CN106093513A - A kind of can measure conventional, electric-resistance, high resistant, superelevation resistance electric bridge - Google Patents

Abstract

One is made up of six brachium pontis for general resistance, high resistant and super high resistance measurement, a kind of have wheatstone bridge, megohm bridge, the electric bridge of superelevation conducting bridge function, its comparison arm is made up of six step discs, has 11 amount limits, can measure the broad range hindered from general resistance to superelevation.

Description

A kind of can measure conventional, electric-resistance, high resistant, superelevation resistance electric bridge

Technical field

The present invention relates to the instrument that D.C. resistance is measured.

Background technology

Current wheatstone bridge cannot measure high resistant, superelevation resistance, can not measure the general electricity of below 1M Ω with megohm bridge Resistance.

Summary of the invention

It is an object of the invention to design and a kind of can measure conventional, electric-resistance, high resistant, the electric bridge of superelevation resistance, it need not megohm box And high value standard resistance, only with resistance 10⁶The general resistance of below Ω, measures the upper limit up to 10¹⁸The resistance of Ω resistance.

The first technical scheme of the present invention is so taked: it has for connecting measured " R_X" one by test arm, have six One of individual step disc composition is compared arm R₂, compare arm R₂The first step disc be have 0,1, the survey of 2 ... 10 totally 11 gears Amount dish I, measurement dish I welds between each two adjacent contacts 10000 Ω resistance one, the second step disc be have 0,1,2 ... 10 The measurement dish II of totally 11 gears, measurement dish II welds between each two adjacent contacts 1000 Ω resistance one, the 3rd step disc Be have 0,1, the measurement dish III of 2 ... 10 totally 11 gears, measurement dish III welds between each two adjacent contacts 100 Ω electricity Hinder one, the 4th step disc be have 0,1, the measurement dish IV of 2 ... 10 totally 11 gears, on measurement dish IV, each two is adjacent touches Weld 10 Ω resistance one between point, the 5th step disc be have 0,1, the measurement dish V of 2 ... 10 totally 11 gears, on measurement dish V Weld 1 Ω resistance one between each two adjacent contacts, the 6th step disc be have 0,1, the measurement dish of 2 ... 10 totally 11 gears VI, measurement dish VI welds between each two adjacent contacts 0.1 Ω resistance one；It is characterized in that it separately has four brachium pontis, with quilt The galvanometer G top node b that test arm connects is through brachium pontis R₃Upper 10 Ω resistance r₀Connect 90 Ω resistance r₁With brachium pontis R behind one end₃× 1 amount limit contact connects, resistance r₁The other end connects 900 Ω resistance r₂With brachium pontis R behind one end₃× 10 amount limit contacts connect, resistance r₂ The other end connects 9K Ω resistance r₃With brachium pontis R behind one end₃×10²Amount limit contact connects, resistance r₃The other end connects × 10³、× 10⁴、×10⁵Amount limit contact, brachium pontis R₃Upper × 10⁶Amount limit contact is through 1 Ω resistance r₄Connect node b, brachium pontis R₃Upper × 10⁸Amount limit Contact is through 100 Ω resistance r₅Connect node b, brachium pontis R₃Upper × 10¹⁰、×10¹²、×10¹⁴Amount limit contact is through 10K Ω resistance r₆ Connect node b, brachium pontis R₃Metal contact ring be connected with electric bridge node c；Galvanometer G other end node e is through brachium pontis R₄Upper 0.1 Ω resistance r₇Afterwards with brachium pontis R₄Upper × 10⁶、×10⁸、×10¹⁰Amount limit contact connects, through brachium pontis R₄Upper 0.01 Ω resistance r₈Afterwards with Brachium pontis R₄Upper × 10¹²、×10¹⁴Amount limit contact connects, brachium pontis R₄Upper its surplus limit contact disconnects with circuit, brachium pontis R₄Metal contacts Ring is connected with node c；Brachium pontis R₅× 1, × 10, × 10²、×10³Amount limit contact is through 10 Ω resistance r₉It is connected with node c, bridge Arm R₅× 10⁴Amount limit contact is through 1 Ω resistance r₁₀It is connected with node c, brachium pontis R₅× 10⁵、×10⁶、×10⁸、×10¹⁰Amount Limit contact is through 0.1 Ω resistance r₁₁It is connected with node c, brachium pontis R₅× 10¹²、×10¹⁴Amount limit contact is through 0.01 Ω resistance r₁₂ It is connected with node c, brachium pontis R₅Metal contact ring is connected with node d；Brachium pontis R₆× 1, × 10, × 10²、×10³、×10⁴、× 10⁵Amount limit contact is all directly connected with node e, brachium pontis R₆×10⁶、×10⁸、×10¹⁰、×10¹², amount limit contact through 10K Ω electricity Resistance r₁₃It is connected with node e, brachium pontis R₆× 10¹⁴Amount limit contact is through 1M Ω resistance r₁₄It is connected with node e, brachium pontis R₆Metal contacts Ring is connected with node d, brachium pontis R₃, brachium pontis R₄, brachium pontis R₅, brachium pontis R₆On brush all put and limit gear in same amount, during rotation four Brush is synchronized；Relatively arm R₂One end connects node d, and the other end connects node a, is connected with node a also by test arm one end and Power supply E one end, is connected node b by the test arm other end, and the power supply E other end connects node c.

The second technical scheme of the present invention is so taked: it has for connecting measured " R_X" one by test arm, have six One of individual step disc composition is compared arm R₂, compare arm R₂The first step disc be have 0,1, the survey of 2 ... 10 totally 11 gears Weld 1000 Ω resistance one between the upper each two adjacent contacts of amount dish I ', measurement dish I ', the second step disc be have 0,1,2 ... 100 Ω resistance one, the 3rd stepping is welded between the upper each two adjacent contacts of measurement dish II ', measurement dish II ' of 10 totally 11 gears Dish be have 0,1, weld 10 Ω between the upper each two adjacent contacts of the measurement dish III ' of 2 ... 10 totally 11 gears, measurement dish III ' Resistance one, the 4th step disc be have 0,1, the upper each two phase of the measurement dish IV ' of 2 ... 10 totally 11 gears, measurement dish IV ' Weld 1 Ω resistance one between adjacent contact, the 5th step disc be have 0,1, the measurement dish V ' of 2 ... 10 totally 11 gears, measurement dish Weld 0.1 Ω resistance one between the upper each two adjacent contacts of V ', the 6th step disc be have 0,1,2 ... 10 totally 11 gears 0.01 Ω resistance one is welded between the upper each two adjacent contacts of measurement dish VI ', measurement dish VI '；It is characterized in that it separately has four Brachium pontis, the galvanometer G top node b being connected with by test arm is through brachium pontis R₃Upper 10 Ω resistance r₀Connect 90 Ω resistance r₁Behind one end With brachium pontis R₃× 1 amount limit contact connects, resistance r₁The other end connects 900 Ω resistance r₂With brachium pontis R behind one end₃× 10 amount limit contacts Connect, resistance r₂The other end connects 9K Ω resistance r₃With brachium pontis R behind one end₃×10²Amount limit contact connects, resistance r₃The other end connects ×10³、×10⁴、×10⁵Amount limit contact, brachium pontis R₃Upper × 10⁶Amount limit contact is through 1 Ω resistance r₄Connect node b, brachium pontis R₃On ×10⁸Amount limit contact is through 100 Ω resistance r₅Connect node b, brachium pontis R₃Upper × 10¹⁰、×10¹²、×10¹⁴Amount limit contact is passed through 10K Ω resistance r₆Connect node b, brachium pontis R₃Metal contact ring be connected with electric bridge node c；Galvanometer G other end node e passes through Brachium pontis R₄Upper 0.1 Ω resistance r₇Afterwards with brachium pontis R₄Upper × 10⁶、×10⁸、×10¹⁰Amount limit contact connects, through brachium pontis R₄Upper 0.01 Ω Resistance r₈Afterwards with brachium pontis R₄Upper × 10¹²、×10¹⁴Amount limit contact connects, brachium pontis R₄Upper its surplus limit contact disconnects with circuit, brachium pontis R₄Metal contact ring is connected with node c；Brachium pontis R₅× 1, × 10, × 10²、×10³Amount limit contact is through 10 Ω resistance r₉With joint Point c connects, brachium pontis R₅× 10⁴Amount limit contact is through 1 Ω resistance r₁₀It is connected with node c, brachium pontis R₅× 10⁵、×10⁶、× 10⁸、×10¹⁰Amount limit contact is through 0.1 Ω resistance r₁₁It is connected with node c, brachium pontis R₅× 10¹²、×10¹⁴Amount limit contact is passed through 0.01 Ω resistance r₁₂It is connected with node c, brachium pontis R₅Metal contact ring is connected with node d；Brachium pontis R₆× 1, × 10, × 10²、× 10³、×10⁴、×10⁵Amount limit contact is all directly connected with node e, brachium pontis R₆×10⁶、×10⁸、×10¹⁰、×10¹², amount limit touch Point is through 10K Ω resistance r₁₃It is connected with node e, brachium pontis R₆× 10¹⁴Amount limit contact is through 1M Ω resistance r₁₄It is connected with node e, Brachium pontis R₆Metal contact ring is connected with node d, brachium pontis R₃, brachium pontis R₄, brachium pontis R₅, brachium pontis R₆On brush all put and limit in same amount Gear, during rotation, four brushes synchronize；Relatively arm R₂One end connects node d, and the other end connects node a, is connected with node a and also has By test arm one end and power supply E one end, being connected node b by the test arm other end, the power supply E other end connects node c.

By above technical scheme, except connecting measured " R_x" measurement arm outside, remaining brachium pontis is all general resistance Resistance is the lowest to the insulating requirements of material, it is also possible to not using shielding measure, owing to resistance is low, power supply avoids the need for High pressure, below 300V is the most permissible.

Accompanying drawing explanation

Fig. 1 is principle of the invention circuit.Dotted portion is for carrying out triangle star-like conversion offer reference.

Fig. 2 is that Fig. 1 carries out equivalent circuit after the star-like conversion of triangle.

Fig. 3 is the circuit diagram of the first scheme of the present invention.

Fig. 4 is the circuit diagram of first scheme of the present invention.

Detailed description of the invention

Embodiment one,

In figure 3, arm R is compared₂The resistance of upper 10 × 10000 Ω of measurement dish I, represents that measurement dish I is by 10 10000 Ω electricity Resistance composition, remaining measurement dish is in like manner.

In figure 3, all brachium pontis, compare heavy black bar on arm represent metal contact ring, hollow small circle represent metal touch Point, four-headed arrow represents metallic brush, long box indicating resistance, and the numeral in long square frame represents this resistance.

Fig. 1 is principle of the invention circuit, to Fig. 1 bridge arm R₄, brachium pontis R₅, brachium pontis R₆Carry out the star-like conversion of triangle:

$R_C=\frac{R_4\×R_5}{R_4+R_5+R_6}\mathrm{...}\left(1\right)$

$R_E=\frac{R_4\×R_6}{R_4+R_5+R_6}\mathrm{...}\left(2\right)$

$R_D=\frac{R_5\×R_6}{R_4+R_5+R_6}\mathrm{...}\left(3\right)$

Can have according to Fig. 2:

$\begin{array}{c}{R}_X=\frac{R_3\×(R_2+R_D)}{R_C}=\frac{R_4+R_5+R_6}{R_4{R}_5}\×\frac{R_2{R}_3(R_4+R_5+R_6)+R_3(R_5\×R_6)}{R_4+R_5+R_6}\\ =\frac{R_2{R}_3{R}_4+R_2{R}_3{R}_5+R_2{R}_3{R}_6+R_3{R}_5{R}_6}{R_4{R}_5}=\frac{R_2{R}_3{R}_6}{R_4{R}_5}+\frac{R_2{R}_3}{R_5}+\frac{R_2{R}_3}{R_4}+\frac{R_3{R}_6}{R_4}\end{array}\mathrm{...}\left(4\right)$

Understand from (4) formula and increase brachium pontis R₂, brachium pontis R₃, brachium pontis R₆Resistance value, reduces brachium pontis R₄, brachium pontis R₅Resistance value, just The resistance that resistance is the biggest can be measured, when electric bridge selects suitable precision, allow latter three can ignore:

$R_X\≈\frac{R_2{R}_3{R}_6}{R_4{R}_5}\mathrm{...}\left(5\right)$

Brachium pontis R₄× 1, × 10, × 10²、×10³、×10⁴、×10⁵Amount departs from bridge circuit in limited time, is at this moment actual Single bridges, so

R_X=R₃/R₅×R₂Brachium pontis R is limited in × 1 amount₃=10 Ω, brachium pontis R₅=10 Ω, so ratio is 1；Limit in × 10 amounts, 10 Ω resistance r₀Connect 90 Ω resistance r, brachium pontis R₃=100 Ω, brachium pontis R₅=10 Ω, so ratio is 10；× 10²Amount limit, bridge Arm R₃=1000 Ω, brachium pontis R₅=10 Ω, so ratio is 10²；× 10³Amount limit, brachium pontis R₃=10000 Ω, brachium pontis R₅=10 Ω, so ratio is 10³；× 10⁴Amount limit, brachium pontis R₃=10000 Ω, brachium pontis R₅=1 Ω, so ratio is 10⁴；× 10⁵ Amount limit, brachium pontis R₃=10000 Ω, brachium pontis R₅=0.1 Ω, so ratio is 10⁵。

Electric bridge is × 10⁶、×10⁸、×10¹⁰×10¹²、×10¹⁴Amount brachium pontis R in limited time₄Access bridge circuit, at this moment R_X= R₃R₆R₂/R₄R₅, × 10⁶Amount limit brachium pontis R₃=1 Ω, brachium pontis R₆=10K Ω, brachium pontis R₄=brachium pontis R₅=0.1 Ω, the most tested Arm R_X=(1 × 10⁴/10^-1×10^-1)×R₂=10⁶R₂, × 10⁸Amount limit brachium pontis R₃=100 Ω, brachium pontis R₆=10K Ω, brachium pontis R₄=brachium pontis R₅=0.1 Ω, at this moment by test arm R_X=(100 × 10⁴/10^-1×10^-1)×R₂=10⁸R₂, × 10¹⁰Amount limit brachium pontis R₃=10K Ω, brachium pontis R₆=10K Ω, brachium pontis R₄=brachium pontis R₅=0.1 Ω, at this moment by test arm R_X=(10⁴×10⁴/10^-1×10^-1) ×R₂=10¹⁰R₂.× 10¹²Amount limit brachium pontis R₃=10K Ω, brachium pontis R₆=10K Ω, brachium pontis R₄=brachium pontis R₅=0.01 Ω, at this moment By test arm R_X=(10⁴×10⁴/10^-2×10^-2)×R₂=10¹⁰R₂.× 10¹⁴Amount limit brachium pontis R₃=10K Ω, brachium pontis R₆=1M Ω, brachium pontis R₄=brachium pontis R₅=0.01 Ω, at this moment by test arm R_X=(10⁴×10⁶/10^-1×10^-1)×R₂=10¹²R₂。

× 10⁶Amount is prescribed a time limit, this circuit brachium pontis R₃Employing takes 1 Ω, brachium pontis R₆, compare arm R₂Also up to 10K Ω (during measurement Electric bridge should use the first step disc), brachium pontis R₄, brachium pontis R₅Resistance value is 0.1 Ω, at this moment

× 10⁶Amount limit

R_X=10¹⁰+3×10⁵Ω

Ignore rear three errors caused:

$\mathrm{\δ}=\frac{3\×{10}^5}{{10}^{10}+3\×{10}^5\mathrm{\Ω}}\≈0.003\%$

When electric bridge precision is 0.05 grade, this error can be disregarded.

× 10⁸Amount limits, × 10¹⁰Amount limits, × 10¹²Amount limit, amount limit error analysis are in like manner.

× 10¹⁴Amount is prescribed a time limit, brachium pontis R₃=10K Ω, brachium pontis R₆=1M Ω, brachium pontis R₄=brachium pontis R₅=0.01 Ω, brachium pontis R₆ =1M Ω compares arm R₂Put 10000 Ω, at this moment

$R_X=\frac{{10}^4\×{10}^4\×{10}^6}{0.01\×0.01}+\frac{{10}^4\×{10}^4}{0.01}+\frac{{10}^4\×{10}^4}{0.01}+\frac{{10}^4\×{10}^6}{0.01}$

R_X=10¹⁸+1.02×10¹²Ω

Ignore rear three errors caused:

$\mathrm{\δ}=\frac{1.02\×{10}^{12}}{{10}^{18}+1.02\×{10}^{12}\mathrm{\Ω}}\≈1\×{10}^{-6}$

Electric bridge precision is up to 0.001 grade.

Embodiment two, in the diagram, brachium pontis R₄× 1, × 10, × 10²、×10³、×10⁴、×10⁵Amount departs from electric bridge in limited time Circuit, at this moment with embodiment one be single bridges, electric bridge is × 10⁶、×10⁸、×10¹⁰×10¹²、×10¹⁴Amount bridge in limited time Arm R₄Access bridge circuit, at this moment R_X=R₃R₆R₂/R₄R₅,

$R_X\≈\frac{R_2{R}_3{R}_6}{R_4{R}_5}+\frac{R_2{R}_3}{R_5}+\frac{R_2{R}_3}{R_4}+\frac{R_6{R}_3}{R_4}\mathrm{...}\left(4\right)$

× 10⁶Amount limit

R_X=10⁹+1.2×10⁵Ω

Ignore rear three errors caused:

$\mathrm{\δ}=\frac{1.2\×{10}^5}{{10}^9+1.2\×{10}^5\mathrm{\Ω}}\≈1\×{10}^{-4}$

Electric bridge can use 0.1 grade, and rear three errors caused can be ignored.

× 10¹⁴Amount is prescribed a time limit, brachium pontis R₃=10K Ω, brachium pontis R₆=1M Ω, brachium pontis R₄=brachium pontis R₅=0.01 Ω, brachium pontis R₆ =1M Ω compares arm R₂Put 1000 Ω, at this moment

$R_X=\frac{{10}^3\×{10}^4\×{10}^6}{0.01\×0.01}+\frac{{10}^3\×{10}^4}{0.01}+\frac{{10}^3\×{10}^4}{0.01}+\frac{{10}^4\×{10}^6}{0.01}$

R_X=10¹⁷+1.02×10¹²Ω

$\mathrm{\δ}=\frac{1.02\×{10}^{12}}{{10}^{17}+1.02\×{10}^{12}\mathrm{\Ω}}\≈1\×{10}^{-5}$

When electric bridge precision is 0.01 grade, rear three errors caused can be ignored.

Claims (2)

1. can measure conventional, electric-resistance, high resistant, an electric bridge for superelevation resistance, it has for connecting measured " R_X" one by test arm, have One of six step disc compositions is compared arm R₂, compare arm R₂The first step disc be have 0,1,2 ... 10 totally 11 gears Measurement dish I, measurement dish I welds between each two adjacent contacts 10000 Ω resistance one, the second step disc be have 0,1,2 ... The measurement dish II of 10 totally 11 gears, measurement dish II welds between each two adjacent contacts 1000 Ω resistance one, the 3rd stepping Dish be have 0,1, the measurement dish III of 2 ... 10 totally 11 gears, measurement dish III welds 100 Ω between each two adjacent contacts Resistance one, the 4th step disc be have 0,1, the measurement dish IV of 2 ... 10 totally 11 gears, on measurement dish IV, each two is adjacent Weld 10 Ω resistance one between contact, the 5th step disc be have 0,1, the measurement dish V of 2 ... 10 totally 11 gears, measurement dish V Weld 1 Ω resistance one between upper each two adjacent contacts, the 6th step disc be have 0,1, the measurement of 2 ... 10 totally 11 gears Dish VI, measurement dish VI welds between each two adjacent contacts 0.1 Ω resistance one；It is characterized in that it separately has four brachium pontis, with The galvanometer G top node b connected by test arm is through brachium pontis R₃Upper 10 Ω resistance r₀Connect 90 Ω resistance r₁With brachium pontis R behind one end₃ × 1 amount limit contact connects, resistance r₁The other end connects 900 Ω resistance r₂With brachium pontis R behind one end₃× 10 amount limit contacts connect, resistance r₂The other end connects 9K Ω resistance r₃With brachium pontis R behind one end₃×10²Amount limit contact connects, resistance r₃The other end connects × 10³、× 10⁴、×10⁵Amount limit contact, brachium pontis R₃Upper × 10⁶Amount limit contact is through 1 Ω resistance r₄Connect node b, brachium pontis R₃Upper × 10⁸Amount limit Contact is through 100 Ω resistance r₅Connect node b, brachium pontis R₃Upper × 10¹⁰、×10¹²、×10¹⁴Amount limit contact is through 10K Ω resistance r₆ Connect node b, brachium pontis R₃Metal contact ring be connected with electric bridge node c；Galvanometer G other end node e is through brachium pontis R₄Upper 0.1 Ω resistance r₇Afterwards with brachium pontis R₄Upper × 10⁶、×10⁸、×10¹⁰Amount limit contact connects, through brachium pontis R₄Upper 0.01 Ω resistance r₈Afterwards with Brachium pontis R₄Upper × 10¹²、×10¹⁴Amount limit contact connects, brachium pontis R₄Upper its surplus limit contact disconnects with circuit, brachium pontis R₄Metal contacts Ring is connected with node c；Brachium pontis R₅× 1, × 10, × 10²、×10³Amount limit contact is through 10 Ω resistance r₉It is connected with node c, bridge Arm R₅× 10⁴Amount limit contact is through 1 Ω resistance r₁₀It is connected with node c, brachium pontis R₅× 10⁵、×10⁶、×10⁸、×10¹⁰Amount Limit contact is through 0.1 Ω resistance r₁₁It is connected with node c, brachium pontis R₅× 10¹²、×10¹⁴Amount limit contact is through 0.01 Ω resistance r₁₂ It is connected with node c, brachium pontis R₅Metal contact ring is connected with node d；Brachium pontis R₆× 1, × 10, × 10²、×10³、×10⁴、× 10⁵Amount limit contact is all directly connected with node e, brachium pontis R₆×10⁶、×10⁸、×10¹⁰、×10¹², amount limit contact through 10K Ω electricity Resistance r₁₃It is connected with node e, brachium pontis R₆× 10¹⁴Amount limit contact is through 1M Ω resistance r₁₄It is connected with node e, brachium pontis R₆Metal contacts Ring is connected with node d, brachium pontis R₃, brachium pontis R₄, brachium pontis R₅, brachium pontis R₆On brush all put and limit gear in same amount, during rotation four Brush is synchronized；Relatively arm R₂One end connects node d, and the other end connects node a, is connected with node a also by test arm one end and Power supply E one end, is connected node b by the test arm other end, and the power supply E other end connects node c.

2. having wheatstone bridge, an electric bridge for two kinds of functions of megohm bridge, it has for connecting measured " R_X" one by test arm, One be made up of six step discs is compared arm R₂, compare arm R₂The first step disc be have 0,1,2 ... 10 totally 11 gears The upper each two adjacent contacts of measurement dish I ', measurement dish I ' between weld 1000 Ω resistance one, the second step disc be have 0,1, 2 ... between the upper each two adjacent contacts of measurement dish II ', measurement dish II ' of 10 totally 11 gears, weld 100 Ω resistance one, the Three step discs be have 0,1, weld between the upper each two adjacent contacts of the measurement dish III ' of 2 ... 10 totally 11 gears, measurement dish III ' Connect 10 Ω resistance one, the 4th step disc be have 0,1, the measurement dish IV ' of 2 ... 10 totally 11 gears, measurement dish IV ' upper every Weld 1 Ω resistance one between two adjacent contacts, the 5th step disc be have 0,1, the measurement dish V ' of 2 ... 10 totally 11 gears, Weld 0.1 Ω resistance one between the upper each two adjacent contacts of measurement dish V ', the 6th step disc be have 0,1, totally 11,2 ... 10 0.01 Ω resistance one is welded between the upper each two adjacent contacts of the measurement dish VI ' of gear, measurement dish VI '；It is characterized in that it is another Having four brachium pontis, the galvanometer G top node b being connected with by test arm is through brachium pontis R₃Upper 10 Ω resistance r₀Connect 90 Ω resistance r₁ With brachium pontis R behind one end₃× 1 amount limit contact connects, resistance r₁The other end connects 900 Ω resistance r₂With brachium pontis R behind one end₃× 10 amounts Limit contact connects, resistance r₂The other end connects 9K Ω resistance r₃With brachium pontis R behind one end₃×10²Amount limit contact connects, resistance r₃Another End connects × 10³、×10⁴、×10⁵Amount limit contact, brachium pontis R₃Upper × 10⁶Amount limit contact is through 1 Ω resistance r₄Connect node b, bridge Arm R₃Upper × 10⁸Amount limit contact is through 100 Ω resistance r₅Connect node b, brachium pontis R₃Upper × 10¹⁰、×10¹²、×10¹⁴Amount limit contact Through 10K Ω resistance r₆Connect node b, brachium pontis R₃Metal contact ring be connected with electric bridge node c；Galvanometer G other end node e Through brachium pontis R₄Upper 0.1 Ω resistance r₇Afterwards with brachium pontis R₄Upper × 10⁶、×10⁸、×10¹⁰Amount limit contact connects, through brachium pontis R₄On 0.01 Ω resistance r₈Afterwards with brachium pontis R₄Upper × 10¹²、×10¹⁴Amount limit contact connects, brachium pontis R₄Break with circuit in upper its surplus limit contact Open, brachium pontis R₄Metal contact ring is connected with node c；Brachium pontis R₅× 1, × 10, × 10²、×10³Amount limit contact is through 10 Ω electricity Resistance r₉It is connected with node c, brachium pontis R₅× 10⁴Amount limit contact is through 1 Ω resistance r₁₀It is connected with node c, brachium pontis R₅× 10⁵、× 10⁶、×10⁸、×10¹⁰Amount limit contact is through 0.1 Ω resistance r₁₁It is connected with node c, brachium pontis R₅× 10¹²、×10¹⁴Amount limit contact Through 0.01 Ω resistance r₁₂It is connected with node c, brachium pontis R₅Metal contact ring is connected with node d；Brachium pontis R₆× 1, × 10, × 10²、×10³、×10⁴、×10⁵Amount limit contact is all directly connected with node e, brachium pontis R₆×10⁶、×10⁸、×10¹⁰、×10¹², amount Limit contact is through 10K Ω resistance r₁₃It is connected with node e, brachium pontis R₆× 10¹⁴Amount limit contact is through 1M Ω resistance r₁₄With node e Connect, brachium pontis R₆Metal contact ring is connected with node d, brachium pontis R₃, brachium pontis R₄, brachium pontis R₅, brachium pontis R₆On brush all put same Individual amount limit gear, during rotation, four brushes synchronize；Relatively arm R₂One end connects node d, and the other end connects node a, with node a even Connecing also by test arm one end and power supply E one end, connected node b by the test arm other end, the power supply E other end connects node c.