# Sensor

## 1. Introduction

Presentation of the basic for force measurement with strain gauges.

A strain gauge is a device used to measure strain on an object. The most common type of strain gauge consists of an insulating flexible backing which supports a metallic foil pattern. The gauge is attached to the object by a suitable adhesive. As the object is deformed, the foil is deformed, causing its electrical resistance to change. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor.   ## 2. Model/Geometry

The first step is to create the model of the object, which we can simply do in the Creo Parametric program. With this program was the fastest and easiest way to create the model.

The finished geometry (Creo) and the meshed model (Gmsh):  ## 3. Materials and boundary conditions

### 3.1. Materials

The beam is made of steel, so we need to use the following data:

• $E = 205 GPa -> 205e3 N/mm^2^$

• $nu = 0.3$

• $rho = 7850 kg/m^3^ -> 7850e-9 kg/mm^3^$

### 3.2. Boundary conditions

The object is fixed in the middle. Holes have opposite sinusodal forces.  ## 4. Results

 The result were run in time (half whole period, but on the pictures can be seen only a quarter period).

### 4.1. Displacement     ### 4.2. Von-Mises Criterions     On the displacement and stress diagrams, it can be clearly seen that this object is perfectly suited as a sensor.