In a PLC system, which timer type preserves its counting value after a power interruption?

In a PLC system, which timer type preserves its counting value after a power interruption?

• A. Retentive timer
• B. Elapsed timer
• C. Pulse timer
• D. On-delay timer

Answer: (A)

Timers can be retentive, meaning they save the accumulated time in memory and keep that value even if power is lost. A retentive timer preserves its counting value across a power interruption, so after power returns it can continue from where it left off. This is why it’s the correct choice for maintaining total elapsed time through outages. The other timer types don’t keep their accumulated time after a power loss: they reset or start fresh once power or input conditions change.

Timers can be retentive, meaning they save the accumulated time in memory and keep that value even if power is lost. A retentive timer preserves its counting value across a power interruption, so after power returns it can continue from where it left off. This is why it’s the correct choice for maintaining total elapsed time through outages. The other timer types don’t keep their accumulated time after a power loss: they reset or start fresh once power or input conditions change.