November 2002 

Near Infrared (NIR) Device Inspection and Moisture Basis 

By G. Diane Lee 

At the 87th NCWM Annual Meeting in 2002, the Conference voted to move the NIR 

Code from a tentative status to a permanent status, which will become effective January 

1, 2003. To adequately inspect NIR devices, a field inspector must know the moisture 

basis of the NIR device under inspection. If the moisture basis of the device is different 

from the moisture basis of the inspector’s grain sample, the constituent value reading of 

the device must be converted so that it represents the same moisture basis as the 

inspector’s grain sample. This article provides background information on the NIR code 

of NIST Handbook 44, an explanation of moisture basis, and an example and equation to 

convert the constituent value reading on an NIR device. 

Background

Prior to moving the code to a permanent status, the National Type Evaluation Technical 

Committee (NTETC) NIR sector conducted a study of the code to determine if the code 

was ready to move to a permanent status and to determine if the tolerances were 

acceptable. The study revealed that the tolerances were acceptable and also that 

additional language was needed to address moisture basis. During discussions of the 

study, grain industry representatives of the Sector expressed the need for industry to have 

the flexibility to use different moisture bases on NIR devices. NIR devices have varying 

moisture bases. 

Moisture Basis and Converting from One Moisture Basis to Another 

When constituent values (protein, oil or starch) of a grain are measured, the values 

depend on the amount of moisture in the grain or the moisture basis (i.e., 14% protein at 

12% moisture). Without knowing the moisture basis of the device, it is not possible to 

accurately compare the results of the device to the known value of your grain sample. 

For example, if a wheat sample used to test an NIR device is 13% protein at 12% 

moisture and the NIR device determines protein on an “as-is” moisture basis, the test 

results must be converted to a 12% moisture basis to adequately compare it to the wheat 

sample. The constituent values of the grain samples used to test NIR devices are 

determined by the Grain Inspection Packers and Stockyards Administration. These 

constituent values are at a constant moisture basis of 12% for wheat protein, 13% for 

soybeans protein and oil, 0% for barley protein, and 0% for corn protein, oil and starch 

(see Table N.1.1. of NIST Handbook 44 Section 5.57). The following is an example and 

equation for converting the meter constituent result to the same moisture basis as the 

grain sample: 

An inspector has a wheat sample that is 13% protein at a 12% moisture basis. The wheat 

sample is used to test an NIR device that gives an “as-is” protein reading of 13.7% at a 

moisture reading of 11.1%. Because the moisture basis of the meter is different from the 
inspector’s grain sample, the protein results of the meter will need to be converted so that 

it represents protein at a 12% moisture basis. 

The equation below should be used to convert the results. 

where 

Cnewmb = constituent value at the new moisture basis 

Cnative = constituent value at native moisture basis (device constituent value 

reading) 

Mnewmb = moisture basis for Cnewmb (moisture basis you are converting to) 

Mnative = moisture basis for Cnative (device moisture basis) 

Note: The "native" moisture basis is the default moisture basis of the sealable 

constituent calibration (the moisture basis of the device). 

 

Therefore, the equivalent meter protein value for field inspection purposes is 13.56% 

protein at 12% moisture, which is within the 0.60 tolerance for individual samples of 

wheat (see Table T.2. of NIST Handbook 44 Section 5.57). 

It is essential that inspectors know the moisture basis of an NIR device under test and as 

necessary convert the meter constituent value reading so that it represents the same 

moisture basis as the inspector’s grain sample. If you have any questions or need 

assistance with inspecting NIR devices, please contact Diane Lee by phone at 301-975-

4405 by fax at 301-926-0647 or by e-mail phone at diane.lee@nist.gov. 

native

newmb

newmb native M

M

C C −

− = 100

100

= −

− = 100 11.1

100 12 Cnewmb 13.7 13.56%

88.9

88 13.7 =