< back to main site

Publications

Design of a bi-directional electrostatic actuator for realising nanonewton to micronewton forces.

Leach, R K; Oldfield, S; Awan, S A; Blackburn, J; Williams, J M (2004) Design of a bi-directional electrostatic actuator for realising nanonewton to micronewton forces. NPL Report. DEPC-EM 001

[img] Text
DEPC_EM1.pdf

Download (894kB)

Abstract

This report describes the design of an electrostatic actuator for incorporation into a low force measuring instrument that operates over the range 1 nN to 10 µN. The force being measured is balanced by applying an equal and opposite electrostatic restoring force. The low force measuring instrument also requires a prior calibration of the capacitance gradient of the actuator. A number of capacitor geometries were considered but the need for a bi-directional actuator and ease of manufacture have led to a system with two sets of parallel plate capacitors (i.e. a four-plate capacitor) with a moving dielectric plate that is displaced by the application of the force being measured. To the authors’ knowledge such a four-plate capacitor arrangement has not been used before and should give a significant improvement over existing low force measuring instruments. The report describes a theoretical model of the four-plate capacitor with moving dielectric. Finite element models that were used to investigate the effects of undesired motion of the dielectric plate are then described. Unlike a two-plate capacitor, a four-plate design requires at least six measurements to determine a capacitance matrix and these measurements are discussed. Finally, the practical realisation of a four-plate capacitor is considered.

Item Type: Report/Guide (NPL Report)
NPL Report No.: DEPC-EM 001
Subjects: Engineering Measurements
Engineering Measurements > Dimensional
Last Modified: 02 Feb 2018 13:16
URI: http://eprintspublications.npl.co.uk/id/eprint/3038

Actions (login required)

View Item View Item