Strain Gauges: Principles, Types, Terminology
and New Applications
Abstract
Among the 12 principles / methods for electrical measurement of mechanical quantities selected by the author, 8 appear in the list of strain gauges (SGs): resistive, capacitive, piezoelectric, magnetoelastic, acoustic (SAW), optic fibers and, having frequency output, vibrating wire and resonator.
A question of terminology that often arises: Are transducers with frequency output digital ? The dimension of the quantity Frequency is 1/Time. And the “Time” is a fundamental quantity ! So, such a transducer can’t be “digital”, having no binary output !
From another viewpoint, that of interdigital (comb or zipper) transducers, similar SGs may also be retrieved here. A so-called “frequency scale” will be presented, with accents on acoustic and electro-magnetic methods. Example: An electromagnetic antenna as a passive wireless strain sensor using a microstrip patch and a resonant cavity with feed-inset operating in IEEE C-band i.e. 5.8 GHz, designed by computer simulation technology (CST).
In the Time domain, the compression frequency was electronically determined with Cardiopump, evaluating the force signal (given by strain gauges or force sensing resistors – FSR) by its zero crossings. Their intervals were measured and, using the last 1.5 cycles, the mean value was computed.
The Micro and Nano applications to be presented are: piezoresistive accelerometer, micropipette and some carbon nano tubes.
Brief Biography
Dan Mihai Ştefănescu was born in Bucharest, 6 April 1946. BS in Applied Electronics (1969), MS in Experimental Stress Analysis (1983) and PhD cum laude in Electrical Engineering (1999), all from the ‘Politehnica’ University of Bucharest. Senior Researcher in Measurement Techniques with the National Institute for Aerospace Research in Bucharest (1969 – 2003). NATO grant at Twente University of Enschede, The Netherlands (2002). Visiting Scientist within Korean Research Institute of Standards and Science, conducting a project on Force Transducers Optimization by Numerical Methods (2004) and then within Center for Measurement Standards in Taiwan, R.O.C., leading a project on Improved Portable Truck Scales (2005). Now is Senior Consultant for the Romanian Measurement Society. Member of Verband Deutscher Electrotechniker (1987), Romanian representative in IMEKO from 1988 and member of the General Council (2015).
