White Paper

Traceable calibration based on

ISO 17025 at Tektronix

I. Introduction

Tektronix is adopting ISO/IEC 17025:2005

as the preferred calibration standard for non-accredited tracea ble

calibration (and for accredi ted calibration, although that is not the subject of this paper). For an increasing selection

of Tektronix products, calibration services at Tektronix manufacturing and service facilities are based on ISO

17025. This paper describes the reasons for adopting ISO 17025, how the standard is being implemented at

Tektronix, and the features of ISO 17025 based certificates of traceable calibration and calibration data reports.

See the white paper “Metrology, Calibration, and Your Tektronix Instrument” for an introduction to metrology and

calibration and to related Tektro nix policies and practices.

II. What is ISO 17025, and why is Tektronix adopting ISO 17025?

ISO 17025 is a complete and well -conceived requirements document that covers all aspects of calibration a nd test

programs, including but not limited to quality system management, measurement method validation and control,

measurement traceability, equipment selection a nd maintenance, and reporting of calibration and test results.

Tektronix is adopting ISO 17025 as the preferred standard fo r traceable calibration primarily because it is the

international standard for test and calibration that is recognized worldwide. ISO 17025 is intended to apply to a

wide range of test and calibration activities in diverse fields. Many Tektronix customers and suppliers use and

accept the ISO 17025 standard.

III. How is Tektronix implementing ISO 17025?

Tektronix is phasing in ISO 17025 as a calibration standard for selected products, starting with oscilloscope

products currently in production in ea rly 2008.

For products not converted to ISO 17025, calibration at Tektronix continues to be based on ANSI/NCSL Z5 40.1-

1994(R2002)

, a United States standard. Tektronix manufacturing and US service facilities issue traceable

certificates that reference Z540.1. Outside of the United States, Tektronix service facilitie s follow the same

metrology policies and pra ctice s as US facilities, although certificates issued by servi ce facilities outside of the

United States do not reference Z540.1.

The calibration procedures used when calibrating a particular Te ktronix instrument are the same throughout

worldwide manufacturing and service. Certificates of traceable calibration and calibratio n data reports for a

Tektronix model have basically the same features re gardless of which Tektronix site generates the documents,

although there may be some differences due to regional requirements.

White Paper

IV. How do Tektronix ISO 17025 based certificates of traceable calibration differ from other Tektronix

traceable certificates?

When calibration is ba sed on ISO 17025, certificates of traceable calibration generated by Tektro nix manufacturing

facilities and by some serv ice facilities include a reference to ISO 17025. In som e regions, however, it is

acceptable to refer to ISO 17025 only on accredited certificates. In those regions, non-accredited traceable

calibration certificates do not include a reference to ISO 17025.

ISO 17025 forbids the inclusion of recommended calibration intervals an d calibration due dates on certificates,

except as requested by clients. Tektronix ISO 17025 based certificates in general include neither a calibration due

date nor a recommended calibration interval. However Tektronix service customers with Tektronix calibration

service agreements may re ceive a calibration due date notification based on the Tektronix recommended

calibration interval. Tektronix new product certificates provide guidance for finding the Tektronix recommended

calibration interval at the Tektronix web site, and for calculating a due date.

ISO 17025 mandates that statements of compliance of measurements with specifications must take into account

measurement uncertainty. Tektronix service certificates that are ba sed on ISO 17025 include the category

“indeterminate” as one of the possi ble received and returned conditions. This category appli es when no

measurements fail and at least one measurement is indeterminate as defined in the next section. Tektronix new

product certificates do not include the “indeterminate” category. Manufacturing test limits in most ca ses are set to

preclude the possibility of shipping products with indeterminate measurements. In the remaining cases

manufacturing test limits are set to provide a high probability that measurements are within published specification s

based on known manufacturing measurement distributions and uncertainties

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V. What are the key features of ISO 17025 calibration data reports?

Calibration data reports are included with all Tektronix service ISO 17025 calibrations, and the reports are available

at a nominal cost with new product ISO 1702 5 calibrations.

The key added features of Tektronix calibration data reports based on ISO 17025 are found in the Uncertainty and

Result columns of the report s.

ISO 17025 mandates that measurement data and associated uncertainties mu st be recorded and available to

clients. Entries in the Uncertainty column show the expanded measu rement uncertainties evaluated and reported

in accordance with ISO/IEC Guide 98: Guide to the Expression of Uncertainty in Measurement (GUM)

. The

coverage factor (k) is 2, with coverage probability of approximately 95 %. Uncertainty values are reported with the

same units as the measured values.

Determinations of compliance with sp ecifications must account for uncertainty, according to ISO 17025. Entries in

the Result column account for uncertainty. Results may be Pass, Fail, Pass*, or Fail*. When a step has Pass or

Fail status, the difference between the measured value and the nearest test limit is greater than the uncertainty,

and the coverage probability of the pass or fail decision is at least 95 %. When a step has Pass* or Fail* status, the

difference between the measu red valu e and the nearest test limit is less than the uncertainty, and the decision may

have reduced probability. Steps with Pass* or Fail* results a re considered to have “indeterminate” status.