Allen-Bradley 1444-AOFX00-04RB, User Manual, Page: 164 / 550

164 Rockwell Automation Publication 1444-UM001D-EN-P - June 2018
Chapter 4 Measurement Definition
Proportional Voltage
Proportional (DC) Voltages are output from various sensors and systems,
representing pressure, amperage, flow, and other attributes. When it is
necessary to measure these values with the 1444 dynamic measurement
module, one or more channels can be defined for Static inputs. And if it is
necessary to provide this measure to the controller via the input assembly then
the measured “Proportional DC” value can be selected for module output.
See
Select Input Data for Input Tag on page 106 .
Proportional voltage measurements are calculated as y = mx + b where:
• m = the channel sensitivity in mV/EU (See Hardware Configuration on
page 112 .)
• x = the measured value in Volts.
• b = the calibration offset, in the selected engineering units
Proportional Voltage measurements are configured using the controls in
Figure 64 .
Figure 64 - Normal Thrust and Proportional Voltage
Table 34 - Configurable Parameters for Proportional Voltage Measurements
Parameters Values Comments
Units Select from presented units The specific unit selections that are presented depend on the Measurement Type setting ( Hardware Configuration
Page ).
For proportional measures, other than temperature (voltage or current), the module does not associate units. In
these cases, the units must be managed in the controller or software.
Time Constant 0.1…60.0 seconds The time constant calculation effectively smooths the measurements as it behaves similarly to a high pass filter.
The smaller the time constant the more responsive the measurement is to rapid changes (or noise).
Calibration Offset -50,000…50,000 Is the “b” parameter in the proportional formula (y = mx + b ).
In most cases, the offset is associated with the type of signal that is provided, such as “1...5 V” (offset = -1) or
“4…20 mA” (offset = -4). However in some cases the required offset is not so obvious. Consult the specific sensor
documentation to verify that an appropriate offset is applied.
For accelerometers that provide a proportional voltage temperature measurement as an additional output see
Configuring Temperature Measurements from Dual Output Accelerometers .