω resistance R ₁₂Electric current also respectively be 1mA.

For ten one the 11 Ω end to end resistance rings of measuring disk II between node A and Node B, resistance R during measuring disk II set ₁To be all 11 Ω resistance in parallel with 10 resistances, when * 10 ranges, flows through resistance R ₁₁Electric current be 1/11mA, the voltage U between node A and the Node B _AB=1/11 * 11mV=1mV; Resistance (R when measuring disk II puts " 2 " ₁+ R ₂) to be all 11 Ω resistance in parallel with 9 resistances, flows through resistance R ₁₁Electric current be 2/11mA, the voltage U between node A and the Node B _AB=2/11 * 11mV=2mV; When in like manner, measuring disk II puts " n " (n=1,2,3 ... 10) voltage U between resistance nodes A and the Node B _AB=nmV; During measuring disk II reset, electric current is without resistance R ₁₁, U _AB=0mV.Measuring disk I, measuring disk II, measure slip III all during reset, U _ABOn 10mV voltage equal to measure 0 voltage of order of slip III to B, so measure and the node A equipotential of slip III at 0.

Working power with the electromotive force of No. 1 battery when 1.4V is following, electric current is stable inadequately, and the electromotive force of new battery reaches 1.65V, all can adjust to standard state to the voltage-measuring equipment working current for realizing supply voltage at 1.4V～1.65V, during * 10 ranges, seal in 66 Ω resistance R ₀, regulate adjustable resistance R _P1, adjustable resistance R _P2, adjustable resistance R _P3The work loop of making always hinders the work loop and always hinders between 666～786 Ω, and the electromotive force of standard cell EN is set up resistance EN by 485 Ω between 1.0188～1.0196V ₁, calibration 0～1 Ω adjustable resistance R _P6Make working current equal 2.1mA; During * 1 range, seal in 1628 Ω fixed resistance R again _a, regulate adjustable resistance R _P1, adjustable resistance R _P2, adjustable resistance R _P3Make the total resistance in work loop between 6660～7858 Ω, set up resistance R N by 4364 Ω ₂, calibration adjustable resistance R _P5Make working current equal 0.21mA, during * 0.1 range, seal in 16250 Ω fixed resistance R again _b, regulate adjustable resistance R _P1, regulate adjustable resistance R _P2, adjustable resistance R _P3The work loop is always hindered between 66600～78580 Ω, set up resistance R N by 43655 Ω ₃, calibration adjustable resistance R _P4Make working current equal 0.021mA.

At * 10 ranges, during the working current standardization, first step disc is put n ₁, second step disc puts n ₂, the 3rd dish puts n ₃(n ₃Represent big lattice indicating value) " U at this moment _x" two measure that voltage is between terminal:

U _x＝1×10n ₁+1×10+n ₂/11×11-0.1×90-0.1×1×(10-n ₃) (mV)

＝10n ₁+10+n ₂-9-1+0.1n ₃ (mV)

＝10n ₁+n ₂+0.1n ₃ (mV)

When * 1 range, sealed in 1628 Ω resistance R a in the circuit, the setting resistance R N corresponding with standard cell RN is 4364 Ω, regulates adjustable resistance R _P5, working current becomes 0.21mA during standardization; At this moment first step disc is put n ₁, second step disc puts n ₂, the 3rd dish puts n ₃(n ₃Represent big lattice indicating value) " U at this moment _x" two measure that voltage is between terminal:

U _X＝n ₁+0.1n ₂+0.01n ₃ (mv)

When * 0.1 range, 16250 Ω resistance R have been sealed in the circuit again _b, the setting resistance R N corresponding with standard cell RN is 43655 Ω, regulates adjustable resistance R _P5, working current becomes 0.021mA during standardization; The indicating value of three dishes is expressed as:

U _X＝0.1n ₁+0.01n ₂+0.001n ₃ (mv)

The standard operation electric current is to determine like this: 200mv standard signal voltage is pressed polarity and voltage-measuring equipment " U _x" two measure terminal and connect voltage-measuring equipment range switch K ₁Put " * 10 " range, it is identical with the standard signal magnitude of voltage that each coils total indicating value, double-point double-throw switch K ₂Throw to the left side, regulate adjustable resistance R _P1, adjustable resistance R _P2And adjustable resistance R _P3, make galvanometer G nulling; Again with double-point double-throw switch K ₂Throw to the right, regulate adjustable resistance R _P6, make galvanometer G nulling, at this moment adjustable resistance R _P6Locking; Again range switch K ₁Put " * 1 " range, 20mV standard signal voltage is pressed polarity and voltage-measuring equipment " U _x" two measure terminal and connect, it is identical with the standard signal magnitude of voltage that each coils total indicating value, double-point double-throw switch K ₂Throw to the left side, regulate adjustable resistance R _P1, adjustable resistance R _P2And adjustable resistance R _P3, make galvanometer G nulling; Again with double-point double-throw switch K ₂Throw to the right, regulate adjustable resistance R _P5, make galvanometer G nulling, at this moment adjustable resistance R _P5Locking; Again range switch K ₁Put " * 0.1 " range, 2mV standard signal voltage is pressed polarity and voltage-measuring equipment " U _x" two measure terminal and connect, it is identical with the standard signal magnitude of voltage that each coils total indicating value, double-point double-throw switch K ₂Throw to the left side, regulate adjustable resistance R _P1, adjustable resistance R _P2And adjustable resistance R _P3, make galvanometer G nulling; Again with double-point double-throw switch K ₂Throw to the right, regulate adjustable resistance R _P4, make galvanometer G nulling, at this moment adjustable resistance R _P4Locking; When using from now on, voltage-measuring equipment is standard according to this.

Claims

1. voltage-measuring equipment, electric current is anodal through the resistance on two step discs between node C, the B and one pair of slide wire discs, range selector K from voltage-measuring equipment 1.5V working power ₁On the resistor network formed of resistance, through setting up resistance to 66 Ω resistance R ₀, connect 0～12000 Ω adjustable resistance R again _P1An end, adjustable resistance R _P1Sliding contact connect 0～1000 Ω adjustable resistance R _P2An end, adjustable resistance R _P2Sliding contact connect 0～82 Ω adjustable resistance R _P3An end, adjustable resistance R _P3Sliding contact and adjustable resistance R _P3, adjustable resistance R _P2, adjustable resistance R _P1The other end be connected in parallel on the working power negative pole, form voltage-measuring equipment work loop; It is characterized in that first step disc between node C, the B has only measuring disk I, it has 0,1,2 ... 22 totally 23 gears, connect one of 10 Ω resistance between each grade contact, second step disc is made up of measuring disk II and bracket panel II ', measuring disk II has 0,1,2 ... 10 totally 11 gears, the resistance that 11 11 Ω are arranged above, the 1st resistance R ₁One end welds the 2nd resistance R ₂One end, resistance R ₂The other end welds the 3rd resistance R ₃One end, resistance R ₃The other end welds the 4th resistance R ₄One end, resistance R ₄The other end welds the 5th resistance R ₅One end, resistance R ₅The other end welds the 6th resistance R ₆One end, resistance R ₆The other end welds the 7th resistance R ₇One end, resistance R ₇The other end welds the 8th resistance R ₈One end, resistance R ₈The other end welds the 9th resistance R ₉One end, resistance R ₉The other end welds the 10th resistance R ₁₀One end, resistance R ₁₀The other end welds the 11st resistance R ₁₁One end, the 11st resistance R ₁₁The other end and the 1st resistance R ₁The other end connect resistance R ₁With resistance R ₂Tie point be connected resistance R through 20 Ω resistance with the 1st contact ₂With resistance R ₃Tie point be connected resistance R through 12 Ω resistance with the 2nd contact ₃With resistance R ₄Tie point be connected resistance R through 6 Ω resistance with the 3rd contact ₄With resistance R ₅Tie point be connected resistance R through 2 Ω resistance with the 4th contact ₅With resistance R ₆Tie point be connected resistance R with the 5th contact ₆With resistance R ₇Tie point be connected resistance R with the 6th contact ₇With resistance R ₈Tie point be connected resistance R through 2 Ω resistance with the 7th contact ₈With resistance R ₉Tie point be connected resistance R through 6 Ω resistance with the 8th contact ₉With resistance R ₁₀Tie point be connected resistance R through 12 Ω resistance with the 9th contact ₁₀With resistance R ₁₁Tie point be circuit node A, node A is connected resistance R through 20 Ω resistance with the 10th contact ₁With resistance R ₁₁The point that connects is a Node B, and Node B is connected with the 0th contact through 30 Ω resistance, is the resistance of 10 0.5 Ω on the bracket panel II ' of second step disc, passes through 200 Ω resistance R between the brush of the second step disc measuring disk II and the brush of bracket panel II ' ₁₂Connect, the 3rd dish is two slide wire discs, two slip thickness materials are identical, resistance all is 10 Ω, and wherein one is measurement slip III, and another root is auxiliary slip III ', the index dial of two slide wire discs divides 10 big lattice, the resistance of every big lattice correspondence is 1 Ω, and every big lattice divide 10 little lattice, and the brush on two slide wire resistances is with a slice metallic brush sheet; Bracket panel II ' the 10th contact and 2300 Ω resistance R ₁₃End point in parallel be node C, node C connects voltage-measuring equipment working power positive pole, the brush of bracket panel II ' connects measuring disk I the 22nd contact and connects the 0th contact connected node A of measuring disk I, resistance R ₁₃The other end connect to measure top " 0 " point of slip III, the end " 10 " of measuring slip III is o'clock through 90 Ω resistance R ₁₄Back connecting circuit Node B; Node B connects DPTT double-pole triple throw range selector K ₁K _1-2The normally closed contact of layer, K _1-2Layer * 0.1 range contact and * 1 range contact between by 43655 Ω setting resistance R N ₃And 0～58 Ω adjustable resistance R _P4Connect K _1-2Layer * 1 range contact and * 10 range contacts between by 4364 Ω setting resistance R N ₂And 0～8 Ω adjustable resistance R _P5Connect K _1-2Layer * 10 range contacts and DPTT double-pole triple throw range selector K ₁K _1-1Set up resistance R N by 485 Ω between the normally closed contact of layer ₁And 0～1 Ω adjustable resistance R _P6Connect K _1-1The normally closed contact of layer connects standard cell EN negative pole, K _1-1Layer * 66 Ω resistance R are passed through in 10 range contacts ₀And adjustable resistance R _P1, R _P2, R _P3To the working power negative pole, K _1-1Layer * 10 range contact and K _1-1Layer * 1 range contact between by 1628 Ω resistance R _aConnect K _1-1Layer * 1 range contact and K _1-1Layer * 0.1 range contact between by 16250 Ω resistance R _bConnect, standard cell EN positive pole is through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂With DPTT double-pole triple throw range selector K ₁K _1-2Layer normally closed contact connects; Voltage-measuring equipment is used to connect measured " U _X" two terminals, anodal terminal is connected with the brush of measuring disk I, the negative pole terminal is by galvanometric change-over switch K ₂Be connected with auxiliary slip III '.