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Calibration models


Enabling a transferable calibration model for metal-oxide type electronic noses


S&A

Electronic nose;
Metal oxide;
Calibration;
Transferability;
Mass production;
Temperature control

Abstract

While electronic noses have been around for over 30 years, little effort has been devoted to the development of transferable calibration models, which are models that can be applied to multiple equivalent devices without adjustment. The majority of published results limit itself to data sets gathered with a single device. This lack of insight in transferable models hampers large scale implementations of eNose-based applications as individual calibration of a multitude of devices for a specific application area is generally unrealistic due to the requirement of actual samples to be measured. For simple gases this may be do-able, but in the case of more complex samples such as biological patient material it is logistically impossible.

In this paper we show the influence of the deviation of the sensor temperature on the measurement reproducibility and by inference on the transferability of calibration models. We introduce the total inertia (φ2) as a measure for the heterogeneity within the measured data. The total inertia is an objective measure known from linear algebra, where it is used to calculate the correspondence between matrices.

We use 5 micro-hotplate metal-oxide sensors from the same wafer, with an inter-sensor heater temperature difference of approximately 15 °C in combination with 2 substances, n-butyl-acetate and hexane. This research demonstrates the increase in heterogeneity of the measured response values in relation to a temperature shift. A shift of 15 °C at the sensor surface causes an increase of heterogeneity that is 10–15 times higher than the increase in heterogeneity caused by inter-sensor responses to the substances when operated at exactly the same temperature. Some mixtures of substances will be separable by pattern recognition under virtually any condition, and strict temperature control will neither improve nor deteriorate results. However the significant contribution of temperature deviation toward data heterogeneity renders it plausible that optimized temperature control, and by inference lower data heterogeneity, is a prerequisite for transferability of a calibration model. This holds true when applied to metal-oxide sensors and for mixtures containing substances showing a fair degree of similarity.



Bangladesh study results

After publication of our study in Bangladesh in Tuberculosis Journal, much attention is given on this new screening method i.e. Bangladesh . At this moment we are setting up efficacy studies in Kenia, South Africa and the Netherlands.


Oct 16 2012

A growing number of health problems can be diagnosed by analyzing a patient’s breath alone.

“Anything you can have a blood test for, there is potentially a breath test for, as long as there is a volatile component,” says Raed A. Dweik, director of the pulmonary vascular program at the Cleveland Clinic’s Lerner Research Institute.



Read more on: bit.ly/breathreveals




Dogs excel in Estrus detection in cattle,but can they compete with the reliability and reproducibility of an electronic nose?

Last week we visited Prof. Dr. Heuwieser at the Clinic of Animal Reproduction of the Freie Universität of Berlin.

Blind test dog sniffing out Estrus on cows

Blind test

He is using our electronic nose device Aerekaprobe (formerly the DiagNose II) in a very interesting project.In this project the performance is compared with human sensory capabilities and even trained dogs.

Apart from the great fun factor of this project, it also reveals surprising insights into the objectiveness of using electronic sensor systems even more than a comparison on accuracy alone.Anticipating the results that are expected to be published this year, we are very enthusiastic about the project approach and have discussed new opportunities in the veterinarian field.

Training phase

Training phase

Aug 9 2012

Last week the ordered Pick & Place machine arrived meaning we can start producing Aerekaprobes and Aeonoses after we have learned how to operate such a thing!

myWPEdit Image

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