Calibration Interval Analysis Freeware from Integrated Sciences Group

Freeware Calibration Interval Analysis

Free Calibration Interval Analysis Software

For many activities, it is not enough to control accuracy at the time of testing or calibration. Instead, such control needs to be extended to cover the periods of equipment usage as well. The principle recourse for extending this control has traditionally been periodic testing or calibration at optimal intervals.

In the late '80s, a recommended practice (RP-1) was published by the National Conference of Standards Laboratories (NCSL) that contained the new methodology (referred to as Method S2). This methodology was refined somewhat and documented in NASA Reference Publication 1342 and again, in 2010, in a revised edition of NCSLI RP-1 Establishment and Adjustment of Calibration Intervals.

Method S2 is the best existing methodology for determining optimal calibration intervals. Unfortunately, implementing the methodology requires considerable programming and advanced statistical modeling expertise. To date, the only known successful rendering of the complete methodology is found in IntervalMAX, available from ISG.

Additionally, method S2 requires that substantial test or calibration history data be available for analysis for each item or item type of interest. Cases where such data were not available, referred to as "sparse data cases," had their calibration intervals based on engineering judgement or on simple algorithms that "search" for the correct interval in response to recent test or calibration results. These calibration interval determination and adjustment methods have been found to be nonviable.

Method A3 Interval Tester

A solution to the sparse data problem is found in ISG's Method A3 Interval Tester, which incorporates the concepts and methods reported in the 1996 edition of NCSLI's RP-1. Method A3 can respond to sparse data, but it does not trigger calibration interval changes unless the current interval has been statistically rejected. When a calibration interval is rejected, a simple yet practical adjustment algorithm is invoked.

We have tested Method A3 extensively as a component of IntervalMAX. In these tests, we have employed actual calibration histories of client organizations that we support with our Interval Service. In all tests to date, the method has proved to be a valuable adjunct to Method S2. Moreover, by all indications, it appears that Method A3 can be used as the principle tool for controlling and adjusting calibration intervals for small sized equipment inventories.

Last Software Revision: 11/19/2016

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Integrated Sciences Group
14608 Casitas Canyon Road • Bakersfield, CA 93306
Phone 1-661-872-1683 • FAX 1-661-872-3669