OLIVER
IGD
The Sensor ONE MAN CALIBRATION Function
This function allows one person to calibrate a sequence of detectors by selecting the function then
applying gas to each detector in turn for 3 minutes. The Tocsin 920 monitors the signal from the
detectors and performs the calibration automatically once it sees a valid steady reading. This is
similar in operation to the walk test function on a smoke detection panel.
Selecting the function will display the set up screen as follows:
Calibration Gas
Bottle Value (as
marked on the gas
bottle to be used)
The min and max
concentration allows
some control over
what is calibrated. The
settling time period is
triggered once the gas
value is within the min
and max limits. The
settle % setting then
determines the
bandwidth the sensor
must be within during
the settle time to allow
calibration. If all
criteria are met then
the sensor will
calibrate automatically
Sensor channels to include in
this calibration session.
Commence
calibration
sequence
The following graphs indicate how the system operates. The max and min concentration settings
determine when the auto calibration routine is triggered. If the settings are left wide then sensors
with bigger calibration errors will be included. Such settings also mean that calibration may take
longer as the system looks at the average reading after the settling time and applies the % settle
setting to determine if the reading is stable enough to allow calibration. If the parameter is not met
then the rolling average continues until either the criteria is met or calibration gas is removed.
Settings should therefore be carefully chosen.
Typically it is advisable to set the min-max setting to be your chosen calibration accuracy for the
system. For instance if you require that the system stays /-5% of range over a 12 month
period between calibrations then for a detector range of say 100 and calibration bottle of 50 set the
min-max to 45 to 55. Detectors that respond outside of this range will not be calibrated but this can
be checked using the sensor check function after using the one man calibration feature. These
detectors can then be interrogated separately to see why calibration has not been maintained and
either replaced, re-calibrated or a more appropriate calibration period chosen.
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