What Is PreTravel (PT)? : OMRON Knowledge Base

Refer to the following table of terms for operating characteristics.

Operating Status

Feature	Term	Abbreviation	Unit	Definition
Force	Operating Force	OF	N, Nm	The force needed to be applied to the Actuator to move from the free position to the operating position.
	Direct Opening Force	DOF (See note 2.)	N, Nm	The force needed to be applied to the Actuator to move from the operating position to the direct opening position.
	Total Travel Force	TTF	N, Nm	The force needed to be applied to the Actuator to move from the free position to the total travel position.
Travel	Pretravel	PT	mm, °	The travel distance or angle from the free position to the travel position of the Actuator.
	Direct Opening Travel	DOT (See note 2.)	mm, °	The travel distance or angle from the free position to the direct opening position of the Actuator.
	Total Travel	TT	mm, °	The travel distance or angle of the Actuator from the free position to the total travel position.
Position	Free Position	FP	mm, °	The Actuator position when no external force is applied.
	Operating Position	OP (See note 1.)	mm, °	The position where the moving contact starts to open or close when an external force is applied to the Actuator.
	Direct Opening Position	DOP (See note 2.)	mm, °	The Actuator position when the moving contacts are directly open when an external force is applied to the Actuator.
	Total Travel Position	TTP	mm, °	The Actuator position when the Actuator has reached the stopper.

Note 1:
For slow-operating safety switches, the operating position (OP) and return position (RP) are almost identical.

Note 2:
The DOF, DOT, and DOP values were specified to ensure that the direct opening mechanism (forcibly opened contacts) functions correctly.