Wireless passive weight sensor
Design and simulation of an RLC-resonance sensor for weight sensing in conveyor belts
R. van den Bos (TU Delft - Electrical Engineering, Mathematics and Computer Science)
R. Bokhorst (TU Delft - Electrical Engineering, Mathematics and Computer Science)
C.J.M. Verhoeven – Mentor (TU Delft - Electronics)
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Abstract
This thesis presents a resonant sensor circuit design that converts the deformation of a load cell in a conveyor belt into a change in resonance frequency. The sensor is inductively coupled to a reader circuit using planar PCB inductor coils. A sensor circuit was designed, fitted on a square PCB with 14.14 mm side length. The circuit consists of a planar squared inductor and a planar interdigital capacitor. The inductor has an inductance of 0.66535 $\mu$H, and the capacitor has a capacitance of 5.157 pF. An additional SMD capacitor was added to reach a resonating frequency range around 27.2 MHz. The deformation of the load cell causes a bend in the sensor PCB, which is directly attached to the diaphragm of the load cell. The bend causes a change in capacitance of the interdigital capacitor, which shifts the resonance frequency of the sensor. The sensor components are designed in MATLAB and simulated and verified in CST studio.