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Transpector MPS Operating Manual
Chapter 3
How The Instrument Works
3.1 Introduction
This section explains how Transpector MPS produces measurements. For a
discussion of how to interpret these measurements, see
3.2 Overview
The Transpector MPS Gas Analysis System is a quadrupole based Residual Gas
Analyzer which analyzes the presence and relative abundance of gases in a
mixture. The Transpector MPS Gas Analysis System consists of three parts:
a sensor, which functions only in a high-vacuum environment
an electronics module, which operates the sensor
software, which resides on an external computer and controls the
electronics module
NOTE:
A
high-vacuum environment
correlates to pressures below
6.7 x 10
-2
Pascals, or approximately 5 x 10
-4
Torr [approx. 6.7 x 10
-4
mbar].
By attaching the sensor to a small vacuum system with a suitable controlled leak
or other gas-inlet device, the Transpector MPS Gas Analysis System can measure
gases or volatile materials at pressures higher than those at which the sensor itself
can operate.
The Transpector MPS sensor analyzes gases by:
ionizing some of the gas molecules (in the ion source)
separating the ions by their mass-to-charge ratio (m/z) (in the quadrupole mass
filter)
measuring the quantity of ions at each mass (in the detector)
The masses and their fragmentation patterns, unique for each substance, can be
used to identify the gas molecules from which the ions were created. The
magnitudes of these signals are used to determine the relative abundance of the
respective gases.
