Traceable dynamic calibration of force transducers by primary means

Abstract

We describe an apparatus for traceable, dynamic calibration of force transducers using harmonic excitation, and report calibration measurements of force transducers using this apparatus. In this system, the force applied to the transducer is produced by the acceleration of an attached mass, and is determined according to Newton’s second law, F = ma. The acceleration is measured by primary means, using laser interferometry. The capabilities of this system are demonstrated by performing dynamic calibrations of two shear-web-type force transducers up to a frequency of 2 kHz, with an expanded uncertainty below 1.2 %. We give an accounting of all significant sources of uncertainty, including a detailed consideration of the effects of dynamic tilting (rocking), which is a leading source of uncertainty in such harmonic force calibration systems.

Characterization of laser Doppler vibrometers using acousto-optic modulators

“…Following ISO Standard 16063-41 Method for the calibration of vibration and shock transducers -Part 41 Calibration of laser vibrometers [1], laser Doppler vibrometers (LDVs) are calibrated by a comparison-type measurement to a laser homodyne interferometer that is defined as the primary standard. Not covered by ISO 16063-41, but for the case where all the components of the LDV system and their associated uncertainties are known, methods can be employed for the direct determination of measurement uncertainty of the LDV [2], [3] or by using a combination of a heterodyne with a homodyne-quadrature configuration [4].…”

“…From the end user perspective, the commercially manufactured LDV system is like a "black box", meaning that the design and internal components of the LDV are not known in detail by the user. Therefore, following an uncertainty determination approach described in [2] or [3] is not possible for such commercial black box systems especially if their internal workings are considered proprietary by the manufacturer. The only possibility provided by the standard for calibrating a such commercial LDV systems is therefore to follow ISO 16063-41 and compare it to a primary heterodyne system, resulting in the LDV system being considered a secondary system.…”

Influences of shaker armature dynamics on periodic force measurement

“…The measurement of dynamic force is widely used in many industrial applications, such as material testing, production processes, and vehicle dynamics. Therefore, a number of national metrology institutes have developed periodic force calibration facilities [1]- [3]. The dynamic behaviour of a periodic calibration is affected by three main factors: the internal structure of the force transducer; the mechanical coupling between the transducer and the shaker armature on one side and between the transducer and the top mass on the other side; and the dynamic behaviour of the shaker armature.…”

Dynamic Force Transducer Calibration Based on Electrostatic Force

“…Measurements of micro/nano dynamic force [1]- [11] are of high importance in many fields, such as precision instruments, microelectromechanical system [1], [2], biology [12], [13], and tribological properties of materials [14]- [17]. In the field of robotics, there is a strong need to measure and control the step force in the typical motion of holding an object [1].…”

“…Much work has been done on the calibration of DFTs to meet the requirements of academia and industry [18]- [21]. The calibration of dynamic force transducers was pioneered by Vlajic [12] and [13], Fujii [3]- [5] and Kumme [6]. Nicholas Vlajic SI-traceably calibrated an impact hammer, by using a mass suspended from a thin line which is cut to produce a known dynamic force.…”