Continuity Testing; Measuring Resistance - Fluke 8010A User Manual

If
you
do
not
know
approximately
what
the current
is,
connect
the
circuit to
the
A
inputterminalfirsttoseeifyouhaveasafe
level for
the
mA/jA
input terminal.
Use
the
mAM
input
terminal
for
current
up
to
400 mA.
When
measuring
current,
the meter's
internal
shunt
resistors
develop
a
voltage
across
the meter's terminals called
"burden
voltage."
This voltage
drop
is
very
low
in
your
meter, but
it
may
affect
precision
circuits
or
measurements.
To
calculate the
burden
voltage:
in
A, multiply
the display
reading by
0.03V;
in
mA,
multiply
the display reading by
1.5
mV;
\r\fiA,
multiply the display reading
by
"IOOaiV.
For example,
at
a
20
mA
display reading, the
burden
voltage
is
20.00 x
1.5
mV =
30 mV.
The approximate
resistance
between
the input terminals
is
0.03
ohms
for A, 1.5
ohms
for
mA, and 100
ohms
for/yA.
Continuity Testing
Continuity testing verifies that circuit
connections are
intact.
To
perform audibl
e con
tinuity tests,
set
the rotary switch to
mil
n
press the
( -mi
)
button,
and connect
the
meter
to
your
circuit.
Test resistances
below
the values
listed in
Table 2
cause
the
meter
to
emit a
continuous
tone.
Use
the
400
ohm
range
for
most
wiring checks.
APPLICATIONS
Measuring
Current
The
continuity
mode
is
extremely
fast
and can be used
to
detect either shorts or
opens
that last for
as
little
as
1
milli-
second.
When
a
change
is
detected, the
beeper
tone
is
"stretched"
to last at least V*
second so you can hear
it
and
detect both shorts
and
opens. This
can be a
valuable trouble-
shooting aid
when
looking
for
intermittents
associated
with
cables, connections, switches,
relays, etc.
If
the
test
value
is
very close
to
the
th
reshol
d
,
erratic
beeps
ca n a
Iso
occur d ue
to
environmental
electrical
noise
(EMI).
Measuring
Resistance
CAUTION
Turn
off
power on
the test circuit
and
discharge
all
capacitors before attempting
in-circuit resist-
ance measurements.
If
an external voltage
is
present across a
component,
it
will
be
impossible
to
take
an
accurate
measurement
of
the
resist-
ance
of that
component.
The
meter measures resistance by passing a
known
current
through
the external circuit
or
component, measuring
the vol-
tage drop,
and
calculating the resistance using
Ohm's Law
(0=V/A).
Remember,
the resistance displayed
by
the meter
is
the
total
resistance
through
all
possible paths
between
the
probes. This explains
why
in-circuit
measurement
of resistors
does
not often yield
the
ohms
value indicated by the
resistor's
color
code.
19