CN100538374C - A kind of device of working sample dielectric property and assay method thereof and application - Google Patents
A kind of device of working sample dielectric property and assay method thereof and application Download PDFInfo
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- CN100538374C CN100538374C CNB2007101789077A CN200710178907A CN100538374C CN 100538374 C CN100538374 C CN 100538374C CN B2007101789077 A CNB2007101789077 A CN B2007101789077A CN 200710178907 A CN200710178907 A CN 200710178907A CN 100538374 C CN100538374 C CN 100538374C
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Abstract
The present invention relates to a kind of instrument and methods and applications of accurate working sample dielectric material characteristic.Described device comprises mandrel 1, interior electrode 2, sample layer 3, external electrode 4, insulating washer 5, internal electrode lead-wire 6a and guard electrode lead-in wire 6b, 6c, described interior electrode 2 adjustable length; Outside described mandrel 1, be socketed with successively described in electrode 2, sample layer 3 and external electrode 4, described in the two ends of electrode 2, sample layer 3 and external electrode 4 be provided with fastening structure; Described internal electrode lead-wire 6a one end is connected with described interior electrode 2.Media samples is installed in the coaxial type capacitor.The interior electrode of coaxial type capacitor adopts the structure of guard electrode type, to eliminate the influence of edge effect.The variable-length of active electrode makes that put into sample has medium and remove the electric capacity that sample do not have under two kinds of situations of medium basic identical.So, can realize the mensuration of example dielectric characteristic by measuring length and the correlation computations that active electrode changes.
Description
Technical field:
The invention belongs to in the electrical measurement field to the measurement of dielectric property, relate in particular to a kind of instrument and methods and applications of accurate working sample dielectric material characteristic.
Background technology:
The dielectric property of insulating material has significant values for the application of material.Industrial, the dielectric loss value component in the dielectric property causes energy loss, even device damage.At the exact instrument manufacture view, the accurate data of dielectric property are also very important for the performance of instrument, sometimes or even critical.Therefore, developed the method for many measurement dielectric properties for many years.But these methods also have the some shortcomings part at present:
1. can only measure plate shaped sample usually, and the size of sample is had requirement, sample area can not be too little.The dielectric property of material is along with place, batch difference of dispatching from the factory of producing this material can change.Accurate in order to guarantee measurement result, generally need to take a sample from the same batch of material of practical application.Sometimes, the material of practical application is less cylindrical bar, is difficult to cut down the planar shaped sample of enough sizes.And have not yet to see the instrument of the cylindrical or cylindrical shape sample dielectric property of direct measurement.
2. the existing basic ideas of measuring the dielectric property method are to make the air condenser of a plate-shaped electrode, measure the electric capacity of putting into and taking out plate shaped sample both of these case, calculate the dielectric property of sample more thus.The electric capacity of such air condenser generally only is several pF.And the problem that low capacitance measurement relates to is a lot.Measuring error is bigger, and particularly the connecting line between air condenser and the surveying instrument can also cause tangible error, and this error becomes along with the variation of measured capacitance amount.Therefore the method for above-mentioned measurement dielectric property has the defective of some principles.If can in measuring process, keep the measured capacitance amount constant, the process of measuring dielectric property will become a kind of alternative measurement, the error that the measuring error of measuring equipment itself and connecting line cause will be by cancellation in the process of twice measurement electric capacity, and the accuracy of measurement of dielectric property is also just along with improve.
Summary of the invention:
In order to overcome in the prior art sample shape size is had requirement and 2 big technical matterss of measuring error, the present invention has designed instrument and the dielectric property assay method that a kind of dielectric property is measured.
One of the present invention, a kind of device of working sample dielectric property is to realize like this
Described device comprises mandrel 1, interior electrode 2, sample layer 3, external electrode 4, insulating washer 5, internal electrode lead-wire (6a) and guard electrode lead-in wire (6b, 6c), described interior electrode 2 adjustable length;
Outside described mandrel 1, be socketed with successively described in electrode 2, sample layer 3 and external electrode 4, described in the two ends of electrode 2, sample layer 3 and external electrode 4 be provided with fastening structure; Described internal electrode lead-wire 6a one end is connected with described interior electrode 2;
By adjust described in the length of electrode 2, it is identical to be used for when described sample layer 3 is put into different medium and measured electric capacity.
In order to solve problem in the prior art, adopt the measured substitution method of measurement.By measuring length and the correlation computations that active electrode changes, can realize the mensuration of example dielectric characteristic.Electrode comprises active electrode part and guard electrode part in described, and described guard electrode partly is arranged on the two ends of active electrode part, and is provided with described insulating washer 5 in the middle of active electrode part and guard electrode part; The adjustable positions of described insulating washer 5, described interior electrode is by the length of the position adjustments active electrode of adjusting insulating washer 5, and then the length of regulating interior electrode 2.
In order to solve the technical matters that need make requirement to sample shape and size in the prior art, the present invention has adopted hollow coaxial type capacitor, can directly measure the dielectric property of cylindrical shape sample.Be that described mandrel 1 is hollow teflon mandrel, the material of described interior electrode 2 and external electrode 4 is a brass, and 3 sample is polytetrafluoroethylmaterial material and air in the described sample layer.
The present invention's two, a kind of device that utilizes the said determination example dielectric characteristic carries out method for measuring and is achieved in that
Described method adopts the measured substitution method of measurement, and described electrode length can be adjusted; Promptly, realize the mensuration of example dielectric characteristic by measuring length and the calculating that described active electrode partly changes; This method is used for when the dielectric property of measuring samples, reduces the poor of capacitance value that medium and two kinds of situations of no medium are arranged, takes a kind of method of alternative measurement.
In concrete method, in the described measured substitution method of measurement,
A, measured medium are non-air dielectrics, promptly put into measured medium
By the length that described interior electrode is regulated in the position of regulating insulating washer, make that the axial length of described active electrode part is l
1, the electric capacity C of calculating ganged condenser
1
B, measured medium are air dielectrics, and promptly sample layer is an air
By the length that described interior electrode is regulated in the position of regulating insulating washer, make that the axial length of described active electrode part is l
2, the electric capacity C of calculating ganged condenser
2
C, the dielectric property of mensuration measured medium
Because by the length of electrode in adjusting, the electric capacity of twice measurement is identical: C
1=C
2, accurately calculate the dielectric property ε of measured medium
r
The present invention's three, a kind ofly utilize the application of the assay method of said determination example dielectric characteristic to be:
Owing to adopted above-mentioned technical scheme, the present invention has broken through the limitation that can only measure plate shaped sample of the prior art for the shape of sample and size requirements, and this method both can be used to measure the dielectric property of cylindrical shape sample, also can measure the dielectric property to plate shaped sample.
Adopt technology contents of the present invention that sample is carried out the mensuration of dielectric property, principal feature is as follows:
1. adopt the measured substitution method of measurement.By measuring length and the correlation computations that active electrode changes, can realize the mensuration of example dielectric characteristic.
2. make hollow coaxial type capacitor, can directly measure the dielectric property of cylindrical shape sample;
3. solved the accurate problem of measuring of dielectric property of little capacitance (in the 10pF); The air condenser that can be generalized to plate-shaped electrode uses in measuring.
Measure a variable-length that characteristics are active electrodes of the coaxial type capacitor of cylindrical shape sample, make that the electric capacity of putting into sample and removing under two kinds of situations of sample is basic identical.Become a kind of process of measured alternative measurement like this with regard to the measurement that makes twice electric capacity.Electric capacity is measured the measuring error of instrument itself and error that connecting line causes can be by cancellation in measuring the process of electric capacity for twice, and the accuracy of measurement of dielectric property also thereby raising.To count different these factors of active electrode length when measuring for twice when certainly, calculating the dielectric property of sample.Interior electrode assembly is whole to be enclosed within on the mandrel of a teflon, makes disassembly process become easy.Mandrel is a hollow, and three connecting lines of electrode are drawn in being convenient to.
Technique scheme is one embodiment of the present invention, for those skilled in the art, on the basis that the invention discloses application process and principle, be easy to make various types of improvement or distortion, and be not limited only to the described method of the above-mentioned embodiment of the present invention, therefore previously described mode is preferably, and does not have restrictive meaning.
Description of drawings:
Fig. 1 is the coaxial type capacitor among the present invention, loads onto the status architecture diagrammatic cross-section after the media samples;
Fig. 2 is the coaxial type capacitor among the present invention, the status architecture diagrammatic cross-section when being medium with the air.
Below in conjunction with embodiment above-mentioned each width of cloth accompanying drawing of the present invention is described in further detail.
Embodiment:
Fig. 1 is the coaxial type capacitor among the present invention, loads onto the status architecture diagrammatic cross-section after the media samples; Fig. 2 is the coaxial type capacitor among the present invention, the status architecture diagrammatic cross-section when being medium with the air.Sample takes out.And by electrode length and insulating mat position in adjusting, electrode length increases about one times in making.The capacitance that takes out under the two kinds of situations in sample front and back is equal substantially.
Profile line is
Material be teflon, profile line is
Material be brass.
Described device comprises mandrel 1, interior electrode 2, sample layer 3, external electrode 4, insulating washer, internal electrode lead-wire (6a) and guard electrode lead-in wire (6b, 6c), described interior electrode 2 adjustable length;
Outside described mandrel 1, be socketed with successively described in electrode 2, sample layer 3 and external electrode 4, described in the two ends of electrode 2, sample layer 3 and external electrode 4 be provided with fastening structure; Described internal electrode lead-wire 6a one end is connected with described interior electrode 2;
By adjust described in the length of electrode 2, it is identical to be used for when described sample layer 3 is put into different medium and measured electric capacity.
In the middle of described inner electrode layer and mandrel, also include a polytetrafluoroethylene floor 7, play insulating effect.And comprise an interior electrode contact ring 8 at this layer 7, be used for drawing internal electrode lead-wire 6a from interior electrode 2.
Described mandrel 1 each outer layer is socketed in mandrel 1 outside, and in addition fastening operation of fastening nut 9 is passed through in the back.
Dielectric property with polytetrafluoroethylmaterial material is measured as example.Drawn among Fig. 1 and Fig. 2 and can be fit to the coaxial type capacitor of cylindrical shape sample.Measure respectively and put into sample and to remove the dielectric property that electric capacity under two kinds of situations of sample just can be obtained sample.The interior electrode of coaxial type capacitor adopts the guard electrode structure of Kelvin's formula.Center section is the active electrode part, and this is a long 23mm, external diameter 20mm, the brass barrel of thick 2mm.The guard electrode part is equipped with at two ends, also is brass barrel, and external diameter is the same with active electrode with thickness, but length has only 14mm.Respectively there is a guard electrode (two sections copper rings of a, b among Fig. 1) at the two ends of active electrode part, and the three is enclosed within one and thoroughly does away with on the teflon mandrel of edge.The thick thin layer insulation spacer of 0.1mm is arranged between active electrode and the guard electrode each other, guarantee insulation each other.Active electrode and guard electrode are in same current potential (earth potential) in measuring process, so just formed the guard electrode structure of Kelvin's formula.The non-uniform electric field that this Kelvin's formula guard electrode structure makes edge effect cause only appears at the guard electrode place, and the electric field of active electrode part then is evenly distributed.Have only the lead-in wire 6a that partly links to each other with active electrode to receive zero indicator during measurement, with the guard electrode then ground connection of 6b and 6c that goes between accordingly.Therefore have only with the corresponding capacitance current of active electrode the balance of measuring bridge is had effect.The corresponding capacitance current of electric field distortion that causes with edge effect only is present in the guard electrode part, flows directly in the ground, does not influence measuring process.Therefore Kelvin's formula guard electrode structure can be eliminated the influence of edge effect to measuring process.Interior electrode assembly is whole to be enclosed within on the mandrel of a teflon, makes disassembly process become easy.Mandrel is a hollow, and three connecting lines of electrode are drawn in being convenient to.
For feasible no medium is approaching identical with the capacitance under two kinds of situations of medium are arranged, the variable-length of the active electrode part of this kind coaxial type capacitor.In order to accomplish this point, actual active electrode partly has been divided into two sections of interior electrode A and interior electrode B.Can be by the order of electrode B section and insulation spacer in the transposing; the electrode B section directly contacts a part of (see figure 1) that becomes the guard electrode part with interior electrode A section insulation with equivalent potential screen ring b section in making; thereby in adjusting, in the electrode effective length, kept the length of whole device constant.
The active electrode outside is overlapped " high-field electrode ", i.e. an external electrode again.This also is a brass barrel.Internal diameter 26mm, thick 2mm.Both keep coaxial active electrode and " high-field electrode ", and promptly both have same axis.The gap that 3mm is arranged between active electrode and the external electrode.When this gap was the clearance, external electrode, active electrode part and two guard electrode parts had just formed one " ganged condenser " together.
First kind of situation: do not have medium, promptly electric capacity is air condenser
If effectively the axial length of electrode is l
1, external diameter is r, and the gap between active electrode and " high-field electrode " is δ, and then the electric capacity of ganged condenser is
Second kind of situation: put into measured medium
The cylindrical shape sample of a polytetrafluoroethylmaterial material on interior electrode jacket.The external diameter of electrode in the internal diameter of sample just in time equals.The thickness of sample cylinder equals the gap delta of original internal and external electrode.。And then put original external electrode-" high-field electrode " in cylindrical shape teflon sample outside.So just constituted a coaxial type capacitor again.Basic identical when making capacitance and first kind of situation, the length of electrode in must suitably adjusting.If electrode length is l in this moment
2
Then electric capacity from (1) formula become for
ε wherein
rBe the relative dielectric constant of measured material teflon sample, just the in-phase component of sample medium characteristic.
For the measurement that makes twice electric capacity becomes a kind of process of alternative measurement, should make the electric capacity of putting into sample and removing under two kinds of situations of sample basic identical.Can make electric capacity measure the measuring error of instrument itself like this and error that connecting line causes can be by cancellation in the process of twice measurement electric capacity, the accuracy of measurement of dielectric property is also just along with improve.Make C as can be known from (1) and (2) formula
1And C
2The condition that equates is
l
1＝ε
rl
2 (3)
Or
In other words, when measuring for the second time, the length of active electrode part should shorten to 1/ ε
r, so just can reach and make C
1And C
2The condition that equates.For example, the relative dielectric constant that checks in the teflon sample from document is about 2.0, so when measuring for the second time, the length of active electrode part should shorten to original half.If specific inductive capacity is not just in time to equal 2.0, the effective length of electrode can be adjusted.For example do some diameters conductive foil identical with active electrode, connect together with half of active electrode, just adjusted the variable quantity of active electrode length in twice measuring process, thereby adapt to specific inductive capacity and be not equal to 2.0 situation, make that the electric capacity of twice measurement is still very approaching, satisfy substituting Testing requirement.
Table 1 is for respectively having carried out 20 time measurement result to cylindrical teflon sample in the situation that medium is arranged and do not have a medium with Fig. 1,2 shown devices.Provided dielectric loss measurement value mean value, standard deviation and residual error under medium and two kinds of situations of no medium simultaneously, the data from table as can be seen.Therefore all residual errors can think that these data all are effective all less than 3 σ.
Annotate: 1. tan δ in showing
1With tan δ
2Standard deviation, be the standard deviation of single measurement, try to achieve by the Bezier formula
2. the standard deviation of tan δ is meant standard error of the mean in the table.
Claims (4)
- The device of 1 one kinds of working sample dielectric properties, it is characterized in that: described device comprises mandrel (1), interior electrode (2), sample layer (3), external electrode (4), insulating washer (5), internal electrode lead-wire (6a) and guard electrode lead-in wire (6b, 6c), described interior electrode (2) adjustable length;Outside described mandrel (1), be socketed with successively described in electrode (2), sample layer (3) and external electrode (4), described in the two ends of electrode (2), sample layer (3) and external electrode (4) be provided with fastening structure; Described internal electrode lead-wire (6a) end is connected with described interior electrode (2);This device be used for by adjust described in the length of electrode (2), electric capacity is identical when making described sample layer (3) put into different medium to measure;Electrode (2) comprises effective electrode part branch and guard electrode part in described, and described guard electrode partly is arranged on the two ends of active electrode part, and is provided with described insulating washer (5) in the middle of active electrode part and guard electrode part; The adjustable positions of described insulating washer (5), described interior electrode (2) is by the length of the position adjustments active electrode of adjusting insulating washer (5), and then the length of regulating interior electrode.
- The device of 2 a kind of working sample dielectric properties according to claim 1 is characterized in that: described mandrel (1) is a hollow teflon mandrel, and the material of described interior electrode (2) and external electrode (4) is a brass.
- 3 use the method according to a kind of working sample dielectric property of the described a kind of working sample dielectric property device of one of claim 1-2, and it is characterized in that: described method adopts the measured substitution method of measurement, and described electrode length can be adjusted; Promptly, realize the mensuration of example dielectric characteristic by measuring the length that described active electrode partly changes and calculating; This method is used for when the dielectric property of measuring samples, reduces the poor of capacitance value that medium and two kinds of situations of no medium are arranged, takes a kind of method of alternative measurement;In the described measured substitution method of measurement,A, measured medium are non-air dielectrics, promptly put into measured mediumBy the length that described interior electrode is regulated in the position of regulating insulating washer, make that the axial length of described active electrode part is l 1, the electric capacity C of calculating ganged condenser 1B, measured medium are air dielectrics, and promptly sample layer is an airBy the length that described interior electrode is regulated in the position of regulating insulating washer, make that the axial length of described active electrode part is l 2, the electric capacity C of calculating ganged condenser 2C, the dielectric property of mensuration measured mediumBecause by the length of electrode in adjusting, the electric capacity of twice measurement is identical: C 1=C 2, accurately calculate the dielectric property ε of measured medium r
- The application of the method for 4 a kind of working sample dielectric properties according to claim 3 is characterized in that: described method is used to measure the dielectric property of cylindrical shape sample and the dielectric property of plate shaped sample.
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| CN102565535A (en) * | 2012-03-07 | 2012-07-11 | 德州学院 | Experimental instrument for resistivity and dielectric constant of biological tissue |
| CN103207288B (en) * | 2013-03-27 | 2015-06-24 | 中国计量科学研究院 | Solid electric compensation auxiliary electrode and application thereof |
| CN103197181B (en) * | 2013-03-27 | 2015-12-23 | 中国计量科学研究院 | A kind of guarded electrode model component and application thereof |
| CN107621490A (en) * | 2017-09-28 | 2018-01-23 | 青岛农业大学 | A kind of grain moisture content determining method |
| CN108181357B (en) * | 2018-01-30 | 2020-09-15 | 天津大学 | Vertical rotational flow split-phase capacitance integrated water content measuring device |
| CN109581159B (en) * | 2018-11-30 | 2020-01-21 | 华北电力大学 | Insulating liquid state, gaseous state and gas-liquid mixture state dielectric property test chamber |
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