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Nemko USA, Inc. 

 
 

 
 

Nemko USA, Inc. 

 

 

 
ISO/IEC 17025:1999 and ANSI/NCSL Z540-1-1994 require that all measurements contained in a test report be 

“traceable”.  “Traceability” is defined in the International Vocabulary of Basic and General Terms in 

 (ISO: 1993) as:  “the property of the result of a measurement... whereby it can be related to stated 

references, usually national or international standards, through an unbroken chain of comparisons, all having 

”.    

 
The purposes of this Appendix are to “state the Measurement Uncertainties” of the conducted emissions and 

radiated emissions measurements contained in Section 5 of this Test Report, and to provide a practical 

explanation of the meaning of these measurement uncertainties. 

 
2.  Statement of the Worst-Case Measurement Uncertainties for the Conducted and Radiated Emissions 

 

HP8568B Spectrum Analyzer with QPA & HP8447F Preamplifier 

30 MHz - 200 MHz  +4.0 dB, -4.1 dB 

HP8568B Spectrum Analyzer with QPA & HP8447F Preamplifier 

200 MHz-1000 MHz 

+/- 3.5 dB 

HP8566B Spectrum Analyzer with QPA & Preselector 

30 MHz - 200 MHz  +3.9 dB, -4.0 dB 

HP8566B Spectrum Analyzer with QPA &  Preselector 

200 MHz-1000 MHz 

+/- 3.4 dB 

HP8566B Spectrum Analyzer with QPA & HP 8449A Preamplifier 

1 GHz - 18 GHz 

+2.5 dB, -2.6 dB 

HP8566B Spectrum Analyzer with QPA & HP8449A Preamplifier 

18 GHz - 40 GHz 

+/- 3.4 dB 

NOTES

: 

1. Applies to 3 and 10 meter measurement distances 

2. Applies to all valid combinations of Transducers (i.e. LISNs, Line Voltage Probes, and Antennas, as appropriate) 

3. Excludes the Repeatability of the EUT 

 

Nemko USA, Inc. 

 

 

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 

 (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. 

 

In the example above, the phrase “k = 2 Coverage Factor” simply means that the 
measurement uncertainty is stated to cover +/-2 standard deviations (i.e. a 95% confidence 
interval) about the measurand. The measurand is the radiated emissions measurement of 
+26.5 dBuV/m at 39.51 MHz, and the 95% bounds for the uncertainty are –3.4 dB to + 3.4 
dB.  One can thus be 95% confident that the “true” value of the radiated emissions 
measurement is between +23.1 dBuV/m and +29.5 dBuV/m.  In effect, this means that in the 
above example there is only a 2.5% chance that the “true” radiated emissions value exceeds 
+29.5 dBuV/m. 

 

Nemko USA, Inc. 

 

 

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 Z540-1-1994, ISO 10012: 2003, ISO/IEC 17025:1999, 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 replaces 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 

 (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).