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information acquired in electrical signals which describe the evolution in time of the physical
phenomena. The instrumentation systems are open and they are destined both to
measurements and analysis of the quantities. [3] An inventory of the main DMSs will reveal the
following types:

1. DMS with serial/parallel communication - it uses the computer in the measurement
process and the information is transmitted from the transducer to the computer using
a serial communication protocol using the universal serial bus.
2. DMS with data acquisition card - Data acquisition devices require specific electronic
parts (digital card) that are usually embedded into computers; the data acquisition cards
work together with conditioners (liaisons between signals provided by transducers and
signals required by data acquisition cards) in order to establish certain intervals for
analogue signals

Signal conditioning

Most analogue signals require some form of preparation before they can be digitized. Signal
conditioning is the manipulation of a signal in a way that prepares it for the next stage of
processing.

signal conditioning
displaying
monitoring
- naturing (consists of fundamental transformation from
non-electrical nature in electrical signal and the in to a recording
data acquisition digital signal)
(sensor and - scalling (consists of amplification of the signal in order to
transducer) signalling
increase the energy taking in to account that the sensors
release signals with low energy content) control alarming
- shaping (includes algorithms that influence the form in
time domain by removing harmonics or frequency
modulation) controlling

Fig. 3.8. Signal conditioning

Signal multiplexing

Signal multiplexing is a process of combining more signals into one signal using a common
environment. There are mainly two types of multiplexers, namely analogue multiplexers and
digital multiplexers. The analogue multiplexers could use one of the Frequency Division
Multiplexing (FDM) or Wavelength Division Multiplexing (WDM) technology, since the digital
multiplexers use the Time Division Multiplexing (TDM) technology.

Frequency Division Multiplexing (FDM) is the most used technique in analogue multiplexing. This
technique uses various frequencies to combine streams of data, for sending them on a
communication environment, as a single signal. In FDM, the signals are electrical signals.

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