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2000-2002 S&T e-Digest Contents


Vol. 39, Issue 1, January 2004, pp. 121-127




Development of a Telemetric System Employing a Passive Force Sensor

and a Resonance Frequency Detector with Intelligent Sweeping



Sergio Francisco PICHORIM, Raul Jose Fernandes de OLIVEIRA

and Paulo Jose ABATTI


Paraná Federal Center of Technological Education

Av. Sete de Setembro, 3165, 80230-901, Curitiba, Paraná, Brazil

Phone: +55.41.310-4696, fax: +55.41.310.4683

E-mails: pichorim@cefetpr.br, rfo@cpgei.cefetpr.br & abatti@cpgei.cefetpr.br



Received:  12 December 2003        /Accepted: 14 January 2004         /Published: 18 January 2004


Abstract: This paper describes a telemetric system designed to measure muscular force remotely. The sensor is composed by a simple LC resonant circuit assembled inside a silicone rubber tube (sensor final dimensions are 22.0 x 2.15 mm). Small rings that fix the sensor transmit the force to the silicone rubber modifying the inductance value, due to the displacement of a small ferrite rod close to the inductor. The resonance frequency of the sensor, which depends on the applied force, is monitored remotely (few centimeters apart) using a frequency detector with intelligent sweep (sweeping range can be modified to find out the sensor resonance frequency in few milliseconds), presenting the sensor resonance frequency on-line. In this work muscular force was simulated using standard weights, showing that the system presents errors smaller than 65 mgf, on a 0 to 17 gf range.


Keywords: passive sensor, telemetry, resonance frequency, force measurement, remote


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