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Appendix A: Cali-
bration Frequency
Recommendation
Sensor Reliability and Accuracy
Today's sensors are designed to pro-
vide years of reliable service. How-
ever, there are a number of reasons a
sensor may unexpectedly lose addi-
tional sensitivity or even fail to re-
spond to gas. Such reasons include
desiccation, poisoning, physical re-
striction of airflow, over exposure,
internal leakage, or mechanical dam-
age due to physical shock and im-
mersion.
Verification of Accuracy
With so many reasons why a sensor
can lose sensitivity and given the fact
that dependable sensors are critical to
survival in a hazardous environment,
frequent verification of sensor perfor-
mance is paramount.
There is only one sure way to verify
that a sensor can respond to the gas
for which it is designed. That is to
expose it to a known concentration of
target gas and compare the reading
with the concentration of the gas to
ensure that it is within a manufactur-
er's recommended tolerable limits.
This is referred to as a "calibration
check" or "bump" test. This test is
very simple and takes only a few
seconds to accomplish. The safest
course of action is to do a calibra-
tion check or bump test prior to
each day's use*.
It is not necessary to perform a full
calibration (adjustment) unless read-
ings for LEL and toxic gases/vapors
are outside of the range of 90% to
120% of the expected value. For oxy-
gen, the acceptable range is consi-
dered to be ±0.5% vol., so 20.4% to
21.4% O2 in ambient clean air or via
application of zero air. Further for
oxygen, for application of Honeywell
Analytics 18.0% O2 balance gases,
the reading should again be within
±0.5% vol., so 17.5% to 18.5% O2.
* The Canadian Standards Associa-
tion (CSA) requires the LEL sensor
to be checked prior to each day's
use with calibration gas containing
between 25% and 50% LEL.
** The Canadian Standards Associ-
ation (CSA) requires the instrument
to undergo calibration when the
displayed LEL value during a bump
test fails to fall between 100% and
120% of the expected value for the
gas.
Lengthening the Intervals between
Verification of Accuracy
The IQ Force is shipped with a
default calibration interval of 30
days. The 30-day calibration inter-
val provides the IQ Management
software with multiple sensor sen-
sitivity data points required for
effective predictive maintenance
features. If you are not using the
predictive maintenance features in
IQ Management system, or do not
wish to calibrate your detector as
often, Honeywell Analytics re-
commends the detector be cali-
brated at least once every 180
days.
4
Honeywell Analytics recom-
mends a daily bump test to en-
sure that the instrument is in
proper working order.
One-Button Automatic Full
Calibration and calibration
Docks
While it is only necessary to do a
"bump" test to ensure that the
sensors are working properly, all
current Honeywell/Sperian and
Honeywell Analytics gas detec-
tors offer a one-button auto full
calibration feature. This feature
allows you to do a full calibration
of a gas detector in about the
same time as it takes to com-
plete a calibration check or bump
test.
The use of calibration docks can
further simplify the tasks, while
automatically maintaining
records of sensor performance.
Please read also the application
note: 13-366 "Use of 'equivalent'
calibration gas mixtures." This
application note provides proce-
dures to ensure safe calibration
of LEL sensors that are subject
to poisoning.
Honeywell Analytics' website is
at:
www.honeywellanalytics.com
A complete list of accessories
compatible with the IQ Force
gas detector can be found
there.
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