5-16
Orbit
The movement of the shaft axis* at constant speed is measured with
two non-contact sensors that are installed in an angular distance of
90 °.
This enables identification of machine faults and damage to
the shaft that become apparent in the vibration behavior of the
shaft and directly affect the path of the shaft (e.g. unbalance,
misalignment, shaft crack, rotation fault - for more details, see
VDI 3839 Sheets 1 and 2). When using 'filtered orbit', the signal is
processed in an order filter and therefore requires a keyphaser to
provide a reference.
A typical measurement installation is shown in the following figure:
- The two displacement sensors are mounted in a single
measurement plane at an angular displacement of 90° on the
machine.
If this angular displacement is not possible, you can mount the
sensors at any angular displacement between 5° and 175°.
Then enter the angular displacement in the measurement setup
('Sensor angle' parameter). However, measurement accuracy is
limited when the sensor angle
≠
90°.
- The sensor on channel A defines the X direction and the 0°
position.
- The keyphaser is mounted in the 0° position.
- Note the setting of the active edge for the trigger signal (see:
Keyphaser Menu/Device Setup, p. 2-23).
The procedure for an orbit measurement is described in the follow-
ing standards: ISO 7919, ISO 10817-1, VDI 3839 Sheet1.
A description of the measurement procedure with VIBXPERT can be
found in the Technical Information CM 18 'Analysis of radial shaft
movement in journal bearings’ - available free on our website.
Typical installation
with inductive displacement sensors
Measurement tasks
Note
filtered
unfiltered
* The movement of the shaft axis while
the machine is running up / coasting
down is recorded with a shaft center-
line plot (see p. 5-12).
Channel A
(VIB 6.640)
Channel B
(VIB 6.640)
Keyphaser
(VIB 6.631)
Summary of Contents for VIB 5.310
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