CN1991374A

CN1991374A - Four-range switching direct current potentiometer utilizing branch line having four measuring plates

Info

Publication number: CN1991374A
Application number: CN 200510062343
Authority: CN
Inventors: 骆乃光
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-12-30
Filing date: 2005-12-30
Publication date: 2007-07-04

Abstract

The invention provides a potentiometer with four measuring discs and diverting branch four range switching for DC voltage measurement, wherein 20X40 Omega is used as a No:1 measuring disc, 10X4.4 Omega is used as a No:2 measuring disc, 9-8.8 Omega is used as a No:3 measuring disc, 10X0,88 Omega is used as a No:2 measuring disc, wherein the on-off switch does not influence measurement result, the two measuring junction knobs and the four measuing discs are connected directly with cables, the contact resistance of the measurement step switch, the variable difference and thermoelectrical potential are eliminated outside the measurement result, and the zero potential can further raise negative potential for compensation, in X0.1 measuring range and X0.01measuring range, a common resistance is employed for dividing the current.

Description

There is four measurement disks to adopt the DC potentiometer of diverter branch four-range conversion

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 2.5mA; It is waited to levy and is that first step disc is made up of I measuring disk that 20 * 40 Ω are respectively arranged and the I ' replacement dish, second step disc is made up of II measuring disk that 10 * 4.4 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 * 8.8 Ω of resistance connection, the III ' replacement the dish of 10 * 8.8 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 * 0.88 Ω resistance form and the IV that 10 * 0.44 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 61.16 Ω resistance R ₁Connect the II ' replacement and coil the 10th point, 0 of II measuring disk connects one 84.84 Ω resistance R ₂The back is connected with 0 of I measuring disk; 0 on the I ' replacement dish connects one 9051.6 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 79.2 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 100 Ω resistance r ₁Be connected in parallel on potential difference meter and measure partly positive pole, resistance r ₁The other end and three cuttves four are thrown range selector K _1-1* 1 range contact connects K in this range _1-2The K of contact and * 10 ranges _1-1The contact connects, K _1-3The contact is by 810 Ω resistance r ₂K with 10 ranges _1-3The contact connects, and this contact is connected the negative pole of Measurement Network resistance; In * 0.1 range, K _1-1The K of contact and * 0.01 range _1-1The contact connection is also passed through 10 Ω resistance r ₃Be connected K with the I ' replacement dish brush _1-290 Ω resistance r are leaded up in the contact ₄K with * 10 ranges _1-1The contact connects the back and is connected with I measuring disk brush, and another road is by 9000 Ω resistance r ₅K with * 0.01 range _1-2The contact connects, K _1-3The contact is by 0.09 Ω resistance r ₆Connect behind this layer * 0.01 range contact through 80.01 Ω resistance r ₇Connect K _1-3* 1 range contact, the K of three cuttves, four throw switches _1-1, K _1-2, K _1-3Three layers of mutual short circuit of normally closed contact are measured the terminal positive pole for two and are connected with the 10th of II measuring disk, and negative pole passes through K switch 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 990 Ω between two brushes of first step disc, and the right resistance equals 9900 Ω, and total resistance is 900 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.

When * 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 10 ranges, 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.At * 0.1 range, total resistance resistance in series r between two brushes of first step disc ₄After, with 99 times to resistance r ₃Resistance and resistance r ₃Parallel connection, make to flow through the measuring disk electric current and be reduced to * 10 ranges 1/100, the amount of making limit is reduced to * 10 ranges 1/100, parallel connection reduces resistance, advances resistance r by series connection in potentiometer circuit ₆Add resistance r ₇Keep total resistance constant, when * 0.01 range, the resistance resistance r that connected between two brushes of first step disc ₄With resistance r ₅After, with 999 times to r ₃Resistance and resistance r ₃Parallel connection is reduced to * per mille of 10 ranges the electric current that flows through measuring disk, makes circuit reduce resistance after the parallel connection, by seal in resistance r in circuit ₇The holding circuit resistance is constant.

Basic range potential difference meter standard operation electric current is 2.5, left side electric current 25/11mA between two brushes of first step disc, the right electric current is 2.5/11mA, 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 407 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＝25/11×4.4n ₂+25/11+(80+4.4+0.44)+25/11×40n ₁-2.5/11×(20-n ₁)×40-2.5/22

×(10-n ₄)×0.88-2.5/22×(10-n ₃)×8.8(mv)

＝10n ₂+2000/11+10+1+1000n ₁/11-2000/11+100n ₁/11-1+0.1n ₄-10+1n ₃(mv)

＝100n ₁+10n ₂+1n ₃+0.1n ₄(mv)

The potential difference meter operating voltage is 4.5V, 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 4.2V～4.95V, gets fixed resistance R ₀=372 Ω, adjustable resistance RP ₁=20 * 15 Ω, RP ₂Be 0～18 Ω.

Claims

A kind of DC potentiometer that has four measurement disks to adopt the conversion of diverter branch four-range, 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 2.5mA; It is waited to levy and is that first step disc is made up of I measuring disk that 20 * 40 Ω are respectively arranged and the I ' replacement dish, second step disc is made up of II measuring disk that 10 * 4.4 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 * 8.8 Ω of resistance connection, the III ' replacement the dish of 10 * 8.8 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 * 0.88 Ω resistance form and the IV that 10 * 0.44 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 61.16 Ω resistance R ₁Connect the II ' replacement and coil the 10th point, 0 of II measuring disk connects one 84.84 Ω resistance R ₂The back is connected with 0 of I measuring disk; 0 on the I ' replacement dish connects one 9051.6 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 79.2 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 100 Ω resistance r ₁Be connected in parallel on potential difference meter and measure partly positive pole, resistance r ₁The other end and three cuttves four are thrown range selector K _1-1* 1 range contact connects K in this range _1-2The K of contact and * 10 ranges _1-1The contact connects, K _1-3The contact is by 810 Ω resistance r ₂K with 10 ranges _1-3The contact connects, and this contact is connected the negative pole of Measurement Network resistance; In * 0.1 range, K _1-1The K of contact and * 0.01 range _1-1The contact connection is also passed through 10 Ω resistance r ₃Be connected K with the I ' replacement dish brush _1-290 Ω resistance r are leaded up in the contact ₄K with * 10 ranges _1-1The contact connects the back and is connected with I measuring disk brush, and another road is by 9000 Ω resistance r ₅K with * 0.01 range _1-2The contact connects, K _1-3The contact is by 0.09 Ω resistance r ₆Connect behind this layer * 0.01 range contact through 80.01 Ω resistance r ₇Connect K _1-3* 1 range contact, the K of three cuttves, four throw switches _1-1, K _1-2, K _1-3Three layers of mutual short circuit of normally closed contact are measured the terminal positive pole for two and are connected with the 10th of II measuring disk, and negative pole passes through K switch ₂Be connected with 0 of III measuring disk.