GasClam 2 Instrument User Manual
Ion Science Ltd.
Unrivalled Gas Detect
ion.
ionscience.com
26
Note:
Specifications obtained under laboratory conditions of gas flow, temperature and humidity. Field performance is
dependent on the correct installation procedures being followed, environmental conditions, frequent sensor cleaning and
regular calibration. Some of the sensors have cross sensitivity, for more information contact your local supplier. Details are
subject to change without notice.
Cross sensitivities and Sensor Performance:
100% Carbon Dioxide (CO
2
)
Carbon Dioxide is measured using an infrared sensor tuned to C=O. There are no other gasses commonly found in
the subsurface that absorb infrared radiation at this wavelength, so the reading will not typically suffer from cross
sensitivity.
5% Carbon Dioxide (CO
2
)
When sampling concentrations up to 5% the sensor will read 90% of the real value after one sample (typically this
will be within error of the sensor). For example, if you are sampling every hour and the real concentration changes
from 0%
–
2.5% in 1 hour (which is unlikely) the senor will read approximately 2.25%. In reality if low concentrations
are present they will change much more gradually i.e.:
•
Sample 1
Real concentration 0.0
Measured 0.000
•
Sample 2
Real concentration 0.1
Measured 0.090 (within error)
•
Sample 3
Real concentration 0.3
Measured 0.279 (within error)
•
Sample 4
Real concentration 0.8
Measured 0.750 (within error)
When concentration decreases the reading will also be 90% of the real value after 1 sample. Below are examples
when 4.7% CO
2
has been sampled and how the sensor/filter clears down in air.
•
Sample 1
4.701
4.738
4.671
•
Sample 2
0.326
0.29
0.468
•
Sample 3
0.071
0.037
0.042
Methane (CH
4
)
Methane is measured using an infrared detector tuned to C-H bonds. The sensor is calibrated using certified
methane calibration gas and will give accurate readings providing no other C-H compounds are present. If
additional hydrocarbons are present they will contribute to the reading.
Oxygen (O
2
)
The oxygen sensor is a Galvanic sensor and very specific. It has a little cross sensitivity with CO
2
, 5 % CO
2
only
causes a 0.1% change in reading. Humidity has a small effect on output, between 0 % to 95% RH the % O
2
change
is < 0.7 %. The sensor can work between 5 - 95 % RH continuously and 0 - 99% short term.
Single Carbon Monoxide (CO)
The Single CO sensor has a filter to reduce the cross sensitivity with H
2
S, NO
2
, NO and SO
2
, the following are the
filter capacities for the given gases:
•
H
2
S
250,000 ppm - hours
•
NO
2
600,000 ppm - hours
•
NO
20,000 ppm - hours
•
SO
2
300,000 ppm - hours
50 ppm NO will read < 5 ppm
