INFICON Composer Elite Gas Concentration Monitor - Manual (Page 141)

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Composer Elite Operating Manual
9.4 Description of Subsystems
Three major components comprise the Composer Elite System:
 Sensor Control Unit
 Multi-Sensor Software
 Acoustic Sensor
9.4.1 Sensor Control Unit and Composer Elite Multi-Sensor Software
The Sensor Control Unit provides all necessary power and electrical signals to the
acoustic sensor, performs all signal processing and stores all parameter values
necessary to calculate concentration.
Composer Elite Multi-Sensor Software works in conjunction with the Sensor
Control Unit to allow remote operation from a computer.
 Refer to section 1.5.2 on page 1-9 for information on the Sensor Control Unit.
 Refer to Chapter 6 for information on the Composer Elite Multi-Sensor
Software.
9.4.2 Acoustic Sensor
The basic Acoustic Sensor element is the resonant chamber with the inlet and
outlet tubes providing a means of transporting the gases from the process tubing,
through the Acoustic Sensor’s case and finally connecting to the structure that
defines the shaped resonant chamber (see
Figure 9-3 and Figure 9-4 on page 9-9 ).
Because the speed of sound in a gas is dependent on its temperature, there is a
mechanism to measure and control the temperature. First, a platinum resistance
thermometer, or RTD, is imbedded into the chamber body. Heater elements are
able to provide a "heat only" means of control. The RTD and heaters are connected
in a feedback control loop that is monitored and executed by the Sensor Control
Unit portion of the Composer Elite System. A thermo-mechanical switch is
attached to the chamber body and automatically interrupts the heaters’ current
should there ever be a fault that would allow the temperature to exceed 71
C
(75 C for the inlet tube heater). Both ends of the resonant chamber are defined by
a tensioned diaphragm. This diaphragm is used to safely seal the chamber and
also to provide a level of flexibility sufficient to impose an acoustic wave on one end
and to allow its transport and detection outside the resonant chamber on the other
end.
The function of all of the above component elements is to provide an ideal
environment for transporting and measuring speed of sound through the resonant
chamber.