Summary of the intercomparison of the force standard machines of the National Institute of Standards and Technology, USA, and the Physikalisch-Technische, Bundesanstalt, Germany

Abstract

A comparison of force measurements performed at the National Institute of Standards and Technology, USA, and at the Physikalisch-Technische Bundesanstalt, Germany is reported. The focus of the study was the intercomparison of the forces realized by the two Institutes rather than the measurement process. The transfer standards used in the comparison consisted of force transducers and associated readout instrumentation. The results of the intercomparison reveal that over a range of 50 kN to 4.5 MN, the forces realized at NIST and at PTB compare favorably. For forces up to 900 kN the agreement is within ±40 ppm; above 900 kN the agreement is within ± 100 ppm.

Creep and creep recovery response of load cells tested according to US and international evaluation procedures

“…These machines, having weights and loading frames made of stainless steel, are described in detail in Refs. [ 6 , 7 ]; therefore, only a short description of the machines is given below. The combined standard uncertainty (estimated standard deviation) in the applied forces due to uncertainties in the adjustment of the weights and variations in air density is 0.0005 % of the nominal applied force.…”

Stress Analysis of Conical Contact Joints in the NIST 4.45 MN Deadweight Machine

“…In 1989, an intercomparison between NIST and Physikalisch-Technische Bundesanstalt (PTB), Germany demonstrated agreement to within ± 40 ppm for forces up to 900 kN [4]. Furthermore, an international force key comparison performed in this machine as part of the US commitment to the Comité International des Poids et Mesures (CIPM)/Bureau International des Poids et Mesures (BIPM) arrangement to promote uniformity and agreement of measurements among National Metrology Institutes (NMIs), also yielded successful measurement results [5].…”