CN1782717A

CN1782717A - Direct current potential difference method of three measuring range conversion

Info

Publication number: CN1782717A
Application number: CN 200510060694
Authority: CN
Inventors: 骆乃光
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-09-09
Filing date: 2005-09-09
Publication date: 2006-06-07
Anticipated expiration: 2025-09-09
Also published as: CN100348986C

Abstract

The DC potentiometer for DC voltage measurement has three measurement ranges of X10, X1 and X0.1 separately. It has 11x40/11 ohm potentiometer in the first measuring disc, 11x0.4 ohm potentiometer in the second measuring disc and 0-4.4 ohm potentiometer in the third measuring disc, and the three measuring discs are connected with wires without contact resistance and variation. The zero potential the lead resistance generates is compensated with the negative potential. The X10 range has upper measuring limit of 111 mV, the X0.1 range has resolution of 0.1 mu V, and the potentiometer has high measurement repeatability.

Description

The DC potentiometer of three ranges conversion

Technical field

The present invention relates to instrument that DC voltage is measured.

Background technology

In the current portable potential difference meter, there are switch contact resistance and variation in potential difference meter inside, also have thermoelectric potential influence, so can not make product accomplish that resolution is 0.1 μ V owing to be used to measure two terminals.

Summary of the invention

Purpose of the present invention is a kind of portable potential difference meter of design, and three ranges are arranged, and resolution reaches 0.1 μ V when the amount limit is minimum, and it can get rid of switch room contact resistance and variation influence, and thermoelectric potential influence is also foreclosed; For the ease of " self check ", three measuring disk all are provided with " 1 " indicating value.

Technical scheme of the present invention is such: working current is regulated resistance R P ₁And RP ₂, the fixed resistance R of fixed power source pressure drop ₀, the setting resistance R N of sampling usefulness during to standard, and metering circuit is connected in the potentiometer circuit; Measure partly with two step discs and a two slide wire disc, first step disc is made up of I ' the replacement dish of 11 * 40/11 Ω I measuring disk and 11 * 40/11 Ω, second step disc is made up of the II measuring disk of 11 * 0.4 Ω and II ' the replacement dish of 11 * 0.4 Ω, two brushes of this step disc interconnect, the promptly two slide wire discs of the 3rd dish, two resistance wire resistances are identical, be all 0～4.4 Ω, its indicating value index dial has 11 big lattice, the corresponding resistance of every big lattice is 0.4 Ω, and 110 little lattice are arranged, every little lattice 0.04 Ω, make III ' dish replacement slip for one in two slips, another root is made the measurement slip of III dish, and the brush on two slide wire resistances of this dish is from getting off with a slice metal upper punch.

I ' replacement is coiled at the 10th and is connected 10.6 Ω resistance R ₁The back is coiled at the 10th with II ' replacement and is connected, and II measuring disk " 1 " point connects I measuring disk " 1 " point, and this coils the 10th connection III measuring disk does not hold, and it is 505.6 Ω resistance R that III ' replacement slip top " 1 " point connects a resistance ₂The back is connected with I ' replacement dish " 1 " point.

I ' replacement dish brush and 5 Ω resistance r ₁Be connected in parallel on the metering circuit positive pole, 5 Ω resistance, the 40.5 Ω resistance r that connect ₄K with double-point double-throw switch _1-1* 0.1 range contact connects, 5 Ω resistance and 40.5 Ω resistance joints, and 45 Ω resistance r again burn-on ₂The back is connected with * 1 range contact, and this contact and * 10 range contacts are with 450 Ω resistance r ₃Connect, * 10 range contacts are connected with I measuring disk brush, the K in the double-point double-throw switch _1-1Normally closed contact be connected on the metering circuit negative pole.

Be used to connect measured U _XTwo terminals, positive pole is connected with the 10th of II measuring disk, and negative pole is measured slip top by galvanometric change-over switch with III and is connected.

Because so three measuring disk all are to connect with lead not have contact resistance and variation problem, the thermoelectrical potential of switch is not also within three measuring disk, only influence the 1.5V supply voltage, influence can be ignored to measurement result, because III measures on the slip negative potential is arranged, the zero potential that lead-in wire produces, lead resistance can solve on the right of increasing between two brushes of first step disc when the slide wire disc zero graduation is located, therefore this circuit is when resolution is 0.1 μ V, and the various disturbing factors of potential difference meter inside all are resolved.

Description of drawings

Accompanying drawing is a principle of the invention circuit

Embodiment

In the drawings, when three measuring disk are thrown " 1 ", the left portion resistance is 40 Ω+10.6 Ω+4.4 Ω=55 Ω between I ' replacement dish brush and I measuring disk brush, the right partly resistance is 40 Ω+4.4 Ω+505.6 Ω=550 Ω, so total resistance is 50 Ω between two brushes of first dish, because the replacement dish reduced a same resistance when measuring disk increased a resistance value, so resistance is constant when measuring disk is thrown other value.When * 10 ranges, with the measuring disk parallel resistance be 500 Ω, at this moment flowing through the measuring disk total current is 2.75mA, electric current is 0.275mA on the 500 Ω resistance in parallel, when * 1 range, with the measuring disk parallel resistance be 50 Ω, the resistance that is cascaded with measuring disk is 500 Ω, so flowing through the measuring disk total current is 0.275mA, in like manner, when * 0.1 range, flowing through the measuring disk total current is 0.0275mA, at this range resistance is reduced, the 40.5 Ω resistance of therefore connecting make the circuit resistance constant.

The right resistance is 10 times of resistances of left side resistance between two brushes of first dish, so left side electric current is 10 times of the right electric current, measures terminal U _XAt the potential difference meter builtin voltage, when * 10 ranges, establish the I measuring disk and throw n ₁, the II measuring disk is thrown n ₂, the III measuring disk is thrown n ₃, U at this moment _XBetween voltage be: 2.5 (0.4n ₂+ 0.4+40/11+40n ₁/ 11) (10-n-0.25 ₁) * 40/11-0.25 (10-n ₃) * 0.4 (mv)

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

＝10n ₁+n ₂+0.1n ₃(mv)

All the other ranges of above numeral expression are the same, and only value unit becomes 0.1mv and 0.01mv, and III coils * 10 range n ₃Represent big lattice, the every little lattice of this range should be 10 μ v mutually, and therefore every little scale value is 0.1 μ v when * 0.1 range.

Measuring disk and range transfer resistance are formed measurement way circuit A, B point-to-point transmission voltage U _AB=2.75 * 50=137.5mv, setting up resistance R N resistance is 336 Ω, other adds 0～1.2 Ω adjustable resistance RP ₃, measure way circuit and reduce to U with setting resistance tail end C point two parts stagnation pressure _AC=1.1575V is because battery is stable to just not moving below the 1.4V, therefore with 80 Ω resistance R ₀Be lifted to 1.4V, electronic potential energy in order there to be the 0.25V scope adjustable, adopted 10 * 8 Ω adjustable resistance RP to 1.65V when dry cell was new ₁, 0～10 Ω adjustable resistance RP ₂

Setting up the resistance adjustable part is to determine like this, 100mv～200mv normal voltage signal is input to measures binding post U _x"+" "-" two ends, range switch K _1-1Throw * 10 ranges and measuring disk indicating value equate K switch with standard voltage value ₂Throw to the left side, regulate RP ₁And RP ₂Make galvanometer G nulling, again with K switch ₂The electromotive force EN that throws and standard cell unsaturated to the right is between 1.0188～1.0196V, by adjusting RP ₃Make inspection statistics G nulling once more, and with RP ₃The value locking.

In amplifying circuit, resistance R ₄With R ₅Resistance will be matched, and is identical as far as possible, the desirable 1M Ω of resistance, resistance R ₆The resistance magnitude relationship to the sensitivity of gauge outfit G, resistance R ₆Resistance is too small, and enlargement factor is too high, operating difficulties not only, and can make gauge outfit G produce shake, resistance R ₆The excessive sensitivity of resistance just reduces, and at 0.05 grade, the potential difference meter full scale changed 5/10000ths o'clock, needle deflection 1mm national standard, at this moment resistance R according to the potential difference meter precision ₆Value should be 200 Ω.Diode D ₁And D ₂The positive and negative input end that is connected on is in order to carry out input protection, resistance R ₇, R ₈, R ₉Form bleeder circuit, signal is the strongest when * 10 ranges, and signal is got R ₉/ (R ₇+ R ₈+ R ₉), when * 1 range, signal is got (R ₈+ R ₉)/(R ₇+ R ₈+ R ₉), when * 0.1 range, more than three ohmically signals all enter amplifier.Resistance R ₇Get 3.3K Ω, resistance R ₈Get 1K Ω, resistance R ₉Get 120 Ω.

K switch ₂Throw to the right and be used for check and correction standard, resistance R ₁₀Get 51K Ω～75K Ω,, regulate RP with restriction unsaturated standard cell discharge current ₁And RP ₂Make galvanometer G nulling, at this moment the potential difference meter working current is by " standardization ", K switch ₂Throw when the left side, at U _XConnect measuredly between two terminals by polarity, make gauge outfit G pointer nulling by regulating range selector and measuring disk, at this moment to be multiplied by multiplying power be measured magnitude of voltage to the measuring disk reading.

Claims

The DC potentiometer of three ranges conversion is regulated resistance R P to working current ₁And RP ₂, the fixed resistance R of fixed power source pressure drop ₀, the setting resistance R N of sampling usefulness during to standard, and metering circuit is connected in the potentiometer circuit; It is characterized in that measuring partly with two step discs and a two slide wire disc, first step disc is made up of I ' the replacement dish of 11 * 40/11 Ω I measuring disk and 11 * 40/11 Ω, second step disc is made up of the II measuring disk of 11 * 0.4 Ω and II ' the replacement dish of 11 * 0.4 Ω, two brushes of this step disc interconnect, the promptly two slide wire discs of the 3rd dish, two resistance wire resistances are identical, be all 0～4.4 Ω, its indicating value index dial has 11 big lattice, the corresponding resistance of every big lattice is 0.4 Ω, and 110 little lattice are arranged, every little lattice 0.04 Ω, make III ' dish replacement slip for one in two slips, another root is made the measurement slip of III dish, and the brush on two slide wire resistances of this dish is from getting off with a slice metal upper punch; I ' replacement is coiled at the 10th and is connected 10.6 Ω resistance R ₁The back is coiled at the 10th with II ' replacement and is connected, and II measuring disk " 1 " point connects I measuring disk " 1 " point, and this coils the 10th connection III measuring disk does not hold, and it is 505.6 Ω resistance R that III ' replacement slip top " 1 " point connects a resistance ₂The back is connected with I ' replacement dish " 1 " point; I ' replacement dish brush and 5 Ω resistance r ₁Be connected in parallel on the metering circuit positive pole, 5 Ω resistance, the 40.5 Ω resistance r that connect ₄K with double-point double-throw switch _1-1* 0.1 range contact connects, 5 Ω resistance and 40.5 Ω resistance joints, and 45 Ω resistance r again burn-on ₂The back is connected with * 1 range contact, and this contact and * 10 range contacts are with 450 Ω resistance r ₃Connect, * 10 range contacts are connected with I measuring disk brush, the K in the double-point double-throw switch _1-1Normally closed contact be connected on the metering circuit negative pole; Be used to connect measured U _XTwo terminals, positive pole is connected with the 10th of II measuring disk, and negative pole is measured slip top by galvanometric change-over switch with III and is connected.