Functional Description
Original instructions
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Introduction
The BMEAHO0412 eX80 HART analog output module supports 4-20 mA analog communication and HART digital communication on each of 4 output channels.
Both the eX80 HART analog output module and the 4-20 mA current loop are powered by the backplane.
NOTE: Because the output module passes 24 Vdc power from the backplane to the current loop, an external power supply is not required for the current loop.
Output Slew Rate
When the HART function is enabled, the slew rate of each analog output is automatically limited. As a result, the output slew does not unintentionally trigger the HART receiver.
When HART is...
The output slew rate is automatically set to...
Enabled
0,8...0,9 mA/ms
Disabled
  • >1500 mA/ms (non-inductive load)
  • >300 mA/ms (1 mH inductive load)
Overshoot/Undershoot Control
Each output on the BMEAHO0412 eX80 HART analog output module operates over a range of 4-20 mA. You can use Control Expert to map up to 3 current ranges for each output.
Upper and lower tolerance detections are enabled regardless of overflow/underflow control.
Depending on the range specified, the module checks for overflow and verifies that the measurement falls between a lower and an upper threshold:
Designation
Description
Nominal range
The specified measurement range
Overshoot area
The range of values located above the upper threshold
Undershoot area
The range of values located below the lower threshold
NOTE: Monitoring of values in the overshoot and undershoot areas can be enabled or disabled in Control Expert.
The values of the thresholds are configurable independently from one another. Both the default values, and the maximum and minimum configurable values are as follows:
Range
BMEAHO0412 Range
Undershoot Area
Nominal Range
Overshoot Area
Default setting
–2,500
–801
–8000
10,300
10,301
10,625
Minimum / Maximum
–32,768
...
...
...
...
32,767
Writing Outputs
The application can provide the outputs with values using the standard display (in %, to 2 decimal places):
Type of Range
Display
4-20 mA
from 0 to 10,000 (0% to 100%)
It is also possible to define the range of values within which measurements are expressed, by selecting:
The lower and upper thresholds can be integers between –32,768 and +32,767.
Output Behavior on Program Interruption
In the event the BMEAHO0412 HART analog module detects an event that stops program execution, depending upon the seriousness of the interruption, each of the outputs undertakes one of the following responses:
Output behaviors:
If the detected event is...
The output response is...
Task in STOP mode, or program missing
Fallback/Maintain (channel by channel)
Communication interruption
Fallback/Maintain (channel by channel)
Configuration detected error
0 mA (all channels)
Internal detected error in module
0 mA (all channels)
Output value out of range (undershoot/overshoot)
Value saturated at the defined limit (channel by channel)
Open circuit
Maintain (channel by channel)
Module hot swapping (processor in STOP mode)
0 mA (all channels)
Reloading program
0 mA (all channels)
Behavior during initial power-up and power off
0 mA (all channels)
Actuator Alignment
The process of alignment involves the elimination of an observed systematic offset, around a specific operating point, for a given actuator. Actuator alignment compensates for a detected variation that is linked to the process. Replacing a module does not require a new alignment. However, replacing the actuator or changing the actuator operating point requires a new alignment.
Conversion lines are as follows:
The alignment value is editable from a programming console, even if the program is in RUN mode. For each output channel, you can:
The alignment offset may also be modified through programming.
Channel alignment is performed on the channel in standard operating mode, without any effect on the channel operating modes.
The maximum offset between measured value and desired (aligned) value may not exceed +/-1,500.
NOTE: To align multiple analog channels on the BMEAHO0412 eX80 HART analog output module, proceed channel by channel, aligning one channel at a time. Test each channel after aligning it before proceeding to align the next channel.