A Comparison of ANSI/NCSL Z540-1-1994 Part I and ANSI/ISO/IEC 17025:2000

In the U.S., there are currently two national standards for calibration laboratories: the ANSI/NCSL Z540-1-1994, Calibration Laboratories and Measuring and Test Equipment—General Requirements (hereafter, “Z540-1”) and the ISO/IEC 17025:1999 General Requirements for the Competence of Testing and Calibration Laboratories (hereafter, “17025”).

The Z540-1 has been an American National Standard since 1994. Part I of Z540-1 is based on the ISO/IEC Guide 25. Part II of Z540-1 is based on MIL-STD 45662A and was included to meet U.S. Department of Defense requirements. Though MIL-STD 45662A was cancelled in 1995, its requirements are still met through the Z540-1 as well as through ISO 10012-1, Quality Assurance Requirements for Measuring Equipment. In July 2001, the Z540-1 writing committee voted “to re-affirm Z540-1 1994 without changes. That reaffirmation continues Z540-1 for five more years.”1

In December 1999, the international community released the 17025. This standard has been accepted by Mutual Recognition Arrangement as the international standard for accreditation of calibration and testing laboratories. Laboratories accredited to ISO Guide 25 must conform to 17025 by December 2001. Any laboratories seeking accreditation will be assessed to 17025. Earlier this year, the 17025 was adopted as a stand-alone American National Standard in the U.S., and has been released by the National Conference of Standards Laboratories International (NCSLI) as ANSI/ISO/IEC 17025:2000. Note that adoption by NCSLI occurred simultaneously with the American Society for Testing and Materials and the American Society for Quality.

Laboratories meeting the requirements of the Z540-1 do not necessarily meet the requirements of the 17025 and some accrediting bodies no longer state accreditation to Z540-1 on accreditation certificates. Accrediting bodies are assessing ways to accommodate labs needing compliance to both standards. The National Voluntary Laboratory Accreditation Program (NVLAP) is developing a checklist of the elements of the Z540-1 Part I that are not contained in the 17025. If customers choose to add these elements to their requirements, their scope of accreditation can reflect compliance to the Z540-1 Part 1. The American Association for Laboratory Accreditation (A2LA) has included the Z540-1 components not addressed in the 17025 in their “Calibration Program Requirements.” For laboratories requesting assessment to both the 17025 and the Z540-1, A2LA will use the additional requirements checklist and issue an accreditation certificate listing both the 17025 and the Z540-1.

Being subject to two different standards can be confusing for both labs and their customers, so it’s important for labs to understand both standards and which is applicable. U.S. labs not needing to conform to international standards can still use the Z540-1. U.S. labs conforming to the 17025, however, need to also recognize that their customers may still require compliance to the Z540-1 as well as the old MIL-STD 45662A. In the remainder of this article, we outline some of the importance differences between the two major standards.
Scope and Philosophy:

The Z540-1 pertains only to calibration laboratories and stresses both calibration and verification of measurement and test equipment (M&TE). Under the Z540-1, calibrations are validated through methods of internal quality control. A system within the laboratory controls the calibration process and verification of the M&TE including laboratory standards. M&TE outside the laboratory is covered under Part II.

The 17025 was written to include the requirements for both calibration and testing laboratories by demonstrating that the laboratory operates in a technically competent manner under the confines of a documented quality system producing valid results. The 17025 focuses on the competency of the legally responsible bodies providing test and calibration services. These bodies may be independent or part of a larger organization.

The philosophy of the 17025 is focused on providing competent measurement services with results that are traceable to appropriate standards. The laboratory and the client must fully understand and agree on the calibration or testing services provided. The validity of the test and calibration results is controlled through internal quality methods. Demonstration of the competency of the laboratory can be accomplished by accreditation or other means such as interlaboratory comparisons.

In summary, the scopes of the Z540-1-1 and the 17025 contain important similarities and differences:

* Both Z540-1-1 and 17025 address calibration laboratory competency requirements.

* Z540-1 Part II includes quality assurance program requirements for M&TE outside the laboratory.

* 17025 addresses testing laboratory competency requirements. Z540-1 was not written for testing laboratories.

Laboratories and their customers therefore need to consider four different situations in deciding which standard to apply.

1. Calibration Services. If the customer requires calibration services only, either standard may be applicable, though only the 17025 meets international requirements.

2. Testing Services. For testing services, only the 17025 applies.

3. Calibration and Testing Services. Only the 17025 covers both calibration and testing services.

4. Products and Services. If customer requirements cover M&TE equipment outside the supplier’s lab, only the Z540-1 Part II applies in the U.S. If international customers have such requirements, they are not covered by the 17025, but rather by ISO 10012.

Calibration Due Dates

The 17025 is more stringent than the Z540-1 on the placement of calibration due dates on calibration certificates and calibration labels. Although manufacturers may designate time periods over which products should perform without degradation, the 17025 makes clear that it is the responsibility of the end-user organization to determine the appropriate calibration interval under the requirements of its own quality system.

The goal of calibration interval analysis is to reduce out-of-tolerance conditions to an acceptable level based on the quality requirements of the organization. Under 17025, a recommendation on the calibration interval or calibration due date may be placed on the calibration report (and/or calibration label) where this has been agreed with the customer or where legally required. Specifically, the calibration interval should be stated in the contract or purchase order or otherwise agreed to with the client before it is indicated on the calibration report or label.
Measurement Traceability

The Z540-1 requires traceability of measurements to national standards, international standards, or intrinsic standards that have been compared to other intrinsic standards, particularly those of national labs. The Z540-1 also requires statements of traceability on calibration reports. While the Z540-1 does not specifically require traceability to International System of Units (SI) units, such traceability would be implied by traceability to national or international standards.

The 17025 requires traceability to SI units. This traceability is established through the laboratory standards in an unbroken chain of calibrations through appropriate primary standards and may be made through national measurement standards. The 17025 states that traceability shall be assured by the use of competent laboratories that demonstrate measurement capability and traceability. Finally, where the Z540-1 requires a traceability statement, the 17025 calls for proof of traceability. (For more information on traceability, refer to the NIST website: www.nist.gov/traceability.)
Measurement Uncertainty

The Z540-1 requires laboratories to ensure that calibration uncertainties are “sufficiently small” so as not to affect the adequacy of a measurement. Documented and defined uncertainty analysis may be used in verifying the measurement process, but when not used, the Z540-1 allows for the collective uncertainty of the measurement standards not to exceed 25% of the acceptable tolerance for each characteristic—i.e. the 4:1 test accuracy ratio (TAR).

The 17025 requires a comprehensive uncertainty analysis for all calibrations under the philosophy that traceability of a measurement cannot be established without knowing the expanded uncertainty. A 4:1 TAR may be stated on the calibration report, however, it must be in addition to the quantified uncertainty of the measurement.
Legal Responsibility

17025 requires laboratories to be legally responsible entities. The Z540-1 is less emphatic on this point and states that the laboratory must be legally identifiable. This is an issue of legal responsibility and accountability for the calibration work performed by the laboratory or organization.

When a calibration laboratory is part of an organization that performs other functions, both standards require that there be a separation between the additional activities of the organization and the calibration lab. While the Z540-1 requires the organization to be structured such that confidence is maintained in the independence of the calibration lab’s activities, 17025 strives to remove potential for conflict by requiring that the responsibilities for positions be clearly identified and governed under policies and procedures.
Confidentiality of Customer Information

Both standards require documented policies and procedures to ensure the confidentiality of customer information. However, whereas the Z540-1 does not specifically address electronic storage and transmission of customer data, 17025 requires documented procedures and policies to protect the confidentiality of such electronic data.
Document Control

The Z540-1 includes a general statement about documentation control that is arguably ambiguous. The 17025 is clearer, requiring written procedures for the control of all quality system documents with regards to approval, issue, review, and change. Both internal and externally generated documentation such as regulations, standards, procedures, test or calibrations instructions, drawings, software procedures, equipment specifications, and manuals are included.
Job Descriptions

The Z540-1 requires job descriptions for key personnel and makes reference to job descriptions for other personnel. The 17025 requires job descriptions for managerial, technical, and key personnel and encourages job descriptions for personnel involved in calibration or testing. The 17025 details the minimum elements of job descriptions and specifies that the quality manual contain the job descriptions for the technical manager and quality manager for the lab.
Corrective and Preventive Actions

The Z540-1 contains a general statement about procedures for corrective actions regarding measurement discrepancies or departures from documented procedures. The statement is contained in a list of 21 items that are to be contained in the quality manual. The 17025 excludes this list but outlines corrective action procedures. Cause analysis, implementation, monitoring, and additional audits are specifically discussed. The 17025 also requires procedures for preventive actions regarding the quality system or technical issues, whereas the Z540-1 does not address preventive actions.
Management Review

An annual management review of the quality system is required by Z540-1. The review is to determine the adequacy and effectiveness of the system. Any changes or improvements to the system should be addressed in the review. Under 17025, management review is completed according to a predetermined schedule, which does not have to be annual. A list of the minimum elements of the review is outlined.
Internal Audits

Procedures for internal audits and review are part of the quality manual requirements of Z540-1. The Z540-1 requires findings and corrective actions resulting from audits to be documented and that the individual responsible for quality should ensure that corrective actions are completed on time. No other follow-up activities are addressed.

The 17025, however, requires internal audits to cover all the elements of the quality system and that they be planned under the quality manager according to a predetermined schedule. The 17025 also requires documentation of follow-up activities (including corrective actions) and their effectiveness.

The Z540-1 requires sufficient laboratory personnel with the necessary technical and educational requirements for their assigned duties. Training of personnel shall be documented and kept up-to-date. Relevant training records of calibration personnel shall be available to the laboratory.

The 17025 states that calibration lab managers shall ensure that personnel are competent to perform tests and calibrations. Qualification for a specific task shall be based on demonstration of the required skills, education, training, and experience. Personnel training on the job shall be appropriately supervised. Contracted personnel shall be competent and work under the laboratory’s quality system. Management shall formulate goals for training, education, and skills. And authorization is required for the performance of certain tasks.
Client or Customer Service Requests

The Z540-1 does not require procedures for contract, request, or tender review. The 17025, however, requires a procedure for the review and retention of all records pertaining to requests, tenders, or contracts. The laboratory shall ensure that the client’s requirements are well defined, documented and understood by all participants. The laboratory’s capabilities and resources shall meet the customer’s requirements. The client and the laboratory must agree upon the appropriate method of calibration. And detailed records must be maintained through the entire process.
Technical Records

The goal of the record system identified in the Z540-1 is to retain sufficient information to repeat a calibration under identical conditions. The identity of the personnel responsible for the calibration should be part of the records and all records should be safely stored for a designated period of time. The 17025 requires laboratories to establish and maintain a procedure for quality and technical records. The requirements of these records are specifically outlined. One major point is the requirement that laboratories maintain records of original observations with sufficient information to establish an audit trail.
Opinions and Interpretations

The 17025 allows for opinions and interpretations to be documented on a test report. The laboratory is required to document the basis of such opinions or interpretations and to clearly identify the remarks in the report. The QA system requires the identification of those individuals who are authorized and considered competent to provide opinions and interpretations and to specify the extent of their capabilities. The Z540-1 does not directly address opinions and interpretations.

We have outlined only some of the differences in these two standards. In general, the 17025 is more prescriptive and has clarified and added to the ISO Guide 25 requirements upon which the Z540-1 Part I is based. Some of the sections of the Z540-1 are ambiguous and subject to interpretation. Laboratories need to fully investigate these two standards and come to an understanding of their differences. No article or discussion of the differences can replace the personal knowledge of the laboratory personnel responsible for implementation of the standards in the organization.

NVLAP is currently in the process of developing the checklist for Z540-1 requirements not addressed in 17025. There will be an announcement on the NVLAP website, www.nist.gov/nvlap, under the “What’s New” section about including Z540-1 in the Scope of Accreditation.

I would like to thank Jesse Morse (Fluke Corporation), the Chair of the NCSLI Writing Committee, and Doug Faison, NVLAP (NIST) for the information they provided.

1 Jesse Morse, Fluke Corporation, NCSLI Writing Committee Chair

2 Official Cancellation of MIL-STD 45662A, Notice 2, Dated: 27 February 1995

3 Doug Faison, NIST