CN202421286U

CN202421286U - Voltage measuring instrument

Info

Publication number: CN202421286U
Application number: CN201120573870XU
Authority: CN
Inventors: 孙笑声
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-12-30
Filing date: 2011-12-30
Publication date: 2012-09-05
Anticipated expiration: 2021-12-30

Abstract

The utility model provides a voltage measuring instrument used for measuring direct current voltage. A first stepping disc of the voltage measuring instrument consists of a measuring disc formed by twenty three 10 ohm resistors; a second stepping disc of the voltage measuring instrument consists of a measuring disc formed by ten 0.1 ohm resistors and a substitute disc; contacts of a third stepping disc, a fourth stepping disc and a fifth stepping disc are connected with corresponding contacts on the measuring disc in the second stepping disc, so that the third, fourth and fifth stepping discs do not need resistors, and the total voltage drop on resistors of internal leads of the voltage measuring instrument is almost zero. The voltage measuring instrument has the advantages that the influence of zero potential and thermoelectric potential can be neglected during the measurement.

Description

Voltage-measuring equipment

Technical field

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

Background technology

Current for the voltage-measuring equipment that five step discs are arranged, in the connection between five step discs, telophragma generally adopts switch to switch, and so just produces the variation of contact resistance, brings restriction to resolution.In order to overcome this problem, generally adopt big brush with the increase contact area, and adopt silver-carbon/carbon-copper composite material; Application number 200810121910.X discloses the new method that the voltage-measuring equipment that five step discs are arranged solves the switch contact resistance variation; Its five step discs all are made up of measuring disk and replacement dish; Do not contain bracket panel, on each measuring disk and the replacement dish resistance is arranged all, measuring disk and replacement dish on its five step discs have been formed bridge circuit in circuit; Its maximum defect is that error is not independent; In case measuring disk point indicating value is overproof, just can't confirms which resistance is overproof and cause that this makes troubles to identifying with maintenance.

The utility model content

The purpose of the utility model is a kind of voltage-measuring equipment that five step discs are arranged of design, and it does not adopt bridge circuit, and error can be independent, and back three step discs have only measuring disk, do not have resistance on the measuring disk, and this can reduce cost, and reduces the instrument volume.

The technical scheme of the utility model is taked like this: from the anodal terminal of the external 3V working power of voltage-measuring equipment E through 60 Ω resistance R ₀, the adjustable resistance R that constitutes by 21 3 Ω resistance _P1, the adjustable resistance R of range of adjustment between 0～3.2 Ω _P2, the adjustable resistance R of range of adjustment between 0～0.15 Ω _P3, the negative pole terminal of getting back to the external 3V working power of voltage-measuring equipment E through five step discs is again formed voltage-measuring equipment work loop; From external saturated standard cell E _NAnodal terminal set up resistance R through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts to 1018 Ω ₈, again through constituting temperature compensation dish W to external saturated standard cell E by 20 0.05 Ω resistance _NThe negative pole terminal form the voltage-measuring equipment standard loop; Be used to connect measured " U _X" two terminals, anodal terminal through five measuring disk after, form the voltage-measuring equipment equalizing network through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts to the negative pole terminal again; It is characterized in that first step disc has measuring disk I; It has 0,1,2 ... 23 totally 24 gears; 23 10 Ω resistance are arranged above, except that the 0th, the 1st contact, connect one of 10 Ω resistance between all the other each grade contacts; Each measuring disk II and replacement dish II ' that is made up of 10 0.1 Ω resistance of second step disc forms; Corresponding contact among the measuring disk III of the 3rd step disc, each contact on the measuring disk V of the measuring disk IV of the 4th step disc, the 5th step disc and second step disc on the measuring disk II connects, and temperature compensation dish W is made up of 20 0.05 Ω resistance; Adjustable resistance R _P3Electronegative potential one end be circuit node D, node D is divided into two-way, the one tunnel through 760 Ω resistance R ₂Last the 23rd contact of measuring disk I that connects first step disc, last the 1st contact of measuring disk I through behind one 10 Ω resistance with second step disc in the 0th contact tie point of measuring disk II be circuit node A, last the 0th contact of measuring disk I also is connected with node A; Another road is through 10 Ω resistance R ₁Back CC node A, the Metal Contact ring of measuring disk V is through 1000k Ω resistance R ₃, measuring disk IV the Metal Contact ring through 100k Ω resistance R ₄, measuring disk III the Metal Contact ring through 10k Ω resistance R ₅All be connected in circuit node B, the 10th contact of replacement dish II ' is through 999 Ω resistance R ₆B is connected with circuit node, and circuit node A is through 112.4986 Ω resistance R ₇The CC Node B, Node B is divided into two-way: the one tunnel through 1018 Ω setting resistance R ₈20 the 0.05 Ω resistance of process temperature compensation dish W are to circuit node C again, and another road is through 113.2222 Ω resistance R ₉C is connected with circuit node, and node C connects voltage-measuring equipment working power negative pole; Be used to connect measured " U _X" two measure terminals, anodal terminal is connected with the Metal Contact ring of measuring disk I, the negative pole terminal is connected with the 10th contact of measuring disk II after through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts.

Through above technical scheme; The first, the 3rd, the 4th, the 5th step disc replacement dish not all, and all do not have resistance on the measuring disk of the 3rd, the 4th, the 5th step disc, five step disc errors are independent; The back identical stepping error of four step discs is consistent, and this brings convenience for debugging and maintenance; Also make voltage-measuring equipment simple in structure, volume-diminished, thus reduced production cost; When five measuring disk resets of voltage-measuring equipment; The internal wiring combined potential of voltage-measuring equipment is an A point current potential; Some current potentials are " 0 "; So the zero potential of this voltage-measuring equipment is very little, the thermoelectrical potential of back four several μ V of each branch road of step disc all is connected in the 1V voltage drop, so thermoelectric potential influence can be ignored.

Description of drawings

Accompanying drawing 1 is the utility model schematic circuit.

In Fig. 1, the expression measuring disk I of last 23 * 10 Ω of the first step disc measuring disk I is made up of 23 10 Ω resistance, in like manner, and adjustable resistance R _P1The expression adjustable resistance R of last 21 * 3 Ω _P1Constitute by 21 3 Ω resistance.

In Fig. 1, thick black line is represented the Metal Contact ring on step disc and the temperature compensation dish, and hollow small circle is represented hard contact, and four-headed arrow is represented metallic brush.

Embodiment

Among Fig. 1; Measuring disk II is identical with the resistance value of each stepping of replacement dish II ' in second step disc; All be 0.1 Ω, the measuring disk II resistance that every stepping increases in circuit equals the resistance that the every stepping of replacement dish II ' reduces, so each stepping of second step disc resistance between node A, B is constant.

Voltage-measuring equipment standard operation current design becomes 10mA, and working current is divided into two-way at node D, and one the tunnel through 760 Ω resistance R ₂And totally 990 Ω of the resistance on the measuring disk I of first step disc, another road is through resistance R ₁Be 10 Ω, so flowing through the ohmically electric current of measuring disk I is that 0.1mA flows through resistance R ₁On electric current be 9.9mA, voltage-measuring equipment 10mA working current is through being divided into five the tunnel: the one tunnel through measuring disk III behind the node A, the one tunnel through measuring disk IV, the one tunnel through measuring disk V, another road is through second step disc, the one tunnel through 112.4986 Ω resistance R again ₇, five road electric currents meet at Node B.Remove through resistance R ₇Outside the branch road, each branch road resistance ratio: measuring disk V: measuring disk IV: measuring disk III between node A, the Node B: second step disc=1000: 100: 10: 1, so, remove and flow through resistance R ₇Outside the branch road, flow through that each branch current ratio is between node A, the Node B: measuring disk V: measuring disk IV: measuring disk III: second step disc=1: 10: 100: 1000, remove resistance R ₇Outside the branch road, resistance is 1000k Ω/1111 between node A, the Node B, lets the total current that flows through measuring disk V, measuring disk IV, measuring disk III and second step disc be 1.111mA, flows through resistance R ₇Electric current be 8.889mA, then 8.889mA * R ₇=1000k Ω/1111 * 1.111mA, resistance R ₇=112.4986 Ω.Voltage-measuring equipment 10mA working current is through resistance R ₇Shunting makes that flowing through measuring disk V electric current is 0.001mA, and measuring disk IV electric current is 0.01mA, and the 3rd step disc electric current is 0.1mA, and the second step disc electric current is 1mA;

When each step disc is put different indicating value between node A and the Node B resistance change, resistance is used resistance R between node A and the Node B _ABExpression, each step disc resistance variable is X,

1/R then _AB≈ 1/ (1000k Ω+X)+1/ (100k Ω+and X)+1/ (10k Ω+X)+1/999 Ω+8889/1000k Ω

Both sides differentiate: (1/R _AB{ 1/ (1000000+X)+1/ (100000+X)+1/ (the 10000+X)+1/999+8889/1000000} '-R of) '= _AB'/RA _B2={ 1/ (1000000+X) ²-1/ (100000+X) ²-1/ (10000+X) ²+ 0+0}R _AB'={ 1/ (1000000+X) ²+ 1/ (100000+X) ²+ 1/ (10000+X) ²R _AB ²

R _ABDerivative be on the occasion of, so when each step disc resistance variable increases, total resistance R between node A and the Node B _ABIncrease.Resistance minimum between node A and Node B during each step disc reset indicating value, at this moment resistance is 100 Ω between node A, the B, resistance R between node A and Node B when each step disc is put " 10 " indicating value _ABMaximum, at this moment resistance R between node A, the B _ABBe 100.002 Ω,

Than minimum resistance big 2/100000ths, therefore when the voltage-measuring equipment precision is not higher than 2/10000ths, when putting what indicating value regardless of each step disc between node A, the B change in resistance can ignore.

After the working current standardization, the I measuring disk is thrown n ₁, the II measuring disk is thrown n ₂, the III measuring disk is thrown n ₃, the IV measuring disk is thrown n ₄, the V measuring disk is thrown n ₅, K switch is thrown to the left side, is positioned at this moment that voltage is between two terminals of measurement:

U _X＝0.1×10n ₁+1×0.1n ₂+0.1×0.1n ₃+0.01×0.1n ₄+0.001×0.1n ₅(mv)

＝n ₁+0.1n ₂+0.01n ₃+0.001n ₄+0.0001n ₅(mv)

Saturated standard cell E _NElectromotive force is about 1.0186V, 1 ℃ of the every increase of temperature, and output voltage reduces 40 μ V approximately, sets up resistance R from 1018 Ω ₈, adding the total resistance of 20 0.05 Ω resistance formation temperature compensation dish W is 1019 Ω, resistance R ₂Resistance 1019 Ω 1/9, therefore flow through resistance R ₂Electric current be 9mA, flow through 1018 Ω and set up resistance R ₈The electric current that reaches temperature compensation dish W is 1mA, and 1018 Ω set up resistance R ₈Last voltage 1.018V, the every stepping bucking voltage 50 μ V of temperature compensation dish W when double-point double-throw switch K throws to the right, can carry out temperature compensation to external saturated standard cell.

The standard operation electric current is to confirm like this: external saturated standard cell is annual to be identified to provincial metrological service; Obtain room temperature exact value in the time of 20 ℃; According to thermometer displayed value on the saturated standard cell of 0.1 degree resolution; The contrast form can be known the electromotive force of saturated standard cell, and perhaps every rising deducts 40 μ V for 1 ℃ to be estimated, and is consistent with the electromotive force value of saturated standard cell according to value on the electromotive force adjusting temperature compensation dish of saturated standard cell; Double-point double-throw switch K is thrown to the right, through regulating adjustable resistance R _P1, adjustable resistance R _P2, adjustable resistance R _P3, make galvanometer G nulling, at this moment working current is 10mA with regard to standardization.

The voltage-measuring equipment WV is 3V, because the every joint stable electrical of A-battery kinetic potential between 1.4V～1.65V, all can be adjusted to standard state to the voltage-measuring equipment working current for realizing supply voltage at 1.35V～1.65V, gets fixed resistance R ₀=60 Ω, adjustable resistance RP ₁=21 * 3 Ω, adjustable resistance RP ₂Be 0～3.2 Ω, adjustable resistance R _P3Be 0～0.15 Ω, being together in series with two groups of A-batteries so just can be used as external 3V working power, also can use the work of external 3V stabilized voltage supply.

Claims

1. voltage-measuring equipment, from the anodal terminal of the external 3V working power of voltage-measuring equipment E through 60 Ω resistance R ₀, the adjustable resistance R that constitutes by 21 3 Ω resistance _P1, the adjustable resistance R of range of adjustment between 0～3.2 Ω _P2, the adjustable resistance R of range of adjustment between 0～0.15 Ω _P3, the negative pole terminal of getting back to the external 3V working power of voltage-measuring equipment E through five step discs is again formed voltage-measuring equipment work loop; From external saturated standard cell E _NAnodal terminal set up resistance R through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts to 1018 Ω ₈, again through constituting temperature compensation dish W to external saturated standard cell E by 20 0.05 Ω resistance _NThe negative pole terminal form the voltage-measuring equipment standard loop; Be used to connect measured " U _X" two terminals, anodal terminal through five measuring disk after, form the voltage-measuring equipment equalizing network through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts to the negative pole terminal again; It is characterized in that first step disc has measuring disk I; It has 0,1,2 ... 23 totally 24 gears; 23 10 Ω resistance are arranged above, except that the 0th, the 1st contact, connect one of 10 Ω resistance between all the other each grade contacts; Each measuring disk II and replacement dish II ' that is made up of 10 0.1 Ω resistance of second step disc forms; Corresponding contact among the measuring disk III of the 3rd step disc, each contact on the measuring disk V of the measuring disk IV of the 4th step disc, the 5th step disc and second step disc on the measuring disk II connects, and temperature compensation dish W is made up of 20 0.05 Ω resistance; Adjustable resistance R _P3Electronegative potential one end be circuit node D, node D is divided into two-way, the one tunnel through 760 Ω resistance R ₂Last the 23rd contact of measuring disk I that connects first step disc, last the 1st contact of measuring disk I through behind one 10 Ω resistance with second step disc in the 0th contact tie point of measuring disk II be circuit node A, last the 0th contact of measuring disk I also is connected with node A; Another road is through 10 Ω resistance R ₁Back CC node A, the Metal Contact ring of measuring disk V is through 1000k Ω resistance R ₃, measuring disk IV the Metal Contact ring through 100k Ω resistance R ₄, measuring disk III the Metal Contact ring through 10k Ω resistance R ₅All be connected in circuit node B, the 10th contact of replacement dish II ' is through 999 Ω resistance R ₆B is connected with circuit node, and circuit node A is through 112.4986 Ω resistance R ₇The CC Node B, Node B is divided into two-way: the one tunnel through 1018 Ω setting resistance R ₈20 the 0.05 Ω resistance of process temperature compensation dish W are to circuit node C again, and another road is through 113.2222 Ω resistance R ₉C is connected with circuit node, and node C connects voltage-measuring equipment working power negative pole; Be used to connect measured " U _X" two measure terminals, anodal terminal is connected with the Metal Contact ring of measuring disk I, the negative pole terminal is connected with the 10th contact of measuring disk II after through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts.