Compensating For Test Lead Resistance; Using The Current Output Functions; Source Mode - Fluke 789 User Manual

789/787B
Users Manual

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
20
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 1. The arrows show the conventional current flow.
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.