Fluke 179 Fluke Multimeters - Detecting Intermittents Application Note
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- Fluke 179 | Fluke Multimeters - Detecting Intermittents Application Note - Page 1
number of test tools that can help make the intermittent troubleshooting process a little easier. These tools range from complex signal analyzers and storage oscilloscopes to handheld digital multimeters (DMM). Of course, you may not have these tools available or the location of the problem makes it - Fluke 179 | Fluke Multimeters - Detecting Intermittents Application Note - Page 2
the MIN MAX record function, you are not limited to using the DMM for problems that only result in signals moving to a minimum or maximum value. To use the Event Logging feature, you will need a Fluke 189 True-rms Multimeter, FlukeView® Forms Documenting Software and a personal computer on which to - Fluke 179 | Fluke Multimeters - Detecting Intermittents Application Note - Page 3
the measured signal stays within a specified percent of the selected range, the meter will keep updating the same set of MIN MAX values. However, should the input signal value change by more than a specific percent of range, the DMM will store the minimum and maximum values it has accumulated so far
Application Note
The elusive electrical intermittent
is one of the most difficult prob-
lems for anyone to troubleshoot.
The difficulty lies primarily in the
timing. Being able to look at the
symptoms while the problem is
present simplifies the trou-
bleshooting process considerably.
However, the old adage “A
watched pot never boils” seems
to be applicable to electrical
intermittents as well. Being pres-
ent, as well as being able to take
an electrical measurement while
the problem exists, are the two
biggest challenges in tracking
down an intermittent.
There are a number of test
tools that can help make the
intermittent troubleshooting
process a little easier. These tools
range from complex signal ana-
lyzers and storage oscilloscopes
to handheld digital multimeters
(DMM). Of course, you may not
have these tools available or the
location of the problem makes it
difficult to bring a large analyzer
to the problem site. A DMM may
be able to tell you a lot about an
intermittent without having to go
back to the shop and haul that
storage scope to the job site. This
article will describe how to use a
DMM as an intermittent trou-
bleshooting tool.
DMM features for hunting
intermittents
Couple the basic measurement
features of a DMM (ac volts, dc
volts and resistance) with some
form of measurement recording
ability, and you have a tool for
detecting the symptoms of inter-
mittents. Not too long ago, you
could buy a voltage or current
measuring tool that was built
around a mechanical strip chart
recorder. Just place the input on
a voltage, or clamp a current
transformer around a conductor
and the recorder would make
progressive marks on a strip of
paper fed under the marking
pen. The maximum length of the
recording was determined by the
amount of paper that could be
placed on a roll of paper. This
same strip chart recorder tech-
nique has been incorporated into
some of today’s DMMs.
Fluke’s 170 and 180 Series
DMMs have a feature called
MIN
MAX AVG Recording Mode
. Just
like the strip chart recorder, the
DMM takes a reading of the input
at regular intervals. But instead
Detecting intermittents
with a DMM
From the Fluke Digital Library @ www.fluke.com/library
of saving each reading, it com-
pares the reading to two previ-
ously stored values to determine
if it is higher than previous high-
est reading or lower than the
previous lowest reading. If it is,
the new reading replaces the old
value stored in high or low read-
ing register. After allowing the
recording process to continue for
a period of time, you can recall
these registers to the display and
see the highest and lowest read-
ing taken during the recording
time. As an added bonus, these
DMMs will also compute and
store the average value of all
readings taken during a given
time period.