Description Of The Operating Principle - Sony Multiscan CPD-1304S Service Manual

Measurement concept of GasLab Q2

3.2 Description of the operating principle

The operating principle is based on the context of the gas quality characteristics heating value,
density at base conditions (rho) and carbon dioxide content with various physical quantities of the
gas. Simpler detectable gas parameters are measured instead of the required target gas
parameters. These gas parameters are consistent with the target gas parameters in a physical
context.
The following parameters were selected for this process:

infrared (IR) transmission of CH-gas

Infrared (IR) transmission of CO2 gas

Heat conductivity of the complete gas

Pressure and temperature of the gas
To measure these parameters, the measuring unit includes an infrared sensor to measure the
absorption of the hydrocarbons and carbon dioxide contained in the natural gas. In addition, a
further sensor detects the heat conductivity of the full mixture of the natural gas. With the
additional information from the heat conductivity detector infrared inactive components, like
Nitrogen, can be determined. By dividing the gas flow into two channels, these two sensors are
measuring the gas in parallel.
Furthermore, the pressure and temperature are measured. The target values are determined
using a special calculation. Even the Wobbe index can be calculated from target values. The
physical background for the successful description of the gas properties by only three parameters
is in the typical composition of natural gas.
All three measurements are subjected to a correlative evaluation and provide as a result of the
heating value, the density at base conditions and the CO2 content of natural gas. These sizes
are required to determine the other properties of the natural gas. The figure shows the operating
principle in a schematic overview (without pressure and temperature).
The infrared measuring method is based on the fact that gas molecules oscillate in the irradiation
of natural gas with white light; this light is weakened at certain wave-lengths in the infrared spectral
range.
Each IR-active oscillating connection in the molecules makes a contribution to the absorption of
light. The different connections cause different absorptions in specific spectral ranges to the
absorption spectrum. The kind of absorption and its spectral distribution gives a view of the
composition of the gas. See figure 3.2.
GasLab Q2
Figure 3.1: Operating principle
G a s Q u a l i t y A n a l y z e r
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