Diode Testing - Fluke 8010A User Manual

APPLICATIONS
Diode
Testing
The measurement
accuracy
of
capacitors
less
than 5
nF can
be improved by
first
using the Relative
mode
to
zero the
dis-
play
and
automatically subtract the residual
meter
and
test
lead capacitance. Since the Relative
mode
also selects
man-
ual ranging,
zero
the residual
capacitance only
when
measur-
ing small value capacitors.
Residual voltage
charges on
the capacitor, or capacitors with
poor
insulation resistance or
poor
dielectric
absorption
may
cause measurement
errors.
To check
capacitors larger
than
5^,
select
fl
with the rotary
switch
(or
press the
BLUE
button
if
you
are
in
the capacitance
mode). Select an appropriate
range from Table
4.
Discharge
the capacitor,
connect
the capacitor
to
the meter,
and
time the
number
of
seconds
it
takes
for
the
charge
to
go from zero
to
full
scale.
At
full
scale,
all
of
the analog display
segments are
on.
To
estimate the value of
the capacitor,
multiply
the
number
of
seconds
times the
charge
rate (j/F/sec)
in
Table
4.
For exam-
ple,
a 10//F capacitor takes
about 33 seconds
to
charge
in
the
4
MQ
range or
3.3
seconds
in
the
400
kd
range.
To
reconfirm
your
estimate,
reverse
the test leads;
when
the capacitor
discharges to
zero
(the
analog
display polarity
switches from
- to
+),
start
timing the
recharge
to
full
scale.
22
Diode Testing
To perform a diode or transistor
junction test plug the
test
leads into the Vf}-«-
and
COM
inputs, turn
the rotary switch
to
-*»-,
and connect the
test
leads across the
diode(s).
In
diode
test,
voltage
is
developed across the
component(s) by
a
test
current (approximately
1
mA
with the
test
leads shorted)
from
the meter.
Voltage
is
read
on
a single to
+3.000V range
that
can measure up
to five silicon
diode
or transistor
junctions
in
series.
For a
silicon
diode, the
typical
forward voltage should
be about 0.6V.
Voltages greater than 3.00V or
open
test
leads
produce an
overload (OL) reading.
If
the
digital
reading
is
the
same
in
both
directions,
the
diode
junction
is
probably shorted.
If
the display
reads
OL
in
both directions,
the diode junction
is
probably open. To
protect sensitive devices, the
open
test
lead
voltage
from
the
meter
will
not
exceed
3.9V.
Negative inputs
(from
an
external
power
source,
for
example) are not
suppressed.
Table
4.
Approximate
Charge
Rate
for
Capacitors
Range 400Q
4kfl
40
kn
400
kO
4MQ
/uF/sec
3000 300 30
3 0.3