Chapter 2 – Using Cascade Control
TestEquity F4T Controller Page 9
Part Control vs. Air Temperature Control
The control mode can be easily changed from
Part Temperature Control or Air Control by
pressing the Air Control button. The default
condition is shown below, with the controller
operating in Part Temperature Control mode (no
green check mark in the Air Control box). Air
Control will always be OFF any time the power is
recycled.
Part Control Mode
When configured for Part Control (Air Control button has no green check mark), the F4T will
attempt to control the temperature at the Part Sensor. In this mode, the Part Sensor must always
be attached to your test sample. Failure to do this will result in erratic temperature control.
The Air Sensor screen will always indicate chamber’s Air Temperature. This will usually be
different from the Part Temperature, especially during temperature transitions. The Air
Temperature will tend to approach the Part Temperature as the part begins to stabilize. The two
temperatures may never be the same, especially with a heavy test sample or an energized test
sample.
The F4T is configured at the factory to allow the Air Temperature to deviate no more than +15°C
or –15°C from the Part Temperature set point. This means if the set point is 85°C, the Air
Temperature could go as high as 100°C if the Part Temperature lagged sufficiently during a heat
up condition, or as low as –55°C if the set point is –40°C.
Part Control Mode During a Profile
Part Control mode has an impact on these profile parameters:
Guaranteed Soak Deviation/Guaranteed Soak Values: The amount by which the actual part
temperature is allowed to differ from the set point for steps with Guaranteed Soak Enable set to
On. In such steps when the actual part temperature differs from the set point by more than this
value, the step timer stops running until the actual part temperature returns to within the band
defined by the set point plus or minus this value. Each profile can have its own set of Guaranteed
Soak values.
Wait For Process: Holds the profile until the part temperature reaches the specified value.
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