Teledyne Mixchek - Helium / Oxygen mixture analyzer - Manual (Page 11)

MIXCHEK Introduction
Teledyne Analytical Instruments 11
Introduction
The Teledyne
MIXCHEK is a dedicated instrument designed to
accurately monitor the composition of a gas during mixing or cylinder
filling operations. A LCD mounted on the front panel of the instrument
displays the percentage of helium and oxygen during the mixing
operation.
There are two basic configurations available both of which offer
oxygen analysis as an option. The wall-mountable unit is housed in an
enclosure equipped with a window for viewing the helium and oxygen
displays. It is powered by a plug-in 6V DC adapter which uses a
conventional 120VAC source (100-240 VAC 50/60 Hz optional).
The portable instrument is housed in a rugged high-impact plastic
watertight enclosure. It has a molded-in handle for easily transporting the
instrument to the mixing or process area. Both models, the standard wall-
mount and the portable instrument, use corrosive-resistant materials where
applicable for enhanced durability in salt air or spray environments. The
wall-mount model is shown in Figure 1-1 and the portable instrument is
shown in Figure 1-2.
NOTE: If your unit is equipped with a Helium only analysis please ignore all
references to the oxygen sections of this manual.
1.1 Overview
The
MIXCHEK analyzes the helium/oxygen concentrations in a gas
mixture using a dedicated two-channel sensor network sharing a common
sample system. The gas to be monitored is drawn into the analyzer and
passed to the sensor network. A high output micro-fuel cell oxygen sensor is
used to determine the oxygen concentration of the gas mixture. The output of
the micro-fuel cell is fed to the display and read out as percent oxygen.
The sample gas is then directed to a thermal conductivity sensor. This
sensor provides a signal that is proportional to the difference in conductivities
between the components of the gas mixture. A microprocessor compares the
sensor output to data contained in an onboard chip and converts the raw data
into a linearized signal that is sent to the helium LCD display.