Teledyne 4020 – Hydrocarbon analyzer (special version for automatic background gas switching) - Manual (Page 25)

Total Hydrocarbon Analyzer Operational Theory
Teledyne Analytical Instruments 7
Operational Theory
2.1 Introduction
The Model 4020 Total Hydrocarbon Analyzer is composed of three
subsystems:
1. Sample System
2. Detector Cell
3. Electronic Signal Processing, Display and Control
2.2 Sample System
Note: The measured component for the Model 4020 is
hydrocarbon content. Hydrocarbon lubricants and
conditioners, as well as synthetic plastics are common to
instrumentation supply processes. Utmost precaution must
be taken at all times to specify hydrocarbon-free gases,
regulator diaphragms, and supplies.
All components used to control the sample and supporting gases, as
well as the combustion portion of the detector cell, are located inside the
enclosure, behind the electronics control panel and are accessible by
sliding the front of the unit out from the rack enclosure. Adjustments are
made using the appropriate control on the front panel.
The basic analyzer consists of an isothermal chamber containing the
pressure regulators, pressure gauges and flow restrictors. The
temperature within the chamber is maintained at 125°F by a heating
element. The regulated temperature of the chamber insures stable gas
flow. An optional AutoCal module is available which when fitted,
mounts inside the instrument enclosure and integrates with the sample
system. It allows convenient switching between sample and calibration
gases. When installed, it is part of the isothermal chamber. The bypass
flow is also controlled from this optional panel.
The software in the Model 4020 allows the system to be used for
analyzing a sample gas in two different backgrounds, O
2
and N
2
. A