# Sensor concept

## Introduction

Within a time dependent study and/or parametric analysis, the results post-processing can be carried out:

- either by one of the solving process steps (selection of one solution)
- or by means of the whole assembly of solving process steps (set of solutions)

## Advantage

A post-processing analysis for a set of solutions enables the analysis of quantities as functions of I/O parameters.

For example, a post-processing analysis for a set of solutions enables:

- plotting the curve of the magnetic field in the center of the air-gap as a function of the air-gap dimension
- plotting in the relief mode the force acting on a piece as a function of the air-gap dimension and of the magnetic permeability of the magnetic circuit

## Sensor concept

To carry out a post-processing analysis for a set of solutions, it is necessary to define “virtual sensors” that can “measure” and/or “compute” the quantities that the user is interested in, during the time dependent study and/or parametric analysis.

A sensor is a varying quantity of the varying analysis that enables:

- measurement of a local quantity such as the magnetic field at a point, the flux through a face, etc.; or
- computation of a global quantity such as the force or torque acting on a piece, the energy, etc.

## Local and global quantities

The local and global quantities that can be computed by sensors are all the available local and global quantities in post-processing. They depend on the application: magnetic, electrical, thermal, etc. (see volume 3 referring to applications).

## Spatial sensor

A spatial sensor combines a support and a formula.

- The support can be of the point, line, surface, volume type or over the entire computation domain.
- The formula can contain a set of spatial quantities, functions and operators.

## Global sensor

A global sensor also associates a support and a formula.

- The support can be a point, line, surface, volume type or over the entire computation domain.
- The formula is predefined: force, torque, energy, losses, …

## Notice

A Flux sensor “measures” a single value for each solution of the solving process.

It is also possible to “measure”:

- the modulus of the magnetic flux density in a point
- the integral of the magnetic flux density on a surface

But it is not possible to “measure”:

- the values of magnetic flux density in the points along a line.