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3.   Practical Explanation of the Meaning of Radiated Emissions Measurement Uncertainties 
 
In general, a “Statement of Measurement Uncertainty” means that with a certain (specified) confidence 
level, the “true” value of a measurand will be between a (stated) upper bound and a (stated) lower 
bound.   
 
In the specific case of EMC Measurements in this test report, the measurement uncertainties of the 
conducted emissions measurements and the radiated emissions measurements have been calculated 
in accordance with the method detailed in the following documents: 
 

o

  ANSI Z540.2 (2002) Guide to the Expression of Uncertainty in Measurement  

o

 NIS 

81:1994, 

The Treatment of Uncertainty in EMC Measurements (NAMAS, 1994) 

o

  NIST Technical Note 1297(1994), Guidelines for Evaluating and Expressing the Uncertainty of 

NIST Measurement Results (NIST, 1994) 

 

The calculation method used in these documents requires that the stated uncertainty of the 

measurements be expressed as an “expanded uncertainty”, U, with a k=2 coverage factor.  The 

practical interpretation of this method of expressing measurement uncertainty is shown in the following 

example: 

 

EXAMPLE:  Assume that at 39.51 MHz, the (measured) radiated emissions level was equal to 
+26.5 dBuV/m, and that the +/- 2 standard deviations (i.e. 95% confidence level) measurement 
uncertainty was +/- 3.4 dB. 
 
 

 

 

 

APPENDIX B 

B. Nemko USA, Inc. Test Equipment & Facilities Calibration Program 

 
Nemko USA, Inc. operates a comprehensive Periodic Calibration Program in order to ensure the 
validity of all test data.  Nemko USA’s Periodic Calibration Program is fully compliant to the 
requirements of NVLAP Policy Guide PG-1-1988, ANSI/NCSL Z540.3: 2006, ISO 10012:2003, 
ISO/IEC 17025:2005, and ISO-9000: 2000.  Nemko USA, Inc.’s calibrations program therefore meets 
or exceeds the US national commercial and military requirements [N.B. ANSI/NCSL Z540.1-1994 
replaced MIL-STD-45662A]. 
 
Specifically, all of Nemko USA’s primary reference standard devices (e.g. vector voltmeters, 
multimeters, attenuators and terminations, RF power meters and their detector heads, oscilloscope 
mainframes and plug-ins, spectrum analyzers, RF preselectors, quasi-peak adapters, interference 
analyzers, impulse generators, signal generators and pulse/function generators, field-strength meters 
and their detector heads, etc.) and certain secondary standard devices (e.g. RF Preamplifiers used in 
CISPR 11/22 and FCC Part 15/18 tests) are periodically recalibrated by: 
 

o

  A Nemko USA-approved independent (third party) metrology laboratory that uses NIST-

traceable standards and that is ISO Guide 25-accredited as a calibration laboratories by 
NIST; or, 

o

  A Nemko USA-approved independent (third party) metrology laboratory that uses NIST-

traceable standards and that is ISO Guide 25-accredited as a calibration laboratory by 
another accreditation body (such as A2LA) that is mutually recognized by NIST; or, 

o

  A manufacturer of Measurement and Test Equipment (M&TE), if the manufacturer uses 

NIST-traceable standards and is ISO Guide 25-accredited as calibration laboratory 
either by NIST or by another accreditation body (such as A2LA) that is mutually 
recognized by NIST; or 

o

  A manufacturer of M&TE (or by a Nemko USA-approved independent third party 

metrology laboratory) that is not ISO Guide 25-accredited.  (In these cases, Nemko USA 
conducts an annual audit of the manufacturer or metrology laboratory for the purposes 
of proving traceabilty to NIST, ensuring that adequate and repeatable calibration 
procedures are being applied, and verifying conformity with the other requirements of 
ISO Guide 25). 

 

 

 

 

 

 

APPENDIX C 

C. NVLAP Accreditation