Kapasîmetmetr

Metra capacitance ji bo taybetmendîyek elektronî ye ku werin lêkurdan capacitance, bêyî kapasîtorên dîsa. Kapasîtor. Metra capacitance di navbera capacitance û time constant derbasdar dike.

Eva tevgera di vê rêzikê de hatîn bikaranîn. Bêyî vê, divê li ser RC circuit sadeke bi berdewamê voltage IN (di jêr bibînin).

Di demê da ku kapasîtor bigerîne, voltage di navbera kapasîtor di her demê de

Demê dibarê ku kapasîtor bigerîne derbasdar 63.5 percent di total input voltage de.
wateye time constant. Bi 'τ' nîşan dide.

Niha, ew dikare kapasîtor bigere bi karî yên constant current source û kapasîtor bigere bi resistor yekî ya fixed resistance. Ji bo pîvanîna capacitance yekê, dikare 555 timer bi koma test apparatus digital bikar bînin. Rêzikê sereke ya pîvanîna capacitance heye bi pîvanîna time period of oscillations. Pirsgirêka hêsan bi nanofarad û microfarad dibe bi hilbijartina charging resistance.

Bi parastîna teknîkên din yên din, metra capacitance dikare electrolytic bigere ku tens of thousands of Farad ye.

Heke kapasîtor testandî heye leakage, ev rêzik dikare value of the capacitance be biçuker ji actual value. Ev rêzik jî efficient indicator e ji behavior yek test capacitor di majority bypass û timing circuits de. Block diagram yek digital metra capacitance bi 555 timer IC di jêr bibînin.

Li vir, 555 timer dikare binînin. Ewer astable multivibrator e. Frequency yek multivibrator dikare bi unknown capacitance value (CX). Output yek multivibrator connected to a digital counter e. Counter dikare length of the cycle of the square wave pîvine.
Cycle length of the square wave which is formed by 555 timers can be calculated using the formula:

On the peak value of the charging curve, a digital counter will get reset. At this time, a clock of 100 kHz pulses is made ON and it is routed to the counter. Next, after the completion of discharge part of the cycle, the display will get updated and we can simply read out the value of the capacitor. To get the direct display of the capacitance value simply and correctly, the selection of charging currents and reference frequency should be apt.

Shielding of leads should be made assure and for low capacity measurements, it should be kept short. This is because the hum of 50 Hz can result in some minor instability.

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