CN100394194C

CN100394194C - Direct current potential difference meter using conversion branch two measuring range conversion

Info

Publication number: CN100394194C
Application number: CNB200510062280XA
Authority: CN
Inventors: 骆乃光
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-12-28
Filing date: 2005-12-28
Publication date: 2008-06-11
Anticipated expiration: 2025-12-28
Also published as: CN1793973A

Abstract

The present invention relates to a direct current potential difference meter of two-measuring range conversion using a conversion branch, and is used for measuring direct current voltage. The present invention uses 20*4 omega as a first measuring disc, uses 10*0.44 omega as a second measuring disc, and uses a slide wire disc of from 0 omega to 4.84 omega as a third measuring disc. The present invention is provided with a 'standard-unknown' converting switch which does not influence a measuring result. Two measuring end buttons and the three measuring discs of the potential difference meter are directly connected by conducting wires. Contact resistance, variation and thermoelectric potential of a measuring stepping switch are excluded out of a measuring result. If zero potential is large, negative potential is enlarged, which leads the zero potential to be compensated. The potential difference meter adopts two resistors of 100 omega and 900 omega to carry out measuring range conversion in a conversion branch mode.

Description

A kind of DC potentiometer that adopts the conversion of branch two ranges

Technical field

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

Background technology

The potential difference meter of current production, when measuring disk has three when above, measure between terminal for two and have switch contact resistance and variation, therefore, even working current is little of 0.1mA, the silver-bearing copper compound substance is not only adopted in the brush of switch and contact, contact area is also done very greatly, variation is brought influence when reducing measuring switch stepping switching, this just makes the instrument volume become big, nonetheless, can not make potential difference meter resolution little to 0.1 μ V, the thermoelectrical potential that also has switch in addition with contact variable thermoelectric potential influence.

Summary of the invention

The problem to be solved in the present invention is, when being used for measure portion in the potential difference meter two step discs, a slide wire disc arranged, and contact resistance and variation that the measuring switch stepping is switched, the switch thermoelectrical potential does not influence measurement result, makes instrumental resolution reach 0.1 μ V.When range was changed, range conversion was the resistance that one digit number or two figure places are taken advantage of 10 integral number power with resistance.

Technical scheme of the present invention is such: it has working current to regulate resistance R P ₁, RP ₂, fixed resistance R ₀, 370 Ω of sampling usefulness set up resistance R N and the adjustable resistance RP of range of adjustment between 0～1 Ω during to standard ₃, and measure portion is connected in the potential difference meter work loop; Galvanometer G is by double-point double-throw switch K _1-2To resistance R ₄And resistance R ₅Switching at different ranges makes input impedance matching; It is characterized in that measure portion is with the two slide wire discs of two step discs and, first step disc is by respectively having 20 * 4 Ω I measuring disk and the I ' replacement dish to form, second step disc is made up of II measuring disk that 10 * 0.44 Ω are respectively arranged and the II ' replacement dish, the brush of the brush of the measuring disk of second step disc and replacement dish is connected to each other, the promptly two slide wire discs of the 3rd dish, two slide wire resistance silk resistances are identical, be all 0～4.84 Ω, the indicating value index dial of two slide wire discs has 11 big lattice, the corresponding resistance of every big lattice is 0.44 Ω, and 110 little lattice are arranged; Make III measuring disk slip for one in two slips, another root is made the III ' replacement dish slip, and the brush on two slide wire resistances of two slide wire discs is with a slice metallic brush sheet; The I ' replacement is coiled at the 20th and is connected 17.6 Ω resistance R ₁The back is coiled at the 10th with the II ' replacement and is connected, and the 0th of II measuring disk connects 8.44 Ω resistance R ₂The back is connected with the 0th of I measuring disk, and the 20th of I measuring disk connects III measuring disk slip end, and it is 1015.16 Ω resistance R that the III ' replacement dish slip top connects a resistance ₃The back is coiled at the 0th with the I ' replacement and is connected; The I ' replacement dish brush and 100 Ω resistance r ₁Be connected in parallel on the measure portion positive pole, resistance r ₁900 Ω resistance r connect ₂, tie point meets double-point double-throw switch K _1-1* 0.1 range contact, resistance r ₂The other end and I measuring disk brush are connected in the double-point double-throw switch * 1 range contact, and the normally closed contact of double-point double-throw switch is connected the measure portion negative pole; Potential difference meter is used to connect measured " U _X" two terminals, anodal terminal is connected with the 10th of II measuring disk, the negative pole terminal is by galvanometric change-over switch K ₂Be connected with III measuring disk slip top.

By above technical scheme, the measuring disk that two step discs and slide wire disc are used for measure portion connects with lead, contact resistance and variation be not in measuring the loop, the just potential difference meter work loop of influence always hinders, because total resistance resistance is very big, so variation can be ignored, the thermoelectric potential influence of several μ V be supply voltage, supply voltage is a volt, and how many μ V are thermoelectrical potential be, both differ 10 the 6 power orders of magnitude, therefore influence can be ignored, even so, even contact resistance variation and thermoelectric potential influence are big to the degree of can not ignore, can be by standard be adjusted RP ₂Resistance obtain revising, zero potential can increase between slide wire disc and the I measuring disk lead resistance to be revised, Just because of this, reduced requirement to switch, after adopting small-sized measurement step switch, it is many that whole instrument overall dimensions reduce, and makes the measurement data of instrument obtain good repeatability.Because the range conversion is that one digit number is taken advantage of 10 integral number power with resistance, available standards resistance is revised with the resistance resistance the range conversion, has improved the accuracy of potential difference meter range ratio.

Description of drawings

Accompanying drawing is a principle of the invention circuit.

Embodiment

In the drawings, by " U _x" anodal through each measuring disk, pass through change-over switch K again ₂To " U _x" negative pole is to measure the loop, by positive source through measuring step switch to setting resistance R N and adjustable resistance RP ₃, arrive resistance R then ₀, adjustable resistance RP ₂And RP ₁After, getting back to power cathode is the work loop, anodal through change-over switch K from standard cell EN ₂, to setting up resistance R N and adjustable resistance RP ₃, be standard loop to the standard cell negative pole again.When three dishes are all thrown " 0 ", left side resistance equals 110 Ω between two brushes of first step disc, and the right resistance equals 1100 Ω, and total resistance is 100 Ω between two brushes of first step disc, therefore 10/11 on the left side of total current flows between two brushes of first dish, and 1/11 flows on the right.

When * 1 range, between two brushes of first step disc all-in resistance by 10 times to self resistance resistance r ₁With resistance r ₂Therefore parallel connection flows through that total current is 10/11 of a potential difference meter working current between two brushes of first step disc, flows through resistance r ₁With resistance r ₂Electric current be 1/11 of potential difference meter working current; When * 0.1 range, resistance resistance in series r between two brushes of first step disc ₂After, with 10 times to resistance r ₁Resistance and resistance r ₁Parallel connection makes resistance r ₁On electric current be that electric current between two brushes of 10/11, the first step disc of potential difference meter working current is 1/11 of a potential difference meter working current, so electric current is reduced to 1/10 on the measuring disk, the amount of making limit is reduced to 1/10.

2.75mA working current is to determine like this, at " U _x" two of two ends measure terminals and connect normal voltage near full scale, K switch by polarity ₂Throw to the left side, the measuring disk indicating value is identical with standard voltage value, regulates resistance R P by regulating working current ₁And RP ₂, make the galvanometer nulling, again with K switch ₂Throw to the right, sampling is 370 Ω with the resistance of setting up resistance R N, and 0～1 Ω adjustable resistance RP has connected ₃, regulate RP ₃, make galvanometer nulling once more, again with K switch ₂Throw to the left side, regulate RP ₂Make the galvanometer nulling, again with K switch ₂Throw to the right and regulate RP ₃Make the galvanometer nulling, when switch points to the left side and the right and do not regulate the equal nulling of galvanometer, the standardization of potential difference meter working current is described, promptly set up ohmically pressure drop and equate, at this moment with RP with the electromotive force of unsaturated standard cell EN ₃Locking, this potential difference meter is from now on just as standard.After the working current standardization, the I measuring disk is thrown n when * 1 range ₁, the II measuring disk is thrown n ₂, the III measuring disk is thrown n ₃, K switch ₂Throw to the left side, be positioned at this moment that voltage is between two terminals of measurement

U _X＝25/11×0.44n ₂+25/11×(8+0.44)+25/11×4n ₁-2.5/11×(20-n ₁)×4

-2.5/11×(10-n ₃)×0.44(mv)

＝n ₂+200/11+1+100n ₁/11-200/11+10n ₁/11-1+0.1n ₃

＝10n ₁+n ₂+0.1n ₃(mv)

More than the resistance of III dish calculate n by big lattice ₃Be expressed as an integer and add the radix point back and have one-bit digital to refer to little lattice in the big lattice, little lattice indicating value unit is 10 μ V during * 1 range, is 1 μ V when * 0.1 range.

Convenient in order to measure, the III dish has a big lattice negative potential.

Circuit work power is 1.5V, can work in the 1.4V-1.65V scope in order to make operating supply voltage, gets fixed resistance R ₀Equal 47 Ω, adjustable resistance PR ₁=20 * 4.3 Ω, PR ₂Be to regulate in 0～5.1 Ω scope.

Double-point double-throw switch K _1-2To resistance R ₄And resistance R ₅Switch in difference amount limit, purpose is to mate in different range input impedance for galvanometer G.

Claims

1. DC potentiometer that adopts branch two ranges conversions, it has working current to regulate resistance R P ₁, RP ₂, fixed resistance R ₀, 370 Ω of sampling usefulness set up resistance R N and the adjustable resistance RP of range of adjustment between 0～1 Ω during to standard ₃, and measure portion is connected in the potential difference meter work loop; Galvanometer G is by double-point double-throw switch K _1-2To resistance R ₄And resistance R ₅Switching at different ranges makes input impedance matching; It is characterized in that measure portion is with the two slide wire discs of two step discs and, first step disc is by respectively having 20 * 4 Ω I measuring disk and the I ' replacement dish to form, second step disc is made up of II measuring disk that 10 * 0.44 Ω are respectively arranged and the II ' replacement dish, the brush of the brush of the measuring disk of second step disc and replacement dish is connected to each other, the promptly two slide wire discs of the 3rd dish, two slide wire resistance silk resistances are identical, be all 0～4.84 Ω, the indicating value index dial of two slide wire discs has 11 big lattice, the corresponding resistance of every big lattice is 0.44 Ω, and 110 little lattice are arranged; Make III measuring disk slip for one in two slips, another root is made the III ' replacement dish slip, and the brush on two slide wire resistances of two slide wire discs is with a slice metallic brush sheet; The I ' replacement is coiled at the 20th and is connected 17.6 Ω resistance R ₁The back is coiled at the 10th with the II ' replacement and is connected, and the 0th of II measuring disk connects 8.44 Ω resistance R ₂The back is connected with the 0th of I measuring disk, and the 20th of I measuring disk connects III measuring disk slip end, and it is 1015.16 Ω resistance R that the III ' replacement dish slip top connects a resistance ₃The back is coiled at the 0th with the I ' replacement and is connected; The I ' replacement dish brush and 100 Ω resistance r ₁Be connected in parallel on the measure portion positive pole, resistance r ₁900 Ω resistance r connect ₂, tie point meets double-point double-throw switch K _1-1* 0.1 range contact, resistance r ₂The other end and I measuring disk brush are connected in the double-point double-throw switch * 1 range contact, and the normally closed contact of double-point double-throw switch is connected the measure portion negative pole; Potential difference meter is used to connect measured " U _X" two terminals, anodal terminal is connected with the 10th of II measuring disk, the negative pole terminal is by galvanometric change-over switch K ₂Be connected with III measuring disk slip top.