Sigma manual C4 vs. CC-3 Differences What’s New

1.5 C4 vs. CC-3 Differences (What’s New)

1.5.1 Hardware & Stability Improvements

The new C4 introduces a number of new improvements to make the controller faster and more reliable than its predecessor.

The C4 has a completely new digital processing board. The new board has a much faster processor, more memory, and a much faster IEEE-488 GPIB controller. Interrupts have been completely restructured to improve stability. The multilayer design is far more tolerant of both static and power line interference. There is now a watchdog timer to detect system lockups in the event that something does interfere with the system. The battery backed RAM has been replaced by an EEPROM. The Vactrol type isolation device in the failsafe circuit has been replaced. The C4 contains no components that have a time based failure mode.

The new firmware also monitors the state and integrity of internal memory. Critical system information is stored in multiple places so that minor errors due to uncontrollable transients or other causes can be repaired on the fly with no disruption in process control. Likewise, both the front panel display and the GPIB interface are monitored constantly to assure that their operation has not been compromised by static discharge or line transient. In the event of a problem, either device can be reset on the fly to allow operations to continue normally.

System integrity is further enhanced by a series of successive shutdown processes that monitor the integrity of the data coming from the sensor probes. In the event that any probe reports a temperature more than 20/C beyond the limits set in the controller, the controller will shut down all heating and cooling and display a warning message. Likewise, in the event that a sensor probe reports an extreme temperature, either hot or cold, the system will assume that a probe has become compromised by an open or shorted circuit and stop applying heat and cooling, shut down the system and display an appropriate warning message..

1.5.2 Hardware Change (EEPROM replaces BBSRAM)

All C4 controllers and CC-3.5controllers converted after January 1998 have the battery backed static RAM (BBSRAM) replaced with an EEPROM. This change was implemented to reduce the possibility that the controller will require service. Although changing the BBSRAM when the battery died (about every 5-12 years) was a fairly simple matter, the necessity for doing so was found to be a nuisance as was diagnosing the need for the change. The BBSRAM or EEPROM provides the non volatile memory where the C4 stores both the setup parameter information and the user programs.

12 C4 Manual Rev 7.5.2