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Chapter 4
Measurement Definition
180
Channel 1/3 DC Page Configuration
The 1444 monitor requires that the long side sensor is input to the second
channel of the pair.
Table 38 - Axial Differential Expansion Configuration - Long Side Sensor
Parameters
Values
Units
Select from presented
displacement units
Time constant
0.1...60.0 seconds
Calibration Units
EU (0)
Volts (1)
Calibration offset
-50000...50000
Overall axial offset -50000...50000
Figure 74 - Module Properties - Long Side Sensor
Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Comments
Differential Expansion measurements are made using eddy current
probes. Configuration of the units, time constant, and calibration
units are the same as for Normal Thrust measurements
Sense control is fixed at "Toward" for the long side probe.
Select EU
For the long side probe, the offset is a combination of the entire
measured range of channel 0/2, as well as the entire offset of
channel 1/3. The latter is due to the measurement starting at the
lowest voltage, so the range from 0 to -17.7 (in the example) must
be accounted for.
Using the above 8 mm probe example:
9.8...88.6 mils (0.25...2.25 mm) gives a measurement range of 78.8
mils (2.0 mm) from the short side sensor channel (channel 0/2).
Add to that the measured distance from total range of the long side
sensor, 88.6 mils (2.25 mm) to get a combined total of 167.4 mils
(4.25 mm).
With the Calibration Units set to EU, the offset can be entered
directly.
No value must be entered into the Overall Axial Offset entry box
unless the starting value for the expansion measurement is required
to start at other than a zero value due to DCS or other control system
requirements.
(page
156).
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