For maintenance and commissioning, how does a programmable controller compare with standard relay logic in terms of machine checkout and troubleshooting?

Introduction / Context:
Commissioning speed and troubleshooting clarity directly affect downtime and productivity. This question compares programmable controllers with traditional relay logic regarding diagnostic features and ease of verifying correct operation during machine checkout and later maintenance.

Given Data / Assumptions:

• Relay logic uses discrete relays, timers, and wiring.
• PLCs offer software logic, status bits, and online monitoring tools.
• The focus is on practical commissioning and service scenarios.

Concept / Approach:

PLCs centralize logic with clear rung or block views, force functions, watch tables, and alarm diagnostics. This enables rapid I O verification and sequence testing. Relay panels require physical tracing of wires and components, which is slower and more error prone. Therefore PLCs shorten checkout and simplify troubleshooting compared with standard relay logic.

Step-by-Step Solution:

Verification / Alternative check:

Maintenance case studies show reduced mean time to repair when teams use PLC software tools over manual relay tracing.

Why Other Options Are Wrong:

Option d is not appropriate because 'all of the above' would redundantly include option c itself. Option e is incorrect since both a and b are valid advantages.

Common Pitfalls:

Ignoring documentation quality and safety lockout procedures, which are still necessary regardless of controller choice.

Final Answer:

Both (a) and (b)