The Importance of Sensor
Triggering in Production
and Process Automation
W
hen measuring the position
downstream monitoring and control
This type of sensor set up provides savings
of moving targets in
units, a permanent measurement output
in terms of the memory of the evaluation
production and process
is often not the best approach. Instead,
system.
automation environments,
the sensor should wait for a signal from an
it is important to understand the different
external source that specifies the time for a
It is important to understand the different
methods of sensor triggering, their impact
measurement to take place, thus initiating
triggering methods available and their
on measurement cycle times and the
the output of data. Triggering is therefore
relationship to sensor measurement rate
benefits they can offer over continuous
often initiated by an external signal.
and cycle time, particularly in fast-moving
measurement, says Chris Jones, Managing
Director at Micro-Epsilon UK.
Triggering is a term often used in sensing
and measurement technology and
includes all the different methods of
initiating a measurement or a controlled
output of measurement data.
Particularly in production and process
automation environments, in order
to reduce the system load on any
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PECM Issue 21
For example, consider a target
object in a high speed production
line, which passes a sensor every
five seconds for a period of one
second. If the sensor has a trigger
function, the output of the sensor
only needs to be switched on
(initiated) every 5s for a duration of
1s. The measurements between
the target objects are of no interest
and so do not need to be evaluated.
processes. Non-contact laser sensors are
often installed in production and process
automation environments to measure
displacement, distance or position.
These sensors can be triggered both via
the ‘edge’ or the ‘level’ of the trigger signal.
The following are implemented as trigger
conditions: rising edge (positive edge),
falling edge (negative edge), High level (H
level) and Low level (L level).