Dan Mihai Ştefănescu, Adriana Vâlcu
MEANS FOR ENSURING SI TRACEABILITY OF MICROFORCES AND / OR MICROMASSES

Over the last period, increasing attention has been paid to measurement of small forces which play a more important role in nanotechnology and other significant areas such as MEMS (Micro-Electro-Mechanical Systems). In this respect, the development of mass standards and measurement techniques below the current limit of 1 milligram is vital to provide traceability to the SI for such measurements. The lowest traceable force realized by a deadweight standard machine is typically around the level of 1 N. The national measurement institutes (NMIs), motivated by the need for small force standards, have started to explore methods for establishing a hierarchy of SI-traceable force standards at low-force level, consisting of a primary realization, a transfer standard, and methods of dissemination to instruments.

Leonard Klaus, Barbora Arendacká, Michael Kobusch, Thomas Bruns
MODEL PARAMETER IDENTIFICATION FROM MEASUREMENT DATA FOR DYNAMIC TORQUE CALIBRATION

For the dynamic calibration of torque transducers, a model of the transducer and an extended model of the mounted transducer with the measuring device have been developed. The dynamic behaviour of a torque transducer is described by model parameters. This paper describes the model with the known and unknown parameters and how the calibration measurements are going to be carried out. The principle for the identification of the transducer’s model parameters from measurement data is described using a least squares approach.

Dirk Röske
UNCERTAINTY CALCULATIONS USING FREE CAS SOFTWARE MAXIMA

There are many computer software packages available for the calculation of measurement uncertainties. Some are free and open source, but many are not free to use or are restricted to non-commercial use. Not in all cases, however, is it necessary or advisable to purchase and learn to use a more or less fully featured software package. Some simple calculations can be done using free spreadsheet software contained in LibreOffice or OpenOffice. Also, MS Excel is often already available on the PC.
In some other cases the calculations are not simple, especially when the partial derivatives of the model functions have to be calculated. It would then be agood idea to use a free computer algebra system (CAS). This software facilitates symbolic mathematics.
This paper shows how to use the free CAS Maxima for calculating uncertainties of the torque values realized in a torque standard machine. The tool can also be used for the independent verification of uncertainty calculation results. Some additional tools can make the use of Maxima even simpler.

Christian Schlegel, Gabriela Kiekenap, Rolf Kumme
UNCERTAINTY CONTRIBUTIONS IN SINUSOIDAL FORCE MEASUREMENT

This paper describes one of the uncertainty contributions which can be derived from sinusoidal force measurements. These measurements are based on the application of a scanning vibrometer and the use of triaxial accelerometers. The measuring of many acceleration points on the top mass of the transducer makes it possible to obtain acceleration distributions from which a standard deviation can be derived; the triaxial accelerometer allow the observance of certain effects, like rocking modes, or other problems related to specific excitation frequencies of the force transducer. Both measurements can be related to each other.

M Nieves Medina, Jorge Luis Robles, Jesus Ángel Trujillo, Jose Ángel Robles Carbonell
ENLARGEMENT OF THE TORQUE MEASUREMENT CAPABILITIES AT CEM: DEVELOPMENT OF A 10 kN·m DEADWEIGHT TORQUE STANDARD MACHINE

Centro Español de Metrología (CEM) is developing a completely new torque 10 kN·m deadweight standard machine. This new torque standard machine operates in a working range up to 10 kN·m, clockwise and anti-clockwise. The designed machine, actually under construction, consists of a torque arm, an air bearing, two concentric sets of weight stacks, a main body and a control system that will be able to operate it almost fully automatically.