Protection
Measurement Types
2 - 6
SKF Multilog O
n-Line System IMx-M
User Manual
Complementary Differential Expansion
Complementary Differential Expansion (CDE)
uses signals from two analog channels
of combined measurements to extend the measurement range.
This setup is required to determine the axial displacement of the proximity probe collar,
due to thermal expansion of the main rotor shaft. As the shaft expands, the proximity
collar moves away from one sensor towards a second sensor, effectively doubling the
total proximity sensing range.
Figure 2 - 6.
Complementary Sensor Setup.
For this example:
•
Sensitivity of sensor S1 and S2 is 1 000 mV/mm.
•
Sensor S1 will be connected to Channel 1 and sensor S2 to Channel 2.
•
We will assume that the collar is closer to sensor S1 when there is no rotor
expansion, but closer to sensor S2 when the rotor is at maximum expansion.
•
Channel 1 will have the target positive direction set as "Active / Normal (away from
probe)" whereas Channel 2 will be set in reverse.
•
Sensor S1 is selected as the master sensor. It is the output of this sensor which will
determine when measuring of the displacement will switch from Sensor S1 to
Sensor S2.