Inside this Issue

Page

Announcing Spring with 

Summer on the Horizon! 1

Grain Moisture Meter Test 

Methods and Tolerances 1

Calendar 2

Now Available the NEW Handbook

133, Checking the Net Contents of

Packaged Goods for 2011 7

Announcing the NCWM 96th Annual

Meeting 7

This Month in 

History

May 5, 1961 - Alan Shepard became the first

American in space. Freedom 7 made a 15

minute 28 second flight to make a suborbital

flight at the altitude of 116 miles (186 km)

above the earth. This took place 23 days

after the Russians, which began the Space

Race.

May 6, 1856 - Explorer Robert E. Peary

(1856 - 1920) was born in Cresson, Pennsylvania. He organized and led eight Arctic expeditions and reached the North Pole on

April 6, 1909. 

May 10, 1869 - The Union Pacific and Central

Pacific railways were linked at Promontory

Point, Utah with a golden spike. 

May 14, 1609 - Jamestown, Virginia, became

the first established English settlement in

America.

1

Volume 2 Issue 2

May 1, 2011

Announcing Spring with 

Summer on the Horizon!

Explore our Training Opportunities

Ah, it’s time to pull out the old barbeque grill and scrub it up for the outdoor cooking season ahead, and the yard is calling for attention after the

winter sleep. With the warmer temperatures, off goes the confining

coats and the trappings of winter and days spent indoors. Spring awakens new energy and promises for the weeks ahead. Today in the Washington Metropolitan area we are embracing a beautiful spring day.

Thoughts of summer vacation are filling our heads as we pull out the calendar to plan the big family get-a-way.

In the Weights and Measures Division, while we are doing the above, we

are also putting on our many hats and all the responsibilities that go with

them. Technical Advisors’ are traveling to various weights and measures

related meetings, and others are traveling to provide training to various

jurisdictions on a variety of topics, and coordinating webinars that you

can attend right from your work or home computer. Check out the training and webinar sessions listed in our side bar under “Calendar.” Take advantage of the opportunities to broaden your knowledge base. Put your

new found energy to use and broaden your horizons!

Grain Moisture Meter Test

Methods and Tolerances

Commercial grain moisture meters are responsible for making measurements that affect large volumes of product per device and have a large

economic impact. Many of the commercial grain moisture meters in service today are meters that must meet the requirements of NIST Handbook

(HB) 44, Section 5.56(a) Grain Moisture Meters. This code applies to all

grain moisture meters manufactured or placed into commercial service

after January 1, 1998. This code identifies two test methods, the Air

Oven Reference Method and the Meter to Like-Type Meter Method; separate tolerances are applied to each method. This article has been written to describe how to use the two test methods and apply the

associated tolerances specified in NIST HB 44 Section 5.56(a) in field testing grain moisture meters. 
Calendar 2011

May 2 - 6

Basic Industry

NIST/WMD

Gaithersburg, MD

Contact: Val Miller at val.miller@nist.gov

May 16 - 20

WRAP (members only)

Anchorage, AK

May 9 - 12

Northeastern Weights & Measures Association - Annual Meeting

Saratoga Springs, NY 

Contact: James Cassidy, at

jcassidy@cambridgema.gov

May 16 - 19

Central Weights & Measures Association

Annual Meeting

Grand Rapids, MI

Contact: Vicky Dempsey at

dempseyv@mcohio.org

May 26

Document Control and Recordkeeping 

(Webinar)

Contact: Val Miller at val.miller@nist.gov

June 20 - 26

NIST, Handbook 130, Checking the Net Contents of Package Goods - Train the Trainer

Salt Lake City, UT

Contact: Lisa Warfield at

Lisa.Warfield@nist.gov

June 30

Proficiency Testing & Root Cause Analysis

(Webinar)

Contact: Val Miller at val.miller@nist.gov

July 7

Calibration Method Validation (Webinar)

Contact: Val Miller at val.miller@nist.gov

July 14

Basic Uncertainty Concepts (Webinar)

Contact: Val Miller at val.miller@nist.gov

July 17 - 21

NCWM Annual Meeting

Missoula, MT

Contact: info@ncwm.net

Website: http://www.ncwm.net

Continued on page 3

W&M Connection 2 Volume 2 Issue 2

Background

To better understand the system for field testing grain moisture meters, it

is necessary to provide some background on the development of calibrations for grain moisture meters. The National Type Evaluation Program

(NTEP) for grain moisture meters differs from the type evaluation program for other commercial devices in that there are two phases to the

program. In addition to a device evaluation, Phase I, in which a limited

number of grains are tested to evaluate the design and calibration of the

device, grain moisture meters are also subjected to an annual calibration

testing program; referred to as Phase II. The Phase II program verifies the

calibration performance with a large number of samples, including difficult to store, high moisture samples, which would be hard to use in Phase

I tests. The Phase II program also facilitates meter calibration and standardization to a national, common sample set and a single air oven laboratory. In the NTEP Phase II program, raw data needed for calibration

updates to grain moisture meters is collected. The collection of this data

is necessary for grain moisture meters because although the device’s

standard features may remain unchanged each year, individual grain calibrations may change to reflect long-term changes in grain characteristics. 

Moisture meters predict moisture content based on an optical (near infrared meter) or dielectric (dielectric meter) measurement of a meter to a

grain sample. The current technology for grain moisture meters is grain

type/class (e.g., wheat is a grain type, durum such as durum wheat is a

class of wheat) specific. As such, a calibration is developed for each grain

type/class based on the characteristics of that grain type/class. Because

the current technology is grain type/class specific, the relationship between moisture and a grain moisture meter’s optical or dielectric response to the biological characteristics of the grain sample (variety, size,

weight, etc.) may change with each crop season, thereby necessitating a

change to the meter’s calibration for that grain type/class. In addition,

there is variation in the calibrations for each type of grain moisture meter

due to the manufacturer’s prediction equations which are used to develop the calibrations for their meter and due to the specific sensing technologies used in different meter types. Simply put, calibrations must be

reviewed and adjusted to account for differences in grain crops from year

to year.

To determine whether or not a calibration change is needed, as noted

above, raw data is collected in the Phase II program on the NTEP laboratory meters using the national grain sample set. The national grain sample set consists of hundreds of current crop year grain samples that are

representative of grains from across the United States for the grain

types/classes in the NTEP program. The raw data from the NTEP laboratory meters is provided to the manufacturers and the manufacturers use

this data to make calibration updates to the grain moisture meters as

needed. An NTEP Certificate of Conformance is available to state weights

and measures officials, which includes the updated calibrations needed

for field inspection of devices. The manufacturers provide the updated

calibrations to the device owners to ensure that all commercial meters

have the latest calibrations installed in the meters. 
July 21

Documenting Traceability and Calibration Intervals (Webinar)

Contact: Val Miller at val.miller@nist.gov

July 28

Software Verification & Validation (Webinar)

Contact: Val Miller at val.miller@nist.gov

August 2 - 4

Packaging and Labeling (Industry Only)

NIST/WMD

Gaithersburg, MD

Contact: Lisa Warfield at Lisa.Warfield@nist.gov

August 4

Internal Auditing (Webinar)

Contact: Val Miller at val.miller@nist.gov

August 11

Management Reviews (Webinar)

Contact: Val Miller at val.miller@nist.gov

August 21 - 25

NSCLI Annual Conference

Gaylord National Convention Center

National Harbor, MD

Contact: http://www.ncsli.org

August 31 - September 1

Weighing Sector Meeting

Sacramento, CA

Contact: info@ncwm.net

September 1

Calibration Report Evaluation (Webinar)

Contact: Val Miller at val.miller@nist.gov

September 8

Calibration Method Validation (Webinar)

Contact: Val Miller at val.miller@nist.gov

September 12 - 15

Central Weights & Measures Association

Cedar Rapids, IA

Contact: Vicky Dempsey at

dempseyv@mcohio.org

September 26 - 30 (Invitation Only)

OIML - TC 6 (Prepackaged Products)

NIST

Gaithersburg, MD

Contact: Kenneth Butcher at

Kenneth.Butcher@nist.gov

301-975-4004

continued on page 4

W&M Connection 3 Volume 2 Issue 2

AIR OVEN REFERENCE METHOD - FIELD TESTS

When using the Air Oven Reference Method, a grain sample with a reference moisture value is used to test field meters. The reference moisture

value of the grain sample is determined using a GIPSA Air Oven test procedure. The field test is performed by measuring the moisture of reference grain samples in the field meter. The field meter moisture

measurement is compared to the reference moisture values of the grains.

This method is a “mini” test or verification of the meter’s calibration; it

determines how well the meter’s calibration responds to the two to three

grain samples (typically of high and low moisture content for each grain

type) that are used for testing. Due to the current technology for developing meter calibrations, there is a probability that the samples selected

may not perform well on all NTEP meter types. Why would this happen?

As discussed in the background section of this article, the current technology for grain moisture meters relies on grain type/class specific calibrations that will vary per meter type. There are a number of samples

represented in the national grain sample set, but due to the secondary

measurement methods (measuring an optical or dielectric response of a

grain sample to predict moisture) and the differences in measurement

technologies (prediction equations and sensing technologies), individual

samples are predicted with differing levels of agreement to the reference

method. Also there is the possibility that if a grain sample that is chosen

to test the meter is not represented (due to its variety or other biological

characteristic) in the national sample set used to develop the calibration

for some measurement technologies, the grain sample may not perform

well on the meter. To prevent this occurrence, it is necessary to screen

the sample by running the samples through laboratory meters that are

maintained in good operating condition, have the latest calibrations installed, and are of the same type as the jurisdiction’s field meters that will

be tested. If the grain sample moisture tested on the laboratory meter

types are within 0.5 % of the reference moisture, the sample can be used

to test field meters. Careful sample selection is needed for this test

method to avoid failing meters that are operating correctly. 

AIR OVEN REFERENCE METHOD – TOLERANCES FOR FIELD TEST

The tolerances that apply to the Air Oven Reference Method are found in

NIST HB 44 Section 5.56. (a) Paragraph T.2.1, Table T.2.1. The tolerances

are the same for both acceptance and maintenance tolerance. See tolerances below:

Type of Grain, Class,

or Seed Tolerance

Minimum 

Tolerance

Corn, oats, rice,

sorghum, sunflower

0.05 of the perdent

moisture content

0.8 % 

in moisture content

All other cereal grains

and oil seeds

0.04 of the percent

moisture content

0.7 %

in moisture content

Table T.2.1.

Acceptance and Maintenance Tolerances 

Air Oven Reference Method

(Amended 2001)
September 26 - 29

Western Weights & Measures Association

San Obisipo, CA

Contact: Brett Saum at bsaum@co.slo.ca.us

October 6

Annual Submission Process (Webinar)

(Limited to State Laboratory Participants)

Contact: Val Miller at val.miller@nist.gov

October 12 - 13

Northeastern Weights & Measures Association Interim Meeting

Norwich, CT

Contact: James Cassidy at

jcassidy@cambridgema.gov

October 13

Document Control & Recordkeeping (Webinar)

Contact: Val Miller at val.miller@nist.gov

October 23 - 26 

Southern Weights & Measures Association

Norfolk, VA

Contact: Dale Saunders at

dale.saunders@vdacs.virginia.gov

November 10

Annual Submission Process (Webinar)

(Limited to State Laboratory Participants)

Contact: Val Miller at val.miller@nist.gov

Calendar 2012

January 22 - 25

NCWM Interim Meeting

New Orleans, LA

Contact: info@ncwm.net

Webinars are conducted by the WMD Laboratory Metrology Group. You can get additional

information by contacting Val Miller at:

301-975-3602 or by e-mail at:

val.miller@nist.gov or viewing the Laboratory Metrology Group web page at:

http://www.nist.gov/pml/wmd/labmetrology/webinars.cfm

Additional details on the above calendar

items can be found at: 

http://ts.nist.gov/WeightsAndMeasures/calendar3.cfm

W&M Connection 4 Volume 2 Issue 2

The minimum tolerance referenced in the table is the minimum tolerance

to be applied to a test; if the calculated tolerance falls below the minimum

tolerance level, the minimum tolerance is applied. To calculate the tolerance, the percent reference moisture of the grain sample that is used for

testing is multiplied by the tolerance in Table T.2.1. 

Example 1:

Corn Sample with a reference moisture of 14.5 %

14.5 % x 0.05 = 0.72 %

Since 0.72 % is less than the minimum tolerance of 0.8 %, the applicable

tolerance for the test is 0.8 %. 

Example 2:

Corn Sample with a reference moisture of 16.0 %

16.0 % x 0.05 = 0.8 %

Since 0.8 % is equal to the minimum tolerance of 0.8 %, the applicable tolerance for the test is 0.8 %.

Example 3:

Corn Sample with a reference moisture of 18.0 %

18.0 % x 0.05 = 0.9 %

Since 0.9 % is greater than the minimum tolerance of 0.8 %, the applicable tolerance for the test is 0.9 %.

METER TO LIKE-TYPE METER REFERENCE METHOD - FIELD TEST

When using the “meter to like-type meter” test method, a grain sample is

used as a comparison medium for a side by side comparison test of a “reference meter” to a field meter of like-type. A reference meter is a meter

that is maintained by the laboratory in good working condition, has the

latest calibrations installed, and is of the same meter type as the jurisdiction’s field meters. The reference meters are used in side-by-side comparisons in the field to test commercial meters of like type. The grain sample

is measured in the reference meter and then measured in the field meter

under test, and the results are compared. The tolerance in NIST HB 44,

Section 5.56(a), Table T.2.1. (see below) is applied to the difference between the two results. It is important to note that the meter to like-type

meter reference method can only be used with NTEP meters because the

Phase II calibration testing performed on NTEP meters is a check of the

calibration accuracy. This test method verifies that the field meter is functioning similarly to the reference meter and determines if a meter is malfunctioning. It is important that the side-by-side comparison of meters be

conducted with a like-type meter, because although the meter calibrations are based on the same sample set, the prediction equations used to

develop the calibrations vary per meter type; the sensing technologies

may also vary, which causes various meter types to measure differently. If

a meter of one type is used to test a meter of another type, errors will be

introduced in the test results because of these differences.

Reviews and reports of the variation between meter types in the NTEP

Phase II program are annually reviewed at the Grain Analyzer Sector

meetings and are included in the reports of the Sector. It should be noted

that these variations are much less than in past years because of the NTEP

Memorial Day 

was originally called Decoration Day (established May 5, 1865) and was first observed in

the United States following the Civil War when

flower were placed on soldiers’ graves.
METER TO LIKE-TYPE METER REFERENCE METHOD – TOLERANCES FOR FIELD TESTS

The tolerances that apply to the meter to like-type meter test method are found in NIST HB 44 Section 5.56(a) Paragraph

T.2.2. The tolerances are the same for both acceptance and maintenance tolerance as shown.

Table T.2.2. 

Acceptance and Maintenance Tolerances Meter to Like-Type Meter Method

W&M Connection 5 Volume 2 Issue 2

Phase II program. The data below include the grain moisture meter Phase II comparisons for Corn, 2007 - 2009 crops

years, which were reported in August 2010. These data illustrate the value of using like-type meters when using a meter

to meter comparison method. In the first graph, the official meter has a bias with respect to the air oven of approximately 0.5 % in the 10 % to 12 % range, while another meter type in the same range has a bias of approximately 0.19 %.

The official meter has a bias to air oven of 0.31 % higher than this NTEP meter type. If a meter of like-type is not used in

the meter to like-type meter test method, any error created by a difference in meter types will be added to the test results. 

Sample Reference Moisture Tolerance

Up to 22 % 0.5 %

in moisture content

(Added 2001)
W&M Connection 6 Volume 2 Issue 2

IN THE FIELD

Is there a W&M topic that you would

like to have discussed in the Weights

and Measures Connection?

How can we better serve our W&M

community?

Do you have a safety tidbit to share?

Do you have a W&M event that you

wish to post in the Connection’s calendar?

Submissions can be sent to the Editor,

Linda Crown at linda.crown@nist.gov

Unlike the air oven reference method for field testing, no calculation is

needed to apply the tolerance for meter to like-type meter. The meter to

like-type meter tolerance is expressed as a percent value within the table

and is applied directly to the difference in the measurement results of the

reference meter of like-type to the measurement results of the field

meter.

Example 1

A corn sample reads 16.0 % on the reference meter of like -type and the

same sample reads 14.5 % on a field meter under test.

14.5 % - 16.0 % = - 1.5 %

Since the difference is greater than ± 0.5 %, the field meter under test

does not meet the tolerance specified in Table T.2.2.

Example 2

A corn sample reads 18.0 % on the reference meter of like-type and the

same sample reads 18.5 % on a field meter under test.

18.5 % - 18.0 % = 0.5 %

Since the difference is equal to ±0.5 %, the field meter under test meets

the tolerance specified in Table T.2.2.

Example 3

A corn sample reads 14.5% on a reference meter of like-type and the

same sample reads 14.7 % on the field meter under test.

14.7 % – 14.5% = 0.2% 

Since the difference is less than ± 0.5 %, the field meter under test meets

the tolerance specified in Table T.2.2.

It is very important that correct test procedures and tolerances be applied

during testing. Grain moisture meters, although few compared to other

commercial devices, affect high dollar values of product per device. 

FUTURE DIRECTION FOR GRAIN MOISTURE METERS

In spite of the limitations of the current technology, there has been

progress. Prior to the NTEP program there was a lack of calibration uniformity due in part to the use of different grain sample sets. Calibrations

for different meter types were developed with grain samples from different areas of the United States. Also many of the meters were designed

such that the user was required to make judgments concerning certain

user-controlled factors that would affect the accuracy of the moisture

measurement. When the NTEP program was developed, the same meter

technology was in use, but the design criteria for the devices changed to

remove many of these user-controlled judgments, including sample

weighing and moisture look-up charts. NTEP meters directly indicate the

moisture on the device and also do not require the user to measure the

weight of the grain sample prior to measuring the moisture content of the

grain. In addition, instead of calibrations being developed based on varying grain sample sets, calibrations for all meter types are based on the

same grain sample set, made up of grains from across the United States.

As the calibrations for NTEP meters become more robust, that is more

and more grain varieties are included in the grain sample set, over time

there may be reduced issues with sample outliers (grain samples that do

MORE THIS MONTH IN HISTORY

May 14, 1804 - Meriwether Lewis and

William Clark made their famous expedition

to explore the Northwest. They left from St.

Louis and arrived on the Pacific coast of Oregon in November 1805. When they returned

to St. Louis in September of 1806, they had

traveled 6000 miles.

May 17, 1792 - Brokers established the New

York Stock Exchange. In good weather they

met to conduct business under a tree on

Wall Street and in bad weather in a local coffeehouse.

May 18, 1980 - Mount St. Helens erupted in

southwest Washington State sending volcanic ash and steam over 11 miles into the

sky. This was the first major erruption since

1857.

May 19, 1930 - The 27th Amendment to the

U.S. Constitution was ratified and prohibited

Congress from giving itself pay raises.

May 27, 1937 - The Golden Gate Bridge celebrated it’s grand opening.
not perform well on a meter) in field evaluations of NTEP meters. 

Currently, grain moisture meters are being developed that use the same dielectric technology but measurements are

made at a higher radio frequency and a uniform equation has been developed. It is anticipated that these new grain

moisture meters will not require separate calibrations for each grain type; will be more stable over time; and with the

uniform calibration equation, will allow the use of the same calibration equation for all grain moisture meter types.

Look for more details on these new grain moisture meters in a future article.

A special thank you goes to Mr. Jack Barber, JB Associates; Ms. Cathy Brenner, USDA, GIPSA; Dr. Richard Pierce, USDA,

GIPSA; and Mrs. Tina Butcher, NIST, WMD for their reviews and comments to this article.

W&M Connection 7 Volume 2 Issue 2

Announcing the 

NCWM 96th Annual Meeting

The 96th Annual Meeting for the National Conference on Weights and Measures (NCWM) will take place Sunday, July 17 through mid day Thursday, July 21, 2011. This year’s meeting theme is “Educating Today for Tomorrow.” The conference will take place in Missoula, Montana, which is surrounded by the majestic Rocky

Mountains and the Clark Fork River. 

The meeting agenda is provided in Publication 16, National Conference on Weights and Measures Committee

Reports for the 96th Annual Meeting, and is available online at: http://www.nist.gov/pml/wmd/pubs/pub16-

11.cfm and http://ncwm.net/content/publication-16.

The NIST Weights and Measures Division has a new homepage at: 

http://www.nist.gov/pml/wmd/index.cfm

Please change your browser’s bookmark.

NOW AVAILABLE THE NEW HANDBOOK 133, CHECKING

THE NET CONTENTS OF PACKAGED GOODS

FOR 2011

The newly revised Handbook 133 is now available online for your immediate reference. The printed editions

will soon be here from the printer. The printed editions will be automatically mailed to those who have requested them through their National Conference on Weights and Measures membership. 

The free online edition is available here: http://www.nist.gov/pml/wmd/pubs/hb133-11.cfm.