Instrumentation & Measurement Magazine 23-9 - 46

iteration number with fixed values for the interpolation error
and denominator iterations [12].

Smart Building Application Scenario
The availability of an EED node in a network of transducers
compatible with the IEEE1451 standard, allows the system
to monitor, in real time, the approach of a potentially dangerous seismic wave. When the earthquake is detected, a warning
message is issued, ordering the water, gas and electricity infrastructures to enter into their protective mode. At the same
time, a network of sensors that record vibrations and displacements at specific spots of the building are ordered to prepare to
start operating. The synchronization of the acquisition process
is achieved using resources provided by the standard.
Fig. 3. Spectrum of a Sinc signal of 15 Hz bandwidth iterated in steps of 10
to 1000 through the MCT process, interpolation error 1E-08. Note the control of
the bandwidth with the number of iterations (© IEEE, 2019).

Early Earthquake Detection Network Node

The analog input sensor transducer channel converts from the
analog to the digital domain the signal generated by the accelerometer transducer. After receiving a trigger command from
the NCAP, this transducer channel begins to acquire a dataset.
Energy( xp , Err , IterN )
 MCT 
	
	(1) At the end of dataset acquisition, the Data Available/Data ProEnergy( xp , Err , IterD )
cessed bit from the analog transducer channel status register is
set. An embedded digital event sensor monitors the status of
where xp is three seconds of seismic signal, Err is the interpola- this bit, and whenever it changes from clear to set, the output
tion error for MCT sampling, IterN number of MCT iterations of the embedded digital event sensor generates a trigger signal
for the numerator and IterD number of iterations for the de- and sends it to the Event Sensor Control Group for analysis of
nominator. If IterN is greater than IterD, then αMCT has a range the last dataset acquired for the occurrence of an earthquake.
from zero to one. Variance was used for energy estimation
Sending a trigger to the event sensor control causes all of
in this paper, since it is easy to compute, but other estimators the transducer channels from the group to also trigger. The
can be used. No signal pre-processing is necessary to calcu- embedded actuator channel computes the αMTC value, using
the samples stored in the last dataset acquired by the analog
late αMCT.
To determine the right amount of iterations to achieve transducer channel. By adjusting the number of samples in
sensitivity in the non-destructive versus destructive earth- the dataset, it is possible to increase or decrease the window of
quake discrimination, the computation of alpha for different seismic observation.
earthquakes was carried out by varying the number of iteraAn analog event sensor differs from a conventional sensor
tions. Fig. 4 shows αMCT values as a function of the numerator in that it detects when a physical quantity exceeds a predefined
threshold, triggering an
event, detected by a change
of the associated state,
rather than providing the
magnitude of that same
physical quantity. To the
event two states {0,1} are associated. On the occurrence
of the event, at event sensor
output, it is also possible to
have a timestamp of the occurrence in addition to the
current state. Upper and
lower limits can be defined.
These boundary limits are
separated by a hysteresis
range, which can be zero,
causing the two limits to
overlap. A seismic event is
Fig. 4. αMCT as function of the numerator iteration number for earthquakes listed in the figure. Interpolation error= 2.0E03, IterD=5 and a signal window of three seconds (© IEEE, 2019).
generated whenever the
46	

IEEE Instrumentation & Measurement Magazine	

December 2020



Instrumentation & Measurement Magazine 23-9

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