iWorX GA-200A Manual

Overview
The GA-200A is an analyzer that integrates a gas
sampling system with sensors to measure and display
the concentrations of oxygen and carbon dioxide in a
sample as the percentage of a gas in the sample by
volume. This method of expressing the concentration of
a gas in a sample is also known as the percent volume
fraction. In addition to the sampling and sensing systems
in the GA-200A, the unit has a fluorescent display used
for programming the unit and observing measurements,
a keypad for programming the unit's operation and
calibration, and analog outputs that allow the unit to be
connected to data recording units like the iWorx 214.
When measuring the concentrations of oxygen and
carbon dioxide in a gas, a sample is pumped from the
input port on the front panel of the GA-200A, through the
sample cell, and out an exhaust port on the back panel
of the unit. Gas samples are drawn into the unit through
an external filter on the input port that protects the
sensors from contamination and through Nafion tubing
on the filter that removes moisture from the samples that
would affect the measurements and the units calibration.
Figure GA-200A-1: The front panel of the GA-200A gas analyzer with filter.
Front Panel: Keypad and Display
The front panel of the GA-200A has a keypad, a
display used to program the modes and parameters of
the unit, and an inlet port for the gas sample (Figure GA-
200A-1 on page GA-200A-1). The main operational
modes of the unit are selected by pressing one of the
following keys: RUN, TEST, CAL 1, CAL 2, FLOW, or
ALARM. After a key is pressed, the settings for that
function will appear in the display window.
GA-200A Carbon Dioxide and Oxygen Gas Analyzer
The oxygen concentration of the gas in the sample cell
is measured using laser diode absorption technology.
The laser diode in the oxygen sensor produces light at a
wavelength (760 nanometers) that is absorbed by
oxygen. The light passes through the gas pumped into
the sample cell and onto the surface of a detector. The
output of the sensor is inversely proportional to the
concentration of oxygen in the sample because the
amount of light reaching the detector decreases as the
concentration of oxygen in the sample increases. The
GA-200A has a very fast response time that enables
breath to breath analysis of gas concentrations because
the unit analyzes the gas sample every 10 milliseconds,
or 100 times per second. During each measurement
interval, the analyzer is zeroed automatically by
electronic tuning of the laser to a wavelength not
absorbed by oxygen.
If the SETUP key is pressed, the user enters a
succession of windows that allow the operations and
measurement parameters of the unit to be programmed.
Pressing the UP or DOWN key will change the mode or
value of the parameter. Pressing the ENTER key stores
the setting or selected value, and pressing the RUN key
exits the Setup menu.
GA-200A-1