Biomedical Engineering Reference
In-Depth Information
Figure 6.19.
An experimental sensor containing six electrodes built-in to achieve a specific
and equal area of contact to the measured liquid. The specific areas from different material
can be seen at the end surface of the sensor unit. Photo courtesy and copyright Peter Wide
c
2010.
ple in the range between
5 volt between the electrodes, depending
on distance between electrodes, amount of liquid, type of contamination etc. and
measuring the response characteristics of the current in the loop between the same
electrodes, the response will describe a fingerprint related to the specific and tested
liquid. The response from the experiment can be viewed by an oscilloscope or sim-
ilar monitoring device, e.g., a computer with suitable measurement programs. In
case of a small contamination is added to the tested object, i.e., in this experiment
on drinking water, then the expected change in the response curve will slightly
change. This effect may be better illustrated if a constant measurement is per-
formed and by focussing on monitoring the dynamical output properties. Hope-
fully, now there is a change in the response signal that will be monitored, and
strengthened if some more or other contamination is added to the water. For ex-
ample, if a small amount of contaminant from an external river or lake water is
added in the experiment, that intended to simulate the contribution of dirty water,
is mixed with the drinking water, then there is expected to be a change in the liq-
uid composition that will further deflect the response signal as seen in Figs. 6.20(b)
and (c).
This simple exercise demonstrates the possibility to discover contamination in
the water, e.g., drinking water from the tap. This operational principle is built upon
the assumption that the normal quality of the water will exhibit a stable response
signal from the measuring device. Then, if a change in the response signal occurs,
we may suspect that some additional compounds are identified, that will affect the
response signal in a specific and predetermined manner.
−
5Vand
+
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