Gauges, Thermometers, & Calibrators Repair Services

United Instrument

NIST Certification and Recertification

The National Institute of Standards and Technology (NIST) develops standards to establish conformity and enhance the quality of products.

The National Institute of Standards and Technology (NIST) is a non-regulatory federal agency under the Department of Commerce. It is the National Measurement Institute (NMI) for the United States. They support and develop measurement standards and technologies to improve efficiency, facilitate trade, and enhance the quality of life.


NIST's mission is to provide certified Standard Reference Materials (SRM). SRMs are used to confirm how accurate, specific measurements are, to complete instrument calibrations, and to encourage the development of new methods of measurement. They are also used to maintain measurement traceability in the US. With every SRM, NIST offers a Certificate of Analysis and a Material Safety Data Sheet (if applicable).

NIST only certifies products that have been tested against an SRM and meet the specific requirements for that product.

United Instrument
United Instrument

NIST Certified Products

  • Temperature calibrator
  • Pressure calibrator
  • Calibration weights
  • Tachometers
  • Thermometers
  • Torque wrench
  • Anemometers
  • Pressure gauges
  • Micrometers

Almost any product that measures something has a NISTSRM equivalent for manufacturers to compare with. It allows manufacturers to determine whether or not a product is working within acceptable limits. A product is sold with a NIST certificate once it is tested against the SRM. All certificates have an expiry date to indicate when the product needs to be retested.

Certificate of Calibration

A certification from NIST can be a NIST Certificate of Calibration, which means that the product has been tested and approved to be on a certain level of accuracy.

Certificate of Compliance

NIST Certificate of Compliance is another type of certification that means the product tested was found to be within the stated tolerance, but no adjustment on the item is possible. Certificates of compliance are typically given to products such as glass tube thermometers or hydrometers.

United Instrument
United Instrument

Traceable Certificates

NIST Traceable Certificates means that the product being tested was not compared to the NIST SRM. Instead, it was tested against another product that has already been compared to an SRM.

For example, a NIST SRM thermometer would check another thermometer. The second thermometer will receive a certificate of compliance according to NIST standards if the proper paperwork is done. Traceability requires the establishment of an unbroken chain of comparisons to stated references.

It is the responsibility of the provider of the traceable product to support the claim of traceability. Still, it is up to the user of the product to determine how legitimate the claim is.


NIST certification does not mean that NIST endorses, approves, or recommends any product, manufacturer, supplier or user of any NIST certified equipment.

High Standards of Repair

Repair services are performed by experienced technicians and include thorough testing, cleaning, electrical repair, and calibration with precision test equipment traceable to the National Bureau of Standards. After repairing and calibration, the units are retested and monitored to ensure our high standards and quality of the repair.

United Instrument
United Instrument

Repair Procedures

  • Clean all working parts of the gauge.
  • Replace all dial, movement, case, and link screws wherever necessary.
  • Where deemed appropriate by our inspection and test standards, replace any severely worn or defective movement and link assembly with good workable parts.
  • Deadweight test and calibrate all gauges repaired.
  • Replace all broken, cracked, or blemished lenses.
  • Clean all mounting threads.
  • Clean and repaint the interior and exterior surfaces of the case and ring.