OdaLog
®
Gas Logger User Manual
P/N: 10-1000
Revision: F, Issued: October 2019
Page: 29
After running in fresh air for around 48 hours, the sensor should recover and again read close to correct level
when exposed to calibration mixture, however, if it is not reading accurately it should be re-calibrated prior to
the next “logging session”.
When the instrument and sensor has been subject to a high humidity environment, the sensor recovery time can
be reduced by the use of an Thermo Fisher Scientific sensor conditioning kit (part no: 25-0390), which will
quickly absorb the moisture trapped in the sensor, so it can return to reading gas levels accurately.
9.8.3 Decay Compensation
This graph option allows a constant sensor decay rate to be applied to all gas readings in that session. By
recording the ‘pre-use’ and ‘post-use’ span check results (See Section 9.8.1 & 9.8.2), you can apply this
information to offset any decay in sensor response during the logging period. For example, an OdaLog
®
calibrated before a logging period to 50ppm H2S, may read 30 ppm when exposed to the same calibration gas at
the end of a logging period.
N.B. The above decay compensation assumes gas exposure to the sensor has occurred in a uniform way rather
than in large bursts. Accordingly, we have used a “straight line” equation as follows:
o
Applying Sensor Decay:
If selected, this allows a constant decay rate to be applied to all gas readings in that session.
The application takes the difference between the ‘Start’ (pre-use span check) and ‘End’ Levels
and divides this by the number of readings that were taken. This value is then cumulatively
adjusted to all gas readings to compensate for any decay in sensor response.
o
Start Level:
‘Pre-use’ Span Check result (preferred value) when applying test gas prior to deployment in
field (See Section 9.8.1). If this value was not recorded, use the Span level that was set during
calibration (cal gas value – as set in the
OdaStat-G™
software).
o
End Level:
‘Post-Use’ Span Check result that was recorded once logging had finished (See Section 9.8.2).
Tip:
Selecting ‘Suppress Negatives’ (See Section 6.14) when applying decay compensation will prevent
a false exaggeration of negative readings.
NOTE
Sensor Decay Compensation will automatically update logged data when entered into
the OdaLog software. This feature requires pre/post data values to be recorded.
