Washington University Department of Electrical Engineering

Characterizing Odors Using Electronic

Nose Sensors

Experimental Setup

This experiment consists of a nut sample exposed to three unique chemical sensors on a breadboard with the appropriate circuitry specified by the sensor manufacturer. The circuitry quantifies odor in to a voltage. The voltage signal goes through a data acquisition system manufactured by Elvis which is then processed by a graphical user interface in Labview. A flowchart of this setup is shown below.

 

 

 

 

 

 

 

 

 

 

The nut sample is contained within a plastic food container. The container has holes at the bottom so that it can be placed over the sensors. The photos below show the experimental setup.

 

 

 

 

 

 

 

 

 

 

 

Chemical Sensors:
Three different sensors manufactured by Figaro Engineering Inc. were used. The sensing element is composed of a metal oxide semiconductor layer on an alumina substrate of a sensing chip with an integrated heater.  When there is a detectable gas/odor, the conductivity of the sensor changes depending on its concentration.  This change in conductivity gets processed by the sensor’s external circuitry in to a voltage.

 

 

 

 

 

 

Odor Samples:
The samples used were crushed almonds, peanuts and hazelnuts. We chose nuts because of their availability and ease of storage, and to gain insight on allergen detection.  Each sample was a fixed mass of either 5 grams or 10 grams. 

DAQ

Signal conditioning circuit

sensors

Nut sample