Table of Contents
Technical Terminology & Cautions for Use
OPERATING CHARACTERISTIC
■ Definition of operating characteristic
The main terminological illustrations and
meanings which are used with snap-
action switches are as follows.
OF
PT
TF
FP
OT
OP
TTP
Center of mounting holes
TECHNICAL NOTES ON MECHANICAL CHARACTERISTICS
■ Actuation Force and Stroke
Adequate stroke setting is the key to high reliability. It is also
important that adequate contact force be 'maintained to ensure
high reliability. For a normally closed (NC) circuit, the driving
mechanism should be set so that the actuator is normally in the
free position. For a normally open (NO) circuit, the actuator
should be pressed to 70% to 100% of the specified stroke to
absorb possible errors.
If the stroke is set too close to the operating point (OP), this may
cause unstable contact, and in the worst case may cause
actuator damage due to inertia of the drive mechanism. It is
advisable that the stroke be adjusted with the mounting plate or
driving mechanism.
The figure at right
shows a typical
example of activation
and contact forces
varying with stroke.
In the vicinity of the
OP and RP, the
contact force is
diminished, causing
chatter and contact
On FP
bounce immediately
On reversal
before or after
On reversal
reversal. For this
On OTP
reason, use the
switch while giving
due consideration to
this. This also causes
the snap action
switch to be sensitive
to vibration or shock.
Classification Terminology
RF
Force
TT
MD
RP
Movement
Position
OF
RF
FP
RP
OP
TTP
MD
PT
OT
NC
NO
Varying
Symbol
Unit
display
method
Operating
OF
N
Max.
Force
Release
RF
N
Min.
Force
Totaltravel
TF
N
Force
mm,
Pretravel
PT
Max.
degree
mm,
Overtravel
OT
Min.
degree
Movement
mm,
MD
Max.
Differential
degree
mm,
Totaltravel
TT
degree
Free
mm,
FP
Position
degree
Operating
mm,
OP
Position
degree
Release
mm,
RP
Position
degree
Total travel
mm,
TTP
Position
degree
■ Changes in Operating Characteristics
Exercise design care so that malfunctions will not occur if the
operating characteristics vary by as much as 20% from, rated
values.
In the OF max. 0.98N specification for FS snap-action switches,
the allowable max. is 0.98 N × (100%+20%) = 1.18 N
In the RF min. 0.15 N min. specification
the allowable min. 0.15 N × (100%–20%) = 0.12 N
■ Mechanical Conditions for Type Selection
Actuator type should be selected according to activation
method, activation speed, activation rate, and activation
frequency.
1) An extremely slow activation speed may cause unstable
contact transfer, possibly resulting in contact failures or contact
fusion.
2) An extremely high activation speed may cause damage to
contacts or contact response failure.
Stroke
■ Driving Mechanism
Use of a driving mechanism which will cause physical impact to
the actuator should be avoided.
Stroke
ー 7 ー
Starting current
The force required to cause contact snap-action. It
is expressed terms of force applied to the the
actuator.
The force to be applied to the the actuator at the
moment contact snaps back from operated
position to total travel position.
Force applied to an actuator required to move from
an operating position to a total travel position
Distance or agree of the actuator movement from
free position to operating position.
The distance or degree which the actuator is
permitted to travel after actuation without any
damage to the switching mechanism.
The distance or degree from operating position to
release position of the actuator.
The migration length or the move angle from the
free position to total travel position of actuator
Position of the actuator when no force is applied
to.
The position of the actuator when the traveling
±
contacts snaps with the fixed contact.
The position of the actuator when the traveling
contact snaps back from operating position to its
original position.
The stopping position of the actuator after total
travel.
Bad
Good
AECTB36E 201811-T
Table of Contents
