Loop Power Supply Mode - Fluke ProcessMeter 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
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.
can be switched in for
Loop Power Supply Mode
32
30
28
26
24
22
20
0 4 8 12
Current (mA)
Loop voltage w/ 250
Figure 9. Loop Power Voltage vs. Current
ProcessMeter
16 20 24
Loop voltage w/o 250
anw020f.eps
29