CN104777074A - Evaluation method for measuring uncertainty of turpentine density - Google Patents

Abstract

The invention discloses an evaluation method for measuring an uncertainty of a turpentine density, and belongs to the technical field of chemical detecting. According to the technical scheme, the method comprises the following steps that firstly, a DM 45 full-automatic density instrument is adopted to measure the turpentine density; secondly, main sources of the uncertainty are analyzed, wherein the sources of the uncertainty comprise repeated measuring, instrument accuracy, instrument density digital displaying and temperature accuracy; thirdly, evaluation is carried out on components of measured uncertainty, wherein the evaluation comprises the evaluation of an uncertainty U1 caused by the repeated measuring, the evaluation of an uncertainty U2 caused by the instrument accuracy, the evaluation of an uncertainty U3 caused by the instrument density digital displaying, the evaluation of an uncertainty U4 caused by the temperature accuracy, the evaluation of a compounding uncertainty Uc and the evaluation of an expanding uncertainty U.

Description

A kind of assessment method measuring terebinthina density uncertainty

Technical field

The present invention relates to a kind of assessment method of substance-measuring density uncertainty, specifically, be a kind of assessment method measuring terebinthina density uncertainty, belong to technical field of chemical detection.

Background technology

Uncertainty of measurement is called for short uncertainty, according to used information, characterizes the non-negative parameter of giving tested value dispersiveness.CNAS-CL01:2006 " testing and calibration laboratories capability Approval criterion " requires the checkout equipment with measurement function, can provide required uncertainty of measurement

Density is one of key property of material, and quality and the quality of density and product are closely related, and it is in the quality control of conversion quantity, acceptance of delivery and some oil product, and simply judges oil property plays an important role.China has abundant terebinthina resource, and it is mainly used in artificial camphor, spices, paint solvent, tackifier, plastic plasticizer, agricultural chemicals, medical product etc.At present, terebinthina density measures according to the regulation in GB/T 12902-200, GB/T 4472-2011, wherein specifies that fluid density adopts density bottle method, Westphal balance method and densimeter method.Now introduce the full-automatic densitometer method of DM45 and measure terebinthine density, this method is quick, few by sample amount, be accurate to radix point after the 5th, and can the density of METHOD FOR CONTINUOUS DETERMINATION different temperatures, there is larger measuring tempeature scope, heating and cooling speed faster and extremely short measuring period.

Summary of the invention

For the problems referred to above, the factor that the object of this invention is to provide a pair full-automatic densitometer method testing process of DM45 affects measurement result carries out analysis on Uncertainty and appraisal procedure, clearly to the influential component of testing result, significant to the accuracy improving testing result further.

Technical scheme provided by the invention is such: a kind of assessment method measuring terebinthina density uncertainty, comprises the steps: successively

1) the full-automatic Density Measuring Instrument of DM45 is adopted to measure terebinthine density measurement terebinthina density;

2) uncertain main source is analyzed:

(1) duplicate measurements;

(2) instrument accuracy grade;

(3) instrument density figures display;

(4) temperature accuracy.

3) evaluation of each component of uncertainty of measurement:

(1) the uncertainty U that causes of duplicate measurements ₁evaluation

Adopt the full-automatic Density Measuring Instrument of DM45 to measure terebinthine density, carry out 10 independent duplicate measurementss;

(2) the uncertainty U that causes of instrument accuracy grade ₂evaluation

The accuracy of DM45 is ± 5 × 10 ^-5g/cm ³, the uncertainty introduced is obeyed and is uniformly distributed, and gets Coverage factor degree of freedom is ∞;

$U_2=\frac{5\×{10}^{-5}}{\sqrt{3}}=2.89\×{10}^{-5}g/{\mathrm{cm}}^3$

(3) instrument density figures shows the uncertainty U caused ₃evaluation

The density resolution of DM45 is 1 × 10 ^-5g/cm ³, degree of freedom is ∞, therefore,

$U_3=\frac{1\×{10}^{-5}}{2\sqrt{3}}=0.29\×{10}^{-5}g/{\mathrm{cm}}^3$

(4) the uncertainty U that causes of temperature accuracy ₄evaluation

Near 20 DEG C, carry out density measurement to terebinthina, draw terebinthina density with temperature situation of change, carry out linear regression analysis to data, the relation equation obtaining terebinthina density and temperature is: D=-0.0008T+0.8960, linearly dependent coefficient R ²=0.9997, draw within the scope of measuring tempeature, the variation factor r=0.0008 of terebinthina density with temperature;

(5) Composite Seismogram U _cevaluation

$\begin{array}{c}{U}_c=\sqrt{({U_1}^2+{U_2}^2+{U_3}^2+{U_4}^2}\\ =\sqrt{({0.32}^2+{2.89}^2+{0.29}^2+{1.15}^2)\×{10}^{-10}}\\ =3.14\×{10}^{-5}g/{\mathrm{cm}}^3\end{array}$

(6) evaluation of expanded uncertainty U

Expanded uncertainty U=k × U _c, get Coverage factor k=2, fiducial probability is 95%, then U=2 × 3.14 × 10 ^-5g/cm ³

＝6.28×10 ^-5g/cm ³

Actually get U=7 × 10 ^-5g/cm ³

Then being expressed as of terebinthina density uncertainty:

D＝(0.87979±0.00007)g/cm ³。

Further, the assessment method of above-mentioned mensuration terebinthina density uncertainty, step 1) described in detected temperatures be 20 DEG C.

Compared with prior art, technical scheme tool provided by the invention has the following advantages:

It is D=(0.87979 ± 0.00007) g/cm that this method adopts the full-automatic Density Measuring Instrument of DM45 to measure terebinthine result ³(Coverage factor k=2, fiducial probability is 95%).Measure the density of liquid according to standard method, American Society Testing and Materials ASTM D4052-2011 defines density at (0.80 ~ 0.88) g/crn ³in scope, repeated franchise r is 0.00011g/am ³, repeatability franchise R is 0.00050g/cm ³; China industry standard SN/T 2383--2009 specifies that density is at (0.67 ~ 0.97) g/crn ³in scope, repeated franchise r is 0.0001g/am ³, repeatability franchise R is 0.0005g/cm ³.Visible, this test full-automatic Density Measuring Instrument of DM45 measures terebinthina density, can meet standard-required preferably.

Embodiment

Mode below by embodiment further illustrates the present invention, but does not form any limitation of the invention, and the amendment of anyone limited number of time made in right of the present invention is still in right of the present invention.

Embodiment 1

1. experimental section

1.1 instruments and reagent

Full-automatic densitometer: plum Teller-Tuo benefit DM45; Automatic sampler: SC30; Absolute ethyl alcohol: analyze pure, cleans for measuring tube; Acetone: analyze pure, dry for measuring tube; Terebinthina: certain Lin Hua company; Sample bottle: some.

The 1.2 instrument scope of applications

It is 0.00 DEG C ~ 91.00 DEG C that this instrument is useful in test temperature, and density is 0.0000g/cm ³~ 3.0000g/cm ³the mensuration of density of liquid, instrument accuracy grade is ± 5 × 10 ^-5g/cm ³.

1.3 experiment condition

Environmental baseline is 5 DEG C ~ 35 DEG C, relative humidity≤80%.

1.4 concise and to the point measuring processs

Switch on power, open DM45 respectively, SC30, instrument carries out self-inspection, and general preheating 30min, first corrects with air, and prompting afterwards adds sample, adds appropriate deionized water or redistilled water in measuring flume, calibrates.Appropriate sample (at least 2mL) is added in right rearward measurement sample bottle, respectively sample bottle is placed on SC30 sample feeding device, setting measurement temperature is after temperature stabilization, instrument is automatically measured about 5min and is gone out a result, after measurement completes, instrument can by sample the automatic recovery in raw sample bottle.Measurement terminates rear instrument and automatically cleans and drying.

2. the main source of uncertainty

2.1 in actual measurement process, and the factor such as measuring equipment, measuring method, measurand, measurement environment, personnel all can on measurement result generation impact to a certain degree, and these are all the sources of uncertainty.From 1.4 concise and to the point measuring processs, uncertainty of measurement can be summarized as the following aspects:

(1) duplicate measurements;

(2) instrument accuracy grade;

(3) instrument density figures display;

(4) temperature accuracy.

The functional relation of 2.2 density and temperature:

It is 20 DEG C that setting measures temperature, and the fluctuation due to temperature can cause the fluctuation of density, and the available following functional relation of impact of temperature on density represents:

D _t=D ₂₀(20 1 t) for+r

In formula, D _t, D ₂₀respectively represent t DEG C and 20 DEG C time density; T is actual temperature; R is terebinthine density for the temperature correction facotor of every degree Celsius.The r value of terebinthina is 0.0008, and its uncertainty can be ignored.

Differentiate according to above formula: dD=-rdt

3. the evaluation of each component of uncertainty of measurement

The uncertainty U that 3.1 duplicate measurementss cause ₁evaluation

Measure terebinthine density with the full-automatic Density Measuring Instrument of DM45 20 DEG C time, carry out 10 independent duplicate measurementss, measure and obtain following data Di (unit g/cm ³): in table 1.

Table 1 10 repeated measuring results

Mean value is $\stackrel{\‾}{D}\left(\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\mathrm{Di}\right)/n=\left(\underset{i=1}{\overset{10}{\mathrm{\Σ}}}\mathrm{Di}\right)/n=0.87979g/{\mathrm{cm}}^3$

Measurement data is normal distribution, and by type A evaluation, the standard deviation that Bessel Formula tries to achieve single measurement is:

$S\left(D\right)=\sqrt{\frac{\underset{i=1}{\overset{10}{\mathrm{\Σ}}}{(\mathrm{Di}-\stackrel{\‾}{D})}^2}{n-1}}=1.00\×{10}^{-5}g/{\mathrm{cm}}^3$

Standard error of the mean, namely

$U_1=S\left(\stackrel{\‾}{D}\right)=S\left(D\right)/\sqrt{n}=S\left(D\right)/\sqrt{10}=0.32\×{10}^{-5}g/{\mathrm{cm}}^3$

Degree of freedom v ₁=10-1=9

The uncertainty U that 3.2 instrument accuracy grades cause ₂evaluation

The accuracy of DM45 is ± 5 × 10 ^-5g/cm ³, the uncertainty introduced can think that obedience is uniformly distributed, and gets Coverage factor degree of freedom is ∞.

$U_2=\frac{5\×{10}^{-5}}{\sqrt{3}}=2.89\×{10}^{-5}g/{\mathrm{cm}}^3$

3.3 instrument density figures show the uncertainty U caused ₃evaluation

The density resolution of DM45 is 1 × 10 ^-5g/cm ³, degree of freedom is ∞.Therefore,

$U_3=\frac{1\×{10}^{-5}}{2\sqrt{3}}=0.29\×{10}^{-5}g/{\mathrm{cm}}^3$

The uncertainty U that 3.4 temperature accuracy cause ₄evaluation

The mensuration temperature of setting is 20 DEG C, because temperature fluctuation can make density change.Therefore near 20 DEG C, density measurement is carried out to terebinthina, draw terebinthina density with temperature situation of change, the results are shown in Table 2.

Terebinthina density measurements under table 2 different temperatures

Carry out linear regression analysis to data, the relation equation obtaining terebinthina density and temperature is: D=-0.0008T+0.8960, linearly dependent coefficient R ²=0.9997.

Therefore draw within the scope of measuring tempeature, the variation factor r=0.0008 of terebinthina density with temperature.

DM45 Density Measuring Instrument temperature accuracy ± 0.05 DEG C, temperature accuracy can cause temperature deviation, i.e. △ t=0.05, and the uncertainty caused by temperature deviation is obeyed and is uniformly distributed, and degree of freedom is ∞.

△D＝r△t＝0.0008×0.05＝4.0×10 ^-5g/cm ³

$U_4=\frac{4.0\×{10}^{-5}}{2\sqrt{3}}=1.15\×{10}^{-5}g/{\mathrm{cm}}^3$

3.5 Composite Seismogram U _cevaluation

$\begin{array}{c}{U}_c=\sqrt{({U_1}^2+{U_2}^2+{U_3}^2+{U_4}^2}\\ =\sqrt{({0.32}^2+{2.89}^2+{0.29}^2+{1.15}^2)\×{10}^{-10}}\\ =3.14\×{10}^{-5}g/{\mathrm{cm}}^3\end{array}$

The evaluation of 3.6 expanded uncertainty U

Expanded uncertainty U=k × U _c, get Coverage factor k=2, fiducial probability is 95%, then

U＝2×3.14×10 ^-5g/cm ³

＝6.28×10 ^-5g/cm ³

Actually get U=7 × 10 ^-5g/cm ³

Then being expressed as of terebinthina density uncertainty:

D=(0.87979 ± 0.00007) g/cm ³(Coverage factor k=2, fiducial probability is 95%)

4. result and discussion

By known to the systematic analysis in uncertainty source in measurement result, the uncertainty U that duplicate measurements causes ₁the uncertainty U caused is shown with instrument density figures ₃, to Composite Seismogram U _ccontribution less, and the uncertainty U that instrument accuracy grade causes ₂with the uncertainty U that temperature accuracy causes ₄to Composite Seismogram U _ccontribution larger.When Density Measuring Instrument density measurement full-automatic with DM45 is described, uncertainty is mainly from accuracy and the temperature control precision of instrument itself, and the impact of other factors on uncertainty is less.

5. conclusion

It is D=0.87979 ± 0.00007 that this method adopts the full-automatic Density Measuring Instrument of DM45 to measure terebinthine result) g/cm ³(Coverage factor k=2, fiducial probability is 95%).Measure the density of liquid according to standard method, American Society Testing and Materials ASTM D4052-2011 defines density at (0.80 ~ 0.88) g/crn ³in scope, repeated franchise r is 0.00011g/am ³, repeatability franchise R is 0.00050g/cm ³; China industry standard SN/T 2383--2009 specifies that density is at (0.67 ~ 0.97) g/crn ³in scope, repeated franchise r is 0.0001g/am ³, repeatability franchise R is 0.0005g/cm ³.Visible, this test full-automatic Density Measuring Instrument of DM45 measures terebinthina density, can meet standard-required preferably.

Claims (2)

1. measure an assessment method for terebinthina density uncertainty, it is characterized in that, comprise the steps: successively

1) the full-automatic Density Measuring Instrument of DM45 is adopted to measure terebinthine density measurement terebinthina density;

2) uncertain main source is analyzed:

(1) duplicate measurements;

(2) instrument accuracy grade;

(3) instrument density figures display;

(4) temperature accuracy.

3) evaluation of each component of uncertainty of measurement:

(1) the uncertainty U that causes of duplicate measurements ₁evaluation

Adopt the full-automatic Density Measuring Instrument of DM45 to measure terebinthine density, carry out 10 independent duplicate measurementss;

(2) the uncertainty U that causes of instrument accuracy grade ₂evaluation

The accuracy of DM45 is ± 5 × 10 ^-5g/cm ³, the uncertainty introduced is obeyed and is uniformly distributed, and gets Coverage factor degree of freedom is ∞;

$U_2=\frac{5\×{10}^{-5}}{\sqrt{3}}=2.89\×{10}^{-5}g/{\mathrm{cm}}^3$

(3) instrument density figures shows the uncertainty U caused ₃evaluation

The density resolution of DM45 is 1 × 10 ^-5g/cm ³, degree of freedom is ∞, therefore,

$U_3=\frac{1\×{10}^{-5}}{2\sqrt{3}}=0.29\×{10}^{-5}g/{\mathrm{cm}}^3$

(4) the uncertainty U that causes of temperature accuracy ₄evaluation

Near 20 DEG C, carry out density measurement to terebinthina, draw terebinthina density with temperature situation of change, carry out linear regression analysis to data, the relation equation obtaining terebinthina density and temperature is: D=-0.0008T+0.8960, linearly dependent coefficient R ²=0.9997, draw within the scope of measuring tempeature, the variation factor r=0.0008 of terebinthina density with temperature;

(5) Composite Seismogram U _cevaluation

$\begin{array}{c}{U}_c=\sqrt{({U_1}^2+{U_2}^2+{U_3}^2+{U_4}^2}\\ =\sqrt{({0.32}^2+{2.89}^2+{0.29}^2+{1.15}^2)\×{10}^{-10}}\\ =3.14\×{10}^{-5}g/{\mathrm{cm}}^3\end{array}$

(6) evaluation of expanded uncertainty U

Expanded uncertainty U=k × U _c, get Coverage factor k=2, fiducial probability is 95%, then U=2 × 3.14 × 10 ^-5g/cm ³

＝6.28×10 ^-5g/cm ³

Actually get U=7 × 10 ^-5g/cm ³

Then being expressed as of terebinthina density uncertainty:

D＝(0.87979±0.00007)g/cm ³。

2. the assessment method of mensuration terebinthina density uncertainty according to claim 1, is characterized in that, step 1) described in detected temperatures be 20 DEG C.