CN1793971A

CN1793971A - Bimeasuring range direct current potential difference meter using divided branch having five measuring discs

Info

Publication number: CN1793971A
Application number: CN 200510062278
Authority: CN
Inventors: 骆乃光
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-12-28
Filing date: 2005-12-28
Publication date: 2006-06-28

Abstract

A two-range DC potential difference meter with five measuring discs and applying distributary branch is prepared as using 20x 20 omega as the first measuring disc, 9x 4.4 omega as the second and the third measuring discs, 10x 0.044 omega as the fourth and the fifth measuring discs; using conductive wire to directly connect resistances on measuring discs between two measuring end buttons to exclude influence of contact resistance variation and thermo voltage from measuring switch on measuring result and using integer power of one digit number multiplying by ten as value of resistance used for range changeover.

Description

There are five measuring disk to adopt the diverter branch two-measuring range DC potential difference meter

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 the step switch that is used for measure portion in the potential difference meter has five, 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 is taken advantage of 10 integral number power with resistance.

Technical scheme of the present invention is such: working current is regulated resistance R P ₁, RP ₂, RP ₃And be used to reduce the fixed resistance R of supply voltage ₀, sampling is with setting up resistance and temperature compensation dish RP during to standard ₄And five resistor networks of measuring on the step switch are connected in the potential difference meter work loop, and working current is 0.5mA when standardization; It is characterized in that first step dish is made up of I measuring disk and I ' replacement dish, 0～20 indicating value is provided, two resistance above the dish are 20 * 20 Ω, second step disc is by " 0 ", non-resistance between " 1 " two contacts, there is the II measuring disk of 9 * 4.4 Ω resistance 1～10 contact, II ' the replacement dish of 10 * 4.4 Ω reaches and is not connected to resistance, 0 contact is independent, the II that all the other contacts link to each other " the bracket panel composition; the 3rd step disc is by " 9 "; non-resistance between " 10 " two contacts; be the III measuring disk of 9 * 4.4 Ω resistance between 0～9 contact; III ' the replacement dish of 10 * 4.4 Ω and the 10th III that all the other each points of independence connect " the bracket panel composition, the 4th step disc is by all being that the IV measuring disk of 10 * 0.044 Ω resistance and IV ' replacement dish and resistance are the IV of 10 * 0.022 Ω " bracket panel forms; the 5th step disc is the V measuring disk of 10 * 0.044 Ω by resistance; V ' replacement dish and resistance are the V of 10 * 0.022 Ω " bracket panel forms, except that first step disc, the replacement dish of all the other four step discs and the brush of measuring disk are connected to each other; I ' replacement dish brush is connected in the metering circuit positive pole, and I ' replacement is coiled at the 20th and connected 30.558 Ω resistance R ₁The back connects IV " bracket panel the 10th point, IV " 0 connection of bracket panel II " bracket panel 0 point; IV " the bracket panel brush connects II " contact of bracket panel except that 0 o'clock, II " the bracket panel brush is divided into two-way, and one the tunnel through 43.56 Ω resistance R ₂Back and IV " replacement coils at the 10th and is connected, and another road connects II ' replacement and coils the 10th point, and II measuring disk the 1st o'clock is through 3.96 Ω resistance R ₃Back IV measuring disk the 10th connection, 0 of 0 of II measuring disk and IV measuring disk all with 42.222 Ω resistance R ₄Connect at one end resistance R ₄The other end is connected with 0 of I measuring disk; 0 on I ' replacement dish connects 4527.78 Ω resistance R ₅Back and V " 0 of bracket panel is connected; V " the 10th connection of bracket panel III " bracket panel the 10th point; V " the bracket panel brush connects III ' bracket panel all the other each contacts except that the 10th contact, III " the bracket panel brush is divided into two branch roads, the one tunnel through 43.56 Ω resistance R ₆The back connects 0 point of V ' replacement dish, and another road connects III ' replacement and coils 0 point, and the 9th of III measuring disk connects 3.96 Ω resistance R ₇The back is connected with 0 of V measuring disk, and the 10th of III measuring disk measured at the 10th with the V dish and all be connected with the 20th of I measuring disk; The I ' replacement dish brush and 50 Ω resistance r ₁Be connected in parallel on potential difference meter and measure partly positive pole, the other end connects triple-pole double throw range selector K _1-1* 0.1 range contact, K _1-2* 0.1 range contact and I measuring disk brush all with triac device K _1-1* 1 range contact connects 405 Ω resistance r ₂One end connects K _1-2* 0.1 range contact, the other end connects K _1-2* 1 range contact, this contact is connected potential difference meter and measures partly negative pole, triac device K _1-1With K _1-2Two normally closed contact short circuits, two terminals of measuring disk are anodal to be connected with the 10th of II measuring disk, negative pole passes through galvanometer change-over switch K ₂Be connected with 0 of III measuring disk.

By above technical scheme, the measuring disk that five step discs are used for measure portion connects with lead, contact resistance and variation, 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 be the volt, how many μ V are thermoelectrical potential be, both differ 10 the 6 power orders of magnitude, and therefore influence can be ignored, even so, even contact resistance variation and thermoelectrical potential are big to the degree of can not ignore, can be by standard is adjusted RP ₃Resistance obtain revising, zero potential can increase between V measuring disk and the I measuring disk lead resistance and revise, 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 this instrumental resolution can obtain good repeatability when being 0.1 μ V.Because the range conversion is that one digit number or double figures are taken advantage of 10 integral number power with resistance, available interim standard resistance is revised with resistance 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 temperature compensation dish RP ₄, arrive resistance R then ₀, adjustable resistance RP ₃, 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 temperature compensation dish RP ₄, be standard loop to the standard cell negative pole again.When five dishes are all thrown " 0 ", left side resistance equals 495 Ω between two brushes of first step disc, and the right resistance equals 4950 Ω, and total resistance is 450 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 second dish threw at 0, second dish equated that with the 4th dish partly resistance in parallel when the 4th dish was thrown different indicating value, the circuit resistance was constant.When second dish is not thrown 0 the time, the 4th dish is thrown different indicating values, the circuit resistance is not having IV " resistance changes during bracket panel; stepping of the 4th every increase of dish; the circuit resistance can increase half resistance of each stepping resistance; for the total resistance of holding circuit constant; at IV " in the bracket panel each stepping reduce same resistance, when second step disc throws 0, the resistance minimum, at this moment allow IV " bracket panel resistance all seals in circuit, makes the circuit resistance constant, in like manner; the right circuit is provided with III " bracket panel and V " bracket panel is that to switch to the total resistance of any indicating value holding circuit constant for the 3rd step disc and the 5th step disc switch; because first dish is made up of resistance identical measuring disk and replacement dish, so what indicating value no matter five dishes throw, circuit always hinders constant.

When * 0.1 range, resistance is 1/9 resistance r of resistance between two brushes of first step disc ₁In parallel with two brushes, the electric current that flows through between two brushes of first step disc is reduced to * 1/10 during 1 range, the amount of making limit is reduced to 1/10, resistance r ₁With resistance value is reduced after two brushes are in parallel, so seal in resistance r in the potentiometer circuit ₂Keep total resistance value constant.

The potential difference meter working current is 0.5mA, left side electric current 5/11mA between two brushes of first step disc, the right electric current is 0.5/11mA, left side electric current flows through II " is divided into two equal branch roads; when second dish threw at 0, two branch roads that flow through II measuring disk and IV measuring disk separated, when the II measuring disk does not throw 0; flow through II measuring disk branch current and all flow through IV measuring disk resistance, and 10 resistance of IV measuring disk add resistance R behind the bracket panel brush ₃Play the effect of the 1st resistance of II measuring disk, when the IV measuring disk is thrown n ₄The time, n ₄Though～0 ohmically electric current is exactly a left side electric current, can regard two branch currents as and be formed by stacking, can be when therefore calculating with separate computations; In like manner, the right electric current is thrown n at the 5th dish between two brushes of first step disc ₅The time, 10～n ₅Electric current regard the stack of two branch currents as, take separate computations during calculating.Sampling is 2036 Ω with setting up resistance R N resistance, when the working current standardization, setting up ohmically pressure drop is 1.018V, the potential difference meter calibrating is carried out in constant temperature enclosure, standard electromotive force of the cell is 1.0186V in the time of 20 ℃, during 20 ℃ of temperature departures, every degree can compensate by-40 μ V, temperature compensation dish RP ₄Be 20 * 0.1 Ω, satisfy the national standard of each step value compensation 50 μ V of 0.02 grade of potential difference meter.

The minimum calibration of thermometer on the standard cell EN is 0.1 ℃, after according to temperature value the temperature compensation dish being regulated, and K switch ₂Point to the right, regulate adjustable resistance RP ₁, RP ₂And PR ₃After, make galvanometer G nulling, potential difference meter working current standardization at this moment, at this moment, the I measuring disk is thrown n ₁, the I measuring disk is thrown n ₁, the II measuring disk is thrown n ₂, the III measuring disk is thrown n ₃The IV measuring disk is thrown n ₄, the V measuring disk throws n ₅

Ux＝5/22×4.4n ₂+5/22×0.044n ₄+5/11×(40+2.2+0.022)+5/11×20n ₁-0.5/11×(20-n ₁×20-0.5/22×(10-n ₅)×0.044-0.5/22×(10-n ₃)×4.4(mv)

＝n ₂+0.04n ₄+200/11+0.01+100n ₁/11-200/11+10n ₁/11-0.01+0.001n ₅-1+0.1n ₃(mv)

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

More than be * during 1 range, five measuring disk indicating values, when * 0.1 range, five measuring disk indicating values are expressed as n1+0.1n ₂+ 0.01n ₃+ 0.001n ₄+ 0.0001n ₅(mv)

The potential difference meter operating voltage is 1.5V, gets fixed resistance R0=312 Ω, adjustable resistance RP for supply voltage is worked in 1.4V～1.65 scopes ₁=20 * 25 Ω, adjustable resistance RP ₂Be=20 * 1.4 Ω, RP ₃=20 * 0.08 Ω.

Claims

A kind of have five measuring disk to adopt the diverter branch two-measuring range DC potential difference meter, and it has working current to regulate resistance R P ₁, RP ₂, RP ₃And be used to reduce the fixed resistance R of supply voltage ₀, sampling is with setting up resistance and temperature compensation dish RP during to standard ₄And five resistor networks of measuring on the step switch are connected in the potential difference meter work loop, and working current is 0.5mA when standardization; It is characterized in that first step dish is made up of I measuring disk and I ' replacement dish, 0～20 indicating value is provided, two resistance above the dish are 20 * 20 Ω, second step disc is by " 0 ", non-resistance between " 1 " two contacts, there is the II measuring disk of 9 * 4.4 Ω resistance 1～10 contact, II ' the replacement dish of 10 * 4.4 Ω reaches and is not connected to resistance, 0 contact is independent, the II that all the other contacts link to each other " the bracket panel composition; the 3rd step disc is by " 9 "; non-resistance between " 10 " two contacts; be the III measuring disk of 9 * 4.4 Ω resistance between 0～9 contact; III ' the replacement dish of 10 * 4.4 Ω and the 10th III that all the other each points of independence connect " the bracket panel composition, the 4th step disc is by all being that the IV measuring disk of 10 * 0.044 Ω resistance and IV ' replacement dish and resistance are the IV of 10 * 0.022 Ω " bracket panel forms; the 5th step disc is the V measuring disk of 10 * 0.044 Ω by resistance; V ' replacement dish and resistance are the V of 10 * 0.022 Ω " bracket panel forms, except that first step disc, the replacement dish of all the other four step discs and the brush of measuring disk are connected to each other; I ' replacement dish brush is connected in the metering circuit positive pole, and I ' replacement is coiled at the 20th and connected 30.558 Ω resistance R ₁The back connects IV " bracket panel the 10th point, IV " 0 connection of bracket panel II " bracket panel 0 point; IV " the bracket panel brush connects II " contact of bracket panel except that 0 o'clock, II " the bracket panel brush is divided into two-way, and one the tunnel through 43.56 Ω resistance R ₂Back and IV " replacement coils at the 10th and is connected, and another road connects II ' replacement and coils the 10th point, and II measuring disk the 1st o'clock is through 3.96 Ω resistance R ₃Back IV measuring disk the 10th connection, 0 of 0 of II measuring disk and IV measuring disk all with 42.222 Ω resistance R ₄Connect at one end resistance R ₄The other end is connected with 0 of I measuring disk; 0 on I ' replacement dish connects 4527.78 Ω resistance R ₅Back and V " 0 of bracket panel is connected; V " the 10th connection of bracket panel III " bracket panel the 10th point; V " the bracket panel brush connects III ' bracket panel all the other each contacts except that the 10th contact, III " the bracket panel brush is divided into two branch roads, the one tunnel through 43.56 Ω resistance R ₆The back connects 0 point of V ' replacement dish, and another road connects III ' replacement and coils 0 point, and the 9th of III measuring disk connects 3.96 Ω resistance R ₇The back is connected with 0 of V measuring disk, and the 10th of III measuring disk measured at the 10th with the V dish and all be connected with the 20th of I measuring disk; The I ' replacement dish brush and 50 Ω resistance r ₁Be connected in parallel on potential difference meter and measure partly positive pole, the other end connects triple-pole double throw range selector K _1-1* 0.1 range contact, K _1-2* 0.1 range contact and I measuring disk brush all with triac device K _1-1* 1 range contact connects 405 Ω resistance r ₂One end connects K _1-2* 0.1 range contact, the other end connects K _1-2* 1 range contact, this contact is connected potential difference meter and measures partly negative pole, and the triple-pole double throw sky closes K _1-1With K _1-2Two normally closed contact short circuits, two terminals of measuring disk are anodal to be connected with the 10th of II measuring disk, negative pole passes through galvanometer change-over switch K ₂Be connected with 0 of III measuring disk.