Looking for soft-sensor example

Hello.

I am looking for an example of a soft-sensor (inferential measurement) algorithm, implemented using Simulink, Matlab, or C.

I'm also looking for general information on soft-sensors, and how they're implemented.

This is for a research paper I'm doing for an automatic control class.

If anyone can help me, or at least point me in the right direction, I would appreciate it.

Thanks in advance,

Alexis Maldonado
Estudiante Ingenieria Electrica
Universidad de Costa Rica