t roe mner mass standards handbook

Troemner MassStandards Handbook

Precision & Balance Matched Only By Nature.

58 Introduction59 Why Accreditation?60 Troemner Weights and

Calibration Services61 Regulations and Standards62 Physical Characteristics66 Tolerance Table69 Conversion Table70 Good Measurement Practices72 Weight Selection Guidelines74 Determining Balance Error76 Weight Care and Maintenance77 Terminology79 The Advantages of Troemner

Alloy 8 Stainless Steel81 Additional Calibration Services

from Troemner

Introduction Troemner ispleased to offer the Mass StandardsHandbook to help clarify the variousweight specifications, classifications,and physical characteristics ofprecision weights, mass standardsand the tolerances used in theirproduction and calibration. Thispublication specifically addressesmass terminology, the regulationsand standards surrounding weights,proper calibration techniques,application selection guidelines, andthe proper use, care and handling ofall calibration masses. There is also asection that explains how todifferentiate balance error fromweight error. Anyone who usesbalances, scales, and associated

calibration weights/weight sets intheir work will find this publication ahelpful and practical aid.

The basis for all mass measurementsrelates to the kilogram which is the SIunit for mass determination. Thekilogram is the last remaining baseunit to be defined as a physicalobject rather than in terms of anaturally occurring constant. This, ofcourse, has its drawbacks since greatcare must be taken in order to ensurethat the mass of this object does notchange due to damage or contamination from thesurrounding environment. All massstandards must ultimately betraceable to this one object. Asscience and industry increase theirrequirements for more accurate waysto measure mass and improve theirprocesses, the informationenumerated in this handbookbecomes increasingly important.

It is Troemners focus to achieve thehighest levels of accreditation forweights, mass standards andcalibration services. Third partyaccreditation by internationallyrecognized organizations providesregular unbiased assessments ofTroemners quality programs andtechnical capabilities. Accreditationassures our customers that Troemnermeets and maintains the mostrigorous testing and manufacturingstandards.

Benefits of Accreditation include:

Buying with Confidence products andservices available though Troemner are heldto world class standards through rigorousindependent third party audits.

International Recognition Troemnersaccreditations are widely recognizedinternationally - companies exportingproducts or services can avoid the cost and time in re-testing products formany markets. In addition, Troemnersaccreditations will support legal orregulatory requirements.

Improved Product and Service Quality avoid failure as a result of relying on invalid test results from poorlycalibrated equipment.

Troemner has achieved registration andaccreditation in various disciplines from ISO,NVLAP and UKAS.

ISO - The InternationalOrganization for

Standardization (ISO) is a worldwidefederation of national standards bodiesfrom some 140 countries, one from eachcountry. Established in 1947, themission of ISO is to promote thedevelopment of standardization andrelated activities in the world with a viewto facilitating the international exchangeof goods and services, and to developingcooperation in the spheres of intellectual,

scientific, technological andeconomic activity.

NVLAP - The NationalVoluntary LaboratoryAccreditation Program(NVLAP) was originally

established in 1976 as an accrediting bodyfor testing laboratories and was expanded in1994 to include accreditation for calibrationlaboratories. NVLAP accredits laboratories forcompliance with ISO/IEC 17025 and on thebasis of their ability to meet the technicalrequirements set forth in NIST Handbook150-2. NVLAP can provide accreditation toANSI/NCSL Z540-1-1994. NVLAP hasbroad international recognition with otheraccreditation organizations. NVLAP mutualrecognition arrangements include TheInternational Laboratory AccreditationCooperation (ILAC), The Asia PacificLaboratory Accreditation Cooperation(APLAC) and The National Cooperation forLaboratory Accreditation (NACLA).

UKAS - Troemner maintainsaccreditation from the UnitedKingdom Accreditation Service.UKAS is widely recognized

internationally through bilateral andmultilateral agreements and through itsparticipation in the European Cooperation forAccreditation Laboratories (EAL), TheInternational Accreditation Forum (IAF) andThe International Laboratory AccreditationCooperation (ILAC). UKAS accreditedlaboratories meet the requirements ofISO/IEC 17025 and EN 45001 - theEuropean standard widely acceptedthroughout the world for competence ofcalibration laboratories.

Mass Standards Handbook Why Accreditation?

59www.troemner.com 800-249-5554

Accredited by the National VoluntaryLaboratory Accreditation Program forthe specific scope of Accreditationunder Lab Code 105013.

No. 0516

Troemner offers the most comprehensive selection of Precision Massesand Mass Standards.

ANY SIZE - 50 micrograms to 2,000 kg, 0.00001 oz to 5000 lbs.

ANY DENOMINATION - metric, avoirdupois, troy ounce, grain,pennyweight, carat, customization is available.

ANY TOLERANCE - All ANSI/ASTM, NIST, OIML, customizedtolerances are available.

ANY MATERIAL - stainless steel, brass, aluminum, cast iron, steel,gold, silver, titanium and more.

ANY SHAPE - Precision, OIML, grip handle, slotted, hook bar,cylindrical, customized shapes are available.

Troemner Calibration Certificate Choices

Troemner NVLAP Weight Calibration Certificate - NVLAPcalibrations/certifications meet all ISO, FDA, GMP, GLP, DOD,ANSI/NCSL Z540-1 and Nuclear requirements and are traceable toNIST. Procedures and processes used to generate this multi-pagecertificate, as well as its format and content, are prescribed by NVLAP.Users held absolutely accountable for their weights should requestNVLAP certification. The document contains:

Customer name & address

Date of calibration

Equipment and standards used in the calibration

Accuracy class

True mass value (mass in a vacuum)

As found mass correction (for recalibration) and as leftmass corrections for each weight

Uncertainty of measurement process for each weight.Uncertainty to tolerance ratios are guaranteed.

Environmental conditions during test

Construction and density of the weight(s)

Calibration procedure used

A statement of traceability to NIST

Helpful list of terms and definitions

Troemner UKAS Certificate of Calibration - Similar in terms of contentto the NVLAP certificate described above, however, this document alsomeets the requirements of the United Kingdom Accreditation Service.

Troemner Traceable Certificate - Our Traceable Certificate includesnominal value, mass correction, uncertainty and tolerance for eachweight in addition to the basic customer information such as name,address, purchase order number, date of calibration, accuracy class,density and statement of traceability to NIST. The Traceable Certificatemeasurement process includes one series of comparisons using a singlestandard.

Additional Troemner Mass Services

Troemner NVLAP Density Determinations - Troemners mass metrologylaboratory can determine the actual density of one-piece massstandards that range in size from 1 g to 5 kg. Troemner provides thisservice to reduce the uncertainty of calibrating one-piece precisionASTM Class O and OIML Class E1 and E2 weights. Utilizing a state ofthe art balance immersed in a fluorinated fluid, a series ofmeasurements are compared to a NIST traceable density standard todetermine the density value.

Troemner NVLAP Magnetic Susceptibility Determinations - Troemnerhas the capability of measuring the magnetic field intensity and thepotential magnetic susceptibility of stainless steel mass standardsbetween 1 g and 10 kg.


Mass Standards Handbook Troemner Weights and Calibration Services

Mass Standards Handbook Regulations and Standards


ASTM E 617-97 (2003): Standard Specification for LaboratoryWeights and Precision Mass Standards - This specification coversvarious classes of weights and mass standards used in laboratoriesranging from Class 0 to Class 7. Tolerances and design restrictionsfor each class are described in order that both individual weightsand weight sets can be chosen for the appropriate applications. Thisspecification also recognizes International Recommendation R 111that describes classes E1, E2, F1, F2, M1, M2, and M3.

OIML R 111: Weights of Classes E1, E2, F1, F2, M1, M2, M3 Thisinternational document describes the physical characteristics andmetrological requirements of reference standard weights withrecommendations for seven classes of weights (Classes E1, E2, F1,F2, M1, M2, M3) in tiers of uncertainty.

NVLAP Handbook 150: Procedures and General Requirements -Outlines the quality system and all of the procedures required inorder to be NVLAP accredited. NVLAP Handbook 150 also containsall requirements specified in ISO/IEC 17025.

ISO/IEC 17025 (formerly ISO Guide 25): General Requirements forthe Competency of Testing and Calibration Laboratories This guidesets out the general provisions which a laboratory must address tocarry out specific calibrations or tests. ISO/IEC 17025 provides thelaboratory direction for the development and implementation of afundamental quality management system.

ANSI/NCSL-Z540-1-1994: Calibration Laboratories and Measuringand Test Equipment-General Requirement (ANSI/NCSL) - Thisstandard provides a mechanism for promoting confidence incalibration laboratories and measuring and test equipment when itcan be shown that they are operated in compliance with its

requirements. Calibration certificates received by NVLAP-accredited testing and calibration laboratories with new or re-calibrated equipment shall meet the requirements of ISO/IEC Guide17025 augmented by ANSI/NCSL Z540-1-1994. The certificatesmust include appropriate statements of uncertainty.

NIST Handbook 105-1: Specifications and Tolerances for FieldStandard Weights These specifications and tolerances are specificfor reference and field standard weights (NIST Class F). Thisdocument sets minimum requirements for standards used primarilyto test commercial or legal for trade weighing devices forcompliance with NIST Handbook 44. These devices include but arenot limited to delicatessen scales, jewelry scales, postal and parcelpost scales and dairy product test scales. This specification permitsthe use of a weight at its nominal value in normal testingoperations, where the tolerance on the item under test is at leastthree times as great as the tolerance of the weight. Thisspecification also specifies the design, marking, adjusting cavities,and density of these weights. Any variation in design fromHandbook 105-1 must be submitted to NIST for approval.

NIST Handbook 44: Specifications, Tolerances, and Other TechnicalRequirements for Weighing and Measuring Devices - This publicationsets forth the specifications, tolerances, and other technicalrequirements for weighing and measuring devices. Handbook 44 ispublished in its entirety each year following the Annual Meeting ofthe National Conference on Weights and Measures. All of thespecifications, tolerances, and other technical requirements of thisbooklet are recommended by the National Conference on Weightsand Measures for official promulgation and use by the states inexercising their control of commercial weighing apparatus.


Mass Standards Handbook Physical Characteristics

This section is a summary of the more widelyused and accepted weight specifications.The most pertinent sections of thesespecifications are listed and not all of thecontents of these specifications are included.

ANSI/ASTM E 617 The informationthat follows is an overview of thespecifications in ANSI/ASTM E 617-97(2003), Standard Specification forLaboratory Weights and Precision MassStandards.

Reference:

Available from: Henry Troemner LLC, 201Wolf Drive P.O. Box 87, Thorofare, NewJersey, 08086-0087 USA, 856-686-1600or American Society for Testing andMaterials, 100 Barr Harbor Drive, P.O. BoxC700, West Conshohocken, Pennsylvania,19428-2959 USA

Maximum Permissible Error (Tolerances)

For classes 0, 1, 2, 3, 4, 5, 6, and 7 weights,the expanded uncertainty U at 95%confidence of the conventional mass shall beless than or equal to one-third of themaximum permissible error given in theTolerance Table 9 (page 66). For eachweight, the absolute value of theconventional mass correction along with itsassociated uncertainty shall not be greaterthan the maximum permissible error for theweights given class as given in the ToleranceTable 9 (page 66).

Construction

Type - Weights are divided into two typesbased upon design:

Type I - These weights are of one-piececonstruction and contain no addedadjusting material. They must be specifiedwhen weights are to be used as standardsfor the calibration of weights of Classes 0,1, 2, and 3, and where maximum stabilityis required. A precise measurement ofdensity can only be made for one-pieceweights.

Type II - Weights of this type can be of anyappropriate design such as screw knob,ring, or sealed plug. Adjusting material canbe used as long as it is of a material at leastas stable as the base material and iscontained in such a way that it will notbecome separated from the weight.

Design - A weight may have any shape thatdoes not introduce features that reduce thereliability. All weights shall be free of raggedor sharp edges or ends. Both sheet metal andwire weights shall be free of cracks such asthose that may be formed from bending.

Surface Area - For Classes 0, 1, 2, 3, and 4the surface area is not to exceed twice thearea of a cylinder of equal height anddiameter for weights 1 g and above. Sheetmetal weights or wire weights may be usedbelow 1 g.

Material

Class 0, 1, 2, and 3 Weights - The hardnessof this material and its resistance to wear andcorrosion shall be similar to or better than thatof austenitic stainless steel.

Class 4, 5, 6, and 7 Weights - The hardnessand brittleness of the materials used forweights of these classes shall be at leastequal to that of drawn brass.

Magnetism

Weights shall not exceed maximumpermissible magnetic properties as listed inTable 1 below for any portion of the weight.

Density

Because of the effect of the buoyant force ofair on a weight, precision measurements ofmass require that the volume of the weightbe known, as well as the density of the air inwhich it is being measured, so thatappropriate corrections can be made. For

Table 1 - Magnetic Properties

*Requirements for these classes have not been developed.

CLASS VOLUME MAGNETIC MAXIMUM SUSCEPTIBILITY () MAGNETIC FIELD

T mG0 0.01 2.0 20

1 0.03 4.0 40

2, 3, 4 0.05 6.0 60

5, 6, 7 * * *

NOMINAL VALUE CLASS 0 CLASS 1 AND 2 CLASS 3 THROUGH 6 CLASS 7

>5 kg 7934 to 8060 7700 to 8200 7000 to 9100 7000

1 g to 5 kg 7920 to 8080 7700 to 8200 7700 to 9100 7000



weights of higher precision, the range ofdensity is limited to values at or near thedensity of well-established standards, suchas are used by primary calibrationlaboratories. As lower precision ofmeasurement is required, so the range ofdensity is broadened. See Table 2.

Finish

The surface of the weights (including thebase and corners) shall be smooth, the edgesshall be rounded, and the weights shall notbe porous. The surface quality of a weightshall not exceed maximum values of surfaceroughness, RA and RZ through visualinspection using a hand held gauge. (SeeTable 3 below).

For weights with recessed areas for easierhandling, their recessed area and handleshould have a finish with surface roughnessno greater than RZ=0.67 m and RA=0.05m. The outer diameter, top and bottomsurface roughness must meet Table 3 below.

Markings

Class 0 - Class 0 weights shall not bear anyindication of nominal value.

Numerical Value for Classes 1, 2, 3, 4, 5, 6,and 7 - The nominal value of each weightshall appear on the surface of each weight.Only the numerical portion of the weightvalue needs to be on the surface of theweights. Weights made of wire are too smallto be marked and shall not be marked, butshould be identifiable by their shape ornumber of bends.

Unit of Weight - Weights 100 g and greatermay be marked with the unit name orabbreviation. In the case of sets of non-metric weights, at least the largest weight ofa particular set should be marked with theunit name or abbreviation. In any case theunit shall not be included where suchmarking would be illegible.

Multiple Weights - Multiple weights of thesame nominal value included in a set ofweights shall have distinguishing marks.

Depth of Markings - Markings shall be clear,shallow, relatively broad, and free of burrsand sharp angles. Markings shall notperforate or crack sheet metal weights.

CLASSES 0 AND 1 CLASSES 2, 3, 4 Classes 5, 6, 7

RA (m) 0.025 0.05 0.8

RZ (m) 0.35 0.67 3.2

Table 3 - Maximum Value of Surface Roughness



OIML INTERNATIONALRECOMMENDATION NO. R 111 The information that follows is an overview ofthe specifications outlined in OIML R 111 forweights of classes E1, E2, F1, F2, M1, M2, M3.

Reference:

Available from: Henry Troemner LLC, 201 WolfDrive P.O. Box 87, Thorofare, New Jersey, 08086-0087 USA 856-686-1600 or OrganisationInternationale De Metrologie Legale, 11 Rue Trugot F-75009, Paris, France

Maximum Permissible Error (Tolerance) The maximum permissible errors for ClassE1, E2, F1, F2, M1, M2, and M3 are providedin the Tolerance Table 9 (page 66). Theuncertainty associated with the maximumpermissible error shall be less than or equalto 1/3 of the maximum permissible error.

Shape Weights 1 g and below may bepolygonal shapes or wires and shallconform to Table 4 below.

Weights 1 g to 50 kg may have the externaldimensions as shown in OIML R 111 AnnexA. Weights of a set shall have the same shapeexcept for weights 1 g and below.

Construction Class E1 and E2 are to bemade with one-piece construction with noadjusting cavities. Classes F1, F2, M1, M2,and M3 may be made of more than one piecefrom the same material and may contain anadjusting cavity.

Material Class E1 and E2 weights equal orgreater to 1 g, the hardness of material and itsresistance to wear shall be similar to or betterthan that of austenitic stainless steel.

For Class F1 and F2 weights equal to orgreater than 1 g, the material shall be at leastas hard as drawn brass.

Material used for rectangular weights forClass M1 from 5 kg to 50 kg shall have acorrosion resistance that is equal to that ofgray cast iron. Class M1 cylindrical weights10 kg and below shall be made of brass or of

another material whose quality is similar orbetter than brass.

Material used for rectangular weights forClass M2 and M3 from 5 kg to 50 kg shall bemade of gray cast iron or another materialwhose quality is similar or better than graycast iron. Class M2 and M3 cylindricalweights 10 kg and below shall be made ofmaterial, which has hardness and corrosionresistance at least equal to cast brass, andbrittleness not exceeding that of gray castiron. Gray cast iron shall not be used forweights below 100 g.

Magnetism The magnetism should notexceed the maximum values given in Table 5below.

The magnetic susceptibility of a weightshould not exceed the maximum values givenin Table 6 below.

WEIGHT CLASS E1 E2 F1 F2 M1 M2 M3

Maximum Magnetism, 0 M (T) 3 10 30 100 300 1000 3000

Table 5 - Maximum Permanent Magnetism, 0 M (T)

NOMINAL VALUES (mg) POLYGONAL SHEETS WIRES

5 50 500 Pentagon Pentagon or 5 segments

2 20 200 Square Square or 2 segments

1 10 100 1000 Triangle Triangle or 1 segment

Table 4 - Shape of Weights 1 g or Less

WEIGHT CLASS E1 E2 F1 F2

Nominal mass 100 g 0.01 0.03 0.07 0.21

Nominal mass < 100 g 0.025 0.075 0.25 0.75

Nominal mass 1 g 0.12 0.37 1.2 -

Table 6 - Maximum Susceptibility,



Density The density of the material used forweights shall be such that a deviation of 10%from the specified air density (1.2 kg/m3)does not produce an error exceeding onequarter of the maximum permissible error.These limits are given in Table 7.

Surface Conditions The surface of theweights shall be smooth and edges shall berounded. The surface of Class E1, E2, F1, andF2 weights shall not appear to be porous andshall present a glossy appearance whenvisually examined. The maximum values ofsurface roughness shall be observed todetermine the surface quality in Table 8.

Marking Class E1 and E2 weights shall notbear any markings of nominal value or classreference.

Class F1 shall bear nominal value notfollowed by a symbol or unit. Nominal value1 g up to and including 500 g shall indicatenumerals representing grams. Weight 1 kgand above shall bear numerals representingkilograms. For example, a 10 g weight will bemarked with a 10. A 1 kg weight will bemarked with a 1. Sheet metal weights shallnot bear any indication of nominal value orclass reference.

Class F2 weights will be marked similar toclass F1 except the letter F will appearbelow the numerical value.

Class M1, M2, and M3 will be marked withnominal value and unit of measure ( ex. 10g, 1 kg, 10 kg, etc). Class M1 will also bearan M or M1, class M2 shall also bear an M2or no class designation, and class M3 shallalso bear an M3 or X.

Duplicate weights in a set shall be clearlydistinguished by an asterisk or point on thecenter of the surface except for wire weights,which shall be distinguished by one or twohooks.

NOMINAL VALUE CLASS E1 CLASS E2 CLASS F1 CLASS F2 CLASS M1 CLASS M2 CLASS M3

> 50 kg 4.4 2.1 > 4.4

100 g to 50 kg 7.9348.067 7.818.21 7.398.73 6.410.7 4.4 2.3

50 g 7.928.08 7.748.28 7.278.89 6.012.0 4.0

20 g 7.848.17 7.508.57 6.610.1 4.824.0 2.6

10 g 7.748.28 7.278.89 6.012.0 4.0 2.0

5 g 7.628.42 6.99.6 5.316.0 3.0

2 g 7.278.89 6.012.0 4.0 2.0

1 g 6.99.6 5.316.0 3.0

500 mg 6.310.9 4.4 2.2

200 mg 5.316.0 3.0

100 mg 4.4

50 mg 3.4

20 mg 2.3

Table 7 - Minimum and Maximum Limits for Density (min, max (103 kg/m3))

CLASS E1 E2 F1 F2

Rz (m) 0.5 1 2 5Ra (m) 0.1 0.2 0.4 1

Table 8 - Maximum Values of Surface Roughness (Rz)

International Organization of Troemner ANSI/ASTMLegal Metrology Recommendation R 111* Ultra- E617ClassSM

E1 E2 F1 F2 M1 M2 M3 0 1 2 3 4Denomination

Metric mg mg mg mg mg mg mg mg mg mg mg mg g & mg5000 kg 25000 85000 250000 850000 1250000 100 g3000 kg 602000 kg 10000 33000 100000 330000 1000000 401000 kg 1600 5000 16000 50000 160000 500000 20500 kg 800 2500 8000 25000 80000 250000 10300 kg 6.0200 kg 300 1000 3000 10000 30000 100000 4.0100 kg 160 500 1600 5000 16000 50000 2.050 kg 25 75 250 750 2500 7500 25000 75 63 125 250 500 1.030 kg 45 38 75 150 300 600 mg25 kg 37 31 62 125 250 50020 kg 10 30 100 300 1000 3000 10000 30 25 50 100 200 40010 kg 5 15 50 150 500 1500 5000 15 13 25 50 100 2005 kg 2.5 7.5 25 75 250 750 2500 7 6 12 25 50 1003 kg 4.5 3.8 7.5 15 30 602 kg 1.0 3.0 10 30 100 300 1000 3.0 2.5 5.0 10 20 401 kg 0.5 1.5 5 15 50 150 500 1.5 1.3 2.5 5.0 10 20

500 g 0.25 0.75 2.5 7.5 25 75 250 0.7 0.60 1.2 2.5 5.0 10300 g 0.45 0.38 0.75 1.5 3.0 6.0200 g 0.10 0.30 1.0 3.0 10 30 100 0.30 0.25 0.50 1.0 2.0 4.0100 g 0.05 0.15 0.5 1.5 5 15 50 0.15 0.13 0.25 0.50 1.0 2.050 g 0.030 0.10 0.30 1.0 3.0 10 30 0.07 0.060 0.12 0.25 0.60 1.230 g 0.044 0.037 0.074 0.15 0.45 0.9020 g 0.025 0.080 0.25 0.8 2.5 8 25 0.044 0.037 0.074 0.10 0.35 0.7010 g 0.020 0.060 0.20 0.6 2 6 20 0.030 0.025 0.050 0.074 0.25 0.505 g 0.015 0.050 0.15 0.5 1.5 5 15 0.020 0.017 0.034 0.054 0.18 0.363 g 0.020 0.017 0.034 0.054 0.15 0.302 g 0.012 0.040 0.12 0.4 1.2 4 12 0.020 0.017 0.034 0.054 0.13 0.261 g 0.010 0.030 0.10 0.3 1.0 3 10 0.020 0.017 0.034 0.054 0.10 0.20

500 mg 0.008 0.025 0.08 0.25 0.8 2.5 0.005 0.005 0.010 0.025 0.080 0.16300 mg 0.005 0.005 0.010 0.025 0.070 0.14200 mg 0.006 0.020 0.06 0.20 0.6 2.0 0.005 0.005 0.010 0.025 0.060 0.12100 mg 0.005 0.015 0.05 0.15 0.5 1.5 0.005 0.005 0.010 0.025 0.050 0.1050 mg 0.004 0.012 0.04 0.12 0.4 0.005 0.005 0.010 0.014 0.042 0.08530 mg 0.005 0.005 0.010 0.014 0.038 0.07520 mg 0.003 0.010 0.03 0.10 0.3 0.005 0.005 0.010 0.014 0.035 0.07010 mg 0.002 0.008 0.025 0.08 0.25 0.005 0.005 0.010 0.014 0.030 0.0605 mg 0.002 0.006 0.020 0.06 0.20 0.005 0.005 0.010 0.014 0.028 0.0553 mg 0.005 0.005 0.010 0.014 0.026 0.0522 mg 0.002 0.006 0.020 0.06 0.20 0.005 0.005 0.010 0.014 0.025 0.0501 mg 0.002 0.006 0.020 0.06 0.20 0.005 0.005 0.010 0.014 0.025 0.050

0.5 mg0.3 mg0.2 mg0.1 mg

0.05 mg

* OIML - International Recommendation R 111 replaces International Recommendation numbers 1, 2, 20, 52.

** NIST 105-1 Class F tolerances are rounded to two significant figures


Mass Standards Handbook Metric Weight Tolerances

The table below is a listing of the tolerances of various classes of masses. The weight value can deviate above or below the nominal value by thetolerance defined. To determine the tolerance of a mass, look at the denomination or nominal value of the weight and the appropriate class you need.

Table 9 - Metric Weight Tolerances

Mass Standards Handbook Metric Weight Tolerances


National Bureau of Standards NIST HandbooksCircular 547 Section 1 105-1** 44

5 6 7 J M S S-1 P Q T FInd Grp Ind Grip Accept Maint Denomination

g & mg g & mg g & mg mg mg mg mg mg mg g & mg g & mg g & mg g & mg mg mg Metric250 g 500 g 750 g 500 g 5000 kg150 300 450 300 3000 kg100 200 300 200 2000 kg50 100 150 20 g 50 g 150 g 100 1000 kg25 50 75 10 25 75 50 500 kg15 30 45 30 300 kg10 20 30 4.0 10 30 20 200 kg5 10 15 2.0 5 15 10 100 kg2.5 5 7.5 500 1.0 2.5 7.5 5.0 50 kg1.5 3 4.5 3.0 30 kg1.2 2.5 4.5 125 250 500 mg 1.2 4.5 2.5 25 kg1.0 2 3.8 100 200 400 1 3.8 2.0 750 1500 20 kg

500 mg 1 2.2 50 100 200 500 mg 2.2 1.0 500 1000 10 kg250 500 mg 1.4 25 50 100 250 1.4 0.50 400 800 5 kg150 300 1.0 15 7.5 30 60 150 1.0 0.30 250 500 3 kg100 200 750 mg 10 5.0 20 40 100 750 mg 0.20 200 400 2 kg50 100 470 5.0 2.5 10 20 50 470 0.10 120 250 1 kg30 50 300 2.5 1.2 5.0 10 30 300 70 mg 88 175 500 g20 30 210 1.5 0.75 3.0 6.0 20 210 60 75 150 300 g15 20 160 1.0 0.50 2.0 4.0 15 160 40 50 100 200 g9 10 100 0.50 0.25 1.0 2.0 9.0 100 20 35 70 100 g5.6 7 62 0.25 0.12 0.60 1.2 5.6 62 10 20 40 50 g4.0 5 44 0.15 0.074 0.154 0.45 0.90 4.0 44 6.0 15 30 30 g3.0 3 33 0.10 0.074 0.35 0.70 3.0 33 4.0 10 20 20 g2.0 2 21 0.050 0.074 0.25 0.50 2.0 21 2.0 8 15 10 g1.3 2 13 0.034 0.065 0.054 0.105 0.18 0.36 1.3 13 1.5 5 10 5 g0.95 2.0 9.4 0.034 0.065 0.054 0.105 0.15 0.30 0.95 9.4 1.3 4 8 3 g0.75 2.0 7.0 0.034 0.065 0.054 0.105 0.13 0.26 0.75 7.0 1.1 3 6 2 g0.50 2.0 4.5 0.034 0.065 0.054 0.105 0.10 0.20 0.50 4.5 0.90 2 4 1 g0.38 1.0 3.0 0.010 0.020 0.025 0.055 0.080 0.16 0.38 3.0 0.72 1.5 3.0 500 mg0.30 1.0 2.2 0.010 0.020 0.025 0.055 0.070 0.14 0.30 2.2 0.61 1.0 2.0 300 mg0.26 1.0 1.8 0.010 0.020 0.025 0.055 0.060 0.12 0.26 1.8 0.54 0.8 1.5 200 mg0.20 1.0 1.2 0.010 0.020 0.025 0.055 0.050 0.10 0.20 1.2 0.43 0.5 1.0 100 mg0.16 0.50 0.88 0.010 0.010 0.020 0.014 0.034 0.042 0.085 0.16 0.88 0.35 0.4 0.8 50 mg0.14 0.50 0.68 0.010 0.010 0.020 0.014 0.034 0.038 0.075 0.14 0.68 0.30 0.3 0.6 30 mg0.12 0.50 0.56 0.010 0.010 0.020 0.014 0.034 0.035 0.070 0.12 0.56 0.26 0.2 0.4 20 mg0.10 0.50 0.4 0.010 0.010 0.020 0.014 0.034 0.030 0.060 0.10 0.40 0.21 0.15 0.3 10 mg 0.080 0.20 0.010 0.010 0.020 0.014 0.034 0.028 0.055 0.080 0.17 0.05 0.1 5 mg0.070 0.20 0.010 0.010 0.020 0.014 0.034 0.026 0.052 0.070 0.14 0.05 0.1 3 mg0.060 0.20 0.010 0.010 0.020 0.014 0.034 0.025 0.050 0.060 0.12 0.05 0.1 2 mg0.050 0.10 0.010 0.010 0.020 0.014 0.034 0.025 0.050 0.050 0.10 0.05 0.1 1 mg

0.010 0.010 0.020 0.014 0.034 0.025 0.5 mg0.010 0.010 0.020 0.014 0.034 0.025 0.3 mg0.010 0.010 0.020 0.014 0.034 0.025 0.2 mg0.010 0.010 0.020 0.014 0.034 0.025 0.1 mg0.010 0.010 0.014 0.05 mg

0.020

0.020

0.020

0.020

0.065

0.154

0.105

0.054

0.034

0.034

0.034


Mass Standards Handbook Avoirdupois and Troy Nominal Tolerances

NIST Handbook 105-1*

Denomination F Denomination F Denomination F Denomination F Denomination FOunce mg Pound g & mg Troy g & mg Grains mg Apothecary mg

12 oz 70 10 000 lb 450 g 500 oz t 1.7 g 10 000 grains 70 12 oz ap 708 oz 45 5 000 lb 230 200 oz t 0.62 5 000 grains 70 10 oz ap 624 oz 23 3 000 lb 140 100 oz t 0.31 3 000 grains 39 6 oz ap 372 oz 11 2 500 lb 110 50 oz t 0.16 2 000 grains 26 5 oz ap 311 oz 5.4 2 000 lb 91 20 oz t 70 mg 1 000 grains 13 4 oz ap 25

1/2 oz 2.8 1 000 lb 45 12 oz t 70 500 grains 6.5 3 oz ap 191/4 oz 1.7 500 lb 23 10 oz t 62 300 grains 3.9 2 oz ap 121/8 oz 1.3 100 lb 4.5 6 oz t 37 200 grains 2.6 1 oz ap 6.2

1/16 oz 1.1 50 lb 2.3 5 oz t 31 100 grains 1.61/32 oz 0.87 30 lb 1.4 4 oz t 25 50 grains 1.3 6 dr ap 4.71/64 oz 0.69 25 lb 1.1 3 oz t 19 30 grains 1.1 5 dr ap 3.9

20 lb 0.91 2 oz t 12 20 grains 0.98 4 dr ap 3.10.5 oz 2.8 10 lb 0.45 1 oz t 6.2 12 grains 0.82 3 dr ap 2.30.3 oz 1.8 5 lb 0.23 1/2 oz t 3.1 10 grains 0.78 2 dr ap 1.70.2 oz 1.6 4 lb 0.18 1/4 oz t 1.7 6 grains 0.65 1 dr ap 1.40.1 oz 1.3 3 lb 0.14 1/8 oz t 1.4 5 grains 0.63 0.5 dr ap 1.1

0.05 oz 1.0 2 lb 91 mg 1/16 oz t 1.1 4 grains 0.58 2 s ap 1.20.03 oz 0.85 1 lb 70 1/32 oz t 0.89 3 grains 0.53 1 s ap 0.980.02 oz 0.75 0.5 lb 45 2 grains 0.47 0.5 s ap 0.780.01 oz 0.60 0.3 lb 27 0.5 oz t 3.1 1 grains 0.38

0.2 lb 18 0.2 oz t 1.6 0.5 grains 0.300.1 lb 9.1 0.1 oz t 1.3 0.3 grains 0.26

0.05 lb 4.5 0.05 oz t 1.0 0.2 grains 0.230.03 lb 2.7 0.02 oz t 0.77 0.1 grains 0.180.02 lb 1.8 0.01 oz t 0.620.01 lb 1.5 0.005 oz t 0.50

0.005 lb 1.20.003 lb 0.99 20 dwt 6.20.002 lb 0.87 10 dwt 3.10.001 lb 0.70 5 dwt 1.7

2 dwt 1.31 dwt 1.0

0.5 dwt 0.830.2 dwt 0.620.1 dwt 0.50

Table 10 - Avoirdupois and Troy Nominal Tolerances

The table below is a listing of the tolerances of various classes of masses. The weight value can deviate above or below the nominal value by thetolerance defined. To determine the tolerance of a mass, look at the denomination or nominal value of the weight and the appropriate class you need.

*NIST 105-1 Class F tolerances are rounded to two significant figures


Mass Standards Handbook Conversion Table

UNITS OF MASS NOT GREATER THAN POUNDS AND KILOGRAMS

APOTHECARIES AVOIRDUPOIS APOTHECARIES AVOIRDUPOISUNITS GRAINS SCRUPLES PENNYWEIGHTS DRAMS DRAMS OUNCES

1 grain = 1 0.05 0.041 666 67 0.036 571 43 0.016 666 67 0.002 285 714

1 apoth. scruple = 20 1 0.833 333 3 0.731 428 6 0.333 333 3 0.045 714 29

1 pennyweight = 24 1.2 1 0.877 714 3 0.4 0.054 857 14

1 avdp. dram = 27.343 75 1.367 187 5 1.139 323 1 0.455 729 2 0.062 5

1 apoth. dram = 60 3 2.5 2.194 286 1 0.137 142 9

1 avdp. ounce = 437.5 21.875 18.229 17 16 7.291 667 1

1 apoth. or troy ounce = 480 24 20 17.554 29 8 1.097 143

1 apoth. or troy pound = 5 760 288 240 210.651 4 96 13.165 71

1 avdp. pound = 7 000 350 291.666 7 256 116.666 7 16

1 milligram = 0.015 432 36 0.000 771 617 9 0.000 643 014 9 0.000 564 383 4 0.000 257 206 0 0.000 035 273 96

1 gram = 15.432 36 0.771 617 9 0.643 014 9 0.564 383 4 0.257 206 0 0.035 273 96

1 kilogram = 15432.36 771.617 9 643.014 9 564.383 4 257.206 0 35.273 96

APOTHECARIES OR APOTHECARIES OR AVOIRDUPOISUNITS TROY OUNCES TROY POUNDS POUNDS MILLIGRAMS GRAMS KILOGRAMS

1 grain = 0.002 083 333 0.000 173 611 1 0.000 142 857 1 64.798 91 0.064 798 91 0.000 064 798 91

1 apoth. scruple = 0.041 666 67 0.003 472 222 0.002 857 143 1295.978 2 1.295 978 2 0.001 295 978 2

1 pennyweight = 0.05 0.004 166 667 0.003 428 571 1555.173 84 1.555 173 84 0.001 555 173 84

1 avdp. dram = 0.056 966 146 0.004 747 179 0.003 906 25 1771.845 195 312 5 1.771 845 195 312 5 0.001 771 845 195 312 5

1 apoth. dram = 0.125 0.010 416 67 0.008 571 429 3887.934 6 3.887 934 6 0.003 887 934 6

1 avdp. ounce = 0.911 458 3 0.075 954 86 0.062 5 28 349.523 125 28.349 523 125 0.028 349 523 125

1 apoth. or troy ounce = 1 0.083 333 333 0.068 571 43 31 103.476 8 31.103 476 8 0.031 103 476 8

1 apoth. or troy pound = 12 1 0.822 857 1 373 241.721 6 373.241 721 6 0.373 241 721 6

1 avdp. pound = 14.583 33 1.215 278 1 453 592.37 453.592 37 0.453 592 37

1 milligram = 0.000 032 150 75 0.000 002 679 229 0.000 002 204 623 1 0.001 0.000 001

1 gram = 0.032 150 75 0.002 679 229 0.002 204 623 1 000 1 0.001

1 kilogram = 32.150 75 2.679 229 2.204 623 1 000 000 1 000 1

UNITS OF MASS NOT LESS THAN AVOIRDUPOIS OUNCESAVOIRDUPOIS AVOIRDUPOIS SHORT HUNDRED-

UNITS OUNCES POUNDS WEIGHTS SHORT TONS LONG TONS KILOGRAMS METRIC TONS

1 avdp. ounce = 1 0.0625 0.000 625 0.000 031 25 0.000 027 901 79 0.028 349 523 125 0.000 028 349 523 125

1 avdp. pound = 16 1 0.01 0.000 5 0.000 446 428 6 0.453 592 37 0.000 453 592 37

1 short hundredweight = 1600 100 1 0.05 0.044 642 86 45.359 237 0.045 359 237

1 short ton = 32 000 2 000 20 1 0.892 857 1 907.184 74 0.907 184 74

1 long ton = 35 840 2 240 22.4 1.12 1 1016.046 908 8 1.016 046 908 8

1 kilogram = 35.273 96 2.204 623 0.022 046 23 0.001 102 311 0.000 984 206 5 1 0.001

1 metric ton = 35 273.96 2204.623 22.046 23 1.102 311 0.984 206 5 1 000 1

Table 11 - Conversion Table (All underlined figures are exact)

There are numerous steps that one can take in order to improve thequality of a mass measurement system. However, they usually fallwithin three main categories: the equipment, the environment, and theoperator. If even one of these areas is neglected, it can have a dramaticnegative impact on your results. Although these suggestions are notmeant to be all encompassing or all-inclusive, the improvements thatcan be made following these simple guidelines are extraordinary.

Equipment

Select weights that have a tolerance that is one third or better thanthe accuracy you require for your application. This way the error of theweight will not dramatically impact the quality of your measurements.For more information, see Weight Selection Guidelines section onpage 72.

The equipment must be of sufficient readability to calibrate ormeasure the weight or sample under test. (Please review the ToleranceTable on page 66).

The balance should be placed on a stable platform free from theeffects of vibration. The most common type of setup involves placingthe instrument onto a balance table that is constructed of marble orgranite.

Never use a balance or scale as soon as it is turned on. The internalelectronic components need to stabilize and warm-up for at leasttwenty-four hours once the equipment has been energized. Troemnerrecommends that you leave this instrument plugged in twenty-fourhours a day, seven days a week.

Never use a balance that has been idle for several hours without firstexercising it and calibrating it. A balance is exercised by repeatedlyplacing and removing weights from the balance pan. We recommendthat this be done at least ten times each with a weight that is 100%of the maximum capacity of the balance. After exercising, the balanceshould be calibrated. If these two techniques are consistentlyemployed, a noticeable improvement will result in both linearity andstability of the measurement.

When weights are not in use, store them in the case(s) in which theyare supplied. If the weights were not supplied with a case, eitherpurchase one or use a clean container to protect the surface(s) thiswill keep airborne particles from getting on your weights betweenuses. Weights should be in thermal equilibrium with the balance sostore weights near your balance(s). Another option is to leavecalibration masses commonly used inside the weighing chamberwhen not in use this assures your weights are in thermal equilibriumwith the balance producing a better measurement.


Mass Standards Handbook Good Measurement Practices


Mass Standards Handbook Good Measurement Practices

Environment

The more stable your environment, the better your measurementresults. Changes in temperature, pressure and humidity affect balanceperformance and weight stability. Ideal room conditions are 200C witha relative humidity between 45% and 60%. Fluctuations intemperature should not exceed 10C per hour. Humidity fluctuationsshould not exceed 10% per hour.

Balances should not be placed in close proximity to anything thatshakes, vibrates, or stirs violently. Avoid placing your equipment nearcentrifuges, vortexers, or shakers.

Do not place your balance and/or scale near anything that generatesheat. Heat will cause the balance chamber to warm and due to theeffects of the thermal expansion introduce large errors into yourmeasurement. Do not place the balance near a window. Sunlight canpenetrate the window, warm the balance chamber at different ratesduring the day, and affect the quality of your work.

Avoid placing the balance near sources of drafts, extreme air currents,or near air conditioning vents. These positions can cause yourreadings to be unstable and can dramatically cool the balancechamber when the air-conditioning system begins to run.

The measurement environment should be clean and free of excessivecontaminants. Contaminants such as dirt and grease can adverselyaffect the weight of an object.

Operator

Never touch a weight with your bare hands! Oils and contaminantsfrom your hand will be transferred to the weight and introduce asignificant error. It is recommended that all weights be manipulatedwith gloved hands or forceps. The two types of gloves that arecommonly used and accepted are either latex (powderless) or cotton.Avoid any metal to metal contact when handling or storing weights this will cause scratches that may introduce error. All weight forcepsand weight lifters should be either nonmetallic (plastic or wood) or ifmetal, covered with a soft protective coating or material to avoidscratches.

Place the weight or sample near the center of the balance pan. Asmall offset from center can have a pronounced effect and introduceundue variation.

Take special care not to breathe onto the weight or into the balancechamber. Back away from the instrument. This will prevent anythermal transfer of heat from your breath or body to the balance, theweight or sample.

Time your measurements. Consistent sample times will provide moreconsistent measurements.

Definitions

Tolerance: The maximum amount by whichthe conventional mass of the weight isallowed to deviate from the assigned nominalvalue. Also defined as Maximum PermissibleError.

Correction: The difference between theactual value of the mass and the assignednominal value. Also defined as Error. If thecorrection on your weight calibrationcertificate is a negative number, the weight isbelow nominal value by that amount. Apositive correction means that the weight isheavier than the nominal value by thatamount.

Uncertainty: A parameter associated with theresult of a measurement, that characterizesthe dispersion of the values that couldreasonably be attributed to the measurand.Typically reported at a 95% confidence level.

Readability: The mass value of the smallestscale or digital interval displayed by theweighing machine.

Repeatability: A measure of a weighingmachines ability to display the same resultwhen repeated measurements are madeunder the same weighing conditions.

Linearity: Plus or minus deviation from thetheoretically straight-lined course of twointerdependent values. In balances, thisexpression is applied to the plus or minusdeviation of the indicated measurementvalue from the true value of the load.

The following are guidelines for selecting theproper calibration weight for an electronicbalance.

1. Refer to the balance operating manual todetermine the calibration load.

2. If the calibration load cannot bedetermined through documentation,contact the manufacturer or put thebalance in the calibration mode. Manytimes the calibration weight needed willflash on the display.

3. Determine the readability of the balance.

4. Determine the calibration weight accuracyby dividing the readability by 3. Refer tothe Tolerance Table on page 66 for thegiven weight and select the tolerance thatmeets or exceeds the requirement.

5. In some cases, the readability will exceedthe best available weight tolerance. In thiscase, purchase the weight with thetolerance that is 1/3 of the accuracyrequired for your measurement.

Example:

A calibration weight is needed for a 1000 gbalance.

1. Referring to the operating manual, it isdetermined that a 1000 g weight isneeded to calibrate the balance.

2. To verify this information, switch thebalance into calibration mode. Thebalance displays a flashing 1000 g whichverifies that 1000 g is the calibration load.

3. Checking the balance display, it isdetermined that the balance reads to 0.01g or 10 mg.

4. Divide 10 mg by 3. The tolerance of the1000 g weight needed should be 3 mg orbetter. Checking the ASTM Class 1Tolerance Table, it lists a tolerance of 2.5mg for 1000 g. In this case, you shouldpurchase a 1000 g Class 1 weight tocalibrate the balance.


Mass Standards Handbook Weight Selection Guidelines


Mass Standards Handbook Weight Selection Guidelines

The following are guidelines for determiningweights to be used for calculating balanceerror at the load in which the balance is used.

1. Determine at what load the balance will be used.

2. Determine what accuracy is required forthe application. Be sure that the weighingequipment can satisfy the measurementaccuracy requirements.

3. The tolerance for the weight should be atleast 1/3 of the accuracy needed for theapplication.

4. Review the Tolerance Table on page 66 todetermine the correct calibration weightfor the application.

Example:

A range of samples from 10 g to 15 g needsto be weighed. An accuracy of 0.5 mg isrequired. The balance has a 100 g capacityand a readability of .00001 g. The balanceneeds to be verified at the minimum andmaximum of the range of samples.

1. The correct weights to select are one 10 gweight and one 5 g weight. To check thebalance at 15 g, use the 5 g and the 10 gweights together.

2. The accuracy of the 10 g and 5 g weightsshould be 1/3 times 0.5 mg or 0.16 mg.The cumulative tolerance of both weightsshould be applied at the 15 g load andshould be considered when selecting thetolerance for both weights.

3. Reviewing the Tolerance Table at 10 g,ASTM Class 2 has a tolerance of 0.074mg. The 5 g tolerance at ASTM Class 2 is0.054 mg. The total tolerance at 15 g is0.128 mg. ASTM Class 2 or better shouldbe chosen as the tolerance for thisapplication.

The following are guidelines for the directreadings of newly purchased or recalibratedweights.

The expected value of the weight whenplaced on the balance will vary according tothe following equation:

Expected Value = (Nominal Value+Correction Linearity)+/- Root Sum Square ofUncertainty andRepeatability

Example:

Expected value of a 100 g Class 1 weight,direct reading on a balance with a readabilityof 0.01 mg.

Correction (Provided by Manufacturer) = 0.18 mg

Linearity of Balance at 100 g = -0.00008 g

Uncertainty of Mass Value (k=1) = 0.000014 g

Repeatability of Balance (k=1) = 0.00003 g

Root Sum Square of Uncertainty andRepeatability (k=2) = 0.00007 g

Expected Value = 100 g + 0.00018 g - 0.00008 g +/- 0.00007 g

Expected Value = 100.00010 g +/- 0.00007 g


Mass Standards Handbook Determining Balance Error

The following method establishes step-by-step performance parametersand verification using calibrated weights for electronic balances.Weights with weight calibration certificates are required.

Using calibrated weights, it is possible to determine balance errorresulting from internal calibration processes. To verify proper balanceperformance using calibrated weights, one needs to establish twoparameters. The first is to determine the balances ability to repeatmeasurements (Repeatability). This is accomplished by calculating astandard deviation and multiplying it by 2 to achieve a 95% confidenceinterval. The second is to determine how much error (or offset) isintroduced when the balance is calibrated.

1. Set-up the balance according to the manufacturers specifications.Allow the balance to settle for at least a 24-hour period to achievethermal equilibrium.

2. Calibrate the balance using the internal calibration function of thebalance and an appropriate calibration weight (see the balancesoperation manual for proper calibration weight selection). Somebalances have built in calibration weights. It is recommended that anexternal calibration weight be used.

3. Select a verification weight that represents the mass of a typicalsample size or a weight that is in the range of the majority ofsamples.

4. Tare or zero the balance so the display reads all zeros.

5. Using the verification weight, make at least 20 measurements andrecord the results of each measurement. Zero the balance beforeeach measurement. After all of the measurements are made,calculate a single standard deviation.

6. Multiply the standard deviation by 2. This is the random error orrepeatability that is expected for the balance with a 95% confidencelevel. The number becomes the upper and lower control limits for theperformance verification.

NOTE: Should the single standard deviation be significantly greaterthan the manufacturers specification for repeatability, try anotherlocation for the balance, and be sure the operator is following goodmeasurement practices. Look for sources of vibration or air currents thatmay be causing the balance to perform poorly. If other locations do notimprove the results, contact the manufacturer and explain the problem.The manufacturer may be able to provide other solutions.

7. Check the weight calibration certificate and obtain the correction ofthe weight that was used to calibrate the balance. This is the errorthat was introduced when the balance was calibrated at that load.Most calibration functions in electronic balances set the linearfunction for the balance from the calibration load down to zero. It isimportant to note that the error introduced at the calibration load isreduced by 50% at 1/2 of the load and by 75% at 1/4 of the load.In other words, as the load on the balance is reduced, the linear errorintroduced by the correction of the calibration weight is reduced. Anestimation of the linear error of the calibration can be made with thefollowing equation:

Linear error = -1 x Error of cal weight x Load/Calibration load

If the balance is calibrated using the internal balance weights, thelinear error cannot be determined without the value of the internalweights.

8. The expected value for your performance verification is calculated as:

Expected value = Actual mass value + Linear error

Where: Actual mass value = Nominal value + Conventional Mass vs. 8.0 correction

9. Verification: Zero the balance and place the verification weight on thebalance. The verification passes if the actual reading is within the randomerror established in Step 6 of the expected value.


Mass Standards Handbook Determining Balance Error

Recommendations:

A. Perform verifications at different times during the day. If theverifications fail during some time periods but pass during others,the laboratorys environmental conditions are changing throughoutthe day.

B. Troemner recommends that calibration weights be recalibrated atleast annually to verify that they are not changing in value. Actualusage will determine the calibration interval.

C. Chart the actual value after each verification. This may identifytrends of drifting or systematic errors that are working into yourprocess.

D. Recalculate the random error periodically to see if the repeatabilityof your balance is changing.

Example:

Given:

100 g capacity balance is readable to 0.1 mgCalibration load: 100 gSamples tested at: 10 g100 g Class 1 weight with a correction of +0.10 mg and anuncertainty of +/- 0.025 mg

10 g Class 1 weight with a correction of +0.010 mg and anuncertainty of +/- 0.018 mg

Taking 20 measurements, the standard deviation is found to be 0.3 mg.The random error is 2 times 0.3 mg or 0.6 mg for a 95% confidenceinterval.

Linear Error = -1 X (0.10 mg X 10 g/100 g) = -0.01 mg

Expected value = 10.00001 g + (-0.01 mg) = 10.00000 g

Verification Range = 10.00000 g +/- 0.6 mg

Over the next 3 days, 7 verifications are performed and are shown below.The Balance Verification Chart below illustrates that the 2nd and 5thmeasurements failed, but the rest of the measurements passed. Usingcontrol charts like this is an effective method in identifying measurementproblems before the quality of your work is affected. Investigation andCorrective Action should be made when measurements fall out ofacceptable range.

TEST # 1 2 3 4 5 6 7

Measurement 10.0003 9.9993 10.0002 9.9996 10.0011 10.0004 9.9999

Balance Verification Chart

10.0012

10.0010

10.0008

10.0006 UCL 95%

10.0004

10.0002

10.0000

9.9998

9.9996

9.9994 LCL 95%

9.99920 1 2 3 4 5 6 7 8

OUT OF RANGE

OUT OF RANGE

Observed Measurement

Mea

sure

d Va

lues

Observations


Mass Standards Handbook Weight Care and Maintenance

Cleaning No cleaning method is perfect. It is important tounderstand that certain cleaning procedures may alter a calibratedmass value of a weight. Substance, whether dirt or actual material, maybe removed during the cleaning process. If proper cleaning proceduresare not followed, residual dirt or solvent may be left on the massstandard, which will also affect the mass value of the weight. There aredifferent recommended cleaning methods for sheet metal and non-sheet metal weights, because of their different physical characteristics.There are also different cleaning methods for periodic or daily cleaningand spot cleaning, which is a more vigorous method to be used whendaily/periodic cleaning methods do not remove foreign matter.

Daily/Periodic Cleaning

Non-sheet metal weights - Before each use clean all weights with acamel hair or other suitable soft brush to remove any particles thatmight have settled on the weight. Remember to pay special attention tothe bottom surfaces, since these tend to be overlooked. One may alsouse a syringe bulb or compressed air to remove loose particles. Ifcompressed air is used, especially if it comes from a can, thetemperature of the weight may be affected and the weight should notbe used for at least 4 hours to allow the weight to return to thermalequilibrium with the environment. If particles are not removed easily,spot cleaning may be necessary.

Sheet metal weights Prior to each use, they should be visuallyinspected for foreign matter and brushed lightly with a camel hairbrush. Special care must also be taken not to overbrush theseweights. Sheet metal weights are the most delicate and fragile weightsmanufactured. Sheet metal weights also have the largest surface tomass ratio, so any effect on a sheet metal weights surface will have agreater impact in its mass value as compared to cylindrical weights.These weights have a tendency to attract foreign matter due to theflatness and raised markings of each piece. Sheet metal weights areadjusted by filing the edges with very fine abrading instrumentation. Asa result, some of the edges may be rough or may have microscopic burrson them. Extra care must be taken when handling and cleaning theseweights. It is highly recommended that sheet metal weights be placedin a protective casing in order to prevent contamination. It is also highlyrecommended that compressed air not be used because compressed airis usually colder (especially if it comes out of a can) which can changethe temperature of the weight and introduce undue error. Instead asyringe bulb should be used to help clean the weight and to blow offparticles.

Spot Cleaning Spot cleaning is recommended when foreignmatter is observed on weights that cannot be removed usingdaily/periodic cleaning methods. Use cheesecloth dampened with ethylalcohol and gently rub the weight surface in order to remove anyresidual or stubborn debris from the weight surface. If using alcoholdoes not remove the foreign debris, repeat the process using othersolvents such as window cleaner or distilled water. If solvents other thandistilled water and alcohol are used, the weights should be cleanedagain using alcohol to remove any residual solvent from the weight.Solvents other than distilled water should never be used on brassweights or cast iron weights since they have a protective coating oflacquer and paint respectively, and solvents will deteriorate coatedsurfaces. For sheet metal weights or other weights made out ofaluminum, alcohol should never be used since alcohol can deterioratealuminum. After spot cleaning, the weight should not be used for aperiod of at least 4 hours in order for the weight to return to thermalequilibrium with the environment.

Painted cast iron weights These weights should be brushed orcompressed air should be employed to remove any foreign material.When cast iron weights are calibrated and the as found data has beenascertained, you may want to add a coat of paint to the weights,especially if there are signs of rust or abrasions. A calibration should beperformed after any paint is applied. Use a lacquer or aluminum-basedpaint that goes on thin. A thick paint like an epoxy-based paint leavestoo heavy a coat and is not recommended. Avoirdupois weights shouldbe painted silver and metric weights should be painted gold.

Brass weights The only cleaning procedure recommended for brassweights is cleaning with a clean cloth dampened with distilled water.

Austenitic - Pertaining to or describing a solidsolution in iron of carbon and sometimesother solutes that occurs as a component ofsteel under certain conditions. Austeniticstainless steels usually offer manyadvantages such as increased strength,corrosion resistance, lower magneticsusceptibility, and desirable mechanical andmagnetic properties.

Calibration - The act of determining the massdifference between a standard of a knownmass value and an unknown test weight orset of weights. The process uses acomparison method and a series ofcalculations to establish the mass value andconventional mass value of the unknownand determines a quantitative estimate of theuncertainty to be assigned to themeasurement process as well as the mass orconventional mass value for the unknown.

Conventional Mass - The conventional value ofthe result of weighing in air, in accordance toInternational Recommendation OIML R 33.For a weight taken at 20 C, the conventionalmass is the mass of a reference weight of adensity of 8000 kg/m3, which it balances in airdensity of 1.2 kg/m3.

Correction - Mass values are traditionallyexpressed by two numbers, one being thenominal mass of the weight and the secondbeing a correction. The mass of the weight isthe assigned nominal value plus the assignedcorrection. Positive corrections indicate thatthe weight embodies more mass than isindicated by the assigned nominal value.

International Prototype Kilogram - Theplatinum-iridium cylinder maintained at theInternational Bureau of Weights andMeasures (BIPM), at Sevres, Frances with aninternationally accepted defined mass of 1 kgwith zero uncertainty.

Mass in a Vacuum The mass of a weight asif it were measured in a vacuum. Also knownas True Mass.

Nominal Mass The mass value as markedon a weight.

Reference Standard - A standard, generally ofthe highest metrological quality available at agiven location, from which measurementsmade at that location are derived.

Mass Standards Handbook Terminology


Troemners online Weight Selector takes theguess work out of choosing the correctweight for your application. Visit us atwww.troemner.com and let us help you findexactly what you need.


Mass Standards Handbook Terminology

Tolerance (Adjustment Tolerance or MaximumPermissible Error) - The maximum amount bywhich the conventional mass of the weight isallowed to deviate from the assigned nominalvalue.

Traceability - Property of the result of ameasurement or the value of a standardwhereby it can be related to statedreferences, usually national or internationalstandards, through an unbroken chain ofcomparisons all having stated uncertainties.In other words, in order to establishtraceability there must be an unbroken and

valid relationship to some nationally orinternationally recognized standard. Astandard itself can not really be traceable,but the value assigned to it can.

Uncertainty - Parameter associated with theresult of a measurement that characterizes thedispersion of the values that could reasonably beattributed to the measurement. This is the rangeof values within which the true value is estimatedto lie. In other words, the uncertainty is ameasure of how confident you are in theaccuracy of the results resulting from ameasurement.

U.S. National Prototype Standard - Platinum-iridium kilogram identified as K20,maintained at the National Institute ofStandards and Technology (NIST), with avalue assigned relative to the InternationalPrototype Kilogram.

Weight (Mass standard) - An objectrepresenting a specific mass, regulated inregard to its physical and metrologicalcharacteristics: shape, dimension, material,surface quality, nominal value, and maximumpermissible error.

Please visit our website at www.troemner.com and click on FAQs todiscover answers to many of your product and calibration questions.

You will also find a comprehensive list of many helpful terms.

Hummingbird Help


In 2003, Henry Troemner LLC beganmanufacturing stainless steel weightsusing a new, unique, material specificallydesigned to meet the many demandsrequired of precision weights. Precisionweight requirements of consistent density,low magnetic properties, extremely smoothsurface finishes, and hardness are noteasily achieved. For example, softerstainless steels developed to obtain bettersurface finishes tend to have highermagnetic properties. Softer stainlesssteels, although easier to machine andpolish, do not have the hardness of lessmachining friendly stainless steels andmay wear more quickly and lose weightfaster when in use. Henry Troemner LLCspent years researching and testing variousstainless steels to characterize the optimalmaterial used for making precision weightsin order to specify a material that would be

far superior to any other stainless steelbeing used. The result is Troemner Alloy 8Stainless Steel, the finest commerciallyavailable stainless steel for high precisioncalibration weights and mass standards.Alloy 8 meets and exceeds all stainlesssteel material specifications that NBS(now NIST) specified when purchasing theoriginal U.S. state laboratory massstandards over 35 years ago.

Troemner weights made from Alloy 8Stainless Steel provide the customer thefollowing benefits:

Low Magnetic Properties - The mostimportant attribute of Troemner Alloy 8 isits extremely low magnetic properties.ASTM E617-97 Standard Specification forLaboratory Weights which covers classes 0,1, 2, 3, 4, 5, 6 and 7 has specificationsfor maximum allowable susceptibility and

magnetic field. See Table 12 below forthese specifications.

OIML International recommendation R111for Weight Classes E1, E2, F1, F2, M1,M2, M3 also has specifications formaximum allowable susceptibility andmagnetic field.

See Table 13 and 14 on page 80 for thesespecifications.

The magnetic susceptibility specificationfor Troemner Alloy 8 is 0.005, whichexceeds ASTM and OIML specifications forall classes.

Why are magnetic properties important?The magnetic field of the weight can reactwith the balances magnetic fields causingcalibration errors. Many of todaysprecision balances have weighing cellswhich are sensitive to magnetic fieldchanges. If one moves a magnetizedweight around a balance pan affecting themagnetic field of the weighing cell, thebalance readings may change, introducingerrors into the measurement.

Magnetic properties in stainless steel canbe characterized in two ways. Magneticsusceptibility is a dimensionless measurethat determines the ability of a material torespond to an external magnetic field.Magnetic field in a material can bemeasured once a material is magnetized.The higher the susceptibility for a material,the easier it is to become magnetized.

Mass Standards Handbook The Advantages of Troemner Alloy 8 Stainless Steel

Table 12 - Magnetic Properties

WEIGHT VOLUME MAGNETIC MAXIMUM CLASS SUSCEPTIBILITY () MAGNETIC FIELD

T mG0 0.01 2.0 20

1 0.03 4.0 40

2, 3, 4 0.05 6.0 60

T = Tesla G = Gauss


Mass Standards Handbook The Advantages of Troemner Alloy 8 Stainless Steel

Austenitic stainless steel has naturally lowmagnetic permeabilities. During themanufacturing process, cold working ofthe metal can change the grain structure ofthe material and increase its ability to bemagnetized. This change in grain structurewill be dependent upon the grade ofstainless steel.

Once a weight exhibits susceptibility it canbe magnetized when placed in a magneticfield. The amount of permanentmagnetization will depend on the strengthof the magnetic field and the susceptibilityof the sample. The magnetic susceptibilityof a sample can be reversed through stressrelieving (annealing) of the sample. Thisprocess does not produce repeatableresults and Troemner does not recommend it.

A weight that becomes magnetized can bede-magnetized by introducing the weightto an electrical magnetic field generatedby a piece of equipment. By holding theweight with its field perpendicular to thefield generated by the piece of equipment,you can reduce the magnetic field of theweight. However, this method is notrecommended since the weight can

become easily magnetized again if it isexposed to another magnetic field.

Alloy 8s composition has extremely lownatural magnetic susceptibility. Troemner,Alloy 8 has been extensively tested forsusceptibility before and aftermanufacturing using our NVLAPaccredited calibration process. Extensivetests were also performed for permanentmagnetism. Weights made of Alloy 8 wereexposed to various magnetic fields andnone of them became magnetized.

For more information on magneticsusceptibility, Troemners NVLAPaccredited measurement process, andinformation on a laboratory inter-comparison, there is a technical paperposted on Troemners web site. Go towww.troemner.com, click on the literaturelibrary tab, then technical literature.

Consistent Density - Because it is a custommaterial, Troemner Alloy 8 is obtainedfrom a single source, and is purchased inmill run quantities (40,000 poundminimum) to assure consistency inmaterial density across different sizes ofweights. Troemner reports a density of

8.03 g/cm3 for Alloy 8 after testing severalsamples using its NVLAP accrediteddensity calibration process. Densitymeasurements across all diameters werewithin +/- 0.006 g/cm3. This is importantfor weights that are subsequentlyrecalibrated after the initial sale becausethe reported density is used to makebuoyancy corrections during calibrations.Variations in material density can have aneffect on the calibrated value assigned toweights. (Check your Certificate orStatement of Accuracy for the density ofyour weights.)

Surface Finish and Hardness - TroemnerAlloy 8 is significantly harder than materialused previously. The benefit to the user of aharder material is it is less susceptible towear and scratches. A weight made of harderstainless steel is less likely to lose enoughmass to carry it out of its adjusted tolerance.

A weight manufactured using TroemnerAlloy 8 will have extremely low magneticproperties, consistent density, and themirror-like, highly polished finish you havecome to expect from Troemner in order tomeet todays rigorous requirements.

WEIGHT CLASS E1 E2 F1 F2 M1 M2 M3

Maximum Magnetism, 0 M (T), of OIML weights 3 10 30 100 300 1000 3000

Table 14 - Maximum Permanent Magnetism, 0 M (T), of OIML Weights

WEIGHT CLASS E1 E2 F1 F2

Nominal value 100 g 0.01 0.03 0.07 0.21

Nominal value < 100 g 0.025 0.075 0.25 0.75

Nominal value 1 g 0.12 0.37 1.2 -

Table 13 - Maximum Susceptibility, of OIML Weights


Pipette Calibration

Services includerepair, calibrationand certification ofpipettes regardlessof manufacturer

NVLAP accredited 0.1 l to 5 ml.Laboratory capability 0.1 l to 100 ml

We can meet your most stringentrequirements including: GLP, GMP, FDA,ISO, NCCLS, CAP and CLIA

Calibration System is accredited byNVLAP to be ISO/IEC 17025

Thermal Mass Flow Calibration

Services include repair, resizing,calibration and certification services forflow meters and controllers

Factory trained technicians

Utilizes state of the art laminar flowtechnology for high precision (2 sccm to100 slpm)

Calibration System is ISO/IEC 17025compliant

TemperatureCalibration

Traceable calibrationservices from -196Cto 1100C

NVLAP accredited for comparisoncalibrations -196C to 660C

Utilizes the latest equipment providinglow uncertainties

Calibration System is accredited byNVLAP to be ISO/IEC 17025 compliant

Humidity Calibration

10% - 95% Rh

Utilizes a twopressure, twotemperature humiditygenerator


Pressure Calibration

0 - 1,000 psi

Utilizes primarypiston gauges and asecondary transferstandard


Electrical, Time and Frequency Calibration

Electrical calibrations cover themeasurement disciplines found in mostmultimeters and oscilloscopes

Calibrations utilize state-of-the-artequipment providing low uncertainties

Calibration System is ISO/IEC 17025compliant





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