Sencore LC102 AUTO-Z - Page 2

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AUTO-Z
POWER
TEST LEAD LEAD ZERO
LEAKAGE
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8 WARNING Fl.ish1ng light md1 c1tes 25 t OOOV
ap~l•ed lo test leads when leakage butlon is pressed
STOP TESTING Protection circ uit or fuse ,.
open Capacitor being tesled may be charged
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Fig. 3: The LC102 gives you two tests with GOOD/BAD readout for error free testing. The coil test sections of your LC102 are color coded
blue.
The Ringer Test Finds Shorted
Turns
The Ringer has been proven reliable by the
tens of thousands of units in use since it
was introduced in the Sencore YF33 Yoke
and Flyback tester back in 1975 . The test
was expanded to test other coils on the
LC53 Z Meter in 1979 . Today, the LC102
has automated the test, so the
microprocessor sets the test levels and
automatically finds the correct resonating
capacitor. All you need to do is press the
test button and view the digital display for
good I bad res u Its .
The LC102's Ringer tests the effective 0 of
the coil , but you don't need to know the
original 0 value. (The 0 of a coil is normally
not published , and is frequency
dependent.) Instead , all you need to
remember is the number "10". Good coils
show a Ringer number higher than 10 and
bad ones a number below 1 O.
The Ringer places a fixed capacitor in
parallel with the coil, and then hits the tank
with a single exciting pulse. The coil and
the capacitor ring at their resonant
frequency. Digital circuits count how many
ringing cycles occur before the signal
drops (damps) below a preset level.
A coil with a high 0 produces more ringing
cycles than one with the same inductance
value and a lower 0. A shorted turn causes
the ringing to dampen very quickly.
The LC102 circuits automatically scale
their sensitivity, depending on which of the
" Component Type" buttons you've
picked. If, for example, you are testing a
deflection yoke or a flyback transformer ,
the digital circuits stop counting the
ringing pulses after their amplitude has
Pulse
Generation
Level
Detector
dropped to the 25 % level . If you are testing
some other inductor , the circuits continue
to count to the 5% level. This automatic
scaling lets you use the same number
"10" for different kinds of coils.
There are two limits you need to know.
First, the Ringer does not test inductors
with laminated iron cores, such as power
chokes and power transformers . The
Matching
hit .. or __ ,
Coil
Under
Test
Pulse
Counter
I :J .
IL rings
Display
Fig. 4: The Ringer test places the coil in parallel with the capacitor. Then pulses the tank
circuit, and digitally counts the resulting oscillations.