Interpreting Capacitor Value Readings; In-Circuit Capacitor Test - Sencore ReZolver LC103 Operation And Application Manual

Change To
Farads Microfar ads
From
Nanofarads Picofarads
Farads
move decimal move decimal
move decimal
6 places right 9 places right 12 places right
Microfarads
move decimal move decimal
move decimal
6 places left 3 places right
6 places right
Nanolarads
move decimal move decimal
move decimal
9 places left 3 places left
3 places right
Picofarads
move decimal move decimal move decimal
12 places left 6 places left 3 places left
Table 11 - Capacitor value conversion chart
LCI03 wi th the PA25 1 AC Power Adapter co nnected to a
prope rly grounded AC ou tlet. The PA25 1 Power Adapter
maintains the third wire ground shie ld and keeps the noise
away from the measuring circuits inside the ReZolve r.
Interpreting Capacitor Value Readings
The LC I 03 ReZolver automatically d isplays the three most
common capacito r values of picofarads (pF) , microfarads
(uF) , an d Farads (F). When measu ring capacito rs with the
LC103, you may encounter som e capac itors wi th a value
marked with o ut a d ecima l, s uch as "25000 pF", but that
read ". 0250 uF" on th e LC103 display. Yo u may also
e ncounter, as a n example, a capacitor which is marked
"3300 pf" by some man ufacturers, ye t a n identi ca l
r e pl aceme nt is marked " .00 33 uF" b y a n oth er
manufacturer.
LC103 returns a ca pacito r value that is hig her than the
capacitor being tested you may want LO remove the
suspect capacito r to Lest it accurately.
2. Sometimes th e LC 103 will return a value and ESR
read ing accompan ied by "SUGGEST REMOVAL." In
this case, there are components surro undin g the
capacitor that have upset the measurem ents. For
re liable test results this capacitor would be best tested
o ut-of-ci rcui
l.
3. Som e circuits req uire ca pacitors with less ESR than the
EIA specifies. Wh en testing these capacitors, the LC103
may show a "GOOD" reading but the capacitor may not
work in th e circuit. Refer to th e m anufacture r's
specifications or compare lo a known-good capacitor.
The following flow cha rt explains how th e ReZolve r decides
whic h indicator LO display with the value a nd ESR readinas
to
when perform ing an in-circuit capacitor test.
Wh en the In-Circuit Capacitor Test buuon is pressed the
LC! 03 begins its para lle l component checks. If this test fai ls
the Re Zolve r displays th e value a nd ESR measurements
alo ng with SUGGEST REMOVAL message.
If
the parallel
component check passes the LC103 checks to see if the
COMPO 1 E1 T PARAMETERS have been entered. If so, it
compares all m eas ure me nts to these values a nd displays a
GOOD m essage a lo ng with the val ue a n d ES R
meas ure m ents if they fall within the specifi ed parameters
IN.CIRCUIT TEST FLOWCHAAT
As these examp les illustra te,
capacitors can be marke d in
pF , uF o r eve n F. A fo urth
value multiplie r, the nanofarad
(nF) is seldom used to ma rk a
capac iLOr , but is u sed
occas io n a lly in d es ig n and
industry. Table 11 will he lp yo u
L O easi ly co n ve rt from o n e
reading to another.
ln·Circu1t
Capacitor Test
In-Circuit Capacitor Test
In many cases it is desira ble to
test a ca pacitor in-circ uit and
the n, if nccessa1-y, remove it to
test it mo re comple tely out-of-
c i r c u it. R e li a bl y tes tin g
c apac itors in c ircuit ca n be
tre mendously time aving. Due
to th e wide variety of circ uits,
there are a few thin gs to kee p
in mind as you use the LC103
to test capacitors in-circu it.
1. Many circuits, especially
power supplies, p lace two
or mo re capacitors in
pa rallel. In th is case, you
will see a h igh capacitor
value reading. This is
normal since parallel
capacitance adds. When the
YES
did either parallel
component test fail?
NO
are all
parameters
entered?
NO
YES
is ESR high?
YES
NO
is value low?
YES
display ' BAD"
NO
'SUGGE~V~~MOVAL'
YES is value high?
NO
I
display "GOOD'
I
Fig. 29: In-Circuit Capacitor Test flow chart.
39
NO
is value
entered?
YES
is tolerance
entered?
YES
is value okay?
YES
default ± 20%
NO
.--is _ty_pe_._en-te-red-?
~
NO
,....-is-m-ea-s-ured~
YES value
>1
µF
YES NO
YES NO
default tant default ceramic
ESR < limit? NO
display 'BAD?'
YES
display 'GOOD?'