Comparison of angle gauges

Project Description

A set of thirteen angle gauges and precision square will be measured during the bilateral comparison. Different measuring methods and instruments will be applied: either an autocollimator and an index table /OFMET/ or a goniometer /GUM/. The goal of the project for OFMET is to test new measuring equipment, for GUM - to compare results GUM-OFMET. Piramidality will be determined by OFMET.

The result of this comparison will be interesting for future discussion about the definition of measurand and recommended method for angle gages calibration.

Final Report 2001-08-22

The main purpose of the comparison was to get more information and experience on measuring of wringing angle gauges. It was especially important for GUM because this kind of angle gauges just becomes popular in Poland.
The set of 14 angle gauges was circulated among the participating institutions. All participants determined, using different instruments and methods, the pyramid errors and the angle deviations in normal and inverted position. GUM carried out the measurements of flatness deviations of all measuring faces.The flatness deviations, representing by the P-V parameter, ranged from 309,8 nm (for gauge of nominal angle 27°) to 38,6 nm (for gauge of nominal angle 0,1’). The clear dependence between the flatness deviation and the differences of the results of angle deviation measurements (differences between normal and inverted position and between participants as well) were not found.
METAS (OFMET) results were considered as reference values, so the GUM and IPQ results were referred to them. The maximum difference (1,33”) of the results obtained from optical methods between GUM and METAS (results taken from normal position) was observed for the gauge of nominal angle 41° and between IPQ and METAS (0,77”) for the gauge of nominal angle 1’. The maximum differences of the results (between GUM and METAS and IPQ and METAS) taken from the inverted position occurred for the same angle gauges. There was observed bigger differences for smaller nominal angles.
There was found that it is very important during angle gauges measurements to determine precisely the area of measuring face from which the data are collected depending on the chosen kind of measuring method (contact or optical method).
The stated combined standard uncertainties equalled: 1,1” for GUM results; 0,18” for IPQ results; (0,04 – 0,07)” for METAS results.

Further information is available in the detailed report of the co-ordinator, issued by the GUM.