Rev. 01/11 -1.13- TFXL-X
CONNECTING THE 4-20 mA OUTPUT
The TFXL is equipped with a ground-referenced 4-20 mA output—
the output shares a common ground with the power supply. The
output transmits a continuous current output that is proportional to
liquid flow rate. The output was scaled at the Dynasonics factory
and the scaling information is recorded on the label located on the
side of the TFXL enclosure. To ensure that the instrument or data
acquisition system that is receiving the 4-20 mA signal
responds properly, it must be spanned identically to the TFXL.
The 4-20 mA output is designed to source current across a loop
resistance that is typically located within a data acquisition system
or other receiving instrument. The maximum resistance that the
TFXL can accommodate is directly related to the DC power source
that is powering the flow meter and the 4-20 mA loop. Chart 1.1
illustrates the range of load resistance that can be used with a given
power supply voltage. Ensure that the loop load resistance is within
the shaded region of the graph or non-linearity and transmitting
errors will occur.
The 4-20 mA output is polarized and since the output shares the DC
common with the power supply, reversing the connections can
cause a short circuit in the DC power circuit. Figure 1.6 on page
1.14 shows a block diagram of how the 4-20 mA interfaces with the
receiving device.
PART 1 - INPUT/OUTPUT CONFIGURATION
Output
Configuration
Chart 1.1
4-20 mA Loop Load
Ope rate
in the
Sha ded
Reg ion
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