178 Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Chapter 4 Measurement Definition
HW Configuration
On the Hardware Configuration Page
, set the Measurement Type for both
channels of the pair, to “Complementary Differential Expansion A (Axial)”.
Figure 72 - HW Configuration
For each of the channels, edit the Xdcr attributes as appropriate to the sensor
input.
Example:
If you use an 8 mm probe from Allen-Bradley® 1442 Series Eddy Current
Probes:
• Set or verify that the transducer (Xdcr) units are “mil”, or “mm”, and the
sensitivity is “200” or “7.87” respectively.
• Set or verify that Xdcr power is “-24V DC, 25 mA”.
• Set the “Xdcr High Limit (V DC)” to -2.
• Set the “Xdcr Low Limit (V DC)” to -17.7.
The high and low limits for the sensors correspond the published linear
range for them, which for the 1442 Series 8 mm probe is 9.8…88.6 mils
(0.25…2.25 mm).
In normal monitoring, the module uses these limits to indicate that the
sensor could be faulted, so can be set outside the linear range of the
sensor. For differential expansion, the module uses these limits to know
when the target is within the linear range of the sensors. Which sensor is
within its linear range, or if both sensors are, determines the
measurement behavior:
• One sensor within its linear range: Output measurement from that
sensor.
• Both sensors are measuring within its linear range: Output is the
average of the measurements from both sensors.
For this example, the transducer bias values are set as shown in
Figure 72
.
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