Investigations of load cells made of single-crystalline silicon with sputrered-on strain gauges

S. Mäuselein, O. Mack, R. Schwartz, G. Jäger

Abstract

This paper presents first results of experimental investigations performed with mechanical springs made of single-crystalline silicon (S-Spring) for load cells (LCs) with sputtered-on thin film strain gauges. The investigations are carried out on a specially manufactured S-Spring load cell (S-Spring-LC) with a nominal load of 6 kg and geometry parameters which are optimized by numerical simulations. <br />This paper deals with load depending deformation measurements of the S-Spring to verify the expected low mechanical after effects. For the first time the investigations are carried out with a Fizeau interferometer, which delivers 3-D topology data of surfaces. This interferometer actually used at PTB features the grand adventure to determine the deformation of a complete surface of a load cell under load within a short time interval and one single measurement. <br />The measurements reveal information about the fraction of deflection generated by tilting effects of the force introduction and which fraction is generated by deformations of the S-Spring. The investigations point out that tilting of the force introduction is not negligible but can be compensated analytically. Only with analytical compensation of tilting effects mechanical after effects of the S-Spring can be determined by recording a multiplicity of 3-D topology data within 30 minutes. As a result the S-Spring investigated shows mechanical after effects which value is about a factor of 100 lower in comparison to conventional metallic material LCs and therewith confirm values given in literature for mechanical after effects of silicon.

Keywords

silicon, load cells, force sensors, mechanical after effects

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IMEKO TC

TC3 - Measurement of Force, Mass, Torque, and Gravity

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