Thread: Manual/Auto
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Old July 27th, 2002, 11:05 AM   #8
Kim Gold

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Join Date: Jun 2002
Location: Stoney Creek, Ontario
Posts: 241
I thought Terry's explanation was excellent.

Depending on your application you can even have a number of automatic modes.
We have an application (Stove control on a Blast Furnace) where we have the following modes:
AUTO MODE (no operator intervention)
SEMI-AUTO (minimal operator intervention) - Operator can select To Gas or To Bottle or To Blast
SINGLE STEP - manual operation, but through PLC
LOCAL MODE - fully manual, no PLC involved

You need to have logic in place to take care of switching between modes, but when switching to Local Mode, PLC is isolated and the only logic will be hard wired logic.

Most operators are happiest on Auto Mode. Each successive step down means a little more work for him, Local mode being the most work. He is even required to leave the control room and walk to each piece of equipment to operate it.
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