Instrumentation & Measurement Magazine 26-1 - 38

preservation, especially indoor
environments such
as museums, through the
adoption of mimetic, ecofriendly
and green aspects
which characterize the
aforementioned systems.
Measurements
Through SoilPlant
Systems: A
Case Study
With the aim to measure
the intensity of radiation in
the UV-A region (315-400
nm), a Dimorphotheca ecklonis
plant was considered.
The working principle is in
line with the description
presented previously. It is
worth noting that the transduction
principle and the
soil redox potential is also
investigated in a Sansevieria
cylindrica. Fig. 4 shows the
picture of both devices and
a typical output voltage,
measured across the electrodes,
in the presence of a
known level of measurand.
With the aim to characterize
the devices, the
following experimental
setup was considered: a
generator of UV-A radiation
able to generate a
maximum power of 22 W
is used to impose a known
Fig. 4. (a) Picture of the living sensors through the adoption of a Dimorphotheca ecklonis and Sansevieria cylindrica. (b) A
typical output voltage generated across the electrodes when a level of UV-A radiation is applied.
radiation intensity level; anode and cathode electrodes (zinc
and copper) electrically connect the plant through the soil;
and a LabVIEWTM
routine acquires the output voltage measured
across the two electrodes. In particular, a NI-6009 DAQ
board was connected to a PC. Furthermore, the processing of
the measurements was accomplished by using MATLAB®
. To
study the plant's ability to convert absorbed energy into an
output voltage, the intensity of ultraviolet light was evaluated
by considering the distribution of irradiance values over the
irradiated surfaces. In this way, the average intensity that the
plant absorbs at different distances was obtained. Fig. 5 shows
the two living sensors able to perform measurements with
each corresponding output voltage as a function of applied UV
irradiance. The characterization is shown for the Dimorphotheca
ecklonis and the Sansevieria cylindrica.
Each graph includes the linear interpolation, and the points
represent the difference between the zero condition (no UV irradiation)
and the radiation level considered. Results display
38
a sensitivity of about 6.6 mV/mW/cm2
about 0.13 mW/cm2
and a resolution of
for the Dimorphotheca ecklonis compared
to the Sansevieria cylindrica which shows a sensitivity of about
11 mV/mW/cm2
and a resolution of 0.10 mW/cm2
. The advantage
of the Sansevieria cylindrica lies mainly in a much lower
need for care and superior transduction performance. In addition,
unlike Dimorphotheca ecklonis, Sansevieria cylindrica only
needs to be watered once a month and has greater adaptation
to the environment and robustness to withstand external influences.
Table 1 synthetizes the features of the two living sensors
considered.
Fig. 6 shows an example of an influence study of the Sansevieria
cylindrica for UV-A measurements which presented
higher performance and insensitivity to unwanted physical
quantities compared to the Dimorphotheca ecklonis. Particular
attention is given to temperature and humidity which represent
two physical quantities which can be found in several
application fields.
IEEE Instrumentation & Measurement Magazine
February 2023

Instrumentation & Measurement Magazine 26-1

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