CN1811468A - Two-measuring range potential differencemeter with five's place reading utilizing shunt branch - Google Patents

Abstract

The present invention relates to a two-range potentiometer for DC voltage. It is characterized by that it has five-digit number readout and adopts shunting branch, and is composed of three measuring disks of 20X10 ohm, 9X2.2 ohm and 10X0.22 ohm and a slide-wire disk of 0-1.21 ohm, it can provide five-digit number readout, all the measuring resistors are directly connected by means of wire. When the minimum resolution is 0.1 microvolt, it also has good reproducibility.

Description

There is five digit reading to adopt the two-range potentiometer of diverter 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 three step discs and 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 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 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 1mA; It is characterized in that first step disc is made up of I measuring disk that 20 * 10 Ω are respectively arranged and the I ' replacement dish, second step disc is by non-resistance between 0 and 1, these two contacts disconnect, all the other contacts are by the II measuring disk of 9 * 2.2 Ω of resistance connection, the II ' replacement the dish of 10 * 2.2 Ω is arranged and be not welded with resistance, 0 independence, the II that all the other contacts connect " form; " form by bracket panel by being all III measuring disk and the III ' replacement dish that 10 * 0.22 Ω resistance form and the III that 10 * 0.11 Ω resistance are arranged for the 3rd step disc by bracket panel, the 4th dish is two slide wire discs, two slide wire resistance resistances all are 0～1.21 Ω, wherein one is IV measuring disk slip, another root is an IV ' replacement dish slip, the index dial of slip indicates 10 big lattice of 0～100 one indicating value, every big lattice have 10 little lattice, 0 indicating value has 5 little lattice to show forward, also be equivalent to " 1 " more forward to slide wire disc top and 5 little lattice resistance arranged backward in slide wire disc inside, the resistance value of every big lattice correspondence is 0.11 Ω, 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 64.79 Ω resistance R ₁All the other are put and are connected II " bracket panel brush one tunnel connects the II ' replacement and coils the 10th point, and 19.8 Ω resistance R are passed through on another road except that 0 o'clock for " bracket panel the 10th point; III " bracket panel 0 connect II " 0 connection of bracket panel; this coil brush and the II " bracket panel that connects III ₂Coil at the 10th with the III ' replacement and be connected, the 1st of II measuring disk connects III measuring disk the 10th point, and it is 20.11 Ω resistance R that 0 of II measurement is connected resistance jointly with 0 of III measuring disk ₃The back is connected with 0 of I measuring disk, and the 20th of I measuring disk connects IV measuring disk the 10th point, and the IV ' replacement dish top connects 2768.79 Ω resistance R ₄The back is connected with 0 on the I ' replacement dish; The I ' replacement dish brush and 30 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 243 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 junction are anodal to be connected with the 10th of II measuring disk, negative pole passes through galvanometer change-over switch K ₂Be connected with IV measuring disk line top.

By above technical scheme, the measuring disk that three step discs and slide wire disc are used for measure portion connects with lead, measure step switch 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 obtain revising by adjusting the slide wire disc zero-bit, or increases between IV measuring disk and the I measuring disk lead resistance and revise, 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 has 297 Ω between two brushes of first step disc, and the right resistance equals 2970 Ω, and total resistance is 270 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 3rd dish partly resistance in parallel when the 3rd dish was thrown different indicating value, the circuit resistance was constant.When second dish is not thrown 0 the time, the 3rd dish is thrown different indicating values, the circuit resistance is not having III " resistance changes during bracket panel; the 3rd dish every increase stepping, circuit resistance can increase half resistance of each stepping resistance, for the total resistance of holding circuit constant; each stepping reduces same resistance in the 3rd bracket panel; resistance minimum when second step disc throws 0, and " bracket panel resistance all seals in circuit, makes the circuit resistance constant at this moment to allow III.Because first dish and the 4th dish are formed by resistance identical measuring disk and replacement dish, so what indicating value no matter four 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 range 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.

Basic range potential difference meter working current is 1mA, left side electric current 10/11mA between two brushes of first step disc, the right electric current is 1/11mA, left side electric current flows through II " is divided into two equal branch roads; when second dish throws at 0; two branch roads that flow through II measuring disk and III measuring disk separate; when the II measuring disk does not throw 0; flow through II measuring disk branch current and all flow through III measuring disk resistance; 10 resistance of III measuring disk play the effect of the 1st resistance of II measuring disk, when the III measuring disk is thrown n behind the bracket panel brush ₃The time, n ₃Though～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;

The 1mA 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 1018 Ω with the resistance of setting up resistance R N, and 0～2 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, when * 1 range, 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＝5/11×2.2n ₂+5/11×0.22n ₃+10/11×(20+0.11)+10/11×10n ₁-1/11×(20-n ₁)

×10-1/11×(10-n ₄)×0.11(mv)

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

＝10n ₁+n ₂+0.1n ₃+0.01n ₄(mv)

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

Top n ₄Calculating by big lattice resistance, is 0.1 μ v at the every little lattice resolution of * 0.1 range therefore.

The potential difference meter operating voltage is 1.5v, gets fixed resistance R for supply voltage is worked in 1.4v～1.65v scope ₀=110 Ω, adjustable resistance RP ₁=20 * 12 Ω, adjustable resistance RP ₂Be 0～13 Ω

The DPTT double-pole triple throw K switch _1-3The input signal of right * 1 range is decayed, and enters amplifier at the whole signals of * 0.1 range, and advancing input signal when * 1 range is R ₉/ (R ₈+ R ₉).

The diode D of the positive and negative connection of amp.in ₁And D ₂Be used for input protection, two integrated amplifier OPA128 carry out the differential output of differential input, feedback resistance R ₅With R ₆Equate, get 1M Ω here, resistance R ₇Get 200 Ω, amplified signal shows with reometer G.

Claims (1)

1. A kind of two-range potentiometer that has five digit reading to adopt diverter 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 1mA; It is characterized in that first step disc is made up of I measuring disk that 20 * 10 Ω are respectively arranged and the I ' replacement dish, second step disc is by non-resistance between 0 and 1, these two contacts disconnect, all the other contacts are by the II measuring disk of 9 * 2.2 Ω of resistance connection, the II ' replacement the dish of 10 * 2.2 Ω is arranged and be not welded with resistance, 0 independence, the II that all the other contacts connect " form; " form by bracket panel by being all III measuring disk and the III ' replacement dish that 10 * 0.22 Ω resistance form and the III that 10 * 0.11 Ω resistance are arranged for the 3rd step disc by bracket panel, the 4th dish is two slide wire discs, two slide wire resistance resistances all are 0～1.21 Ω, wherein one is IV measuring disk slip, another root is an IV ' replacement dish slip, the index dial of slip indicates 10 big lattice of 0～100 one indicating value, every big lattice have 10 little lattice, 0 indicating value has 5 little lattice to show forward, also be equivalent to " 1 " more forward to slide wire disc top and 5 little lattice resistance arranged backward in slide wire disc inside, the resistance value of every big lattice correspondence is 0.11 Ω, 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 64.79 Ω resistance R ₁All the other are put and are connected II " bracket panel brush one tunnel connects the II ' replacement and coils the 10th point, and 19.8 Ω resistance R are passed through on another road except that 0 o'clock for " bracket panel the 10th point; III " bracket panel 0 connect II " 0 connection of bracket panel; this coil brush and the II " bracket panel that connects III ₂Coil at the 10th with the III ' replacement and be connected, the 1st of II measuring disk connects III measuring disk the 10th point, and it is 20.11 Ω resistance R that 0 of II measurement is connected resistance jointly with 0 of III measuring disk ₃The back is connected with 0 of I measuring disk, and the 20th of I measuring disk connects IV measuring disk the 10th point, and the IV ' replacement dish top connects 2768.79 Ω resistance R ₄The back is connected with 0 on the I ' replacement dish; The I ' replacement dish brush and 30 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 243 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 junction are anodal to be connected with the 10th of II measuring disk, negative pole passes through galvanometer change-over switch K ₂Be connected with IV measuring disk line top.