Trace the Data of Equal-pressure Method in ASTM D 3985

Exception. Full and more theses on:United States Department of Commerce/National
In Equal-pressure method gas permeability testBureau of Standards, NBS SPECIAL
standard ASTM D3985, it is specified thatPUBLICATION 260-58 presents a detailed
calibrations should use referential material providedintroduction to basic information of SRM 1470 as
by NIST. However, many standard executors dowell as its application:
not fully understand the material of suchThis SRM takes the form of 23?m thick sheets
referential medium and the method to obtain itsof poly (ethylene terephthalate) film.
standard value. This article presents a detailedThe NBS computer-controlled manometric
introduction to the traceability of referentialpermeation measuring facility was employed for
material as well as the referential material adoptedthe collection of the data.
in ASTM equal-pressure method gas permeabilityThe permeance is a function of the following
test standards. It also analyzes the position ofquantities which must be measured: 1.The rate of
each test method in gas permeability test field. pressure rise 2.The downstream cell volume 3.The
1?About Traceabilityeffective area of gas transmission 4.The inlet
The term traceability means that a measurementreservoir pressure 5.The absolute temperature
or the value of measured standard can link withThis Standard Reference Material is intended for
primary standard of measuring through ause in the measurement of the oxygen gas
continuous comparison chain with a definedtransmission rate of thin polymeric films using
uncertainty. With the peculiarity of traceability, allmanometric, volumetric, or coulometric methods.
quantity values of the same kind are traceable toFrom these documents we can conclude that
their source, or can be traced back to the sameSRM 1470 is 23?m thick PET film. Its standard
primary standard of measurement(nationalvalue is obtained through differential-pressure
standard or international standard) once beingmethod and is used for manometric, volumetric,
calibrated in accordance with this comparisonor coulometric methods to calibrate standard
chain, which guarantees the accuracy andvalue. According to the description of NIST, it can
consistency technically. Otherwise, multiple sourcesbe obviously seen that test data of the material
will inevitably results in technical and managementused for traceability is obtained with
disorder.differential-pressure method.
The traceability concept of referential materialOne thing to be noted here is that NBS (National
highlights the meaning of 'well-established standardBureau of Standards,) namely NIST (National
method' in determining measured value. InInstitute of Standards and Technology,), is
measured systems, the uncertainty of providedestablished in 1901 and change its name to NIST
referential value can facilitate users understandingin 1988. The information of SRM 1470 is issued in
reliability transferred by standard material. As the1979. That is why the name employed by SRM is
value of standard material is set to establishstill NBS.
standard value directly, and this setting is the key3? Discuss the Position of Each Method from its
of referential material traceability, the first thing toTraceability of Standard Material
be considered in developing referential materials isAmong the standard materials adopted in gas
to determine the way in which standard value ispermeability testing, SRM 1470 recommended by
set. Generally, the commonly recognized methodNIST is known to be the most widely used one.
of that property will be adopted.That is why the method in which standard value
2?Referential Materials Adopted in Gasof SRM 1470 is obtained enjoys such a
Permeability Testing of Equal-pressure Methodcommonality. It is clearly stated in the description
2.1 Referential Material Adopted in ASTM D 3985part of SRM 1470 that its standard value is
In ASTM D 3985, NIST referential material isobtained with differential-pressure method.
mentioned several times and is descried in theTherefore, SRM 1470 can be more appropriate
'significance and use' item as below :The oxygendescribed as the standard material 'provide by
transmission rate of a standard reference materialNIST with its standard value traceable to
as determined manometrically by NIST, is in gooddifferential- pressure method'
agreement with the values obtained in theAs is stated previously, in developing standard
coulometric interlaboratory test using materialmaterial, selecting the method to set standard
from the same manufacturing lot. In thevalue is the critical point of traceability. Generally,
description part of JIS K 7126-1987 Testingthe authority method of that property will be
Method for Gas Transmission Rate through Plasticselected. According to the method selection of
Films and Sheetings, item eight contains suchSRM 1470 we can see that the fundamental
explanation. 'In ASTM D3985, SRM 1470 providedposition of differential-pressure method in gas
by NBS is recommended as standard referentialpermeability testing is unassailable.
material '. Therefore, it can be believed that SRMIn conclusion, differential-pressure method is the
1470, with its traceability provided by NBS, isbasic method in gas permeability testing.
what ASTM D 3985 used as standard material.Equal-pressure method instruments can only use
2.1 SRM 1470single data of standard material 'traceable to the
SRM 1470: POLYESTER FILM FOR OXYGEN GASstandard value of differential-pressure method' to
TRANSMISSION MEASUREMENTS Issued bypartly evaluate their data system.