Instrument calibration policies

Calibration reports

The copyright on reports of calibrations or other services is owned by NRC. Reports may be reproduced in whole without prior approval. However, reproduction of a report in part requires the written prior approval of NRC and the owner of the equipment covered in the report.

The results of calibrations performed by NRC apply only to the particular instrument or standard used and only at the time of calibration, unless otherwise stated.

The provision of a report by NRC does not imply approval by NRC of the client's products and laboratory practices or procedures, unless otherwise stated.


Contractual agreements often require that measurements made by contracting laboratories be "traceable" to national and international measurement standards and that the laboratories be able to support these claims of traceability with valid, current documentation and records of the equipment used in the calibration process. Incorrect traceability claims may make a company liable for damages.

The requirement for traceability implies the ability to relate individual measurement results, with a stated uncertainty, through an unbroken chain of comparisons to a stated reference source, usually the Canadian national measurement standards maintained by NRC, or to intrinsic standards based on fundamental natural constants with values assigned or accepted by NRC.

To adequately establish an audit trail outside NRC for purposes of traceability, a calibration result should include: the assigned value, a stated uncertainty, the identity of the standard(s) used in the calibration, and the specification of any environmental conditions of the calibration that require the application of correction factors if the standard or equipment is to be used under different environmental conditions.

NRC supports the practice of making its clients aware of traceability to national measurement standards and providing them with details on how traceability was established.

Measurement uncertainty

Unless otherwise specified, the uncertainty of the measurement contained in an NRC calibration report, in terms of NRC's realization of the internationally-adopted representation of the unit in question, is an expanded uncertainty representing a confidence level of approximately 95% obtained by multiplying the combined standard uncertainty (one standard deviation) by a coverage factor of k = 2. (ISO Guide to the Expression of Uncertainty in Measurement, First Edition, 1993).

Calibrations at larger uncertainties should be arranged through accredited laboratories and the NRC's Calibration Laboratory Assessment Service (CLAS). A list of these laboratories is available on the Directory of Accredited Calibration Laboratories from the CLAS website.

The quoted uncertainty is normally the actual uncertainty of NRC measurement results, including the effect of such influencing factors as temperature and humidity, which may not have been fully controlled during the measurement. It does not normally include estimates of the uncertainties likely to be introduced by the transfer of the measured device to the client's laboratory and its use there as a standard for other measurements. Such uncertainties are due to effects that include, but are not limited to, transportation of the measured device to the client's laboratory, temperature, humidity, passage of time, chemical reactions, mechanical damage, and conditions of use in the client's laboratory.

Environmental conditions

Calibration of client equipment is normally performed in the ambient conditions of the laboratory concerned. Some calibrations are performed in a special micro-climate environment, as required by the client.

Reference to NRC in advertisements

NRC calibration reports shall not be used in any way that could indicate or imply that NRC approves, recommends or endorses the manufacturer, supplier or user of any instruments or standards, or that NRC in any way guarantees or predicts the performance of items after calibration. No reference shall be made to NRC, or to reports or results provided by NRC in any advertising or sales promotions that would indicate or imply that NRC approves, recommends or endorses any proprietary material, instrument or product.


Commercial products, materials, and instruments are identified within these pages and in NRC reports solely to describe calibration procedures. Such identification does not in any way imply a recommendation or endorsement by NRC of a particular product nor does it imply that an identified material, instrument, or product is necessarily the best for the purpose that it serves, unless explicitly stated.


Technical advice and consultation are available on a wide range of metrological activities: the technical aspects of specific measurements, the application of specific metrological capabilities, and legislation and regulation in the field of metrology. Brief consultations are generally provided at no cost. Please contact the Business Office at

Special services

NRC is prepared to undertake calibrations other than those listed in these pages. In such cases, the fees will be based on the NRC staff time involved plus the cost of associated equipment and materials. Inquiries should be directed to the appropriate contact.