EAGLE 2 Operator’s Manual
Measuring Mode, Normal Operation • 37
Monitoring Combustible Gas in the PPM Range
There are special considerations that must be taken into account when monitoring
combustible gas in the ppm range with the catalytic combustible channel. Because of the
high sensitivity in the lower part of the ppm range, the catalytic combustible channel
needs more time than the warm-up period to stabilize after the EAGLE 2 is turned on if it
is going to be used for ppm level detection. The reading increments in the ppm range are
smallest in the lower part of the range and increase as the reading increases as follows:
•
5 ppm increments from 0 ppm to 200 ppm
•
10 ppm increments from 200 ppm to 1,000 ppm
•
50 ppm increments from 1,000 ppm to 10,000 ppm
•
250 ppm increments from 10,000 ppm to 50,000 ppm
If the catalytic combustible channel is configured for the user defined gas in Setup Mode
(see “Configuring the Combustible Gas” on page 101), the ppm ratio defined for the gas
must be considered. For example, if the ppm ratio is set higher than 50,000 ppm, then
when the display units are set as ppm, the reading will not go above 50,000 ppm which is
equivalent to 33 % LEL and 5 %volume. So if the gas reading is higher than 50,000 ppm,
the ppm unit reading will indicate 50,000 ppm and also indicate an overscale condition.
The %LEL and %volume unit readings will still increase up to 100% LEL and 15
%volume respectively, which are equivalent to 150,000 ppm.
The catalytic combustible sensor is slightly affected by humidity. This is not apparent
when the EAGLE 2 is used for %LEL or %volume detection, but because of the high
sensitivity in the ppm range, significant humidity changes can affect the ppm reading,
especially in the lower part of the range. Take care to allow the unit to acclimate to a new
environment for about a minute and perform a demand zero in a fresh air location when
you move between areas of different humidity.
CAUTION:
If the catalytic combustible channel is being calibrated with a gas
concentration of 1000 ppm or lower, the a 24 inch humidifier must be used
for accurate calibration. See “Chapter 4: Calibration Mode” on page 54
for more explanation and instructions for calibration.
To monitor for combustible gas in the ppm range:
1. Start up the EAGLE 2 as described in “Start Up” on page 27.
2. Allow the EAGLE 2 to run for 3 - 5 minutes after the startup sequence is complete
and it is in Measuring Mode. This allows the catalytic combustible sensor to stabilize
sufficiently for ppm monitoring.
NOTE:
This extra stabilization period is not necessary if monitoring in the %LEL or
%volume range.
3. Set the catalytic combustible channel’s units to be ppm by using the RANGE
▼
SHIFT button.
4. Perform a demand zero as described in “Performing a Demand Zero” on page 31.
5. Proceed to monitor for gas as described in “Monitoring an Area” on page 33.
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