Fluke 789, User Manual, Page: 28 / 54

789
Users Manual
20
Compensating for Test Lead Resistance
Use the relative reading feature (
Q
on the display) to set
the present measurement as a relative zero. A common
use for this feature is to compensate for test lead
resistance when measuring ohms.
Select the
Ω
measure function, touch the test leads
together, and then press
r
. Until
r
is pressed
again, or the meter is switched to another measurement
or source function, the readings on the display will
subtract the lead resistance.
Using the Current Output Functions
The meter provides steady, stepped, and ramped current
output for testing 0-20 mA and 4-20 mA current loops.
Choose source mode, in which the meter supplies the
current, simulate mode, in which the meter regulates
current in an externally powered current loop, or loop
supply mode, where the meter powers an external device
and measures the loop current.
Source Mode
Source mode is selected automatically by inserting the
test leads into the SOURCE
+
and
−
jacks as shown in
Figure 7. Use source mode whenever it is necessary to
supply current into a passive circuit such as a current loop
with no loop supply. Source mode depletes the battery
faster than simulate mode, so use simulate mode
whenever possible.
The display looks the same in source and simulate modes.
The way to tell which mode is in use is to see which pair
of output jacks is in use.