CN100587503C - Four-range voltage measuring instrument - Google Patents

Abstract

The invention relates to a voltage measurer with four measuring ranges, wherein a first step disc is composed of a measuring disc, an auxiliary disc I' and an auxiliary disc I'' without resistances, asecond step disc uses a 11X110omega resistance ring to form a measuring disc and uses a 10X5omega resistance to form an auxiliary disc, each third step disc is composed of a 10X10omega measuring discand a replace disc, each contactor of a fourth step disc is connected with relative contactors on the measuring disc of the third step disc, the measuring discs are connected via wires without switched by switch, therefore avoids the effects of variable difference and thermoelectric force. The inventive has four measuring ranges as X10, X1, X0. 1, X0. 01, while the maximum measured voltage is 2.31V and the minimum resolution is 0. 1muV.

Description

A kind of four-range pressure measuring instrument

Technical field

The present invention relates to instrument that DC voltage is measured.

Background technology

Current for the potential difference meter that four measurement disks is arranged, in the connection between the four measurement disks, 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 200510062369.6 discloses the new method that the potential difference meter that four measurement disks is arranged solves the switch contact resistance variation, its first, each is made up of second step disc measuring disk and replacement dish, measuring disk is identical with resistance on the replacement dish, resistance of the every increase of measuring disk, the replacement dish just reduces same resistance, its the 3rd, the 4th step disc respectively has measuring disk, replacement dish and bracket panel are formed, because the 3rd step disc was declined at 10 o'clock, the total resistance of circuit changed when the 4th step disc was put different indicating value, the 3rd step disc was put at 10 o'clock, the total resistance of circuit was constant when the 4th step disc was put different indicating value, the 3rd step disc removes for this reason measuring disk, outside the replacement dish, increased bracket panel distinguish step disc put 10 and the circuit of declining 10 two kinds of situations connect, the 4th step disc has also increased bracket panel, has 10 resistance to insert or cut out several resistance respectively above and makes the total resistance of circuit constant.Four measurement disks is connected two and measures between terminal, and the brush on the step disc switch is got rid of outside the measurement loop, does not exist switch to switch between the resistance on the four measurement disks, does not also just produce variation; Because 15 ° of angles are rotated in each stepping of potential difference meter step disc switch, every layer of 24 contact that can distribute, the measuring disk of first step disc and replacement dish are 21 contacts, two-layer inside and outside needing, every layer all has resistance, and internal layer resistance is overproof makes troubles to maintenance, the measuring disk of the 4th step disc, replacement dish and each half storey of bracket panel, the step disc switch also needs inside and outside two-layer, and internal layer also has resistance, and maintenance is also inconvenient.

Summary of the invention

The objective of the invention is to design a kind of four-range pressure measuring instrument, in the connection of four measurement disks, do not switch by switch, first step disc cancellation replacement dish, and make four resistance on the step disc can both be contained in one deck.

Technical scheme of the present invention is taked like this: from the positive pole of external 15V working power through the resistance measurement network formed by four step discs, range transfer resistance and range selector setting resistance R to 463 Ω _NAnd the lockable adjustable resistance R of 0～1 Ω _P3Again through 0～70 Ω adjustable resistance R _P2And 20 68 Ω adjustable resistance R _P1The negative pole of getting back to external 15V working power is formed the work loop of pressure measuring instrument; Standard cell E _NAnodal through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂To setting up resistance R _NAnd lockable adjustable resistance R _P3Sliding contact, again through 75K Ω current-limiting resistance R to standard cell E _NNegative pole is formed the standard loop of pressure measuring instrument; Be used to connect two measured terminals, anodal terminal is through behind the four measurement disks, again through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂The equalizing network of forming pressure measuring instrument to the negative pole terminal; It is characterized in that first step disc has measuring disk I, it has 0～22 totally 23 gears, except that between 0,1 contact, directly connecting, connect one of 100 Ω resistance between all the other each grade contacts, other has bracket panel I ' and bracket panel I "; the brush of bracket panel I ' and bracket panel I " the tie point that is connected with lead of brush be circuit node B, bracket panel I ' and bracket panel I " 0 contact isolated, all the other all contacts connect with lead; Second step disc is made up of measuring disk II and bracket panel II ', and measuring disk II has 0～10 totally 11 gears, has the resistance of 11 110 Ω to connect circlewise 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, the 10th resistance R ₁₀The other end and the 11st resistance R ₁₁An end tie point be circuit node C, the 11st resistance R ₁₁The other end and the 1st resistance R ₁The other end be connected in 0 contact of measuring disk in the 3rd step disc, 0 contact of measuring disk is circuit node D in the 3rd step disc, resistance R ₁With resistance R ₂Tie point be connected resistance R through 200 Ω resistance with the 1st contact ₂With resistance R ₃Tie point be connected resistance R through 120 Ω resistance with the 2nd contact ₃With resistance R ₄Tie point be connected resistance R through 60 Ω resistance with the 3rd contact ₄With resistance R ₅Tie point be connected resistance R through 20 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 20 Ω resistance with the 7th contact ₈With resistance R ₉Tie point be connected resistance R through 60 Ω resistance with the 8th contact ₉With resistance R ₁₀Tie point be connected resistance R through 120 Ω resistance with the 9th contact ₁₀With resistance R ₁₁Tie point be connected resistance R through 200 Ω resistance with the 10th contact ₁With resistance R ₁₁The node D that connects is connected with 0 contact through 300 Ω resistance, is the resistance of 10 5 Ω on the bracket panel II ' of second step disc; The 3rd step disc is made up of measuring disk III that is both 10 10 Ω and replacement dish III ', and the brush of the brush of measuring disk III and replacement dish III ' is with a slice metallic brush sheet; The 4th step disc has only measuring disk IV, and the corresponding contact on its each contact and the measuring disk III connects; Bracket panel II ' the 10th contact and 62 Ω range transfer resistance R ₂₀An end be parallel to node A, node A connects the positive pole of the external working power of pressure measuring instrument, 0 contact of bracket panel II ' connects bracket panel I " 0 contact, the brush of bracket panel II ' connects bracket panel I " other contact except that 0 contact, the brush of measuring disk II is through 1900 Ω resistance R ₁₂Back connected node B, bracket panel I ' other contacts except that 0 contact connect measuring disk I the 22nd contact, measuring disk I the 0th, 1 contact is connected with node C, and 0 contact of bracket panel I ' is connected with node D after through 2200 Ω resistance, the brush series connection 1000k Ω resistance R of measuring disk IV ₁₅Back and 47.25 Ω resistance R ₁₆An end tie point be circuit node E, the 10th of replacement dish III ' series connection 99950 Ω resistance R ₁₄Back connected node E, 5293.92 Ω resistance R ₁₃One end connected node D, other end connected node E, 47.25 Ω resistance R ₁₆The other end and 55800 Ω resistance R ₁₇An end be connected in range selector K ₁* 10 range contacts, 55800 Ω resistance R ₁₇The other end and 5580 Ω resistance R ₁₈An end be connected in range selector K ₁* 1 range contact, 5580 Ω resistance R ₁₈The other end and 558 Ω resistance R ₁₉An end connect after through 5022 Ω resistance R ₂₁With range selector K ₁* 0.1 range contact connects range transfer resistance R ₁₉The other end and 62 Ω range transfer resistance R ₂₀The other end connect after through 5574.42 Ω resistance R ₂₂With range selector K ₁* 0.01 range contact connects range selector K ₁Normally closed contact connect to set up resistance R _NNoble potential one end; Pressure measuring instrument is used to connect two measured terminals, and positive pole is connected with measuring disk I brush, and negative pole is through double-point double-throw switch K ₂The back is connected with the 10th contact of measuring disk III.

By above technical scheme, first step disc need not the replacement dish, does not all have resistance on the two-layer bracket panel, can be contained in the switch nexine, and measuring disk I is contained in the switch skin; Second step disc need not the replacement dish, 15 ° of angles are rotated in each stepping of switch, each 11 contact of the bracket panel II ' of second step disc and measuring disk II are distributed in same one deck of switch, resistance is contained in the switch skin, three, the 4th step disc does not all have bracket panel, resistance can be contained in the switch skin, unloads when resistance is overproof and loads onto easily, and this brings convenience for debugging and maintenance; This makes pressure measuring instrument simple in structure, and volume-diminished has also reduced production cost; On the total circuit partly in pressure measuring instrument internal compensation loop and work loop, there is not switch, so there is not variation influence, when the reset of pressure measuring instrument four measurement disks, the zero potential of pressure measuring instrument is the zero potential that D is ordered, in equalizing network, do not exist working current to flow through lead resistance, so this pressure measuring instrument zero potential is very little, owing on the total circuit partly in pressure measuring instrument internal compensation loop and work loop, do not have switch to switch, so this pressure measuring instrument thermoelectrical potential and variable thermoelectrical potential are also very little.

Description of drawings

Accompanying drawing is a principle of the invention circuit.

Embodiment

Among the figure, measuring disk II is 11 the 110 end to end resistance rings of Ω between node C and node D, when measuring disk II puts " 5 " or puts " 6 ", the brush of measuring disk II is to being that 5 110 Ω resistance are in parallel with 6 110 Ω resistance between the node D, back in parallel resistance is 300 Ω to the maximum, other contact of measuring disk II all is connected to 300 Ω to the resistance value between the node D and is as the criterion, and corresponding point directly are connected on 5,6 contacts and the resistance ring; When measuring disk II put " 4 " or puts " 7 ", the brush of measuring disk II was to being that 4 110 Ω resistance are in parallel with 7 110 Ω resistance between the node D, and back in parallel resistance is 280 Ω, so 4,7 contacts are connected with corresponding point on the resistance ring through 20 Ω resistance; When measuring disk II put " 3 " or puts " 8 ", the brush of measuring disk II was to being that 3 110 Ω resistance are in parallel with 8 110 Ω resistance between the node D, and back in parallel resistance is 240 Ω, so 3,8 contacts are connected with corresponding point on the resistance ring through 60 Ω resistance; When measuring disk II put " 2 " or puts " 9 ", the brush of measuring disk II was to being that 2 110 Ω resistance are in parallel with 9 110 Ω resistance between the node D, and back in parallel resistance is 180 Ω, so 2,9 contacts are connected with corresponding point on the resistance ring through 120 Ω resistance; When measuring disk II set or when putting " 10 ", the brush of measuring disk II is to being that 1 110 Ω resistance is in parallel with 10 110 Ω resistance between the node D, and back in parallel resistance is 100 Ω, so 1,10 contacts are connected with corresponding point on the resistance ring through 200 Ω resistance; When measuring disk II reset, the brush of measuring disk II is between the node D being the connections of 300 Ω resistance.

The first step disc reset, second step disc are put " n " (n=0,1,2,3 ... 10) time, Node B is that two resistance that are both 2200 Ω are in parallel with resistance value between the node D, is 1100 Ω resistance values therefore.

First step disc is put " n " (n=0,1,2,3 ... 22), during the second step disc reset, Node B and resistance value between the node D also are that the resistance of two 2200 Ω is in parallel, also are 1100 Ω resistance values therefore.

When first, second step disc during not reset, except that second step disc was put " 10 ", the calculating of the resistance value between Node B and the node D need be carried out triangle-star conversion.

During the second step disc set, the calculating of the resistance value between Node B and the node D: establish 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 * 110 * 110/11 * 110 Ω=90 Ω

r ₁’＝R ₁×R ₁₁/(R ₁+R ₂+…+R ₁₀+R ₁₁)＝110×110/11×110Ω＝10Ω

r ₁”＝(R ₂+R ₃+…+R ₉+R ₁₀)×R ₁/(R ₁+R ₂+…+R ₁₀+R ₁₁)＝9×110×110/11×110Ω＝90Ω

Resistance value between Node B and the node D equals (2100 Ω+r ₁) * (1900 Ω+200 Ω+r ₁")/(2 * 2190) Ω+r ₁'=2190 Ω/2+10 Ω=1095 Ω+10 Ω=1105 Ω

When second step disc is put " 2 ", the calculating of the resistance value between Node B and the node D: 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=80 Ω r ₂'=20 Ω r ₂"=160 Ω

Resistance value between Node B and the node D equals (2100 Ω+r ₂) * (1900 Ω+120 Ω+r ₂")/(2 * 2180) Ω+r ₂'=2180 Ω/2+20 Ω=1090 Ω+20 Ω=1110 Ω.

In like manner, when second step disc was put " 3 ", the resistance value between Node B and the node D was 1115 Ω,

When second step disc was put " 4 ", the resistance value between Node B and the node D was 1120 Ω,

When second step disc was put " 5 ", the resistance value between Node B and the node D was 1125 Ω,

......

When second step disc was put " 10 ", the resistance value between Node B and the node D was 1150 Ω.Because the every stepping of measuring disk II increases by 5 Ω, so the every stepping of bracket panel II ' reduces by 5 Ω, makes the total resistance of circuit constant; When the first or second step disc reset, the resistance value between Node B and the node D is 1100 Ω, and 10 * 5 Ω resistance of bracket panel II ' all enter circuit.

When three, the 4th step disc was put different indicating value, the resistance between node D and node E changed between 5002.728 Ω～5002.780 Ω, and node E connects 47.25 Ω resistance R ₁₆After, pass through node D to K switch from node A ₁* resistance value between 10 range contacts is 6200 Ω, the change in resistance of 0.05 Ω, to the relative variation of 6200 Ω less than 100,000/, influence can be ignored.

Electric current is 2.2mA during the standardization of pressure measuring instrument working current, when * 10 ranges, passes through node D to K switch from node A ₁* 6200 Ω resistance values between 10 range contacts and the resistance R of 62000 Ω ₁₇, resistance R ₁₈, resistance R ₁₉And resistance R ₂₀The sum parallel connection, the electric current that therefore flows through bracket panel II ' is 2mA, flows through resistance R ₁₇, resistance R ₁₈, resistance R ₁₉And resistance R ₂₀Electric current be 0.2mA; When * 1 range, resistance R ₁₇Changed the position, the circuit resistance is constant, and node A arrives range selector K through measuring disk ₁* 1 range contact totally 62000 Ω, node A is through resistance R ₂₀, resistance R ₁₉, resistance R ₁₈To range selector K ₁* 1 range contact is 6200 Ω, therefore flows through bracket panel II ' process measuring disk to range selector K ₁* electric current of 1 range contact is 0.2mA, flows through resistance R ₂₀, resistance R ₁₉And resistance R ₁₈Electric current be 2mA; When * 0.1 range, node A arrives range selector K through Node B ₁* 0.1 range contact between, the 6200 Ω resistance resistance R of having connected ₁₇And resistance R ₁₈Sum is 67580 Ω and its parallel resistor R ₂₀And resistance R ₁₉Sum is 620 Ω, and resistance value ratio is 109 times, flows through resistance R ₂₀, resistance R ₁₉Electric current also be 109 times with the current ratio that flows through Node B, so 2.18mA current flowing resistance R ₂₀, resistance R ₁₉, the 0.02mA electric current flows through the 10th the process Node B of bracket panel II ' to range selector K ₁* 0.1 range contact, the resistance that back in parallel circuit reduces is by sealing in 5022 Ω resistance R ₂₁The holding circuit resistance is constant; During * 0.01 range, node A arrives range selector K through Node B ₁* 0.01 range contact, the 6200 Ω resistance resistance R of having connected ₁₇, resistance R ₁₈And resistance R ₁₉Sum is 68138 Ω and its parallel resistor R ₂₀Be 62 Ω, resistance value ratio is 1099 times, so 2.198mA current flowing resistance R ₂₀, the 0.002mA electric current flows through node A and arrives range selector K through Node B ₁* 0.01 range contact, the resistance that back in parallel circuit reduces is by sealing in 5574.42 Ω resistance R ₂₂The holding circuit resistance is constant.

When * 10 ranges, the electric current that flows through bracket panel II ' is 2mA, and measuring disk II puts " n " (n=1,2,3 ... 9) time, I is to being equivalent to resistance r for Node B process measuring disk _n, r _n', r _n" intersection point Q _n(n=1,2,3 ... 9) with through 1900 Ω resistance R ₁₂To intersection point Q _nResistance value equates that when measuring disk II put " 10 ", I was to the resistance value of node C and through 1900 Ω resistance R for Node B process measuring disk ₁₂Resistance value to node C all equals 2100 Ω, so flow through measuring disk I and 1900 Ω resistance R ₁₂Electric current also respectively be 1m A.It is 100mV that 1m A electric current flows through the ohmically voltage of 100 Ω, and the every stepping of measuring disk I is 100mV.

When not considering measuring disk I, ten one the 110 Ω end to end resistance rings of measuring disk II between 1～10 contact, resistance R during measuring disk II set ₁To be all 110 Ω resistance in parallel with 10 resistances, flows through resistance R ₁₁Electric current be 1/11mA, the voltage U between node C and the node D _CD=1/11 * 110mV=10mV; Resistance (R when measuring disk II puts " 2 " ₁+ R ₂) to be all 110 Ω resistance in parallel with 9 resistances, flows through resistance R ₁₁Electric current be 2/11mA, the voltage U between node C and the node D _CD=2/11 * 110mV=20mV; (n=1,2,3 when in like manner, measuring disk II puts " n " ... 10) voltage U between resistance nodes C and the node D _CD=n * 10mV; When measuring disk I and measuring disk II reset, electric current is without resistance R ₁₁, U _CD=0mV.

The electric current that flows through measuring disk I when not reset of measuring disk I is superimposed upon on the measuring disk II at the 100mV voltage between node C, the D, the resistance between 0,1 contact of replacement measuring disk I.

The 2mA working current is divided into three the tunnel: the one tunnel through measuring disk IV through first, second step disc behind node D, another road is through replacement dish III ', and one the tunnel through 5293.92 Ω resistance R again ₁₃, three road electric currents meet at node E.When three, the 4th step disc is put different indicating value between node D and the node E resistance change, three, resistance minimum between node D and node E during the 4th step disc reset indicating value, resistance maximum between node D and node E when three, the 4th step disc is put " 10 " indicating value, get intermediate value, resistance is not having resistance R between node D and the node E when the 3rd, the 4th step disc is put " 5 " indicating value for this reason ₁₃When in parallel is (10 ⁶÷ 11+50) Ω is 0.11mA in order to make the total current that flows through the 3rd, the 4th step disc, with 5293.92 Ω resistance R ₁₃The electric current of shunting 1.89mA; Three, during the 4th step disc reset indicating value, the total current that flows through the 3rd, the 4th step disc is 0.11001mA, and when the 3rd, the 4th step disc was put " 10 " indicating value, the total current that flows through the 3rd, the 4th step disc was 0.10999mA, error is ten thousand/, influence can be ignored; Flow through resistance R ₁₄With resistance R ₁₅The current ratio exact value be 10, when the 3rd, the 4th step disc reset indicating value, flow through resistance R ₁₄With resistance R ₁₅Current ratio be 9.995, when the 3rd, the 4th step disc is put " 10 " indicating value, flow through resistance R ₁₄With resistance R ₁₅Current ratio be 10.005, error is 5/10000ths owing to be last two dishes, influence also can be ignored; The 3rd step disc is got the 0.1mA electric current on the resistance of measuring disk III, and the 4th step disc is got the 0.01mA electric current, and the resistance on the measuring disk III is 10 Ω, and the every stepping of the 3rd step disc is 1mV, and the every stepping of the 4th step disc is 0.1mV.

When * 10 range working current standardization, first step disc is put n ₁, second step disc puts n ₂, the 3rd step disc puts n ₃, the 4th step disc puts n ₄, " U at this moment _x" two measure that voltage is between terminal:

U _x＝100n ₁+10n ₂+1n ₃+0.1n ₄ (mV)

When * 1 range working current standardization, first step disc is put n ₁, second step disc puts n ₂, the 3rd step disc puts n ₃, the 4th step disc puts n ₄, " U at this moment _x" two measure that voltage is between terminal:

U _x＝10n ₁+n ₂+0.1n ₃+0.01n ₄ (mV)

When * 0.1 range, first step disc is put n ₁, second step disc puts n ₂, the 3rd step disc puts n ₃, the 4th step disc puts n ₄, " U _x" two measure that voltage is between terminal:

U _x＝1n ₁+0.1n ₂+0.01n ₃+0.001n ₄ (mV)

During * 0.01 range, when first step disc is put n ₁, second step disc puts n ₂, the 3rd dish puts n ₃, the 4th step disc is put n ₄, " U at this moment _x" two measure that voltage is between terminal:

U _x＝0.1n ₁+0.01n ₂+0.001n ₃+0.0001n ₄ (mV)

At this moment resolution reaches 0.1 μ V.

Because the electromotive force of standard cell disperses, between 1.0188V～1.0196V, standardized working current is 2.2mA, therefore sets up resistance R _NGet 463 Ω, add the lockable adjustable resistance R of 0～1 Ω _P3, variation range that can the coverage criteria cell emf.

Node A is to range selector K ₁Normally closed contact between the resistance of four ranges all be 62000/11 Ω, the setting resistance R of 463 Ω _NWith 0～1 Ω adjustable resistance R _P3Be 464 Ω, amount to 6100 Ω, bear about 13.42V voltage; The pressure measuring instrument external power supply is as adopting dry cell power supply, will ten groups of dry cells series connection, and under new, former affection condition, can both make the working current of pressure measuring instrument be adjusted to standardization in order to make dry cell, for this reason, get adjustable resistance R _P1Be 20 * 68 Ω, adjustable resistance R _P2Be 0～70 Ω, dry cell voltage usable range is between 13.42V～16.57V, and the suggestion of this pressure measuring instrument external power supply adopts Xinxin Electronic Instrument Factory, Shanghai to produce YJ49b type stabilized voltage supply, and it has many grades of high stability voltage outputs.

The normalized current of pressure measuring instrument is such acquisition: 2V standard signal voltage is pressed polarity and pressure measuring instrument " U _x" two measure terminal and connect, the total indicating value of each step disc of pressure measuring instrument is identical with the standard signal magnitude of voltage, double-point double-throw switch K ₂Throw to the left side, regulate adjustable resistance R _P1And adjustable resistance R _P2, make galvanometer G nulling; Again with double-point double-throw switch K ₂Throw to the right, regulate adjustable resistance R _P3, make galvanometer G nulling, repeat once again after, adjustable resistance R _P3Locking, at this moment the working current of pressure measuring instrument is with regard to standardization.

Claims (1)

1, a kind of four-range pressure measuring instrument, from the positive pole of external 15V working power through the resistance measurement network formed by four step discs, range transfer resistance and range selector setting resistance R to 463 Ω _NAnd the lockable adjustable resistance R of 0～1 Ω _P3Again through 0～70 Ω adjustable resistance R _P2And 20 68 Ω adjustable resistance R _P1The negative pole of getting back to external 15V working power is formed the work loop of pressure measuring instrument; Standard cell E _NAnodal through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂To setting up resistance R _NAnd lockable adjustable resistance R _P3Sliding contact, again through 75K Ω current-limiting resistance R to standard cell E _NNegative pole is formed the standard loop of pressure measuring instrument; Be used to connect two measured terminals, anodal terminal is through behind the four measurement disks, again through being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts ₂The equalizing network of forming pressure measuring instrument to the negative pole terminal; It is characterized in that first step disc has measuring disk I, it has 0～22 totally 23 gears, except that between 0,1 contact, directly connecting, connect one of 100 Ω resistance between all the other each grade contacts, other has bracket panel I ' and bracket panel I "; the brush of bracket panel I ' and bracket panel I " the tie point that is connected with lead of brush be circuit node B, bracket panel I ' and bracket panel I " 0 contact isolated, all the other all contacts connect with lead; Second step disc is made up of measuring disk II and bracket panel II ', and measuring disk II has 0～10 totally 11 gears, has the resistance of 11 110 Ω to connect circlewise 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, the 10th resistance R ₁₀The other end and the 11st resistance R ₁₁An end tie point be circuit node C, the 11st resistance R ₁₁The other end and the 1st resistance R ₁The other end be connected in 0 contact of measuring disk in the 3rd step disc, 0 contact of measuring disk is circuit node D in the 3rd step disc, resistance R ₁With resistance R ₂Tie point be connected resistance R through 200 Ω resistance with the 1st contact ₂With resistance R ₃Tie point be connected resistance R through 120 Ω resistance with the 2nd contact ₃With resistance R ₄Tie point be connected resistance R through 60 Ω resistance with the 3rd contact ₄With resistance R ₅Tie point be connected resistance R through 20 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 20 Ω resistance with the 7th contact ₈With resistance R ₉Tie point be connected resistance R through 60 Ω resistance with the 8th contact ₉With resistance R ₁₀Tie point be connected resistance R through 120 Ω resistance with the 9th contact ₁₀With resistance R ₁₁Tie point be connected resistance R through 200 Ω resistance with the 10th contact ₁With resistance R ₁₁The node D that connects is connected with 0 contact through 300 Ω resistance, is the resistance of 10 5 Ω on the bracket panel II ' of second step disc; The 3rd step disc is made up of measuring disk III that is both 10 10 Ω and replacement dish III ', and the brush of the brush of measuring disk III and replacement dish III ' is with a slice metallic brush sheet; The 4th step disc has only measuring disk IV, and the corresponding contact on its each contact and the measuring disk III connects; Bracket panel II ' the 10th contact and 62 Ω range transfer resistance R ₂₀An end be parallel to node A, node A connects the positive pole of the external working power of pressure measuring instrument, 0 contact of bracket panel II ' connects bracket panel I " 0 contact, the brush of bracket panel II ' connects bracket panel I " other contact except that 0 contact, the brush of measuring disk II is through 1900 Ω resistance R ₁₂Back connected node B, bracket panel I ' other contacts except that 0 contact connect measuring disk I the 22nd contact, measuring disk I the 0th, 1 contact is connected with node C, and 0 contact of bracket panel I ' is connected with node D after through 2200 Ω resistance, the brush series connection 1000k Ω resistance R of measuring disk IV ₁₅Back and 47.25 Ω resistance R ₁₆An end tie point be circuit node E, the 10th of replacement dish III ' series connection 99950 Ω resistance R ₁₄Back connected node E, 5293.92 Ω resistance R ₁₃One end connected node D, other end connected node E, 47.25 Ω resistance R ₁₆The other end and 55800 Ω resistance R ₁₇An end be connected in range selector K ₁* 10 range contacts, 55800 Ω resistance R ₁₇The other end and 5580 Ω resistance R ₁₈An end be connected in range selector K ₁* 1 range contact, 5580 Ω resistance R ₁₈The other end and 558 Ω resistance R ₁₉An end connect after through 5022 Ω resistance R ₂₁With range selector K ₁* 0.1 range contact connects range transfer resistance R ₁₉The other end and 62 Ω range transfer resistance R ₂₀The other end connect after through 5574.42 Ω resistance R ₂₂With range selector K ₁* 0.01 range contact connects range selector K ₁Normally closed contact connect to set up resistance R _NNoble potential one end; Pressure measuring instrument is used to connect two measured terminals, and positive pole is connected with measuring disk I brush, and negative pole is through double-point double-throw switch K ₂The back is connected with the 10th contact of measuring disk III.

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