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Nemko USA, Inc. 

 

 

 
ISO Standard 17025 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 Metrology (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 stated uncertainties”.    
 
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. 
 

 

HP8568B Spectrum Analyzer with QPA and HP8447F Preamplifier 

150 kHz - 30 MHz 

+/- 3.0 dB 

HP8566B Spectrum Analyzer with QPA and  Preselector 

9 kHz - 30 MHz 

+/- 2.9 dB 

 

 

 

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 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  ISO Guide to the Expression of Uncertainty in Measurement (ISO, 1993) 
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. 
 
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 

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 10012-1 (1993-05-01), ISO Standard 
17025, ISO-9000 and EN 45001.  Nemko USA, Inc.’s calibrations program therefore meets or exceed 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 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). 

Nemko USA, Inc. 

 

accredited third-party antenna calibration laboratory, or by the antenna’s OEM if the OEM is NIST or 
NVLAP ISO Standard 17025-accredited as an antenna calibration laboratory using the procedures 
specified in the latest version of SAE ARP-958. 
 
In accordance with FCC and other regulations, Nemko USA recalibrates its suite of antennas used for 
radiated emissions tests on an annual basis.  These calibrations are performed as a precursor to the FCC-
required annual revalidation of the Normalized Site Attenuation properties of Nemko USA’s Open Area 
Test Site.  Nemko USA, Inc. uses the procedures given in both Subclause 16.6 and Annex G.2 of CISPR 
16 (2003), and ANSI C63.4 (2001) when performing the normalized site attenuation measurements.