Push button micro switch travel describes movement of the switch actuator between defined positions. Measuring it accurately means recording where movement begins, where the switch operates, and where it releases, while keeping those positions distinct from the button’s external motion and the contacts’ electrical state. The names for these intervals depend on defined endpoints, not on a universal travel distance.
A repeatable measurement therefore needs a clear reference position, a consistent direction of movement, and a stated way to identify operation and release. The switch’s own documentation determines which limits apply. The terms below describe specific relationships between actuator positions; they should not be treated as interchangeable measurements.
What push button micro switch travel describes
Travel is displacement of the actuator, measured as a distance or angle between specified positions. For a push-button arrangement, the button is the accessible part used to move the actuator. Its measured external displacement may not equal movement inside the switch, and it does not by itself state when the contacts change state. Keep mechanical movement and electrical observation separate in the record.
Before measuring, identify the position from which displacement will be recorded. The free position is the actuator’s reference position before it is operated. The operating position is the position associated with operation. The releasing position is the position to which the actuator returns during release. Use the terminology and limits supplied for the particular switch and actuator arrangement rather than assigning generic values to these points.
The measurement reference matters because a reading is meaningful only in relation to its stated starting point. A displacement measured at the button surface, for example, describes that measurement point; it should not be presented as internal contact movement. Likewise, a recorded operating point is a position, while a continuity observation is an electrical indication used to identify or confirm that point. They are related observations, not identical quantities.
Push button micro switch travel terms and endpoints
Pretravel is the distance or angle through which the actuator moves from the free position to the operating position. It describes movement up to operation, not all movement available after operation. Record its two endpoints explicitly so that the value is not mistaken for total actuator movement.
The operating position marks the endpoint of pretravel. Overtravel describes a different interval: the distance or angle between the operating position and the extreme position to which the actuator may be moved. It therefore begins at operation and ends at the permitted extreme position. Do not use “overtravel” to mean movement from free position, or assume that the extreme permitted position is a target for routine measurement.
Movement differential, also called differential travel, is the distance or angle through which the actuator travels from the operating position to the releasing position. This is return-related movement between two defined positions. It is not another name for pretravel or overtravel: each term starts and ends at different points.
Release force is a separate quantity, not a travel distance. It is the force or torque to which force on the actuator must be reduced to permit the contacts to return to the unoperated position after operation. Do not report a force or torque observation as differential travel, or infer a travel distance from release force alone.
These definitions establish the endpoints, but they do not provide a universal numerical travel value or a general measurement tolerance. The applicable specifications for the specific switch and its actuator arrangement must supply those limits.
How to measure push button micro switch travel
Use a displacement indicator suitable for the movement being measured, and secure the switch so it cannot shift during the test. The mounting must not obstruct the actuator. Identify the point on the actuator or button where displacement is read, then record the reference position and the direction in which the actuator will move. Keeping that point and direction consistent makes repeated readings more comparable.
Begin at the free position and record the indicator reading. Move the actuator in its intended direction while observing displacement. Identify the operating position using an electrical continuity check or another criterion specified for the test. Record the displacement and the criterion used to identify operation. This separates the measured position from the electrical observation that helps locate it.
If measuring pretravel, use the reading difference from free position to operating position. Continue beyond operation only if the documented travel limit and test purpose allow it. Any further movement must remain within the stated permitted limit; overtravel, when specified, is measured from the operating position to the extreme permitted actuator position. Do not push the actuator to an endpoint simply to obtain a reading if doing so would exceed its documented limit.
To record return movement, release the actuator and observe where it reaches the releasing position. Use the same displacement reference and record the return point. The distance or angle from operating position to releasing position corresponds to movement differential where that definition applies. A continuity observation can help identify contact return, but it should be logged separately from the displacement reading.
For a repeatable report, include the reference position, measurement point, actuation direction, operating-position criterion, observed operating and release readings, and the method used. Repeat the procedure consistently if additional readings are needed. Do not claim a value is acceptable merely because it can be measured; compare it with the specific switch documentation and its stated limits.
Why measured travel differs between setups
An external displacement reading can change when the measurement point changes. Button shape and actuator arrangement affect where the indicator contacts the moving part, so readings taken at different locations do not automatically describe the same displacement. State the measurement point rather than treating all button readings as directly comparable.
Mounting alignment and loading direction also matter to the setup. If the switch shifts, the indicator reference changes; if the actuator is approached in a different direction, the movement path being observed is no longer the same test condition. Secure mounting, consistent alignment, and a recorded direction help distinguish setup differences from differences in the switch’s defined positions.
A measurement reference can also create an apparent discrepancy. One reading may begin at free position while another uses a different starting point. Those readings cannot be compared as if they measured the same interval. Identify the endpoints before comparing values, and separate external button displacement from the defined actuator travel interval.
These factors explain why a measured value alone cannot establish whether travel is within limits. Use the relevant documentation for the particular switch and actuator arrangement. The supplied definitions specify how to name intervals and positions, but do not set a universal acceptable distance or angle.
Related guides
Avoiding travel measurement errors
Do not force the actuator beyond its stated permissible travel to locate an extreme point. Use only documented limits, and stop any measurement that would require exceeding them. The extreme position in the definition of overtravel is the permitted limit for actuator movement, not permission to push farther.
Do not compare readings that use different reference points, measurement locations, or movement directions as though they represent the same interval. Record those conditions so another reader can tell what was measured. If the test uses an electrical continuity check to identify operation or release, record that criterion separately from the displacement value.
Finally, keep the terms tied to their endpoints: pretravel runs from free position to operating position; overtravel runs from operating position to the extreme permitted actuator position; and differential travel runs from operating position to releasing position. Push button micro switch travel is most useful as a measurement when the report names those endpoints, states the reference and method, and compares the result only with the applicable specifications.
Sources and references
- Defense Logistics Agency ASSIST: MIL-PRF-8805K: Switches and Switch Assemblies, Sensitive, Snap Action, General Specification For