Calibration of Precision Instruments to NIST Standards

Precision measurement tools like a nautical alidade theodolites are used in many industries — from surveying to navigation. While they provide accurate measurements that help users deliver quality charting and distance measurements, their accuracy degrades over time, mainly due to natural wear and tear. However, this can also be caused by external shocks (it can be electrical or mechanical) to the equipment or less than favorable storage conditions.

This is why performing periodic calibrations is important.

Calibration is the process of comparing a certain instrument to a standard measurement to determine its level of accuracy (or inaccuracy). Necessary repairs are performed afterward to ensure that the precision device is well-calibrated and can indeed provide accurate readings in the future. Experts advise calibrating precision tools as per the recommendations of the manufacturer of precision alignment equipment guidelines.

In the United States, the National Institute of Standards of Technology (NIST) has set a standard for proper calibration practices. Founded in 1901, it was established to create equitable standards that will help advance measurement science. Its core competencies include measurement science, rigorous traceability, and the development and use of standards.

Performing A NIST Traceable Calibration

Today, there are instrument companies that don’t just offer precision tools like alidades for sale or lease. They also perform NIST traceable calibration services to help guarantee a device’s accuracy.

Simply put, an NIST traceable calibration is a calibration performed in accordance with the measurement standards set by NIST.

In calibration terms, the property of the measurement result is one that “can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty.” In general, the NIST refers to measurement as an “experimental process that produces a value that can reasonably be attributed to a quantitative property of a phenomenon, body, or substance.”

A NIST traceable calibration service can produce different classes of certifications, depending on your requirements (including budget):

A basic certification that doesn’t contain any reading

A certification that provides readings taken after the calibration

A certification that has readings before and after the calibration is done (this is considered the highest level of calibration certification)

However, take note that calibration services themselves don’t guarantee that you’ll get the results you want. This is why the NIST is clear in its reports wherein calibration results feature not just measurement values but measurement uncertainties as well. These uncertainties include the environment in which the calibration was done (e.g., temperature, pressure) and other inherent factors in the instrument.

If you’re a manufacturer of precision alignment equipment or an owner of one, it’s important to select the right calibration partner for your devices.

Your provider must have comprehensively trained technicians and engineers to perform instrument calibration that adheres to NIST standards. These professionals must be familiar with the different calibration services that the NIST offers (including special tests). Additionally, they must be knowledgeable about the latest updates on the agency’s policies and procedures.