ISO 17025

ISO 17025 replaced ISO Guide 25 in 1999, and incorporates the "text" of ISO 9001:94 with the laboratory specific language of ISO Guide 25 to make a laboratory quality management system requirement.
Regular ISO registrars can not accredit laboratories, there used to be only A2LA with the bulk of the work, and the NIST (National Institute of Standards and Technology, the old National Bureau of Standards) NVLAP. Then the big 3 required that all calibrations and outside lab work be done by accredited laboratories and there was a gold rush. A2LA was backed up for over a year for a while. Since then more organizations gave developed the credentials to accredit laboratories, see list below.

Being accredited as a lab is much like registering to ISO 9001, and if you are registered it makes it that much easier. You apply to be accredited for certain tests, the more tests you are accredited for, the more they charge. Your certificate lists the tests coverfed by your accreditation, and your customers need to find the test you perform for ythem on that list. You have to have a manual and procedures (which for example A2LA requires you send in for review before they even schedule your on-site audit. These are pretty much like those required for ISO 9001.
Uncertainty

Uncertainty of measurement is the doubt which exists about the result of any measurement. There is always doubt, expressed as +/- something. Uncertainty is a quantification of the doubt about the measurement result. Calculating uncertainty is a pain, and likely the most difficult part of the 17025 registration.

To calculate the uncertainty of a measurement, firstly you must identify the sources of uncertainty in the measurement. Then you must estimate the size of the uncertainty from each source. Finally the individual uncertainties are combined to give an overall figure.

There are clear rules for assessing the contribution from each uncertainty, and for combining these together. NIST has a good description. Good luck. Midwest is glad to help with this (and any other) aspect of your ISO 17025 registration preparation.

NAVLAP
The National Voluntary Laboratory Accreditation Program (NVLAP) provides third-party accreditation to testing and calibration laboratories. NVLAP's accreditation programs are established in response to Congressional mandates or administrative actions by the Federal Government or from requests by private-sector organizations. NVLAP is in full conformance with the standards of the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC), including ISO/IEC 17025 and Guide 58. NVLAP identifies its accredited laboratories in a published directory,

The National Institute of Standards and Technology (NIST) administers the National Voluntary Laboratory Accreditation Program (NVLAP). NVLAP is comprised of a series of laboratory accreditation programs (LAPs) which are established on the basis of requests and demonstrated need. Each LAP includes specific calibration and/or test standards and related methods and protocols assembled to satisfy the unique needs for accreditation in a field of testing or calibration. NVLAP accredits public and private laboratories based on evaluation of their technical qualifications and competence to carry out specific calibrations or tests.

Accreditation criteria are established in accordance with the U.S. Code of Federal Regulations (CFR, Title 15, Part 285), NVLAP Procedures and General Requirements, and encompass the requirements of ISO/IEC 17025 and the relevant requirements of ISO 9002. Accreditation is granted following successful completion of a process which includes submission of an application and payment of fees by the laboratory, an on-site assessment, resolution of any deficiencies identified during the on-site assessment, participation in proficiency testing, and technical evaluation. The accreditation is formalized through issuance of a Certificate of Accreditation and Scope of Accreditation and publicized by announcement in various government and private media.

NVLAP accreditation is available to commercial laboratories; manufacturers' in-house laboratories; university laboratories; and federal, state, and local government laboratories. Laboratories located outside the United States may also be accredited if they meet the same requirements as domestic laboratories and pay any additional fees required for travel expenses.