39
C4 Manual Rev 7.5.2
than cold, or visa versa. To properly protect your object you need to be able to
constrain the air temperature in the chamber (and thus the surface temperature
of the object) such that the difference between surface temperature and the core
temperature does not exceed some difference the object can tolerate. It would be
useful to be able to specify such a differential tolerance for both the high and low
thermal limits of the object.
4.2 Preparing for Intelligent 2 Probe Control
The Sigma Systems C4 controller, using Intelligent 2 Probe Control, provides
temperature control based upon all of the factors discussed above. The process is
very simple. You will first need to set all the limits that the C4 will need. Then,
you use the normal commands or operations, in Local mode, Program mode, or
Remote mode, to go to temperatures, ramp to temperatures, hold temperatures,
etc.
The limits for the UUT temperature extremes are set in Setup parameter fields
F27 (lower limit) and F28 (upper limit). These values can be set in Setup mode as
described in Section 8, or by using the SL (Set UUT Temperature Limits)
command from Remote mode as described in Section 7.6.4.
The UUT temperature differential limits are set in Setup parameter fields F29
(lower differential limit) and F30 (upper differential limit). These values can be
set in Setup mode as described in Section 8, or by using the SD (Set UUT
Temperature Differential Limits) command from Remote mode as described in
Section 7.6.5.
Note that the low limit you set is the allowable differential between the air stream
temperature (platform surface temperature) as measured by probe 1 and the UUT
core temperature as measured by probe 2 at the UUT low temperature limit as
described by Setup parameter F27. Likewise, the high limit you set is the
allowable differential between the air stream temperature (platform surface
temperature) as measured by probe 1 and the UUT core temperature as measured
by probe 2 at the UUT high temperature limit as described by Setup parameter
F28. For example:
If the lower UUT limit (F27) is set to -100/ and the the lower differential
limit (F29) is set to 60/, and the setpoint is set to -80/ while the UUT is
considerably warmer than that, then the controller will try to take the
temperature of the chamber down below the setpoint (max -100/) to speed
the down ramp. However, because the differential limit is 60/, the
controller will be constrained to keep the amount of thermal lead (difference
between probe 1 in the air stream and probe 2 in the UUT core), to 60/. The