Measuring Ac Or Dc Current; Understanding Ac Zero Input Behavior Of True Rms Meters - Fluke 175 User Manual

Models 175, 177 & 179
Users Manual

Measuring AC or DC Current

X W
To avoid personal injury or damage to the Meter:
Never attempt to make an in-circuit current measure-
ment when the open-circuit potential to earth is
1000 V.
Check the Meter's fuses before testing. (See "Testing
the Fuses".)
Use the proper terminals, switch position, and range
for your measurement.
Never place the probes in parallel with a circuit or
component when the leads are plugged into the
current terminals.
Turn power OFF, break circuit, insert Meter in series, turn power
on.
8
Warning
HOLD MIN MAX RANGE
mA
A
+
CAT
CAT
+
AIK08F.EPS

Understanding AC Zero Input Behavior of True RMS Meters

Unlike averaging meters, which can accurately measure only pure
sinewaves, True RMS meters accurately measure distorted
waveforms. Calculating True RMS converters require a certain
level of input voltage to make a measurement. This is why AC
voltage and current ranges are specified from 5% of range to
100% of range. Non-zero digits that are displayed on a True RMS
meter when the test leads are open or are shorted are normal.
They do not affect the specified AC accuracy above 5% of range.
Unspecified input levels on the lowest ranges are:
AC voltage: below 5% of 600 mV AC, or 30 mV AC
AC current: below 5% of 60 mA AC, or 3 mA AC
DC