Casella CEL Airborne bacteria sampler - Manual (Page 8)

2. Ensure that the turntable is at its lowest position by rotating control
A in Figure 2 fully anti clockwise and remove the sampling head by
releasing the two clips on either side.
3. Place the sampling media (petri dish containing agar) centrally on the
turntable and ensure that the zero, on the red degree scale around
the edge of the turntable, is aligned with the indicator.
If the scale is not aligned rotate the turntable clockwise until aligned.
4. Replace the sampling head with the air intake nozzle attached and
reclip in position on the sampler unit, ensuring that a good seal is
achieved between the cover and the rubber sealing ring.
5. Switch on the mains power to the unit by depressing switch B in
Figure 2.
6. Raise the turntable by turning control A clockwise until the light C
in Figure 1 begins to glow (do not rotate further).
At this point a conduction switch registers that the surface of the
agar is 2 mm below the slits, which will result in the most efficient
collection of airborne bacteria.
5.4 Selection of Turntable Rotation Speed
The speed of rotation of the turntable is dependant on which one of three
constant speed motors is selected to drive it, the motors not in use free
wheel automatically. Selection of the motors is made using the three way
switch D in Figure 2.
If the switch is set at its upper position, the turntable makes a full revolution
in half a minute, while at the intermediate and lower positions a full revolution
of the turntable is achieved every two or five minutes respectively. The
selection of the speed of rotation of the turntable is dependant on the
sampling requirements as discussed in Chapter 6.
5.5 Selection of Flow Rates
The pump incorporates a High/Low flow switch. The low position provides
flow rates up to 30 litres/minute and is generally not required for current
sampling methods. This switch should remain in the high position for current
bacteria sampler models.
The flow rate, or rate at which air is sampled by the instrument and passed
over the collection media, is a function of the number of slits open in the
Operation
Page 8 of 16
BACTERIA SAMPLER
User Manual