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Note: After resetting, the ramp begins from a temperature of 0°C. There will be a
considerable delay before the ramp reaches the temperature of the sample and current
starts to flow in the windings of the furnace to keep the furnace temperature at the level of
the ramp. The RESET switch sets the ramp back to 0°C.
Select DOWN to reduce the temperature at the same (or some new) rate. At any time the current
temperature can be HELD but, if this facility is to be used, a low ramp rate should be selected to
minimise the effects of sample thermal time lag.
There are no restrictions on the way in which the controller is used, other than to avoid pre-
setting a cold furnace to a high temperature, and thereby subjecting it to high in-rush current
and thermal shock. If rapid heating is required, observe the ammeter and keep the current below
4A.
Note: Fluctuations in line supply voltage can cause loss of temperature regulation at high
temperatures and a conditioning transformer may be required.
Under equilibration conditions, thermal gradients for a sample correctly positioned within
the sample cavity will be circa 2-3
o
C anywhere within the sample. However, when subjected
to varying temperature, the centre of the sample will thermally lag behind the surface of the
sample. This thermal gradient can be calculated from the empirical formula:
G = R/1.6
where G = thermal gradient in
o
C/7mm
R = ramp rate in
o
C/minute
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