17-10-2012, 04:24 PM
Piezoelectric vibration sensors
[attachment=36576]
Applications
Vibration sensors of this type are suitable for
the detection of structure-borne acoustic
oscillations as can occur for example in case
of irregular combustion in engines and on
machines. Thanks to their ruggedness,
these vibration sensors can be used even
under the most severe operating conditions.
Areas of application
– Knock control for internal-combustion
engines
– Protection of machine tools
– Detection of cavitation
– Monitoring of bearings
– Theft-deterrent systems
Design and function
On account of its inertia, a mass exerts
compressive forces on a ring-shaped
piezo-ceramic element in time with the
oscillation which generates the excitation.
Within the ceramic element, these forces
result in charge transfer within the ceramic
and a voltage is generated between the
top and bottom of the ceramic element.
This voltage is picked-off using contact
discs – in many cases it is filtered and
integrated – and made available as a
measur-ing signal. In order to route the
vibration directly into the sensor, vibration
sensors are securely bolted to the object
on which measurements take place.
Measurement sensitivity
Every vibration sensor has its own individual
response characteristic which is closely
linked to its measurement sensitivity. The
measurement sensitivity is defined as the
output voltage per unit of acceleration due
to gravity (see characteristic curve). The
production-related sensitivity scatter is
acceptable for applications where the
primary task is to record that vibration is
occurring, and not so much to measure its
severity.
[attachment=36576]
Applications
Vibration sensors of this type are suitable for
the detection of structure-borne acoustic
oscillations as can occur for example in case
of irregular combustion in engines and on
machines. Thanks to their ruggedness,
these vibration sensors can be used even
under the most severe operating conditions.
Areas of application
– Knock control for internal-combustion
engines
– Protection of machine tools
– Detection of cavitation
– Monitoring of bearings
– Theft-deterrent systems
Design and function
On account of its inertia, a mass exerts
compressive forces on a ring-shaped
piezo-ceramic element in time with the
oscillation which generates the excitation.
Within the ceramic element, these forces
result in charge transfer within the ceramic
and a voltage is generated between the
top and bottom of the ceramic element.
This voltage is picked-off using contact
discs – in many cases it is filtered and
integrated – and made available as a
measur-ing signal. In order to route the
vibration directly into the sensor, vibration
sensors are securely bolted to the object
on which measurements take place.
Measurement sensitivity
Every vibration sensor has its own individual
response characteristic which is closely
linked to its measurement sensitivity. The
measurement sensitivity is defined as the
output voltage per unit of acceleration due
to gravity (see characteristic curve). The
production-related sensitivity scatter is
acceptable for applications where the
primary task is to record that vibration is
occurring, and not so much to measure its
severity.