This circuit can be used to test metal film ceramicapacitors and other types
of capacitors in a range of values between 470 pF to 10 uF.
The device is formed by an audio-oscillatorhat produces atone determined
by the capacitor under test. Probes connect the capacitor to the circuit. The
frequency of the produced tone is higher for lower-value capacitors. A falling
tone indicates abad capacitor.
Testing capacitors in the range between 1 and 10 uF, the oscillator will produce separated audio pulses, working like a metronome.
The circuit is powered by two or four AA cells, and current drain is very low.
P1 is adjusted to set an audible tone at the speaker, according the value of
the capacitor being tested.
You can also use this device to compare capacitor values. Two capacitors
with the same value will give the same tone.
The schematic diagram of the Capacitor Tester is shown in Figute 1. The
circuit has as its heart two complementary transistors working as a direct coupled amplifier. Feedback is provided by resistor R1 and the capacitor under test.
Components placement on a terminal strip is shown in Figure 2. Use this
parts placement as a guide when assembling the terminal strip and when
housing the circuit into a box.
Termination components should be short as possible to avoid instability.
Position of the polarized components, such as the electrolytic capacitor and
power supply, should be observed when mounting. The capacitor under test
is placed in the circuit by two alligator clips as shown in Figure 2.
The circuit can be housed in a small plastic box.
Parts List - GapacitorTester
Q1 - 8C548 general-purpose NPN transistor
Q2 - 8C558 general-purpose PNP transistor
R1 - 1,000 ohm, 114W,5% resistor
R2 - 4,700 ohm, 114W,5% resistor
P1 - 1,000,000 ohm, 114W,5% resistor
Cl - 100 uF, 6 WVDC electrolytic capacitor
Cx - capacitor in test
S1 - SPST toggle or slide switch
81 -3orOV-2or4M-cells
SPKR - 4 to 8 ohms - 2to4 in. loudspeaker
No comments:
Post a Comment