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2.2 Calibration Notes :-
1.
When using a standard Fume Cupboard with Vertical Sliding sashes open the sash
to the normal max safe working height for the Low Air sample.
2.
For the Higher Air sample close the sash to approx 50% of the opening used for the
Lower Air sample. If the Higher air sample value is too close to the Lower Air sample
the alarm will detect this and ask you to repeat with a higher value.( The min
difference between the Low & High air samples is set to 0.3 m/sec )To do this close
the sash a little more and repeat the sample. Avoid closing the sash below 150mm.
3.
The face velocity readings on the open sash may vary at different points on the
measuring grid by up to 0.1m/sec. This is quite acceptable in terms of the fume
cupboard performance so long as no individual point is below the designated Low Air
alarm point .The figure entered for the calibration point can be taken as the average
value of all the measuring grid readings or could be taken as the individual lowest
point on the grid. For most fume cupboards this low point is on the bottom row in the
centre and is a convenient position to measure and for future reference when
checking the alarm during annual maintenance.
4.
Take time when measuring the face velocities for the calibration procedure to allow
for the velocities across the open sash to stabilise. If the velocities are changing or
are turbulent during the sampling period the alarm will detect this and ask you to
repeat the sample.
5.
When using a Fume Cupboard with Horizontal Sliding sashes open the sashes to the
normal max safe working opening for the Low Air sample.
6.
When calibrating or re-calibrating the alarm it is important to ensure that the ‘Vent kit’
is connected to the SM6 sensor on the fume cupboard. If the vent kit is not connected
the sensor will not ‘see’ a change in the airflow during the calibration procedure and
will show “Sensor Difference too low - Check sensor”.
This only applies during the
calibration mode. If in normal running after successful calibration the vent kit
becomes disconnected the air flow across the sensor will fall and the alarm will go
into the AIR FAIL condition.
