9
8
5.2.4 Effect of Electromagnetic Radiation
Tested over a 26 MHz to 1000 MHz electromagnetic field, the analyzer is sus-
ceptible at all frequencies tested except those between 930 and 990 MHz.
Never operate the analyzer near equipment capable of emitting high levels of
electromagnetic radiation. Do not continue to operate the analyzer if the read-
ing becomes unstable.
5.3 Sampling Procedure
1. Assure that the analyzer is calibrated, giving a stable reading, and is in
sampling mode. Note: Sampling mode is the default screen. Nothing
needs to be done to get to this screen, assuming you are out of all menus
and modes.
2. Open the gas tank until you hear a slight ’hissing noise’
3. Hold the hole at the bottom of the black dome adaptor firmly against the
tank’s gas outlet.
4. Ensure there is a good connection between the dome adaptor and the gas
tank to prevent ambient air from leaking into the gas being measured.
5. Once the sensor is exposed to the gas stream, allow the reading to stabi-
lize as displayed by the LCD.
6 Maintenance
6.1 Cleaning Instructions
Clean the device only when needed. The carbon monoxide sensor and acces-
sories can be cleaned with a soft cloth dampened with either water or mild
isopropyl alcohol solution (70% isopropyl alcohol solution in water). Allow the
components to air-dry after cleaning.
6.2 Battery Replacement
The Palm CO Carbon Monoxide Analyzer is powered by two
1.5V AA alkaline batteries with an approximate life of 450
hours.
The LDC displays a low battery indicator ‘bA’ when the
battery falls below the necessary voltage for reliable opera-
tion of the analyzer, FIG 1. The batteries are located in
the top section or front of the analyzer and secured by
terminals mounted directly on the PCB assembly. FIG 1
5 Operation
5.1 Principle of Operation
The device utilizes an electrochemical carbon monoxide sensor intended to
measure carbon monoxide levels in gas streams. Carbon monoxide, diffusing
into the sensor through a gas permeable barrier, reacts chemically at the sens-
ing electrode to produce an electrical current output proportional to the carbon
monoxide concentration in the gas phase.
A battery powered state-of-the-art micro-processor converts the sensor’s signal
output, which represents the partial pressure of carbon monoxide in the gas
stream being analyzed. The resulting carbon monoxide reading is displayed by
an easy to read screen that has a resolution of 1 PPM carbon monoxide.
5.2 Application Considerations
5.2.1 Effect of Temperature
At constant temperature, the sensor’s electrical current signal varies linearly
with carbon monoxide concentration. Over the temperature range of 0-40⁰C,
the output varies approximately ±10% from its value at 20⁰C. For this reason,
it is highly recommended that the analyzer be calibrated at a temperature close
to that of the environment in which it is intended to be used.
5.2.2 Effect of Pressure
The electrochemical sensor measures the partial pressure of carbon monoxide
in a gas stream to which it is exposed. The sensor is accurate at any pressure
within the rated range of 80-120 kPa, provided the ambient pressure is con-
stant during sampling and calibration.
5.2.3 Effect of Humidity
Changes in humidity will produce transients in sensor output that last for about
ten minutes. Therefore, it is recommended that at least ten minutes be pro-
vided before taking measurements after a sudden humidity change, which may
occur if the analyzer is removed from a sealed bag of different humidity than
the ambient environment or a dramatic change in the weather. It is not neces-
sary that the analyzer be powered on during this period.
