OperatIOn
The FB-08C calibration Fluidised Bath is capable of precise performance, but for reliable and consistent
results it must be used by personnel conversant with its operation.
For temperature stability the heat input to the bath must exactly equal heat losses; the heat input from
the immersed heaters is varied by the controller which has a characteristic time constant for its response
to a change in demand. The heat losses from the bath are due to:
heating fluidising air
1.
radiation from the top of the bath
2.
conduction through the insulation
3.
conduction along loads inserted into the bath
4.
heating the mass of cold objects placed in the bath.
5.
Changing any of these will affect the temperature of the bath, but it will
recover under the controller's influence; this does mean, however, that after any
parameter is changed or the load in the bath is changed, there is a delay before the
bath temperature re-stabilises.
start-up
1 Check the fluidised bath has been set up as described earlier and that it isconnected to the correct
electrical and compressed air supplies.
2 Ensure that the extraction air switch is in the ON position.
3 Turn on the mains power switch, the bath will fluidise and the extraction system will operate, illuminating
the green lamp. The temperature controller will be illuminated and will indicate the actual temperature
of the bath.
4 Check that the surface of the alumina when fluidised is just above the top of the 'hair pin' bend in the
heater assembly. Also check that the alumina is correctly fluidised, the surface of the alumina should
be flowing with the motion like violently boiling cream. Any fine alumina particles emitted from the
surface of the bath should be entrained by the extraction system when the probe plate is positioned
above the bath.
5 Remove the controller from its sleeve and make the link as shown in the 818P manual to modify the
parameters. Replace the controller in its sleeve.
Set the values as follows:
Press and hold this key:
Pr1-9
PL1-9
Pd1-9
HB off
PLC 1
SP1 4.8
SP2 25.0
St Disabled
At Disabled
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