Supplying Loop Power - Fluke 741B User Manual

741B/743B
Users Manual

Supplying Loop Power

The calibrator supplies loop power at 28V or 24V dc.
The 28V setting supplies enough current for two or
three 4-20 mA devices on the loop in addition to the
two-wire transmitter but uses more battery power.
Use the 24V setting if there are two or fewer devices
on the loop in addition to the two-wire transmitter.
(Each device on a typical 4- to 20-mA loop has a
resistance of 250 , thus dropping 5V at 20 mA. A
typical transmitter must have 11V minimum in order
to operate correctly at its top end.)
When loop power is enabled, the mA (middle
column) jacks are dedicated to sourcing and
measuring the current loop. This means that the
SOURCE mA, measure RTD, and measure
functions are not available (see Table 8, later in this
manual.)
48
Connect the calibrator in series with the instrument
current loop as Figure 18 shows. Proceed as follows
to source loop power:
1. Press for Setup mode.
2. Note that following
Loop Power, Disabled
highlighted. Press
3. Use the or arrow keys to select
or
24V Enabled 28V.
4. Press .
5. Press the softkey.
Done
is
.
Enabled