The kilogram is the unit of mass in the International System of Units (SI) and has been defined as the mass of the International Prototype Kilogram (IPK) since 1889. In the future, a new definition of the kilogram will be based on precise measurements of the Planck constant. The new definition will occur in a vacuum environment by necessity, so NIST is developing a mass calibration system in which a kilogram artifact in air can be directly compared with a kilogram realized in a vacuum environment. This apparatus uses magnetic levitation to couple the kilogram in air to a high precision mass...
Torque wrenches (TW) are widely used in the automotive, aviation and building industry. TW are used to control torque in assembly and fastening operations. Regular calibration of torque tools guarantees traceability to international standards. At KEBS, a torque wrench calibrator with four interchangeable torque transducers and torque meters are used to calibrate both type I and type II torque wrenches as per ISO 6789:2003. In compliance to “Guide for evaluation of uncertainty in measurement” (GUM), it is a requirement that a complete measurement result should include its uncertainty, a...
This paper describes the 16.5 MN hydraulic amplification machine of PTB after modernization. The control system of the hydraulic amplification machine is described. The amplification factor and the temperature influence of the machine are determined by comparisons with deadweight machines.
This paper gives an introduction and an overview about the structure and the research work carried out in the new EMRP Joint Research Project SIB63 “Force” with the title “Force traceability within the meganewton range”.
The first results of gravimetric measurements of the growth of the oxide layer on single-crystal silicon spheres are presented and compared with a theoretical model and with measurements of the surface layer based on X-ray and ellipsometric methods. From the results, conclusions can be drawn about the quantitative influence of the growth of the oxide layer on the mass stability of silicon spheres.
It is visible on the market for reference transducers that there is a growing demand for higher forces. In the last years several new sensors came up, such as the C18/5MN which offer a low measurement uncertainty combined with measurement ranges in the Mega newton ranges. This article presents a strain gauge based transducer for tensile forces of up to 6.5 MN features four galvanic insulated Wheatstone bridges.
The maximum resolution when measuring transducers, which operate on the strain gage principle, is physically limited. Possible sources of errors and their compensation to achieve the high accuracy class of 0.0005 (5 ppm) are shown. In addition to the actual extraordinary high measuring accuracy and long term stability, for the new precision instrument DMP41 the autocalibration cycles could also have been omitted. An innovative method allows to measure for the first time in this accuracy class without any interruptions caused by an auto-calibration.
Traceability of force/torque laboratories around the world widely relies on the strain gauge principle. In order to reach a high overall accuracy of the measuring chain reference transducers always have to be completed by an ultra-precision instrument for strain gauges. Therefore a very special architecture of A/D conversion & signal processing is used. GUI and interface realization determines the good interconnectivity of the device.
In order to improve measurement performance in sea water densimetry which is important in global environmental monitoring, a hydrostatic weighing system is under development in the NMIJ. A 100 g silicon sinker is used as a density reference and it is required to calibrate its mass and volume with higher accuracy that the conventional calibration procedures. In the present study, sub multiple mass measurement was conducted by using 1 kg silicon sphere and newly designed silicon disc weight set. The mass uncertainty was decreased to less than 0.01 mg for the silicon sinker. The volume of the...