Loop Power Supply Mode - Fluke 789 User Manual

Loop Power Supply Mode

The Loop Power Supply Mode can be used for powering
up a process instrument (transmitter). While in Loop
Power Mode, the meter acts like a battery. The process
instrument regulates the current. At the same time, the
meter measures the current that the process instrument is
drawing.
The meter supplies loop power at a nominal 24 V dc. An
internal series resistance of 250 Ω can be switched in for
communication with HART and other smart devices by
pressing J (Blue). Pressing J (Blue) again switches out
this internal resistance.
When loop power is enabled, the meter is configured to
measure mA and > 24 V dc is sourced between the mA
and A jacks. The mA jack is the common and the A jack is
at > 24 V dc. Connect the meter in series with the
instrument current loop as Figure 10 shows.
info@Fluke-Direct.com
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Figure 9. Loop Power Voltage vs. Current
Fluke-Direct
ProcessMeter™
Loop Power Supply Mode
0 4 8 12 16 20 24
Current (mA)
Loop voltage w/ 250 Loop voltage w/o 250
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