User`s manual

1–2 Introduction
SRS QMS Gas Analyzer
Introduction
The QMS 100 series instruments are modern mass
spectrometers designed for the analysis of light gases.
The three systems, 100, 200 and 300, differ only in
the mass range they can detect. A quadrupole mass
spectrometer performs the task of analyzing the gas.
The spectrometer operates at high vacuum and
therefore, pumps are required to draw the gas into the
instrument and maintain the vacuum. State-of-the-art
pumps are used that allow the entire instrument to be
contained in a small transportable package. The inlet
continuously samples gas at low flow rates (several
milliliters per minute) making the instrument ideal for
on-line analysis. The inlet can be equipped to sample
at pressures from above atmospheric to as low as 10
mbar. Not only is data acquired continuously (as
opposed to batch sampling employed by gas
chromatographs) but the response is fast. A change
in composition at the inlet can be detected in less than
1/2 second. The system allows data to be collected
quickly; a complete spectrum can be acquired in
under one minute and individual masses can be
measured at rates up to 25 ms per point. This
modern system allows many new applications where
the traditional mass spectrometer was too large and
heavy.
The QMS can be considered as two main
subsystems: gas handling and the analyzer. The
analyzer is the quadrupole mass spectrometer, which
can only operate in high vacuum. The class of
quadrupole mass spectrometer employed belongs to
a class referred to as residual gas analyzers (RGA).
These spectrometers specialize in large dynamic range
measurements of light gases. The gas handling system
consists of pump and valves that deliver the sample
gas to the analyzer. These components are controlled
from the front panel. Using the QMS does not require a detailed understanding of the quadrupole or the
principles of the pressure reducing inlet. This manual (User’s Manual) discusses the aspects of the
instrument that are relevant to someone who only operates and acquires data with the QMS. The
instrument contains a microcontroller that assures correct operation of the pumps and valves. The
software controls the spectrometer and provides many data acquisition modes, which should fulfill the
Figure 1-1. Front Panel View