Trigger via pin 2 (Index 121)
Alternatively, pin 2 can be triggered by a falling or rising signal edge or both on the
hardware side. The setting via which a signal edge is to be triggered takes place in
4474, Subindex 2. At the same time, pin 2 in Index 121 must be configured as a trigger
signal (
see "Configuration of digital outputs", page 44
4.3.4
Activity detection (Index 4479-4480)
The sensor updates the indication values even when there is no vibration. In this case,
the indication values are calculated from the noise signal of the vibration sensor. Espe‐
cially the impulse factor (
see "Vibration in time range (Index 4483-4539)", page 16
)
can assume very high values, which can lead to misinterpretations of the machine
condition and undesired alarms.
An applied vibration can therefore be registered via activity detection. When the func‐
tion is used, Index 4480 outputs whether an activity is detected or not.
If no vibration is detected, all current indication values are set to 0, the minimum and
maximum values are not updated. This has the advantage that, for example, the limit
value of the impulse factor is not exceeded as long as no vibration is present. Activity
detection is based on the
a-RMS
magnitude value (or in single-axis mode, on the
a-RMS
value of the selected axis). If the
a-RMS
value exceeds the “activity limit” set in Index
4470 Subindex 2, an activity is recognized as such. If the
a-RMS
value falls below the
limit value set in Subindex 3, no activity is detected accordingly.
4.3.5
Vibration in time range (Index 4483-4539)
The Multi Physics Box, as shown in
, provides indication values in the time
range calculated block by block. These values provide information about the vibration
intensity and the type of vibration signal.
A total of 9 statistical and vibration-specific values are provided for interpretation. The
mathematical basis of the indication values is described below. Which error cases and
effects can represent changes of the respective characteristic values is described in
.
a-RMS
(Index 4483-4485)
a-RMS
stands for
acceleration - Root Mean Square
. The value, given in [g = 9.81 m/s
2
], is
the effective value of the acceleration signal and a measure of the energy contained
in the vibration. It can be used to estimate the strength of the vibration. In general, it
can be assumed that the
a-RMS
value is more sensitive to changes in vibration above
1,000 Hz than the
v-RMS
value.
v-RMS
(Index 4486-4488)
In line with the
a-RMS
, the
v-RMS
(
velocity - Root Mean Square
) in [mm/s] represents
the effective value of the speed signal. This value is also a measure of the energy
contained in the vibration. Unlike the
a-RMS
, the
v-RMS
is more sensitive to changes in
vibration below 1,000 Hz than the
a-RMS
.
Variance
(Index 4489-4491)
The variance is a statistical measure that indicates how widely the signal values are
scattered around their mean value. In the context of vibration analysis, this is a meas‐
ure of the strength of a vibration analogous to the RMS value.
4
PRODUCT DESCRIPTION
16
O P E R A T I N G I N S T R U C T I O N S | MPB10
8028041/2022-08-16 | SICK
Subject to change without notice
