GMP 13

**Good Measurement Practice**

**for**

**Ensuring Traceability**

1.  Introduction

    1.1 Purpose

    Traceability is defined as "the property of a result of a
    measurement or the value of a standard whereby it can be related to
    stated references, usually national or international standards,
    through an unbroken chain of comparisons all having stated
    uncertainties".[^1] Traceability ensures that the measurements are
    accurate representations of the specific quantity subject to
    measurement, within the uncertainty of the measurement.

    To ensure traceability, suitably calibrated standards that are
    appropriately maintained and cared for, proper standard operating
    procedures, continuous measurement control, surveillance, and
    suitable documentation must all be present.

    Test numbers issued by NIST should not be used nor required as proof
    of the adequacy or traceability of a test or measurement. Having a
    NIST number does not provide evidence that the measurement value
    provided by another organization is traceable. (See section 1.3.3.)

    1.2 Prerequisites

    Traceability can be characterized by the following essential
    elements:

    1.2.1 *Unbroken chain of comparisons.* A documented system of
    comparisons going back to a standard acceptable to the parties,
    usually a national or international standard;

    1.2.2 *Measurement uncertainty.* The measurement uncertainty for
    each step in the traceability chain must be calculated according to
    defined methods and must be stated so that an overall uncertainty
    for the whole chain may be calculated (see SOP 29);

    1.2.3 *Documentation.* Each step in the chain must be performed
    according to documented and generally acknowledged procedures (see
    GMP 12) and the results must be documented (i.e., in a calibration
    report, see SOP 1);

    1.2.4 *Competence.* The laboratories or bodies performing one or
    more steps in the chain must supply evidence of technical competence
    (e.g., by maintaining appropriate training records, participating in
    interlaboratory comparisons, and by demonstrating that they are
    accredited by a recognized accreditation body);

    1.2.5 *Realization of SI Units.* The primary national, international
    or intrinsic standards must be primary standards for the realization
    of the SI units;

    1.2.6 *Periodic recalibration.* Calibrations of standards (and
    equipment where appropriate) must be repeated at established (may be
    defined through measurement assurance) and appropriate intervals to
    preserve the traceability of the standard over time and use (see GLP
    4, GMP 11); and

    1.2.7 *Measurement assurance.* A proper measurement assurance
    program must be established to ensure the validity of the
    measurement process and the accuracy of standard used (see SOP′s 9,
    17, 20, 30).

    1.3 Responsibility

    1.  *Provider.* Providing support for the claim of traceability of
        the result of a measurement or value of a standard is the
        responsibility of the calibration provider. Calibration reports
        and certificates must contain a traceability statement.

    2.  *User.* Assessing the validity of a claim of traceability is the
        responsibility of the user of that result or value. Verifying
        claims of traceability often includes obtaining a calibration
        directly from a national metrology institute or another
        laboratory that has achieved recognition or accreditation
        through a recognized accrediting body.

    3.  *Use of, or reference to, official test numbers of a national
        metrology institute.* Having an authentic test number does not
        provide assurance or evidence that the measurement value
        provided by another organization is traceable. Not only must
        there be an unbroken chain of comparisons, but each measurement
        must be accompanied by a statement of uncertainty associated
        with the value. Test report numbers should not be used nor
        required as proof of the adequacy or traceability of a test or
        measurement. National and international standards dealing with
        test and measurement quality requirements, such as ANSI/NCSL Z
        540-1, ISO 10012, ISO/IEC 17025 and the ISO 9000 series do not
        require the use or reporting of specific test numbers to
        establish traceability.

    ```{=html}
    <!-- -->
    ```
    3.  Safety

No outstanding safety concerns

2\. Methodology

2.1 Summary

Traceability is maintained through comparison to appropriate standards
with suitable procedures and measurement uncertainties. Procedures are
outlined in SOPs and GMPs. Examples of possible hierarchies of the
standards leading to the traceability of a calibration are provided in
this document.

2.2 Procedure

The charts in this GMP show examples of the traceability hierarchy for
mass, length, volume, and temperature measurement disciplines. Each
laboratory must define the exact traceability system in their operating
quality manual. (A worksheet is included as an Appendix to help in the
definition of the traceability system.)

3\. Calculations

There are no calculations in this GMP.

4\. Assignment of Uncertainty

> The uncertainty associated with reported calibration values is
> included within the uncertainty analysis for each SOP and in SOP 29,
> Calculating and Reporting Uncertainties.

**Mass - Option A**

**Mass** **- Option B**

**Mass** **- Option C**

**Volume - Option A**

**Volume - Option B**

**Length**

**Temperature**

# Appendix A - Traceability worksheet

### Parameter: Mass, Volume, Length, Temperature, Other

+----+------+-------------------------+----------+---------+---------+
| ## |      | **Metric (g, L, m, C)** | ### C    | ### C   | ### I   |
|  P |      |                         | al. date | al. Lab | nterval |
+----+------+-------------------------+----------+---------+---------+
|    | *    |                         |          |         |         |
|    | *Ran |                         |          |         |         |
|    | ge** |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      | **Customary (lb, gal,   |          |         |         |
|    |      | ft, F)**                |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    | *    |                         |          |         |         |
|    | *Ran |                         |          |         |         |
|    | ge** |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+

+----+------+-------------------------+----------+---------+---------+
| ## |      | **Metric (g, L, m, C)** | ### C    | ### C   | ### I   |
|  W |      |                         | al. date | al. Lab | nterval |
+----+------+-------------------------+----------+---------+---------+
|    | *    |                         |          |         |         |
|    | *Ran |                         |          |         |         |
|    | ge** |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      | **Customary (lb, gal,   |          |         |         |
|    |      | ft, F)**                |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    | *    |                         |          |         |         |
|    | *Ran |                         |          |         |         |
|    | ge** |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+

+----+------+-------------------------+----------+---------+---------+
| #  |      | **Metric (g, L, m, C)** | ### C    | ### C   | ### I   |
| #  |      |                         | al. date | al. Lab | nterval |
| S~ |      |                         |          |         |         |
| c~ |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    | *    |                         |          |         |         |
|    | *Ran |                         |          |         |         |
|    | ge** |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      | **Customary (lb, gal,   |          |         |         |
|    |      | ft, F)**                |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    | *    |                         |          |         |         |
|    | *Ran |                         |          |         |         |
|    | ge** |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+
|    |      |                         |          |         |         |
+----+------+-------------------------+----------+---------+---------+

[^1]: ISO VIM, 2^nd^ ed., 1993, definition 6.10