X90 mobile modules
172
X90 mobile system User's manual V 1.20 - Translation of the original manual
5.4.1.5.7.2 RMS value
The RMS value is also known as the quadratic mean, or the root-mean-square. Along with the amplitude, it also
takes the energy content of the oscillation into consideration and is the mathematical background for many char-
acteristic values of assessment.
If the RMS is calculated to be above the oscillation velocity, this can be referred to as oscillation speed. In the RMS
value, everything contributing to the oscillation is added up. The high oscillation amplitudes of an imbalance are
the same as the low oscillation level of bearing damage that is just beginning to occur.
If the RMS value is measured broadly, changes in individual elements contributing to the oscillation can be masked
by the averaging. The ability to detect damage early, e.g. due to defects in roller bearings, is limited.
Iso10816
Name:
Iso10816_01 to Iso10816_04
Registers for reading the RMS value (per ISO 10816) of the respective channel.
Iso10816 is formed from the raw signal of the oscillation velocity in a frequency range from 10 Hz to 1 kHz.
This broad characteristic value is often used in the assessment of the machine condition since assessment limits are
specified for this characteristic value in the standard. These depend on the type of machine and type of installation
(rigid or elastic). The characteristic value limits for a pre-warning or a warning are given according to their defined
classification.
Machine type
Bottom mounting
Group
Inflexible
Elastic
Inflexible
Elastic
Large machines
15 kW < P < 300 kW
Large machines
300 kW < P < 50 MW
Group 2
Group 1
Motors
160 mm < H < 315 mm
Motors
315 mm < H
0 - 1.4
1.4 - 2.3
2.3 - 2.8
2.8 - 3.5
3.5 - 4.5
4.5- 7.1
7.1 - 11.0
>11.0
RMS
value
of vibration
velocity
10
-
1000
Hz
when:
n
>
600
rpm
rpm>
n
>
120
rpm)
V
eff, rms
in
[mm/s]
Zone D: Danger of machine damage
Zone C: Limited operability
Zone B: Continuous operation without limitations
Zone A: Newly commissioned machine
(2
-
1000
Hz
at 600
Figure 37: DIN assessment scheme
If the machine condition is in order, this characteristic value is low. If damage occurs, then this value increases
severely. If the RMS is assessed in the range of the oscillation velocity, lower frequency portions such as drive
speed (and associated imbalance and/or misalignment) that are emphasized more and reflected more heavily in
the characteristic value.
Format
Unit
Value on overflow
REAL
mm/s
16777.21
