IGCAR : Annual Report - Indira Gandhi Centre for Atomic Research

IGC
Annual Report 2007
V.C.9. Wireless Signal Transmission from
Pulsating Sensors
The pulsating sensors, have
several attractive features for
deployment besides their high
performance. One such aspect
is their adaptability in a simple
way for pulse-by-pulse wireless
transmission of primary signals
in the form of trains of digital
pulses from the sensors to data
receiving stations located
elsewhere in a building or in
fields. In-house development of
appropriate
wireless
transmission and reception
modules in support of the
pulsating sensors is described
here.
The transmission and
reception modules are
designed in such a manner that
the pulsed signal output
profiles before transmission are
practically reproduced during
reception as if the signals were
received by wired means,
thereby making them
indistinguishable for the
subsequent signal handling and
data processing systems which
were earlier developed for
direct use. Transmission and
receiver modules make use of
available low power consuming
5 V DC driven modulation and
demodulation chips, enabling
transmission on a carrier
frequency of about 433 MHz
falling under ISM band for use
in industrial, scientific and
medical applications.
The developments have been
made for two types of uses: (i)
mains/battery operated
transmitter - receiver pair for
use with one sensor at a time,
usable fully for field
applications, and (ii) transmitter
- receiver pair for simultaneous
use with seven pulsating
sensors by time division
multiplexing, mainly for use
within a building. In the second
type, the tasks of pulse
counting, data processing and
presentation are carried out at
a signal receiving location by a
PC, feeding output signals from
the receiver directly through the
parallel port. The block
diagram of the transmitter and
receiver modules made in the
laboratory is given in Fig.1.
Modules were made and
tested with highly satisfactory
results. Fig.2 shows seven
different sensors which sense
diverse parameters namely
conductivity (in ch-2), chemical
emf (in ch-3), pH (in ch-4),
temperature (in ch-5) levels of
a non-aqueous and aqueous
liquids (in ch-6 and ch-7) and
differential pressure (in ch-8),
are connected to the transmitter
module in one room. The
transmitted pulsed signals are
received in another location a
few rooms apart. Signals are
being processed and data are
displayed in real time as
histograms as well as in time
dependent plots for all the eight
Fig.1 Block diagram of the
wireless transmitter and
receiver modules for
simultaneous use with seven
different pulsating sensors.
140 ENABLING TECHNOLOGIES