Comparison on Uncertainty Calculations in Flow Calibration

Project Description

Earlier flow inter-comparisons have shown differences in uncertainty judgements not only in size but also in fundamental understanding which aspects should be covered by an calibration uncertainty statement and which not. Since a few years we have the Guide to the Expression on Uncertainty in Measurement. But the older ISO-Standard 5168 also still exists. However it seems appropriate to work for a harmonisation in this field. Such a task could be performed in different ways. We propose to let the interested laboratories make an uncertainty evaluation on a given calibration result.

We suggest to start with an actual example of a gravimetric calibration of a flow meter at our laboratory. Together with a short description of the flow rig and the way the calibration was performed all the raw data and the calculation of the final values are given. The participating laboratories are then asked to start an evaluation of the uncertainty for this calibration. In doing so it will probably be necessary to ask for additional information. We then intend to answer incoming questions concerning different aspects of the work done or the test equipment used.

As a result of the exercise each participating laboratory presents not only the final uncertainty figures but also a detailed presentation of the evaluation. Our laboratory will then put together the different contributions and analyse similarities and differences. On the basis of this we both could learn from each other and form the basis for a common approach.

It is certainly necessary to discuss the outcome of such a comparison. However it is quite time consuming to meet. Further it is most probable that more than one person from each laboratory would be engaged in this discussion. A new way of administrating such a discussion could be to start a bulletin board on internet where everyone from the participating laboratories could both give his view and read everyone else

Further Information

If the participants will find this exercise useful it could be proceeded by putting forward a somewhat different calibration example involving for instance a volumetric example or using a master meter and a two stage

calibration technique. It also would be possible for other laboratories not engaged from the beginning to join later on. Further on even more complicated calibration situations could be analysed of those interested.

Flow (F)
Peter Lau, SP (Sweden)
Phone: +46 3316 5462
Fax: +46 3310 6973
Coordinating Institute
RISE (Sweden)
Further Partners