What is the meaning of 'redundancy' in DDC systems and why is it used?

• A. Using a larger sensor to capture more range.
• B. Duplicate sensors/controllers/communication paths to improve reliability and availability.
• C. Running loops faster to reduce waiting times.
• D. Deleting old data to free up space.

Answer: (B)

Redundancy in DDC systems means duplicating critical components and pathways so the system can keep operating even if one part fails. Think of having a second sensor measuring the same process variable, a backup controller ready to take over in case the primary controller goes down, and an extra communication path so data can still move if a link breaks. This setup boosts reliability and availability, reduces downtime, and helps protect safety-critical operations because there’s no single point that, if it fails, brings the whole system to a halt. The other ideas—using a larger sensor, running loops faster, or deleting old data—don’t provide that protective fallback. A bigger sensor doesn’t fix a failed measurement, faster loops don’t help if the hardware or network fail, and deleting data is about storage management rather than keeping the process under control.