CN103777051A

CN103777051A - Voltage measuring instrument

Info

Publication number: CN103777051A
Application number: CN201110459617.6A
Authority: CN
Inventors: 孙笑声
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-12-30
Filing date: 2011-12-30
Publication date: 2014-05-07

Abstract

Provided is a voltage measuring instrument used for measuring direct voltage. A first stepping disc includes a measuring disc composed of 23 1-ohm resistors. A second stepping disc includes a measuring disc and a replacing disc, wherein the measuring disc is composed of 10 0.1-ohm resistors. A third stepping disc also includes a measuring disc and a replacing disc, wherein the measuring disc is composed of 10 0.1-ohm resistors. Contacts of a fourth stepping disc and a fifth stepping disc are connected with corresponding contacts of the measuring disc of the third stepping disc so that the fourth stepping disc and the fifth stepping disc need no resistor. As special wiring is adopted in the second stepping disc, voltage drop on a lead resistor inside the voltage measuring instrument is almost zero, and the influence of zero potential can be ignored when measurement is carried out by the voltage measuring instrument.

Description

Pressure measuring instrument

Technical field

The instrument that the present invention relates to DC voltage to measure.

Background technology

The current pressure measuring instrument for there being five step discs, in the connection between five step discs, telophragma generally adopts switching over, so just produces the variation of contact resistance, brings restriction to resolution.In order to overcome this problem, generally adopt large brush with enlarge active surface, and adopt silver-carbon/carbon-copper composite material; Application number 200810121910.X discloses the new method that has the pressure measuring instrument of five step discs to solve switch contact resistance variation, its five step discs are all coiled by measurement and replacement dish forms, not containing bracket panel, on each measurement dish and replacement dish, there is resistance, measurement dish and replacement dish on its five step discs have formed bridge circuit in circuit, the defect of its maximum is that error is not independent, once it is overproof that certain some indicating value is coiled in measurement, just cannot determine which resistance is overproof causes, this makes troubles to identifying with maintenance.

Summary of the invention

The object of the invention is to design a kind of pressure measuring instrument that has five step discs, it does not adopt bridge circuit, and error can be independent like this, and latter two step disc only has measurement dish, on measurement dish, there is no resistance, and this can reduce costs, and reduces instrument volume.

Technical scheme of the present invention is taked like this: from the anodal terminal of the external 3V working power of pressure measuring instrument E through 44 Ω resistance R ₀, the adjustable resistance R that formed by 21 3 Ω resistance _p1the 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, then get back to the negative pole terminal composition pressure measuring instrument work loop of external 3V working power E through five step discs, the anodal terminal of external standard cell EN is 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 ₁, then through forming temperature compensation dish W to external standard cell E by 20 0.05 Ω resistance _nnegative pole terminal composition pressure measuring instrument standard loop, be used for connecting measured " U _x" two terminals, anodal terminal after five measurement dishes, then through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts to negative pole terminal composition pressure measuring instrument equalizing network, it is characterized in that the first step disc has measurement dish I, it has 0, 1, 2, 23 totally 24 gears, except the 0th, outside the 1st contact, between all the other each grade of contacts, connect one of 1 Ω resistance, the second step disc is all by having 0, 1, 2, 10 totally 11 gear measurement dish II and replacement dish II ' compositions, measurement dish II is except the 0th, outside the 1st contact, measurement dish II and replacement dish II ' are connected one of 0.1 Ω resistance between each grade of contact, the measurement dish III that the 3rd step disc is respectively made up of 10 0.1 Ω resistance and replacement dish III ' form, the measurement dish IV of the 4th step disc, each contact on the measurement dish V of the 5th step disc connects with the corresponding contact on measurement dish in the 3rd step disc, temperature compensation dish W is made up of 20 0.05 Ω resistance, in the second step disc, the Metal Contact ring of replacement dish II ' connects adjustable resistance R _p3electronegative potential one end, replacement dish II ' the 10th contact connects the 23rd contact of measurement dish I, the 1st contact of measurement dish I connects the Metal Contact ring of measurement dish II after a 1 Ω resistance, the 0th contact of measurement dish I connects the 10th contact of measurement dish II, the 0th contact of measurement dish II and the 0th contact tie point of measurement dish III are circuit node A, the 1st contact of measurement dish II is connecting circuit node A after a 0.1 Ω resistance, and the Metal Contact ring of the measurement dish V of the 5th step disc is through 100K Ω resistance R ₄, measurement dish IV Metal Contact ring through 10K Ω resistance R ₅all be connected in circuit node B, the 10th contact of replacement dish III ' is through 999 Ω resistance R ₆b is connected with circuit node, and circuit node A is through 112.486 Ω resistance R ₃connecting circuit Node B, Node B is divided into two-way: resistance R is set up through 1018 Ω in a road ₁20 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 ₂c is connected with circuit node, and node C connects the negative pole terminal of the external 3V working power of pressure measuring instrument E, be used for connecting measured " U _x" two measure terminals, anodal terminal is connected with the Metal Contact ring of measurement dish I, negative pole terminal is through being connected with the 10th contact of measurement dish III after being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts.

By above technical scheme, the first step disc need not replacement dish, all replacement dishes not of the 4th, the 5th step disc, and four, on the measurement dish of the 5th step disc, all there is no resistance, five step disc errors are independent, and the error that rear two dish synchronised forward (FWD)s come is consistent, and this brings convenience to debugging and maintenance; Also make pressure measuring instrument simple in structure, volume-diminished, thus reduce production cost; In the time of five measurement dish resets of pressure measuring instrument, the internal wiring combined potential of pressure measuring instrument is A point current potential, some current potentials are " 0 ", so the zero potential of this pressure measuring instrument is very little, the thermoelectrical potential of rear three several μ V of each branch road of step disc is all connected in 1V voltage drop, and therefore thermoelectrical potential is to " U _x" two measure terminals impacts and can ignore;

Accompanying drawing explanation

Accompanying drawing is principle of the invention circuit.

In Fig. 1, the resistance of measurement dish II and upper 10 × 0.1 Ω of replacement dish II ' in the second step disc, represents that measurement dish II and replacement dish II ' are respectively made up of the resistance of 10 0.1 Ω, in like manner upper 23 × 1 Ω of measurement dish I, expression measurement dish I formed by 23 1 Ω resistance, adjustable resistance R _p1the expression adjustable resistance R of upper 21 × 3 Ω _p1formed by 21 3 Ω resistance.

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

Embodiment

In Fig. 1, in the second step disc, measurement dish II is identical with the resistance value of the each stepping of replacement dish II ', is all 0.1 Ω, and the measurement dish II resistance that every stepping increases in circuit equals the resistance that the every stepping of replacement dish II ' reduces, so total resistance is constant in circuit; The 3rd step disc carrys out holding circuit with measurement dish III and replacement dish III ' and always hinders invariance principle with the second step disc.Pressure measuring instrument working current is designed to 10mA, pressure measuring instrument 10mA working current is divided into four tunnels through first, second step disc after node A: a road is through measurement dish IV, one tunnel is through measurement dish V, and another road is through the 3rd step disc, and Zai Yi road is through 112.486 Ω resistance R ₃, four road electric currents meet at Node B.Except process resistance R ₃outside branch road, each branch road resistance ratio between node A, Node B: measurement dish V: measurement dish IV: the 3rd step disc=100: 10: 1, so, except flowing through resistance R ₃outside branch road, flow through each branch current ratio between node A, Node B and be: measurement dish V: measurement dish IV: the 3rd step disc=1st: 10: 100, except resistance R ₃outside branch road, between node A, Node B, resistance is 100K Ω/111, allows the total current that flows through measurement dish V, measurement dish IV and the 3rd step disc be 1.11mA, flows through resistance R ₃electric current be 8.89mA, 8.89mA × R ₃=100K Ω/111 × 1.11mA, resistance R ₃=112.486 Ω.Pressure measuring instrument 10mA working current is through resistance R ₃shunting, making to flow through measurement dish V electric current is 0.01mA, and measurement dish IV electric current is 0.1mA, and the 3rd step disc electric current is 1mA; When each step disc is put different indicating value, between node A and Node B, resistance changes, resistance resistance R between node A and Node B _aBrepresent, each step disc resistance variable is X, 1/R _aB≈ 1/ (100K Ω+X)+1/ (10K Ω+X)+1/1K Ω+889/100K Ω

Both sides differentiate: (1/R _aB{ 1/ (100K+X)+1/ (10K+X)+1/ (1000)+889/100K} ' of) '=

-R _AB′/R _AB ²＝{-1/(100K+X) ²-1/(10K+X) ²+0+0}

R _AB′＝{1/(100K+X) ²+1/(10K+X) ²}R _AB ²

R _aBderivative be on the occasion of, so when each step disc resistance variable increases, total resistance R between node A and Node B _aBincrease.Resistance minimum between node A and Node B when each step disc reset indicating value, at this moment between node A, B, resistance is 100 Ω, 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, B _aBbe 100.002 Ω, than minimum indicating value large 100,000/, therefore, when pressure measuring instrument precision is not higher than 2/10000ths time, no matter what indicating value each step disc puts, between node A, B, change in resistance can be ignored.

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

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

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

Saturated standard cell E _nelectromotive force is about 1.0186V, 1 ℃ of the every increase of temperature, and output voltage approximately reduces 40 μ V, 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 set up resistance R ₈and the electric current of temperature compensation dish W is 1mA, 1018 Ω set up resistance R ₈upper 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.

Standard operation electric current is to determine like this: external saturated standard cell is identified to provincial metrological service every year, 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 electromotive force of the known saturated standard cell of contrast form, or 1 ℃ of every rising deducts 40 μ V and estimates, 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, by regulating adjustable resistance R _p1, adjustable resistance R _p2, adjustable resistance R _p3, make galvanometer G nulling, at this moment working current, with regard to standardization, is 10mA.

Voltage-measuring equipment operating voltage is 3V, because the every joint stable electrical of dry cell kinetic potential is between 1.4V～1.65V, all voltage-measuring equipment working current can be adjusted to standard state for realizing supply voltage at 1.35V～1.65V, gets fixed resistance R ₀=44 Ω, adjustable resistance RP ₁=21 × 3 Ω, adjustable resistance RP ₂be 0～3.2 Ω, adjustable resistance R _p3be 0～0.15 Ω, be together in series and just can be used as external 3V working power with two groups of A-batteries like this, also can work by external 3V stabilized voltage supply.

Claims

1. a pressure measuring instrument, from the anodal terminal of the external 3V working power of pressure measuring instrument E through 44 Ω resistance R ₀, the adjustable resistance R that formed 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, then get back to the negative pole terminal composition pressure measuring instrument work loop of external 3V working power E through five step discs, external standard cell E _nanodal terminal is 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 ₁, then through forming temperature compensation dish W to external standard cell E by 20 0.05 Ω resistance _nnegative pole terminal composition pressure measuring instrument standard loop, be used for connecting measured " U _x" two terminals, anodal terminal after five measurement dishes, then through the double-point double-throw switch K that is connected to galvanometer G between two normally closed contacts to negative pole terminal composition pressure measuring instrument equalizing network, it is characterized in that the first step disc has measurement dish I, it has 0, 1, 2, 23 totally 24 gears, except the 0th, outside the 1st contact, between all the other each grade of contacts, connect one of 1 Ω resistance, the second step disc is all by having 0, 1, 2, 10 totally 11 gear measurement dish II and replacement dish II ' compositions, measurement dish II is except the 0th, outside the 1st contact, measurement dish II and replacement dish II ' are connected one of 0.1 Ω resistance between each grade of contact, the measurement dish III that the 3rd step disc is respectively made up of 10 0.1 Ω resistance and replacement dish III ' form, the measurement dish IV of the 4th step disc, each contact on the measurement dish V of the 5th step disc connects with the corresponding contact on measurement dish in the 3rd step disc, temperature compensation dish W is made up of 20 0.05 Ω resistance, in the second step disc, the Metal Contact ring of replacement dish II ' connects adjustable resistance R _p3electronegative potential one end, replacement dish II ' the 10th contact connects the 23rd contact of measurement dish I, the 1st contact of measurement dish I connects the Metal Contact ring of measurement dish II after a 1 Ω resistance, the 0th contact of measurement dish I connects the 10th contact of measurement dish II, the 0th contact of measurement dish II and the 0th contact tie point of measurement dish III are circuit node A, the 1st contact of measurement dish II is connecting circuit node A after a 0.1 Ω resistance, and the Metal Contact ring of the measurement dish V of the 5th step disc is through 100K Ω resistance R ₄, measurement dish IV Metal Contact ring through 10K Ω resistance R ₅all be connected in circuit node B, the 10th contact of replacement dish III ' is through 999 Ω resistance R ₆b is connected with circuit node, and circuit node A is through 112.486 Ω resistance R ₃connecting circuit Node B, Node B is divided into two-way: resistance R is set up through 1018 Ω in a road ₁20 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 ₂c is connected with circuit node, and node C connects the negative pole terminal of the external 3V working power of pressure measuring instrument E, be used for connecting measured " U _x" two measure terminals, anodal terminal is connected with the Metal Contact ring of measurement dish I, negative pole terminal is through being connected with the 10th contact of measurement dish III after being connected to the double-point double-throw switch K of galvanometer G between two normally closed contacts.