Watlow D4T Data Logger
•
66
•
Chapter 5 Function Reference
Analog Outputs
Use this block to operate an external device that takes an analog or process signal such as 4
to 20 mADC or 0 to 10 VDC.
These FBs are found on the canvas in the Function Block Diagram editor. The number of these
FBs available depends on the number of flex modules with analog outputs installed in the da-
ta logger.
These FBs can be used to operate a control element such as a proportional valve based on
the output of a retransmit a signal proportional to a process value or set point to another in-
strument such as a chart recorder. The illustrations below show examples of these two uses.
For a
power output
to a 4 to 20 mADC output, the value received is scaled proportionally
from the 0 to 100% input range to the 4 to 20 output scale. When the input is 25%, the output
is 8 mADC.
For a
retransmit output
to a 0 to 10 VDC output, the value received at input In is scaled pro-
portionally from the 50 to 250° input range to the 0 to 10 output scale. When the input is
100°, the output is 2.5 VDC.
Note that the settings of the Range Low and Range High settings do not limit the physical
output signal. The physical output is set according to the line defined by the range and scale
parameters and is limited by the range of values input to the function and the electrical limi-
tations of the hardware. If the input signal is limited to 0 to 100%, the Range Low is set to
0%, and the Range High is set to 100%, the output can be limited by setting the Scale Low and
Scale High parameters to the desired minimum and maximum signal levels.
