X20 system modules • Other functions • X20CM4810
X20 system User's Manual 3.10
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Magnitudes of influence on the sensors
Mounting direction - Preferred direction
Oscillation sensors can be fitted at any location. The installation position usually results from the measuring task
itself. Nevertheless, oscillation sensors have a preferred measurement direction that is usually indicated on the
housing of the sensor.
Of course, oscillations in cross direction to the installation position also act upon the sensor. These can be com-
pensated as much as possible through appropriate constructive measures and suitable selection of the piezoelec-
tric crystal.
Installation position
The 0ACS100A.00-1 oscillation sensor from B&R is designed to measure the longitudinal axis; the 0ACS100A.90-1
sensor is designed to measure the lateral axis.
0ACS100A.00-1
0ACS100A.90-1
Cross-sensitivity
Oscillations in all directions act upon the sensor. The sensor should ideally transfer oscillations in its main direction,
i.e. in the direction of the sensor. Oscillations that deviate from this main direction are still registered by the sensor,
however, and transferred to the overall signal at different strengths depending on its type.
Cables
When transferring a signal over a connector, errors such as noise, ground loops and contortions may occur. This
influence is particularly important in the transfer of charges since system noise is a function of the cable's capacity.
When using IEPE technology, the sensor produces a high voltage signal with a low source impedance due to its
internal electronics.
As a result, this technology is well suited for signal transmission over long lines.
The supply unit provides constant current to supply the IEPE electronics in the sensor. The maximum frequency
that can be transferred via the test lead without considerable loss depends on the length of the cable, the cable
capacity and the ratio between the output amplitude and the constant current.
Information:
Maximum cable length when using the 0ACCxxx0.01-1 cable from B&R: 20 m.
Temperature influence
All piezoelectric materials also have a distinct pyroelectric effect. This describes the change in the electric polar-
ization of ferroelectric materials as a result of a change in temperature. This effect is undesirable since it often
leads to charge separations in the oscillation measurement. These arise from the change in temperature and not
through the mechanical vibrations occurring in the measured object.
This effect can be limited by the design, however. The interferences are grouped together in the interference
transfer factor for temperature changes.
Temperature drift:
The values specified in the sensor's technical data have been determined as a step response to a change in
temperature for the lower electrical limit frequency f
u
= 1 Hz.
Changes in temperature, in particular, cause interference in the low frequency domain below f = 10 Hz since this
is generally a low frequency event.
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