Published: September 2020
The international standard that specifies calliper depth gauges has been updated to make it more user-friendly. This blog post describes its contents and lists what’s new.
Calliper depth gauges are a basic measuring instrument. As such they’re not glamourous, but they are important if you need to very precisely measure thickness from the depth of one surface to another, or the depth of a hole. This is done using the movement of a slider relative to a measuring scale on a rigid beam.
Two international specifications ensure the accuracy and reliability such gauges: they are Part 1 and Part 2 of BS EN ISO 13385. Part 2 of the standard has now been updated by ISO, with input from UK experts on the UK national mirror committee which included representatives from measuring equipment manufacturers and suppliers, measuring instrument users, laboratories that test and calibrate instruments, UKAS – the UK’s assessment body, and NPL – the National Physical Laboratory. The result is: BS EN ISO 13385-2:2020 Geometrical product specifications (GPS). Dimensional measuring equipment. Design and metrological characteristics of calliper depth gauges.
Metrological characteristics
BS EN ISO 13385-2:2020 is a geometrical product specification (GPS) standard. It specifies the most important design and metrological characteristics of calliper depth gauges with analogue indication, i.e. vernier scale or circular (dial) scale; and with digital indication: i.e. digital displays.
The standard begins by looking at design characteristics, specifically general design and nomenclature and then dimensions. The following section then gets into the detail of metrological characteristics, covering general characteristics, rated operating conditions, reference points, test methods, partial surface contact error, shift error, MPE values and special cases.
Next, the specification turns to the determination of conformity to specifications. This includes measurement uncertainty and decision rule. The standard’s concluding section is on marking. It then provides three annexes, respectively on calibration guidelines for metrological characteristics, default MPE (maximum permissible errors) values for metrological characteristics and finally on the standard’s relation to the GPS matrix model.
Dimensional quantity
This standard is used in a wide range of industries, including aerospace, defence, automotive, nuclear and rail. Users will be mechanical engineers, quality control and verification personnel, inspection officers and metrologists. In addition, it will be invaluable to measuring equipment manufacturers and suppliers, and to laboratories that test and calibrate the instruments.
The 2020 standard is a technical revision that replaces the first version published in 2011. The aim of the revision was to make the document more useful. To that end, general design characteristics for calliper depth gauges have been removed from this edition of the standard and now appear in the revised version of the generic measuring instruments standard BS EN ISO 14978:2018, Geometrical product specifications (GPS). General concepts and requirements for GPS measuring equipment.
As well, the figures in the standard have been updated to show more modern technology that users can more easily relate to. The metrological characteristics have also been clarified and modified, and new requirements for test methods have been added. One final important change is that for the first time, default values for maximum permissible errors have been added.
