Characterization of flexure hinges for the French watt balance experiment

Abstract

Abstract. In the French watt balance experiment, the translation and rotation functions must have no backlash, no friction, nor the need for lubricants. In addition errors in position and movement must be below 100 nm. Flexure hinges can meet all of these criteria. Different materials, profile shapes and machining techniques have been studied. The flexure pivots have been characterized using three techniques: 1) an optical microscope and, if necessary, a SEM to observe the surface inhomogeneities; 2) a mass comparator to determine the bending stiffness of unloaded pivots; 3) a loaded beam oscillating freely under vacuum to study the dynamic behavior of loaded pivots.

Automatic alignment technique for the suspended coil in the joule balance

“…It is a pendulum structure with several flexure hinges, inspired by the LNE Kibble balance [13,14]. The overlapped flexure hinge shown in figure 3(b) contributes to the postures and positions of both the suspended coil and the mass pan [34][35][36]. We used three piezo mini-motors (N-470K067, PI) to modify the rod length and adjust the posture of the suspended coil.…”

Simplified fundamental force and mass measurements

“…Flexures have been used for many years for the precise guiding of seismometer-like instruments such as the 'Super Spring' vibration isolators [12] used in gravimeters [13]. In the LNE watt balance flexures are used in the guidance mechanism [14] but, to obtain sufficient sensitivity for the weighing, a separate flexure-based balance is employed. In the design considered here specially designed flexures, suitable for both weighing and moving, are likely to be used initially but it is now possible to consider other approaches to this guidance problem.…”