The Different Types of Sensor Triggers

A trigger is an event that causes a sensor to start a measurement cycle. Today’s all-in-one 3D smart sensors include a selection of trigger sources to simplify system integration for specific applications.

Time Based Trigger

Time based triggering is based on the sensor’s internal clock that can be used to generate fixed-frequency triggers at a user-defined rate. An external input can be used to enable or disable the time triggers. Time based triggers are used to profile targets, which are moving past the sensor at a fixed travel speed. Time based triggering (or free running mode) is also useful during sensor setup and diagnostics.

Time Trigger + Conveyor

Encoder Based Trigger (for Displacement and Profile Sensors)

Almost all industrial transport mechanisms will vary in speed over time. To insure uniform spacing of profiles, an encoder should be mounted on the conveyor/transport mechanism to trigger the sensor at specific motion intervals, for example, every 1mm.

For applications where the conveyor/transport mechanism may reverse travel direction, smart sensors provide the option of triggering the sensor only at forward motion increments (ignoring reverse motion resulting in complete target profiles without duplication), or triggering on every encoder pulse, regardless of travel direction.

All-in-one smart sensors accept an encoder input directly to the sensor, and support encoder calibration so encoder ticks correspond to engineering units to accurately produce 3D surfaces.

Encoder Trigger + Conveyor

External Input Triggers

A sensor can be triggered from an external source, such as a photocell. An external input can also be used to enable when time or encoder triggering is active. For example, as long as a target is detected by a photocell, the external input would enable internal triggering of scans. When the object has passed through the scan plane (no longer detected by the photocell), then triggering would stop.

External Input Trigger + Conveyor

Software Trigger

A software trigger can be generated by an application running over the sensor network to start a measurement cycle. One example would be a robot-mounted sensor receiving a trigger from the robot controller at each measurement position.

Software Trigger + Robot Arm