Sigma C4 manual Preparing for Intelligent 2 Probe Control

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

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