CN1793966A - Three measuring range direct current potential difference using conversion branch having four measuring disks - Google Patents

Abstract

A three-range DC potential difference meter with four measuring discs and applying transposition branch is composed of four measuring discs as 20x 2 omega, 10x 0.22 omega, 9x 0.44 omega and 10x 0.044 omega. It features that all measuring resistances are directly connected by conducting wire to exclude contact resistance and variation from measuring-stepping switch out of measuring result and integer power of one or two digit number multiplying by ten is used as value of resistance being used for range changeover.

Description

There is four measurement disks to adopt the three measuring ranges DC potentiometer of branch

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 four step discs 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: working current is regulated resistance R P ₁And RP ₂, be used to reduce the fixed resistance R of supply voltage ₀, sampling is associated in the potential difference meter work loop with the resistance string of setting up on resistance R N and the measurement step switch during to standard, sets up ohmically voltage drop when equating with the potential difference meter internal attachment standard, and its working current equals 5.5mA; It is waited to levy and is that first step disc is made up of I measuring disk that 20 * 2 Ω are respectively arranged and the I ' replacement dish, second step disc is made up of II measuring disk that 10 * 0.22 Ω are respectively arranged and the II ' replacement dish, the 3rd step disc is by non-resistance between 9 and 10, these two contacts disconnect, all the other contacts are by the III measuring disk of 9 * 0.44 Ω of resistance connection, the III ' replacement the dish of 10 * 0.44 Ω is arranged and be not welded with resistance, 10 independences, the III that all the other contacts connect " form; " form by bracket panel by being all IV measuring disk and the IV ' replacement dish that 10 * 0.044 Ω resistance form and the IV that 10 * 0.022 Ω resistance are arranged for the 4th step disc by bracket panel, except that first step disc, all the other respectively coil measuring disk and are communicated with in twos separately with the brush of replacement dish; The I ' replacement coils at the 20th by 8.558 Ω resistance R ₁Connect the II ' replacement and coil the 10th point, 0 of II measuring disk connects one 4.242 Ω resistance R ₂The back is connected with 0 of I measuring disk; 0 on the I ' replacement dish connects one 507.58 Ω resistance R ₃The back connects IV " bracket panel 0 point; IV " bracket panel the 10th with III " bracket panel the 10th contact is connected; IV " the bracket panel brush connects III " bracket panel all contacts except that the 10th contact; the III ' bracket panel brush one tunnel connects the III ' replacement and coils 0 point, and another road connects 3.96 Ω resistance R ₄The back is connected with 0 on the IV ' replacement dish, and the 10th of III measuring disk directly is connected with the 20th of I measuring disk; The 9th of III measuring disk connects IV measuring disk 0 point, and the 10th of IV measuring disk is connected with the 20th of I measuring disk; The I ' replacement dish brush and 5 Ω resistance r ₁Be connected in parallel on potential difference meter and measure partly positive pole, resistance r ₁45 Ω resistance r in order connect ₂, 450 Ω resistance r ₃, resistance r ₁With resistance r ₂The junction, weld 40.5 Ω resistance r ₄With DPTT double-pole triple throw range selector K _1-1* 0.1 range contact connects resistance r ₂With resistance r ₃Tie point be connected resistance r with * 1 range contact ₃With I measuring disk brush and range selector K _1-1* 10 range contacts connect range selector K _1-1Normally closed contact be connected potential difference meter and measure partly negative pole; Two terminals of measuring junction are anodal to be connected with the 10th of II measuring disk, and negative pole is by galvanometer change-over switch K ₂Be connected with 0 of III measuring disk.

By above technical scheme, the measuring disk that four 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 ₂Resistance obtain revising, zero potential can be revised by increasing between IV measuring disk and the I measuring disk lead resistance, so 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

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 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 RP ₃, be standard loop to the standard cell negative pole again.When four dishes are all thrown " 0 ", left side resistance is 55 Ω between two brushes of first step disc, and the right resistance equals 550 Ω, and total resistance is 50 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 the 3rd dish threw at the 10th, the 4th dish equated that with the 3rd dish partly resistance in parallel when the 4th dish was thrown different indicating value, the circuit resistance was constant.When the 3rd dish is not thrown at the 10th, the 4th dish is thrown different indicating values, the circuit resistance is not having IV " resistance changes during bracket panel; the 4th dish every increase stepping, circuit resistance can reduce half resistance of each stepping resistance, for the total resistance of holding circuit constant; at IV " in the bracket panel each stepping increase same resistance, resistance minimum when the 3rd step disc throws at the 10th, " bracket panel resistance all seals in circuit, makes the circuit resistance constant at this moment to allow IV.Because second dish and first dish are formed by resistance identical measuring disk and replacement dish, so what indicating value no matter four dishes throw, circuit always hinders constant.

At * 10 ranges, resistance is by 10 times of resistance r to self resistance between two brushes of first step disc ₁, resistance r ₂, resistance r ₃Therefore series connection back swallow connection flows through that total current is 10/11 of a potential difference meter electric current between two brushes of first step disc, flows through resistance r ₁, r ₂R ₃Electric current be 1/11 of potential difference meter working current; When * 1 range, the resistance resistance in series r between two brushes of first step disc ₃The back 10 times to the resistance r of mutual series connection ₁And resistance r ₂Be in parallel, make to flow through the measuring disk electric current and be reduced to * 10 ranges 1/10; When * 0.1 range, total resistance r that connected that hinders between two brushes of first step disc ₂With r ₃Back and resistance r ₁Parallel connection, the resistance after the series connection is r ₁109 times, therefore flow through that total current is 1/110 of a potential difference meter working current between two brushes of first step disc, this electric current is * electric current during 10 ranges 1/100.

Basic range potential difference meter standard operation electric current is 5.5mA, left side electric current 50/11mA between two brushes of first step disc, the right electric current is 5/11mA, the right electric current flows through III " is divided into two equal branch roads; when the 3rd dish throws at the 10th; two branch roads that flow through III measuring disk and IV measuring disk separate; when the III measuring disk does not throw at the 10th; flow through III measuring disk branch current and all flow through IV measuring disk resistance; 10 resistance of IV measuring disk play the effect of the 10th resistance of III measuring disk, when the IV measuring disk is thrown n behind the bracket panel brush ₄The time, n ₄Though～10 ohmically electric currents are exactly the right electric current, can regard two branch currents as and be formed by stacking, can be with separate computations when therefore calculating;

The standard operation electric 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 185 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 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, K switch ₂Throw to the left side, be positioned at this moment that voltage is between two terminals of measurement:

Ux＝50/11×0.22n ₂+0.5/11(4+0.22+0.022)+50/11×2n ₁-5/11×(20-n ₁)×2-5/22×(10-n ₄)×0.044-5/22×(10-n ₃)×0.44(mv)

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

＝10n ₁+n ₂+0.1n ₃+0.01n ₄(mv)

More than be * during 10 ranges, the four measurement disks indicating value, when * 0.1 range, the four measurement disks indicating value is expressed as 0.1n ₁++ 0.01n ₂+ 0.001n ₃+ 0.0001n ₄(mv).

The potential difference meter operating voltage is 1.5V, because the every joint stable electrical of dry cell kinetic potential between 1.4V～1.65V, all can be adjusted to standard state to the potential difference meter working current for realizing supply voltage at 1.4V～1.65V, gets fixed resistance R ₀=23 Ω, adjustable resistance RP ₁=20 * 2.2 Ω, RP ₂Be 0～2.5 Ω.

Claims (1)

1. A kind of two-measuring range DC potential difference meter that has four measurement disks to adopt branch, it has working current to regulate resistance R P ₁And RP ₂, be used to reduce the fixed resistance R of supply voltage ₀, sampling is associated in the potential difference meter work loop with the resistance string of setting up on resistance R N and the measurement step switch during to standard, sets up ohmically voltage drop when equating with the potential difference meter internal attachment standard, and its working current equals 5.5mA; It is waited to levy and is that first step disc is made up of I measuring disk that 20 * 2 Ω are respectively arranged and the I ' replacement dish, second step disc is made up of II measuring disk that 10 * 0.22 Ω are respectively arranged and the II ' replacement dish, the 3rd step disc is by non-resistance between 9 and 10, these two contacts disconnect, all the other contacts are by the III measuring disk of 9 * 0.44 Ω of resistance connection, the III ' replacement the dish of 10 * 0.44 Ω is arranged and be not welded with resistance, 10 independences, the III that all the other contacts connect " form; " form by bracket panel by being all IV measuring disk and the IV ' replacement dish that 10 * 0.044 Ω resistance form and the IV that 10 * 0.022 Ω resistance are arranged for the 4th step disc by bracket panel, except that first step disc, all the other respectively coil measuring disk and are communicated with in twos separately with the brush of replacement dish; The I ' replacement coils at the 20th by 8.558 Ω resistance R ₁Connect the II ' replacement and coil the 10th point, 0 of II measuring disk connects one 4.242 Ω resistance R ₂The back is connected with 0 of I measuring disk; 0 on the I ' replacement dish connects one 507.58 Ω resistance R ₃The back connects IV " bracket panel 0 point; IV " bracket panel the 10th with III " bracket panel the 10th contact is connected; IV " the bracket panel brush connects III " bracket panel all contacts except that the 10th contact; the III ' bracket panel brush one tunnel connects the III ' replacement and coils 0 point, and another road connects 3.96 Ω resistance R ₄The back is connected with 0 on the IV ' replacement dish, and the 10th of III measuring disk directly is connected with the 20th of I measuring disk; The 9th of III measuring disk connects IV measuring disk 0 point, and the 10th of IV measuring disk is connected with the 20th of I measuring disk; The I ' replacement dish brush and 5 Ω resistance r ₁Be connected in parallel on potential difference meter and measure partly positive pole, resistance r ₁45 Ω resistance r in order connect ₂, 450 Ω resistance r ₃, resistance r ₁With resistance r ₂The junction, weld 40.5 Ω resistance r ₁With DPTT double-pole triple throw range selector K _1-1* 0.1 range contact connects resistance r ₂With resistance r ₃Tie point be connected resistance r with * 1 range contact ₃With I measuring disk brush and range selector K _1-1* 10 range contacts connect range selector K _1-1Normally closed contact be connected potential difference meter and measure partly negative pole; Two terminals of measuring junction are anodal to be connected with the 10th of II measuring disk, and negative pole is by galvanometer change-over switch K ₂Be connected with 0 of III measuring disk.